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mage New im space’s biggest star Instant Expert WHAT IS ZODIACIAL LIGHT?
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All eyes have been on comet C/2020 F3 (NEOWISE) this month
Welcome
© Stuart Hilliker
As I write this, I've just come back from a successful early morning session observing Comet NEOWISE. It's currently glowing at magnitude +3, slightly dimmer than when I first pointed my camera at it a few nights ago. Even without optical aid the comet is an incredible nakedeye sight, visible even in areas of moderate light pollution. Did you manage to spot it? According to the All About Space e-mail inbox and social channels, we've discovered that many of you did, and this issue we've featured your spectacular images as part of our picture gallery on page 6. If you missed our call for submissions, then not to worry – we're still accepting your images of NEOWISE over the next few issues. Details of our social
channels can be found below and over on our contents page. Elsewhere in the magazine, new research suggests that the details of how our Moon formed could be different to how we initially envisaged. Will the history of our Solar System need to be rewritten? Turn to page 14 for the full details. Over on page 42, our special report reveals Earth's action plan on what will happen when – of if – we make contact with intelligent alien life. Find out how us earthlings will be informed by officials, what the steps will be and what will happen if it turns out that our alien counterparts are less than friendly… Enjoy the issue, see you soon!
Ourcontributorsinclude… Chris Hadfield
Nour Raouafi
Lee Cavendish
Space science writer If we can get a true understanding of how our natural satellite was made, we could uncover how we came to thrive on Earth. Colin has the details on page 14.
Astrophysicist The project scientist of NASA's Parker Solar Probe reveals the latest results, images and what's next for the craft – and how the next decade is the golden age for solar research.
Former astronaut Chris Hadfield answers your space questions alongside our expert panel of astronomers, astrophysicists and space exploration experts on page 64.
Staff writer How big is supergiant Antares? Lee reveals the brand-new images from the Very Large Array that have provided a new look at the red gem that lies in Scorpius.
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THE CRASH THAT
WITH THE UNIVERSE 06 Your photos of Comet NEOWISE, the discovery of a gigantic galactic structure that stretches billions of light years and NASA's latest update on getting humans back to the Moon
FEATURES
14 The crash that 38 How big made our Moon is Antares? Understanding the intricacies of our lunar companion's formation could explain our existence
22 Future tech Interstellar ramjet 24 The end of space and time To better understand the universe, we may need to kill off Einstein's famous idea
32 Instant expert What is zodiacal light? 34 Interview Parker Solar Probe: two years on Dr Nour Raouafi reveals the Sun as its never been seen before and what's next for the solar space mission
The local red supergiant star has been mapped in extraordinary detail by radio telescopes
42 What happens when we contact alien life? How we'll prepare the world for the biggest discovery in the history of humanity
50 Shooting for the Moon How NASA trained Neil Armstrong and his crewmates to land on the lunar surface
14
56 On board a topsecret space shuttle
NEW IMAGES OF THE SUN
An X-37B has been sent into orbit for its sixth mystery mission. What has the ex-NASA spacecraft been up to?
64 Ask Space Your questions answered by our space experts
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STARGA AZER Your complete guide to o the night sky
MADE
68 What’s in the sky? Even with NEOWISE E dimming and the Perseids departing, there's still plenty to observe
72 Month's pla anets Gaseous duo Jupiterr and Saturn still make a stunning pair before they dip below the horizon h
74 Moon tour To the south of Plato o are xploring with mountains worth ex a telescope
75 Naked eye y and binocular targets Time to meet some of o the summer Milky Way’s treasurees
76 Deep sky ch hallenge Glittering star clusteers, a dead star’s corpse and a beautifful double star
78 The Northe ern Hemispherre
38
56
THE END OF SPACE AND TIME?
HOW BIG IS ANTARES?
Aquarius and Pegasu us grace the skies going into September
80 Telescope review Is the Sky-Watcher Explorer-130PS the right telescope for you? Here's our full test
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COMET NEOWISE EDITION
NEOWISE blazes brightly over O’Brien’s Castle Photographer: Cormac Coyne This photo was taken from Inisheer, the smallest of the Aran Islands that sits in the middle of Galway Bay on the west coast of Ireland. Just after midnight on 11 July, photographer Cormac Coyne climbed up to one of the highest points on Inisheer that overlooks O’Brien’s Castle. “When I was setting up above the castle, noctilucent clouds were just beginning to form,” he said. To capture NEOWISE, Coyne used a Canon EOS, coupled with a Canon 70-200mm f/2.8 Mark 3 lens. Despite being a naked-eye comet, Coyne also observed NEOWISE through binoculars. “I took the photos into Adobe Camera Raw, processed them and then saved them as a JPEG file,” he added.
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Strokes of celestial and artificial light Photographer: Björn Hoffmann “In the early morning of 10 July I was able to capture some stunning images of Comet C/2020 F3 (NEOWISE) and noctilucent clouds in Stuttgart, Germany,” said Björn Hoffman. “Together with the dark clouds, a beautiful contrast formed.” Hoffman stacked photos in software Sequator, followed by processing in Adobe Lightroom, Topaz DeNoise AI and Luminar Flex. By stacking images, it becomes possible to dive deep into the image and reveal fine detail.
The comet captured at Corfe’s ruin Photographer: Kevin Ferriolo Having seen other photographers’ images of NEOWISE, Kevin Ferriolo ventured further afield on a clear night to capture the comet himself. This image was taken on 11 July at 02:39 at Corfe Castle, Dorset, UK, using a Canon 450D with the Canon EF-S 55-250mm f/4-5.6 lens, shot at 55mm. The panoramic portion was shot with a ten-second exposure and ISO sensitivity of 1,600. The foreground was lit up by the moonlight, while minor adjustments were made in Adobe Lightroom to adjust shadows and contrast.
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Close up of a space snowball Photographer: Stuart Hilliker Stuart Hilliker captured these images in Angmering, West Sussex, UK, on 12 July 2020. “I used a William Optics Megrez 72 telescope, a Canon 700D camera and an AstroTrac camera mount,” said Hilliker. Eight minutes worth of useful data was captured over a two-hour period. Various exposure times and ISOs were used, with the most successful being at 15 seconds with an ISO of 1,600. The images were processed and refined using DeepSkyStacker and later, Adobe Photoshop.
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’Partial supernova’ blasts white dwarf star across the Milky Way Words by Charles Q. Choi
strange white dwarf star hurtling
atmosphere. This mix sets this white dwarf apart
through the Milky Way may be the survivor of a ‘partial supernova’, a
from any other previously known. In the research the scientists also found that
noted that the elements seen in the white dwarf’s atmosphere could have all been produced in the
new study finds.
the white dwarf was travelling at about 900,000 kilometres per hour (560,000 miles per hour) in
first thermonuclear reactions of a supernova. However, there is a clear absence of what is
the opposite direction of the way the galaxy is rotating. Moreover it had an especially low mass
known as the iron group of elements – iron, nickel, chromium and manganese.
for a white dwarf – only about 40 per cent the mass of our Sun. “When we found this unusual
“That’s what makes this white dwarf unique – it did undergo nuclear burning, but stopped
white dwarf was really low in mass and moving
before it got to iron,” said Gänsicke. “When it
Scientists zeroed in on the white dwarf SDSS J1240+6710, located about 1,430 light years from
really fast, that really triggered my curiosity into what happened to it in its past,” said Boris
had its supernova event, it was likely just brief, maybe a couple of hours.”
Earth. Discovered in 2015, prior work found
Gänsicke, an astrophysicist at the University of Warwick, UK.
The explosion would have blasted SDSS J1240+6710 away from its companion, ripping
What might explain all these strange details about this white dwarf? The researchers think
matter off the small white dwarf and hurling it through deep space at the speed at which it
that a thermonuclear explosion didn’t completely destroy the white dwarf, but rather a ‘partial
orbited its partner. The scenario — the researchers said — would
supernova’ blasted what remained of the object across the Milky Way.
help to explain the white dwarf’s speed, puny size and bizarre atmosphere.
A
White dwarfs are the cool, dim Earth-sized cores of dead stars that are left behind after average-sized stars have exhausted their fuel and shed their outer layers. Our Sun will one day become a white dwarf, as will more than 90 per cent of the stars in the Milky Way.
this white dwarf had an unusual atmosphere that seemed to possess neither hydrogen or helium, but instead was composed of a weird mix of oxygen, neon, magnesium and silicon. The Hubble Space Telescope was used to take a closer look at the white dwarf, and it identified carbon, sodium and aluminium in the object’s
In the case of SDSS J1240+6710, the scientists
© University of Warwick
The strange white dwarf doesn’t contain any iron like most postsupernova stars do
10
Strange ancient ‘failed stars’ found by citizen scientists
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Citizen scientists recently helped direct astronomers
Infrared Survey Explorer, and the objects that the
to a pair of objects that straddle the line between planets and stars. These newly spotted substellar
collaboration recently found, now called WISE 1810 and WISE 0414, are weird.
objects are brown dwarfs, which share many elements in common with stars. However, unlike
When scientists studied them, they were surprised to see that these two brown dwarfs have
stars these gaseous bodies don’t have enough mass to start nuclear fusion in their core, so they
very little iron compared to what’s usually observed in brown dwarfs. This is a telltale sign that they are
resemble planets more than stars.
ancient, with each estimated to be about 10 billion
These newfound brown dwarfs have very unusual compositions. They are the most planet-
years old. Both dwarfs have a mass of about 75 times the mass of Jupiter.
like brown dwarfs to be observed in the Milky Way’s oldest populations of stars. They also might
If these brown dwarfs formed with low levels of metal, so might ancient exoplanets. This could be
help researchers learn more about planets outside the Solar System.
a reason to search for old metal-poor exoplanets or alien worlds that orbit ancient metal-
The citizen scientists who spotted both objects were part
poor stars. Further research into this brown dwarf population
of the ongoing NASA-funded
could answer questions about
Backyard Worlds: Planet 9
how dependent the planet
project. They were looking through spacecraft data from
formation process is on the presence of metals.
C L/JP SA NA ©
NASA’s WISE and NEOWISE missions; both missions are chapters in the life of a single spacecraft called the Wide-field
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NASA representatives said Backyard Worlds: Planet 9 has contributed to more than 1,600 brown dwarf discoveries.
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Gigantic structure stretching 1.37 billion light years across discovered Words by Adam Mann
current structural record holder, the Hercules-
Corona Borealis Great Wall, which spans 10 billion light years – more than a tenth the size of the visible universe. The resulting map of the South Pole Wall shows a mind-boggling bubble of material more or less centred on the southernmost point of the sky, with a great sweeping wing extending north on one side in the direction of the constellation Cetus and another stubbier arm opposite it in the direction of the constellation Apus.
© D. Pomarede, R. B. Tully, R. Graziani, H. Courtois, Y. Hoffman, J. Lezmy.
Spectacular 3D maps of the universe have revealed one of the biggest cosmic structures ever found – an almost-inconceivable wall stretching 1.37 billion light years across that contains hundreds of thousands of galaxies. The South Pole Wall, as it’s been dubbed, has been hiding in plain sight, remaining undetected until now because large parts of it sit half a billion light years away behind the bright Milky Way galaxy. The South Pole Wall rivals in size the Sloan Great Wall, the sixth-largest cosmic structure discovered. One light year is roughly nine trillion kilometres (six trillion miles), so this cosmic structure is mind-bendingly humongous. Astronomers have long noticed that galaxies are not scattered randomly throughout the universe, but rather clump together in what’s known as the cosmic web, enormous strands of hydrogen gas in which galaxies are strung like pearls on a necklace that surround gigantic and largely empty voids. Previous cosmographic work has charted the extent of other galactic assemblies, such as the
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Curiosity starts road trip up Martian mountain Words by Elizabeth Howell NASA’s Curiosity rover is embarking on a road trip on © CSIRO
Mars. The nearly eight-yearold mission will be guided through a traverse roughly
Four mysterious objects spotted in deep space
1.6-kilometres (one-mile) long that will see it climb farther up a mountain to learn more about the planet’s history –
Words by Mara Johnson-Groh
There’s something unusual lurking out in the depths of space: astronomers have discovered four
fits the bill for all four new ORCs. After ruling out objects like supernovae, star-forming galaxies,
and whether it could have been habitable for microbial
faint objects that at radio wavelengths are highly circular and brighter along their edges. And they’re
planetary nebulae and gravitational lensing – a magnifying effect caused by the bending of space-
unlike any class of astronomical object ever seen
time by nearby massive objects – among other
an area on the 5.5-kilometre
before. The objects, which look like distant ring-
things, the astronomers speculate that the objects
(3.4-mile) high Mount Sharp
shaped islands, have been dubbed odd radio circles (ORCs) for their shape and overall peculiarity.
could be shock waves from some extragalactic event or possibly activity from a radio galaxy.
(Aeolis Mons) nicknamed the ‘sulphate-bearing unit’.
Astronomers don’t yet know exactly how far away these ORCs are, but they could be linked to distant galaxies. All the objects were found away from the Milky Way’s galactic plane and are around one arcminute across – as a comparison, the Moon’s diameter is 31 arcminutes. The astronomers offered several possible explanations for the phenomena, but none quite
“[The objects] may well point to a new phenomenon that we haven’t really probed yet,” said Kristine Spekkens, astronomer at the Royal Military College of Canada and Queen’s University, who was not involved with the new research. “It may also be that these are an extension of a previously known class of objects that we haven’t been able to explore.”
Sulphates are usually formed around water as it evaporates, and these leftovers could provide more information about how the surface of Mars changed roughly 3 billion years ago when the planet lost most of its atmosphere and running water was no longer possible on the surface. If all goes to plan Curiosity will reach the sulphate unit later this year, during our Northern Hemisphere’s autumn. Like any road trip, however, the rover drivers may stop their machine along the way if they spot something interesting.
Above: It’s still unknown what could be causing the radio circles
life in its ancient past. Curiosity is on its way to
NASA human spaceflight chief makes no guarantees on return to Moon
Words by Hanneke Weitering
the deadline. At a NASA town hall in
12
AS A
December Loverro even said that “it is going to be easy to make this happen”. Before Lueders became the head of human spaceflight at NASA she served as the manager of NASA’s Commercial Crew Program. Those missions have faced years of delays and other challenges. When NASA created its Commercial Crew Program in 2010, the agency planned to have its astronauts regularly riding private vessels to and from the space station by 2015. Now, five years later, the first commercial crew mission has only just arrived at the orbiting lab. “It’s very important to have an aggressive goal,” Lueders said in a teleconference on 18 June. “We had an aggressive goal in Commercial Crew, and I think that aggressive goal ensured that we were able to accomplish things as quickly as we could.”
Left: Aeolis Mons lies in Gale crater, forming its central peak Right: Lueders is the first woman to head human spaceflight at NASA
© NASA/JPL-Caltech
Putting astronauts back on the Moon by 2024 will be no small feat, and NASA’s new human spaceflight chief Kathy Lueders has been careful not to make any promises. “I don’t have a crystal ball,” Lueders said when asked about the feasibility of a 2024 Moon landing. “I wish I knew that answer. That’d make my job a lot easier. We’re going to try.” Lueders, who recently became the associate administrator for NASA’s Human Exploration and Operations Mission Directorate after Doug Loverro’s abrupt resignation, was a bit more pragmatic about the timeline of NASA’s Artemis program than her predecessor. While Lueders seems cautiously optimistic about getting astronauts to the Moon by 2024, Loverro was confident and unwavering in his assertion that NASA would make © N
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13
What made our Moon?
© Getty; Tobias Roetsch
THE CRASH THAT MADE
14
What made our Moon?
Understanding how our lunar companion was formed might just explain how we came to be here Reported by Colin Stuart
I
t’s the brightest thing in our night sky. Over the course of history it has been revered as a god, trampled across by 12 men and immortalised in poetry. The Moon is our steadfast companion, our only natural satellite as we endlessly orbit the Sun. Yet for an object that has received such scrutiny, arguments rage about where exactly the Moon came from. A suitable explanation needs to take into account what is perhaps the Moon’s greatest oddity: its size. It is the fifthlargest moon in the Solar System, trumping most of the satellites of our much bigger planetary neighbours. If you compare the size of moons to the size of their host planet, ours comes out at the very top. Many of the smaller moons of the Solar System are thought to be captured worlds – bodies that wandered too close to a planet before getting snared in its gravitational pull. Given the size of our Moon, it’s hard to imagine that’s how it ended up circling Earth. As far back as 1878, George Darwin – the astronomer son of famous naturalist Charles
15
What made our Moon?
© NASA
Left: Astronaut Harrison Schmitt is seen covered in lunar dirt while collecting samples during the Apollo 17 mission
Darwin – instead proposed that Earth and the Moon were once one body and that the latter formed
ust have when a young Earth was still forming. been this early because the rocks brought b c
from material thrown off the spinning Earth. This, he said, would explain why the Moon was moving
from the Moon are that old. Astronomers have lo believed that the Solar System had a tempestuous
a little further away from us each year. Supporters of this idea even pointed to the lack of land in the
infancy, throwing around huge lumps of rock and metal before eventually calming down. What if one
Pacific Ocean – which stretches across half of our planet – as the birthplace of the Moon. However,
of these objects – perhaps one the size of Mars – hit the young Earth, with the Moon forming out of the
scientists later realised that any force capable of
hot, spinning debris?
dislodging such a large amount of Earthly material would likely have destroyed the rest of our planet at
On the face of it this idea makes a lot of sense. We know from the dark patches on the lunar
the same time. Attention turned instead to the idea of a giant
surface that parts of the Moon were once molten. The Moon also has a pretty small iron core – much
impact – one that occurred 4.5 billion years ago
smaller than Earth’s – and it is less dense than Earth. This also fits, because during an impact
“If the Moon was mostly formed from a smashedapart Theia during a glancing blow with Earth, it should have its own unique oxygen isotope signature. Yet instead it matches Earth’s exactly”
the lightest material would have been thrown the furthest, leaving the heavier stuff here on Earth. Astronomers have a name for this proposed Marssized impactor: Theia, named after the Titan who gave birth to the Moon goddess Selene in Greek mythology. Computer modelling has been used to try and figure out what this impact must have been like in order for it to form the modern Moon.
How the Moon wasn’t made
It was flung off a rapidly spinning Earth
It was made elsewhere and captured by Earth
It was formed at the same time as Earth
What is it?
What is it?
What is it?
An idea which was popular for decades was that the material which makes up the Moon was once part of Earth. It suggested the Moon separated from Earth while it was semi-molten and spinning rapidly, and many saw the Pacific Ocean as a void created by the departing material. Darwin backed up the idea with solid and accurate calculations.
Many of the moons in our Solar System are thought to be captured objects – Phobos and Deimos around Mars are good examples. It isn’t inconceivable that Earth could have captured the Moon, as this would explain why the Moon and Earth appear to have different densities.
The co-accretion idea is that Earth and the Moon formed together in the early Solar System from the debris around the newborn Sun. Support came from observations of double stars. If two distinct stars could form out of a nebula, then it seemed at least possible that two worlds might coalesce side by side in orbit around a single star.
Why it’s wrong
For Earth to capture a large Moon, both objects would have to travel slowly – a collision was more probable. It’s also unlikely that Earth’s gravity would’ve been able to hold the Moon for so long.
16
Why it’s wrong While the oxygen isotopes may be the same, the densities of Earth and the Moon and the amounts of iron on each are different.
© Tobias Roetsch
By the 1930s calculations showed that Earth would have had to spin at an inconceivable rate to throw off enough material to form the Moon.
Why it’s wrong
What made our Moon?
How the Moon was made
ia approaches th ars-sized object is on an unalterable collision course with the early Earth.
1 2
2
Earth gets hit
The impactor hits Earth in a head-on collision, vaporising both Theia and Earth’s mantle.
4
Smaller objects begin to condense out of the vapour while continuin o orbit around Ea
3
3
Debris gathers
4
Material is thrown out
The vaporised material from both bodies mixes and is thrown outwards by the huge impact.
5 The Moon 5shape takes
6
6
Our companion is formed
© Science Photo Library
Many of the smaller objects stick together to form a protoMoon in orbit around Earth.
Eventually all the pieces come together to form the basis of the Moon that we see today.
17
What made our Moon?
Theia by numbers
6,000KM
1974 60-80° The year the giant-impact hypothesis was first presented at a conference
The axial tilt of Earth after Theia collided with the planet
The width of the Theia impactor, which is about the same size as Mars
4.5 billion The number of years ago it is thought Theia collided with Earth to form the Moon
45°
© Science Photo Library
Although new research suggests a head-on collision, the old picture had a 45-degree glancing blow
Traditionally the best fit seems to come from a glancing blow – Theia clipping Earth at an angle of about 45 degrees – and at a relatively slow speed. The debris from the impact, mostly formed from the leftover remnants of Theia, would have formed a ring around Earth, which then coalesced into the Moon. But recent analysis of Moon rocks returned to Earth during the Apollo missions appears to throw a spanner in the works. It is all to do with isotopes. What sets different chemical elements apart is the number of protons present in the nucleus of their atoms. Oxygen, for example, always has eight. Add another proton and you get an entirely different element – fluorine in this case. But several versions of the same element
but a differing number of neutrons. Scientists call these different flavours of the same element ‘isotopes’. Oxygen, for example, has three stable isotopes, with eight, nine or ten neutrons. When it comes to planetary geology, the relative amounts of each of these isotopes present on a celestial object are a key measurement, a bit like a fingerprint. “Each body in the Solar System has a unique oxygen isotope signature,” says Dr Kun Wang, assistant professor of Earth and planetary sciences at Washington University in St Louis. And therein lies the problem. Analysis of the Apollo samples shows that Moon rocks have exactly the same oxygen isotope signature as Earth. If the Moon was mostly formed from a smashed-apart
have its own unique oxygen isotope signature. Yet instead it matches Earth’s signature exactly. Scientists first discovered this as far back as 2001, but many believed that this apparent similarity was just an artefact of the precision of the experiments – that one day more accurate analysis would show there to be a tiny difference after all. However, the latest research published found that even with much more precise measurements, the oxygen isotope signature is still identical. Therefore the Moon did not form from Theia alone. Wang believes this points to a much more violent collision, one which melted the outer layers of both Earth and Theia. This material then mixed together to form a vapour – a cloud of material – stretching
can exist, each with the same number of protons
Theia during a glancing blow with Earth, it should
from our planet out to 500 Earth radii. The Moon
18
What made our Moon?
2000 The year that the name Theia was proposed by English geochemist Alex Halliday
then condensed from this cloud, explaining why both bodies now have the same oxygen isotopes. “Once they mix together it doesn’t matter what the oxygen isotopes of the two bodies were before,” says Wang. But if the notion of a more catastrophic impact is to be accepted, it needs more than one
Left: Marssized Theia approaches the still-molten Earth before the collision
Moon rock analysis The age of the Moon
strand of supporting evidence, so that is exactly what Wang set out to find.
Analysis of lunar rocks suggests the Moon is almost as old as Earth, meaning the collision happened within Earth’s first 100 million years.
He analysed seven different Moon rock samples from multiple Apollo missions, along with samples of Earth rocks, measuring the different abundances of isotopes of potassium using a technique tentimes more accurate than previously possible.
Matching oxygen isotopes
In October 2016, along with his colleague Stein Jacobsen from Harvard University, he published his results. He found that the Moon rocks had a greater abundance of one particular potassium
The relative abundances of the three stable isotopes of oxygen are the same on Earth and the Moon, suggesting a common origin.
isotope at the level of 0.4 parts per 1,000 more than Earth. “Potassium is a lot more volatile than oxygen, meaning it is more likely to vaporise and be mobile after the collision,” says Helen Williams, an
No sign of water
Earth scientist at the University of Cambridge. The potassium was therefore much more likely to end
The Moon rocks show no signs of past interaction with water. All the geology can be explained as rocks being under pressure.
up far away from Earth and become incorporated as part of the Moon. But for potassium to be vaporised in the first place, the collision must have vaporised both Theia and much of Earth’s surface. To Wang that has all the hallmarks of a head-on collision rather than a glancing blow.
Differing potassium isotopes
“The Moon rocks had a greater abundance of one particular potassium isotope at the level of 0.4 parts per 1,000 more than Earth”
Source: Wikipedia Commons © Bryce Edwards
© NASA
Left: Wearing special germfree clothing, Dr Robert Gilruth (right) inspects lunar samples from the Apollo 17 mission
There is slightly more of one particular potassium isotope on the Moon, pointing to it being vaporised during a headon collision.
19
What made our Moon? ©
But even if he is correct there are still some
current orbit suggests
NA SA
4.5 billion years,” says
outstanding Moon mysteries in need of explanation
Theia’s impact was a
Hamilton. At the same
– none more so than the unusual tilt of the Moon’s orbit around Earth. The Moon would have initially
lot more calamitous for our planet than
time Earth’s axis started to straighten up to its
formed in an orbit matching the orientation of Earth’s equator. As it moved further from our
previous models have suggested.
planet, the gravitational pull of the Sun would have forced it into line with the orbits of the
The almighty wallop from Theia
other planets – a plane known as the ‘ecliptic’. Yet
would have sent Earth
today’s Moon orbits at an angle of five degrees to the ecliptic. “That might not sound like much,
spinning much faster. More than twice as fast, in fact,
but all the other big moons of the Solar System are inclined at less than a degree to their planets
as other previous models have suggested. What’s more, Earth would have been knocked over
still occupying teams of astronomers around the world. But it seems we are getting closer.
– so the Moon really stands out,” says Douglas Hamilton, professor of astronomy at the University
almost on its side, with its axis tilted somewhere between 60 and 80 degrees to the ecliptic – today it
And that’s very important, because discovering the Moon’s history is a key step in understanding
of Maryland. A team led by Hamilton has recently attempted to explain this strange anomaly. They
is only tilted by 23.4 degrees. This high inclination affected the Moon as it
how likely such events are in the wider universe. This in turn might help us answer a much bigger
ran many computer simulations of the giant impact,
retreated from Earth, forcing it into an orbit tilted
question: whether we are alone in the universe.
with slightly different parameters each time. The one that gave the closest match to the Moon’s
at an angle of around 30 degrees to the ecliptic. “It then settled down to five degrees over the last
That’s because many scientists have speculated that the churning of the oceans by a Moon that was
“Earth would have been knocked over almost on its side, with its axis tilted somewhere between 60 and 80 degrees to the ecliptic”
present position. It just goes to show that our ideas about the formation of the Moon are still very much in flux. Quite how we came to have such a large Moon on an inclined orbit is a puzzle
much closer to Earth than it is today could have played a key role in the early development of life on Earth. Its gravitational pull also stabilises Earth’s axis, keeping our seasons steady and reliable every year. This flurry of recent research has put us one step closer to understanding how our Moon came to be, and may one day help us understand our place in the universe.
Above: Unlike Mars’ moon Deimos, our Moon wasn’t captured as it passed by our planet
© NASA
Left: We are still not certain on how the Moon ended up in orbit around Earth
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What made our Moon?
Lunar make-up 1 Crust
2 Lithospheric mantle
3 Partially molten asthenosphere
4 Maria (lunar seas)
5 Core
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2 ©
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tty
Ge
0.12% manganese
Elemental composition of the crust 43% oxygen
3% calcium
20% silicon
Moon core
Fe Iron
Ni Nickel
0.18% titanium
19% magnesium
Moon mantle Orthopyroxene
Clinopyroxene
Opx
Cpx Olivine
10% iron
3% aluminium
Also found in Earth's
Moon crust
Mantle
Crust
O
Si
Mg g
Oxygen
Silicon
Magnesium m
Fe
Ca
Al
Iron
Calcium
Aluminium m
Core
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Future tech Interstellar ramjet
INTERSTELLAR RAMJET Travelling between stars takes a lot of energy, but we might be able to pick some up on our way through space
T
he trouble with rockets is that you
1 Fusion reactor
have to pack everything before you go. While earthly modes of
The hydrogen would be used to fuel a fusion reactor which would fuse hydrogen into helium, releasing a tremendous amount of heat energy.
transport all work within their
environment, shooting around air or water or rolling along a surface, rockets must carry whatever they are going to shoot out the back – reactive mass – with them. This effect is exacerbated because the reactive mass you’ll be using at the end of the flight is just dead weight at the start. So you need even more mass and energy at the start just to lift the mass and energy you will need later on. This is why it is so challenging and expensive to get into space. Rockets are so big compared to the payloads they launch because they need to be more than 90 per cent full of propellants at take off. Once you’re in space you have more options: craft don’t need to be aerodynamic and the engines don’t need to support a craft against gravity, so a small thrust over a long time is equivalent to a large one over a short time. However, if we want the space travel of fiction, to voyage across the stars to find other planets and life, the challenge gets even greater. Proxima Centauri, the nearest star beyond the Sun, is 4.2 light years away, so traditional rockets would take thousands of years to get there. Worse still, if we are to approach light speed to minimise the travel time we have to drag even
5
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2 Exhaust The ramjet produces forward thrust by directing the ions produced from fusion out of the exhaust at a high velocity.
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3 Fissionless
4 Nuclear fusion
Current nuclear technology uses fission, where heavy atoms like uranium are split to release energy. But this does leave behind longlived nuclear waste.
The ramjet uses nuclear fusion. This releases energy by combining light atoms into heavier ones. It is cleaner and more powerful, but more difficult to achieve.
Interstellar ramjet
7
8 8 Interstellar space Though we think of space as empty, there is quite a lot of gas and dust between the stars.
7 Magnetic scoop The ramjet needs a magnetic scoop because the hydrogen atoms are so spread out. The scoop has to be many kilometres across to collect sufficient fuel.
Fusion does not produce the same radioactive waste as fission, but when running on hydrogen the crew would need protection from neutrons and the exhaust heat.
5 Fuel tanks The spacecraft needs to be able to run the reactor to power its systems, including the scoop, from a standstill. It would probably use deuterium, an easier fuel to fuse.
more propellant up to super-high speeds. As a result the Daedalus fusion-powered interstellar probe concept would stand nearly as tall as the Empire State Building and weigh 54,000 tonnes – 50,000 tonnes being propellant. But space isn’t as empty as it appears, so what if we could make use of the resources already out there? In 1960 nuclear physicist Robert Bussard proposed such a system: the Bussard ramjet. A ramjet is an engine that uses its forward speed to
nuclear power stations use nuclear fission where energy is released by splitting heavy atoms, but in nuclear fusion energy is released by combining light atoms, which is cleaner and more powerful. The hydrogen molecules would be fused together, producing a hot jet of helium gas to push the spacecraft along while it collects more fuel. There are challenges of course: the scoop would have to gather one trillion cubic
ram air into the engine, instead of the fan blades seen on jet engines. With the Bussard ramjet a craft would be initially set moving by a fusionpowered rocket using internal fuel, and then it would generate a huge funnel-shaped magnetic field. This could collect the free hydrogen molecules that float around in interstellar space and duct them back to the spaceship. Once collected the hydrogen molecules could be used as fuel for a fusion-powered rocket.
kilometres (240 billion cubic miles) of space to pick up one kilogram (2.2 pounds) of hydrogen. Scooping up the hydrogen may create more drag than the engine can overcome, and hydrogen itself is not easy to fuse. Some studies have suggested it might be better to just use the interstellar hydrogen as a reactive mass, heated up by a separately fuelled fusion reactor. Though the Bussard ramjet is still a theoretical concept, it has already had a cultural impact
Nuclear fusion is the most powerful reaction we have available from ordinary matter. Current
as the ‘Bussard Ramscoop’ on the front of the Starship Enterprise in Star Trek.
© Adrian Mann
6 Thermal and radiation shield
23
End of space and time
IS THIS THE END OF SPACE AND TIME? kill off Einstein’s long-standing theory
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End of space and time
A
s in history, revolutions are the lifeblood of science. Bubbling undercurrents of disquiet boil over
until a new regime emerges to seize power. Then attention turns to toppling the new ruler. The king is dead, long live the king. This has happened many times in the history of physics and astronomy. First we thought the Earth was at the centre of the Solar System – an idea that stood for over a thousand years. Then Copernicus stuck his neck out to say we are just another planet orbiting the Sun. Despite much initial opposition, the old geocentric picture buckled under the weight of evidence from the newly invented telescope.
with mass have a gravitational attraction towards each other. According to his ideas we orbit the
© NASA
Then Newton came along to explain that gravity is why the planets orbit the Sun. He said all objects
cat hinges on that measurement, but quantum physics says that until such a measurement is made the particle is simultaneously in both states, which means the vial is both broken and unbroken and the cat is alive and dead. Such a picture cannot be reconciled with a smooth, continuous fabric of space-time. “A gravitational field cannot be in two places at once,” says Sabine Hossenfelder, a theoretical physicist at the Frankfurt Institute for Advanced Studies. According to Einstein, space-time is warped by matter and energy, but quantum physics says matter and energy exist in multiple states simultaneously – they can be both here and over there. “So where is the gravitational field?” asks Hossenfelder. “Nobody has an answer to that question. It’s kind of embarrassing,” she . Try and use general relativity and qu tum theory together and it doesn’t work. ea certain energy you get probabilities t at are larger than one,” says Hossenfelder. One is e highest probability possible – it means an ome is certain. You can’t be more certain certain. Equally, calculations sometimes give you the answe infinity, which has no real ph meaning. The two theories re therefore mathematically i consistent. So, like many monarchs t ughout
Above: Black holes bend space and time with their great masses Below: Newton came up with his ideas on gravity after seeing an apple fall
ain om
s© on m m Co ia ed p i ik :W rce u So
ruled for two-and-a-half centuries before Albert Einstein turned up in 1915 to usurp him with his general theory of relativity. This new picture neatly explained inconsistencies in Mercury’s orbit, and was famously confirmed by observations of a solar eclipse off the coast of Africa in 1919. Instead of a pull, Einstein saw gravity as the result of curved space. He said that all objects in the universe sit in a smooth, four-dimensional fabric called space-time. Massive objects such as the Sun warp the space-time around them, and so Earth’s orbit is simply the result of our planet following this curvature. To us that looks like a Newtonian gravitational pull. This space-time picture has now been on the throne for over 100 years and has so far vanquished all pretenders to its crown. The discovery of gravitational waves in 2015 was a decisive victory, but like its predecessors, it too might be about to fall. That’s because it is fundamentally incompatible with quantum theory. The quantum world is notoriously weird. Single particles can be in two places at once, for example. Only by making an observation do we force it to ‘choose’. Before an observation we can only assign probabilities to the likely outcomes. In the 1930s Erwin Schrödinger devised a famous way to expose how perverse this idea is. He imagined a cat in a sealed box accompanied by a vial of poison attached to a hammer. The hammer is hooked up to a device that measures the quantum state of a particle. Whether or not the hammer smashes the vial and kills the
cD bli Pu
© Toboias Roetsch
Sun because it is pulling on us, and the Moon orbits Earth because we are pulling on it. Newton
End of space and time
the two theories to play nicely if they do with one of the central tenets of genera ativity: that space-time is a smooth, continu fabric. Instead, they argue, space-time is ade up of a series of interwoven loops – it as structure at the smallest scales. This is a bit ke a length of cloth. At first glance it looks li one smooth fabric. Lo closely, however, and ee it is really made a network of stitches. Alternat , think of it like a photograph on a computer scree oom in an you’ll see it is really made of individua xels. The trouble is that when LQG physicist y small, they mean really small. These defects in space-time would only be apparent on the leve f the Planck scale – around a trillionth of a trill nth of a trillionth of a metre. That’s so tiny that theree
l d loop quantum gravity (LQG). They can get
would be more loops in a cubic centimetre of spa
e: Sourc
Right: Einstein dispensed with the Newtonian picture of gravity as a force, replacing it with space-time
“If we understand the quantum structure of space-time better, that will h e impact on future technologies” Sabin ossenfelder
history, physicists are seeking a marriage between rival factions to secure peace. They’re searching for a theory of quantum gravity – the ultimate diplomatic exercise in getting these two rivals to share the throne. This has seen theorists turn to some outlandish possibilities. Arguably the most famous is string theory. It’s the idea that subatomic particles such as electrons and quarks are made from tiny vibrating strings. Just as you can play strings on a musical instrument to create different notes, string theorists argue that different combinations of strings create different particles. The attraction of the theory is that it can reconcile general relativity and quantum physics, at least on paper. However, to pull that particular rabbit out of the hat, the strings have to vibrate across eleven dimensions – seven more than the four in Einstein’s space-time fabric. As yet there is no experimental evidence that these extra dimensions really exist. “It might be interesting mathematics, but whether it describes the spacetime in which we live, we don’t really know until there is an experiment,” says Jorma Louko from the University of Nottingham. Other physicists have turned to an alternative
ain c Dom Publi ons© m m o edia C Wikip
Above: You’d need a machine 1,000 trillion-times more powerful than the LHC to probe the Planck scale
© CERN
End of space and time
Why can’t relativity and quantum mechanics get along? Quantum mechanics Particles are waves and waves are particles This wave-particle duality is central to quantum physics. Light can be thought of as being made of particles called photons, or as a propagating electromagnetic wave.
Values in quantum physics are a bit like shoes – they only come in set sizes. Physicists call these ‘quanta’. An electron, for example, can only orbit the atomic nucleus in a limited number of configurations.
The speed of light is sacrosanct
Space and time are space-time
Nothing can travel through space faster than the speed of light, yet entangled particles appear to defy this rule. As of yet there is no agreed explanation for this phenomenon.
The three dimensions of space and one of time that we experience are really wrapped up together in a four-dimensional fabric called space-time. This fabric is smooth and continuous.
Objects exist in many states at once
Non-locality: spooky action at distance
Physicists say electrons exist in a ‘superposition’ of states. It’s not in a definite state until we measure it, and beforehand we can only assign probabilities to the likely outcome.
Take a pair of entangled particles, change the properties of one and the other will change instantly. Einstein called this ‘sp y action at and
Gravity is geometry
eration and gravity
Newton was wrong – gravity isn’t a pull from a massive object. Instead it is the effect we see of bodies following a curved path through spacetime as the result of a massive object, like a star, warping it.
The equivalence principle says you cannot distinguish between a gravitational pull and an acceleration. Accelerate through space and you’ll experience the same ‘gravity’ as on Earth.
© Ge
tty
Below: Einstein’s work struggles to explain how two entangled particles seemingly communicate an the
All properties are ‘quantised’
than cub universe. “If space-t scale then this would be diffic particle accelerator,” says Louko. You’d n smasher 1,000 trillion-times more powerful than the Large Hadron Collider (LHC) at CERN. How can you detect space-time defects that small? The answer is to look across a large area of space. Light arriving here from the furthest reaches of the universe has travelled through billions of light years of space-time along the way. While the effect of each space-time defect would be tiny, over those istances interactions with multiple defects might dd up to a potentially observable effect. For ecade astronomers have been using light amma-ray bursts to look for evidence. shes are the result of massive e ends of their lives, and there distant detonations we eir spectrum has a says Hossenfelder. But something that happens f it’s something to do with the ts themselves. The jury is still out. ogress we might have to go a step saying space-time isn’t the smooth,
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End of space and time
1
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The Big Bang
The first light
380,000 years after the Big Bang, space-time had cooled enough for atoms to form, and light that had previously been trapped flooded the universe.
According to general relativity, space-time began in a singularity 13.8 billion years ago. It has been expanding ever since.
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The first stars
After 100 to 200 million years, slightly denser regions of space-time collapsed to form the first stars. Incredibly massive, they lived fast and died young.
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icho las F ord
er
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The first galaxies
Around a billion years after the Big Bang, stars clustered into dense regions of space-time which drew in even more material to make the first galaxies.
History of space-time thee 100 CE
1543
The Ptolemaic model Claudius Ptolemy creates a model with Earth at the centre of creation with the Sun, Moon and planets orbiting around us. There’s no explanation of why they behave that way.
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Copernicus publishes his heliocentric model
Ne Newton’s book Principia is published
John Dalton proposes indivisible atoms
Polish mathematician Nicolaus Copernicus argues that the Sun is in the centre of the Solar System. His book De revolutionibus orbium coelestium is one of the most important scientific texts of all time.
In his landmark work Newton sets out his law of universal gravitation. All masses attract all other masses in space with a force related to the distance between them.
The English chemist says that all matter is made up of tiny, unbreakable and indestructible building blocks called atoms. He was able to successfully explain a lot of chemistry using this idea.
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End of space and time continuous fabric Einstein suggested. According to Einstein, space-time is like a stage that
General relativity explained
remains in place whether actors are treading its boards or not – even if there were no stars or planets dancing around, space-time would still be there. However, physicists Laurent Freidel, Robert Leigh and Djordje Minic think that this picture is holding us back. They believe spacetime doesn’t exist independently of the objects in it. Space-time is defined by the way objects interact. That would make space-time an artefact
Free fall and floating Einstein realised that freefalling because of gravity is the same as floating with no gravity. He concluded that gravity cannot be a force, as Newton had said.
Gravity and acceleration
The bending of light
of the quantum world itself, not something to be combined with it. “It may sound kooky,”
Light from a torch would appear to bend as you accelerate. Acceleration is the same as curved spacetime, so light should also be bent by it.
Accelerating in a vehicle pushes you into your seat. Gravity and acceleration feel the same, so they have the same cause: a curved path through space-time.
says Minic, “but it is a very precise way of approaching the problem.” The attraction of this theory – called modular space-time – is that it might help solve another long-standing problem in theoretical physics regarding something called locality and a notorious phenomenon in quantum physics
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The universe accelerates
called entanglement. Physicists can set up a situation whereby they bring two particles together and link their quantum properties.
The here and now
Today Earth is home to physicis who are pondering how best to combine quantum theory with Einstein’s picture of space-time.
Having gradually slowed since the Big Bang, space-time begins to stretch at an accelerating pace due to something called dark energy.
They then separate them by a large distance and find they are still linked. Change the properties of one and the other will change instantly, as if information has travelled from one to the other
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The Sun forms
8
Around 4.6 billion years ago a cloud of gas collapsed to form the Sun. Space-time is warped so much that planets soon form around it.
1915 Einstein publishes the general theory of relativity In a direct challenge to Newton’s idea, Einstein says the force of gravity is a mirage. Instead it is caused by the curvature of the four-dimensional fabric of space-time.
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The Big Rip
As dark energy takes hold, the universe will eventually expand so much that even the space between atoms is stretched sufficiently to tear the universe apart.
1919
1974
1988
Eddington eclipse vindicates Einstein
String theory arrives on the scene
Loop quantum gravity emerges
Observations of a 1919 solar eclipse by English astronomer Arthur Eddington showed that the Sun bends light by the exact amount predicted by Einstein’s general theory of relativity.
Dalton’s idea of indestructible atoms looks even more outdated as the electrons found inside atoms are proposed to themselves be made of tinier vibrating strings vibrating across multiple dimensions.
Physicists including Lee Smolin and Carlo Rovelli formulate the basic principles of LQG – a way of thinking space-time might be made of building blocks in the same way matter is constructed from atoms.
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End of space and time
Replacing space-time String theory Fundamental particles such as electrons are made of tiny strings that vibrate across ten spatial dimensions, plus one time dimension. This picture manages to avoid infinities when combining quantum theory and general relativity, but it cannot currently be tested.
© Getty
Loop quantum gravity (LQG)
ter than han the speed of light. Einstein was so r rbed by this phenomenon that he called it ‘spooky action at a distance’. Modular space-time can accommodate such behaviour by redefining what it means to be separated. If space-time emerges from the quantum world, then being closer in a quantum sense is more fundamental than being close in a physical sense. “Different observers would have different notions of locality,” says Minic, “it depends on the context.” It’s a bit like our relationships with other people. We can feel closer to a loved one far away than the stranger who lives down the street. “You can have these non-local connections as long as they are fairly small,” says Hossenfelder. Freidel, Leigh and Minic have been working on their idea for the last eight years, and they believe they are slowly making progress. “We want to be conservative and take things step by step,” says Minic, “but it is tantalising and exciting.” It’s certainly a novel approach, and one that looks to ‘gravitationalise’ the quantum world rather than quantising gravity as in LQG. Yet as with any scientific theory, it needs to be tested. At the moment the trio are working on how to fit time into their model.
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“Whether it describes the spacetime in which we live, we don’t really know until there is an experiment” Jorma Louko
Space-time is not a smooth fabric, but is made up of a network of tiny stitches instead. This is potentially testable by looking at light reaching us from gammaray bursts (GRBs) in the distant universe.
Modular space-time Space-time is only a stage when it has actors on it. In other words, interactions between objects create space-time. This can potentially explain the quirks of non-locality and quantum entanglement.
Supergravity This may all sound incredibly esoteric, but it could have a more profound effect on our everyday lives. “We sit in space, we travel through time, and if something changes in our understanding of spacetime this will impact not only on our understanding of gravity, but of quantum theory in general,” says Hossenfelder. “All our present devices only work because of quantum theory. If we understand the quantum structure of space-time better, that will have an impact on future technologies – maybe not in 50 or 100 years, but maybe in 200,” she says. The current monarch is getting long in the tooth, and a new pretender is long overdue, but which of the many options is most likely to succeed? When we decide, the resulting revolution could bear fruit not just for theoretical physics, but for all.
Above: One way to reconcile general relativity and quantum theory says reality is made of vibrating strings
This is the combination of general relativity with a popular but unproven theory called supersymmetry – the same theory is the leading candidate to explain dark matter.
Causal set theory Space-time is not a continuous fabric, but does have a structure based on regions that have a link between past and future. It is based on work by David Malament and Rafael Sorkin.
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Instant expert
WHAT IS ZODIACAL LIGHT? I
f you go to an area with low light pollution, you may notice that the western sky in the evening appears
bright even after twilight. The dim light appears to be distributed from the ecliptic plane and lingers until late evening. A similar phenomenon occurs in the morning towards the east. This is zodiacal light. It is a phenomenon where dust particles near Earth are illuminated by sunshine and the light is reflected towards ground-based observers. Astronomers have debated for over a century about the origin of the dust particles. As is well known, comets – small icy bodies from the outer Solar System – eject dust and gas when they approach the Sun. Asteroids also emit dust due to collisions or rapid rotation. Some asteroids in the outer asteroid belt – between the orbits of Mars and Jupiter – may contain ice underneath and eject dust together with gas. These small bodies of the Solar System are significant dust sources that become observable as zodiacal light. The contribution of dust particles from beyond the Solar System used to be discussed, but was conjectured to be ignorable. However, motivated by the recent discoveries of interstellar comets such as ‘Oumuamua, astronomers may consider the contribution of interstellar dust once again. Before modernisation, it should have been possible to observe zodiacal light from almost every part of the world, with records of it being visible from the centre of Tokyo, Japan, during World War II. However, due to rapid industrial growth and the increase of artificial light around us, zodiacal light has been obscured behind severe haze and light pollution. The night sky illuminated by artificial light is indistinguishable from zodiacal light and, for this reason, it is now challenging to observe this phenomena in most areas of the world.
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1
Where should you be looking?
Three words: follow the ecliptic. The ecliptic is the imaginary path in the sky that the Sun follows. This will reveal where the star sets and rises and whether you should look east or west.
is the best time 2 When to see it? The times will vary depending on the seasons and your position on Earth, but it can be seen an hour before sunrise and an hour after the sunset. This is dependant on minimal light pollution.
Zodiacal light 4
4
Is it similar to the Milky Way?
Although it does give off a rare celestial glow, zodiacal light and the Milky Way are not comparable. The Milky Way glows due to the shining of millions of stars, whereas zodiacal light is reflecting the Sun’s light via debris.
BIO Professor Masateru Ishiguro Japanese scientist Ishiguro is a professor in the department of physics and astronomy at Seoul National University, South Korea. His main area of research revolves around primitive bodies in the Solar System, especially interplanetary dust particles. His research means he is something of an expert when it comes to zodiacal light, having investigated it for a quarter of a century.
3
would you 3 How recognise it? It can be best described as a pyramid of light coming from the horizon – it can stretch out around 20 or 30 degrees along the horizon – and has an eerie and hazy glow to it.
2
© ESO
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Interview Dr Nour Raouafi
© Laurence Honnorat
INTERVIEW BIO
© Johns Hopkins APL/Ed Whitman
Dr Nour Raouafi
Raouafi is a Tunisian astrophysicist at Johns Hopkins Univerisity’s Applied Physics Laboratory (APL) in Maryland and the project scientist for NASA’s Parker Solar Probe mission. He is an expert in many solar and heliospheric topics, including solar magnetic fields, coronal plumes and jets, coronal mass ejections (CMEs), solar wind, solar energetic particles and many other areas. For the last two years the Parker Solar Probe has been beaming back unique data sets while breaking records when it comes to how close a human-made object has been to the Sun and how fast it travels. Its latest encounter reached within 18.7 million kilometres (11.6 million miles) of the Sun and sped past at 393,000 kilometres (244,225 miles) per hour.
Dr Nour Raouafi
PARKER SOLAR PROBE: TWO YEARS ON
“THIS COMING DECADE WILL BE THE GOLDEN AGE OF SOLAR AND HELIOPHYSICS RESEARCH” All About Space catches up with the project scientist for NASA’s incredible Parker Solar Probe mission, Dr Nour Raouafi – a spacecraft continuously breaking records and surpassing all expectations as it orbits the Sun Interviewed by Lee Cavendish
What is the major mystery surrounding the Sun and its corona that astronomers are desperately trying to solve, and are hoping the Parker Solar Probe will help shed light on? There are a few phenomena that were discovered decades ago, but we are still struggling to understand. I think the one that is most puzzling is what we call the ‘coronal heating problem’. The corona, which is the outermost layer of the solar atmosphere, is 300-times hotter than the solar surface. And we know that all the energy is coming from inside the Sun, so in a way it’s counter-intuitive that the source is cooler than the environment around it. But the Parker Solar Probe is giving us clues and hints as to what might be causing excess heating there. Another phenomenon, which is very closely related to coronal heating as well, is what we call the acceleration of solar wind. The solar wind is a flow of charged particles – electrons, protons,
ionised helium and heavy elements – that are constantly flowing away from the Sun to the rest of the Solar System. The issue with the solar wind is that low down [within the solar atmosphere] these particles are flowing at very slow speeds, but they get accelerated to hundreds of kilometres per second in a very short distance. We don’t know exactly what is the physical mechanism that gives them the energy to accelerate to these high speeds. The third phenomenon, and we are impacted by it every day, is big explosions on the Sun. Whenever there is a flare or a coronal mass ejection (CME) erupting on the Sun, there is a population of particles that get accelerated to almost the speed of light. We call them solar energetic particles. The Parker Solar Probe was built specifically to be able to shield its instruments in a really dangerous environment. How has its heat shield been constructed so that it can withstand such dangerous temperatures and radiation while remaining relatively lightweight? The heat shield is basically made of carbon foam. Most of it is a vacuum. It’s like a sponge made out of carbon that is sandwiched between two sheets, which are also compressed carbon. The other thing that is specific to the Parker Solar Probe is a plasma spray that is white and is on top of the heat shield. The goal here is to reflect as much light from the Sun as possible. When we are closest to the Sun in 2024, that side of the heat shield will be more than 2,500 degrees
Fahrenheit [1,371 degrees Celsius]. 4.5 inches (11.5 centimetres) inward, which is the other side of the heat shield, will be at almost 700 degrees Fahrenheit [371 degrees Celsius], so there we have already lost a lot of heat. And from that backside of the heat shield to the bus, where the instruments are mounted, it is at room temperature.
Right: The closest-ever approach to the Sun planned for the Parker Solar Probe will occur in 2024.
© NASA
How’s the Parker Solar Probe doing? Are there any updates that we should be aware of? The Parker Solar Probe is doing great. We are going through our fifth encounter and recently we were the closest we’ve ever been to the Sun. After a period of five days where we could not communicate with the spacecraft, it sent us a signal that it’s healthy and it’s doing what it’s supposed to do. In terms of science, it’s just amazing. Whenever the spacecraft gets closer to the Sun, we are learning new things that we’ve never seen before.
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What impacts can space weather and solar wind have to us on Earth?
A lot of them. One of my favourite moments – I may not have enjoyed it when it happened, but now
2025 we will be at the maximum of the solar cycle. What I want to see from the Parker Solar Probe
Let me start by saying, we are now starting to think
with hindsight I enjoyed it a lot – was the launch of
is to basically complete a whole cycle, going from
about sending women and men to the Moon, and maybe to Mars in the near future. If we are going
the mission. I mean, we have been waiting for the Parker Solar Probe for 60 years, and on 12 August
the maximum to the other minimum, which is an extension of the mission by five to six years. I
to do that, we need to protect these people out there. We cannot just launch them out there. If we
2018 we put it on top of the most powerful rocket in existence, and all you hope for is that everything
would love to see that.
don’t protect them sufficiently, these solar energetic
goes smoothly. I was so stressed when I was
Could this information be used for stars beyond
particles will not be good for them and also for the space equipment. It will have a different impact on
watching it, and it all went really well. But after that, what we have discovered is
our Solar System as well? That’s a very good remark. By understanding how
our environment here on Earth and also the other planets as well.
something amazing. The spacecraft we designed at APL is functioning way better than we had thought
the Sun works, we can actually project all we gain from what we learned about the Sun to other stellar
Just as a simple example: we rely a lot on GPS, which is functional because we have spacecraft
it would. What we are getting back from this machine is amazing. Let me give you an example
systems. Other stellar systems are so far away that we cannot study them in detail as we are currently
orbiting Earth. And if there is a big explosion on the Sun and it burns some of these satellites out, some
in terms of science data: we are bringing three to four times the volumes we thought we would do
doing with the Sun. What we learn from the Parker Solar Probe, by explaining all these big phenomena
of us will be in trouble because GPS will not be
pre-launch. We also thought pre-launch that we
we talked about at the beginning, we can basically
working anymore. Another example is if we have a huge CME or
were only going to operate instruments when we were close to the Sun and after launch. We are now
take that and project it onto other stellar systems – and why would you want to do that?
flare that will cause a humongous geomagnetic storm here on Earth – that can cause a shutdown
basically operating the instruments almost all of the time.
It’s because we are so curious about whether there are other planets out there and whether there
The planned mission duration is currently seven
is habitability around other stars. The interaction between the stars and the planets is so crucial
years. Do you think it could possibly reach ten years or more? If by the end of the seven years, if everything is going well, it’s a no-brainer that we will request an extension of the mission. During these seven years we will have basically covered half of the solar cycle. We launched at the minimum, and by
for life and for habitability. By understanding how the Sun behaves and how it interacts with us here on Earth and other planets, it will help us tremendously in understanding other stellar systems. In a way the Parker Solar Probe is our ambassador to other stellar systems as well, as it will help us understand other stellar systems.
of power grids. That will be devastating for the economy and for the societal fabric. That’s actually why space weather is a big topic now for research and for all of us here. It’s been two years now since the Parker Solar Probe was launched. Do you have any favourite moments or a favourite result that has come from the mission so far?
Top: The heat shield is an integral part of the spacecraft and keeps the instruments at room temperature
© NASA
Interview Dr Nour Raouafi
© NASA/ESA
Right: Solar Orbiter’s Extreme Ultraviolet Imager (EUI) has recently revealed omnipresent tiny solar flares, now referred to as ‘campfires’
36
In December 2019 news came out around the Parker Solar Probe regarding the release of the first year of scientific results. Could you explain some of the main news stories that came out after this first year? That was really an ideal time for the Parker team, but also for everybody. For humanity. Flying a
Right: Our Sun from the first batch of solar images taken by ESA/NASA’s Solar Orbiter on 30 May 2020
© NASA/ESA
Dr Nour Raouafi
spacecraft around this star is something very challenging. In terms of science, it was amazing. But before going into this, let me say this. You will have to wait a little bit, probably a few months, and you will be seeing another wave of big discoveries from the Parker Solar Probe. We just got the new data from orbit four, which is the closest perihelion to the Sun, and we are seeing new things that we have not seen before. Going back to what we released in December and later on in February in a special issue in the Astrophysical Journal, there are a key number of discoveries that are breakthrough discoveries. One of them is what we call the ‘dust-free zone’. When you look at the heliosphere, there is dust almost everywhere. The dust comes from asteroids and comets that grind up in the Solar System, but the closer the dust particles get to the Sun, the smaller they get. At a certain point they will evaporate. The result of that is you create a zone around the Sun where there is no dust. This was hypothesised in 1929, and since then people have looked for it over and over again, but nobody has seen it. The Parker Solar Probe is giving the first hints that this dust-free zone exists. The objectives of the mission are obviously to explain the heating and the acceleration of the plasma in the coronal heating and acceleration of the solar wind. In other terms, what we are looking for are energy sources that we cannot see from Earth, and the Parker Solar Probe is giving us one possible smoking gun. When the Parker Solar Probe got closer to the Sun, it saw kinks in the magnetic field. Magnetic fields essentially make an S-shape. They bend all the way back to the Sun and outward again in a matter of a few tens of seconds to several minutes. The reason why this is so important is that you cannot do that to a magnetic field easily. Creating this structure and maintaining it means that there is a big source of energy creating that. That’s exactly what we are looking for.
that mission is over. The second one is a probe that
Surely with this mission, the fact that it’s achieving so many milestones and performing so well, that’s going to inform what kind of mission you could do next, and what sort of boundaries you could push. You are touching on a very sensitive nerve there. Go back in history to the 1960s. There was a committee that proposed three key missions that NASA had to implement. One of the missions was a probe that
will orbit the Sun within the orbit of Mercury. That is the Parker Solar Probe. We did it after 60 years. It has been challenging, but we did it. The third one is a probe that will fly out of the Solar System, very, very far away. We are working on that, but why have we started working on that? It’s because we realised the success of the Parker Solar Probe. Now the community is so bold. Realising that a challenging mission like the Parker Solar Probe can be so successful, we are able to do it for other missions as well. The outer solar probe is certainly one of them. It’s an extremely challenging mission, but we started working on it at APL and hopefully one day it will see the light. There is another idea out there, which is having a solar polar mission, which is an amazing mission. This is a mission that will fly above the poles of the Sun for an extended period of time, and that’s also not easy at all. Getting a spacecraft out of the ecliptic is extremely hard, but again, realising the success of the Parker Solar Probe is pushing the
orbits the poles of the Sun, which has already been implemented. This was the Ulysses mission. Now
community to be bold and start thinking about these big challenges.
The European Space Agency (ESA) recently launched the Solar Orbiter spacecraft in collaboration with NASA. Are there any plans to coordinate on observations with the Parker Solar Probe and the Solar Orbiter? These two solar missions can complement each other in many ways. I can tell you that working together will provide the scientists – and also everybody else – with way more than the sum of the two missions. I’m almost sure that with these two missions, and also if you add DKIST, the Daniel K. Inouye Solar Telescope, which is a large solar telescope in Hawaii, this coming decade will be the golden age of solar and heliophysics research. I don’t think we have ever witnessed the amount of enthusiasm around the Parker Solar Probe, Solar Orbiter and DKIST as we are seeing now, and honestly we have never been able to achieve this much in such a short amount of time. Having a mission that is approaching the Sun like never before, having another mission that is flying above the ecliptic to see the poles for the first time and also having the largest solar telescope on the ground… it’s amazing.
37
Antares
38
HOW
ANTARES?
Antares
T
he night sky, especially when viewed from an area with low to no light pollution, can reveal a beautiful array of celestial gems – twinkling stars that
generations before have marvelled at. The difference between then and now is that our generation has the capability to map these stars with precision. New research has taken this to a whole new level by mapping the famous star Antares, learning more about its atmosphere and how this can be applied to other red supergiant stars. Throughout the years people have gazed upon ruddy Antares, the brightest star in the constellation of Scorpius and one of the brightest stars in the night sky, which lies 554 light years from Earth. As telescopes, spectroscopy and multi-wavelength observations have become more advanced, we have been able to learn more about the stars. Scientists have been able to categorise Antares
Using the best radio telescopes in the world, this local red supergiant star has recently been mapped in extraordinary detail
as a red supergiant star that has swollen as it approaches the end of its life, despite it being only 11 million years old. By comparison the Sun is 4.6 billion years old. This is because Antares weighs 12
Below: ALMA currently holds the title of the world’s largest radio telescope
Reported by Lee Cavendish
solar masses – 12 times the mass of our Sun – and with stars the biggest and brightest burn out the quickest. Astronomers have deduced over many years of visible-light observations that Antares is approximately 700-times wider than the Sun, and previous research into its climate has suggested that the temperature of the red supergiant star’s chromosphere should be between 5,700 and 12,700 degrees Celsius (10,000 and 22,900 degrees Fahrenheit). Now the plot has thickened as researchers have been able to map the atmosphere of Antares with unprecedented levels of precision, revealing unusually cool regions residing in localised bubbles in addition to highlighting the true extent of the star’s impressive stellar wind. This research was only made possible by utilising two of the
TO100 0.7 MILLIMETRES
© ESO
© ESO
The wavelength range that Antares was observed in using the two radio telescopes.
39
Antares
© ESO
Famous red supergiants Antares Constellation: Scorpius Distance: 554 light years Age: 11 million years Solar masses: 12 Solar radii: 700
VY Canis Majoris Constellation: Canis Major Distance: 3,820 light years Age: 8.2 million years Solar masses: 17
© ESO
Solar radii: 1,420
Betelgeuse Constellation: Orion Distance: 700 light years Age: 10 million years Solar masses: 11
Mu Cephei Constellation: Cepheus Distance: 5,258 light years Age: 10 million years Solar masses: 19 Solar radii: 1,650
CE Tauri Constellation: Taurus Distance: 1,794 light years Age: 14 million years Solar masses: 14 Solar radii: 587
most powerful tools in radio astronomy: the Atacama Large Millimeter/submillimeter Array (ALMA) located in the Atacama Desert, Chile, and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA), located in New
on the star’s surface. This had never been detected at radio wavelengths before for an evolved star,” explains
O’Gorman. “The inhomogeneous nature of the chromosphere is the result of the complex environment that exists in the atmospheres of these stars – Antares and Betelgeuse – and stars in
been able to measure the temperature and size of
general,” he continues.
Antares’ stellar atmosphere, publishing their results in a new scientific paper.
Astronomers had already deduced that Antares is roughly 700-times wider than the Sun; it would
“We had looked at Betelgeuse a lot already at radio wavelengths, albeit with the old VLA, and
extend to somewhere around the asteroid belt if it was placed into the Sun’s spot at the centre of
at one wavelength with ALMA,” O’Gorman tells All About Space. “Antares is the only other red
our Solar System. Now the star’s chromosphere through to the region containing its stellar wind
supergiant that can currently be resolved at radio wavelengths, so we decided to focus on it. We could
have been mapped in unrivalled detail using ALMA for shorter wavelengths and the VLA for
then compare our results to what we already knew
longer wavelengths. These new results have shown
about Betelgeuse.” However, something unexpected arrived in
that the chromosphere is ‘lukewarm’ at best. The temperatures peak around 3,500 degrees Celsius
the results. “[The results] have revealed a new ‘lukewarm’ chromosphere component,” explains paper co-author Dr Keiichi Ohnaka, associate
(6,400 degrees Fahrenheit) and then gradually decrease the further out it gets from the energy source. This is minuscule compared to the Sun’s
professor at the Universidad Católica del Norte in Chile, to All About Space. “It is not known why the temperature goes up in the chromosphere instead of falling off, so this new lukewarm component is important for deciphering the heating mechanism of the chromosphere.” “[This discovery] is important firstly because we have managed to resolve a star’s atmosphere at many different radio wavelengths, a feat which is very, very difficult to do,” says O’Gorman. “These observations allowed us to find out a lot about the size and temperature of the chromospheres of red supergiant stars.” But what exactly is the chromosphere? “A chromosphere is an atmospheric layer just above a star’s surface that is heated to high temperatures
chromospheric temperature of around 20,000 degrees Celsius (36,000 degrees Fahrenheit). “[This result] does not mean that the temperatures of 5,700 to 12,700 degrees Celsius (10,000 to 22,900 degrees Fahrenheit) from the previous works are wrong. Such hot gas does exist. If we take into account the infrared images of Antares, there should also be cool gas at temperatures lower than 1,700 degrees Celsius (1,400 degrees Fahrenheit),” says Ohnaka. “Therefore we conjecture that both ‘hot’ and ‘lukewarm’ chromospheres, as well as cool gas, may coexist in distinct cells or pockets. As we think that Antares and Betelgeuse are representative of red supergiants, the inhomogeneous atmosphere is probably a usual trait in this class of star.” The inhomogeneous nature of Antares is an extremely intriguing aspect in itself. It appears that because of the evolved nature of the star the temperature decreases in random pockets of the star’s atmosphere, and the mysterious magnetic fields and shock waves emanating from the star’s surface are the reason for this. Something else that the study revealed is the true size of Antares, as the chromosphere stretches out to 2.5 times the star’s radius – extraordinary considering the Sun’s chromosphere is only 0.5 per cent of its radius. However, astronomers’ current understanding of heliophysics is limited, and they are still unable to understand these different features, factors and mechanisms for our own Sun, let alone a star over 550 light years away. When O’Gorman and his team observed Antares in longer wavelengths, courtesy of the VLA, they
Left: The VLA is comprised of 28 25-metre (82-foot) radio telescopes Right: Red supergiant stars eventually phase into an extravagant supernova explosion
40
by mechanisms due to the motion of the plasma taking place beneath or
Mexico. Dr Eamon O’Gorman of the Dublin Institute for Advanced Studies in Ireland and his team have
© NRAO
Source: Wikipedia commons © Sephirohq
Solar radii: 890
This is the first time another star’s chromosphere has been detected and measured using radio waves.
were able to make a clear distinction between the chromosphere and the region where Antares’ stellar wind begins to form. This is the first time
Antares
The latest look at Antares
1 Photosphere
This is commonly referred to as the star’s ‘surface’. Sunspots and faculae usually occur on the photosphere. In Antares’ case its face is burning at roughly 3,400 degrees Celsius (6,200 degrees Fahrenheit).
ALMA and the VLA combined their powers to break down the atmospheric layers of a star over 550 light years away
2
Lower chromosphere
3
Upper chromosphere
4
The wind acceleration zone
This layer was observed in the shortest wavelength ALMA has to offer. The temperature of the gas in this region is approximately 2,400 degrees Celsius (4,400 degrees Fahrenheit).
3
Jupiter
SUN Earth MARS
ALMA
4
5
VLA Uranus
2
Saturn
1
The space between the upper and lower chromosphere would be the equivalent of Jupiter’s orbit around the Sun. The temperature peaks in this region at about 3,500 degrees Celsius (6,400 degrees Fahrenheit).
The VLA was able to study this region in longer wavelengths, and the results show that this region is roughly 2,600 degrees Celsius (4,700 degrees Fahrenheit). It is unknown what accelerates the stellar wind.
5
Wind
© ESO
Stellar wind, illuminated in this research by Antares B, appears relatively cool at less than 1,500 degrees Celsius (2,700 degrees Fahrenheit). This wind carries heavy elements into the universe.
10,000 this distinction has been detected, and it is shown in amazing clarity. The images that the VLA took show a huge gust of stellar wind that is illuminated by Antares B, Antares’ smaller but hotter companion star. This wind is carrying stellar material out into the cosmos. At the start of Antares’ life it had a mass 15 times that of the Sun, but has lost three solar masses worth of material during its lifetime This all originates from the interior of the star. In the interior of a red supergiant there is more than just hydrogen and helium and the occasional bit of lithium burning, as in most stars. Instead there is an iron core with layers of different elements being burned to keep the star shining for
oxygen, nitrogen and so on, which can all find themselves in the stellar wind and sent out into starforming clouds throughout the cosmos. This is similar to the elements that were once in the Solar System’s original cloud of dust and gas. This is the carbon that is the basis for our DNA, the oxygen we breathe and the nitrogen that makes up most of Earth’s atmosphere. There are so many stars in the night sky, each with its own story, and only by investigating them in all sorts of wavelengths and using different methods can we begin to build a firm understanding of how all stars differ, how they
just a little bit longer. These layers contain carbon,
evolve and their overall influence on the cosmos.
© NASA
At visual wavelengths, Antares is 10,000-times brighter than the Sun.
41
Alien contact
WHAT HAPPENS WHEN WE
CONTACT ALIEN LIFE? Preparing the world for the biggest discovery in the history of humanity
© Shutterstock; Alamy; Getty
Reported by Jonathan O’Callaghan
42
Alien contact
I
n August 2016 the entire world was gripped with the news that a possible signal from an intelligent alien race
had been received. Picked up by a Russian radio telescope, its discoverers had no explanation for the signal, which appeared to be artificial, and suggested it could be our first sign of alien life. Alas, it was not to be. The signal, like so many before it, turned out to be interference from
“Desspite evidence suggestting theere shoould be plentyy of habbitable woorldss out therre, we sttill haven’t heaard anything”
Alien contact: who will be the first to know? The news will hit a number of individuals before the general public is informed
Earth, most likely a satellite in orbit. But the event
when it happens it is likely to be the biggest story in human history.
Harp, the director of the Center for SETI Research at the SETI Institute, tells All About Space. “But
Most of our searches for intelligent alien life have been primitive and poorly funded. At the moment,
we’ve never seen anything that could remotely be a signal from ET.” The obvious reason why is that
perhaps the most well-known organisation leading the charge is the SETI (Search for Extraterrestrial
we just haven’t looked hard enough yet. In its early days SETI relied on a catalogue of several thousand
Intelligence) Institute in California, which performs
potentially habitable systems, called HabCat, to
searches with a suite of antennae known as the
direct the searches. But since the launch of NASA’s
Allen Telescope Array. But there are other groups and organisations around the world involved in the
Kepler space telescope in 2009, thousands of planets have now been found – some of them
hunt too. For the most part it’s a small community. Information is shared, discussions are held and the ramifications of a discovery are considered. More recently Russian billionaire Yuri Milner invested $100 million (about £79 million) in the Breakthrough Listen project, a ten-year initiative to buy telescope time and accelerate the search for life. The uncomfortable truth at the moment, however, is that we haven’t heard anything, despite decades of searching. With 100-400 billion stars in our galaxy – most thought to host at least one planet – and 2 trillion galaxies in the universe, there are a lot of potential homes for life out there… so where is everyone? “There have been a couple of times
similar to Earth – and are attracting our attention. Once planets were thought to be rare, but now we know they are common, even plentiful. The stars we’re looking at have changed too. Originally searches focused on stars like our own Sun. After all, we know Earth has life – why not look for a world similar to our own? But we now know that red dwarfs, much smaller stars, make up 80 per cent of the stars in the sky, and they might be habitable to life too, so have been added to the search. Space is also unforgiving, even to radio or electromagnetic transmissions. It’s likely that if there is intelligent life out there, we’ll need bigger and more powerful telescopes to listen to them.
1
Source: Wikipedia Commons © Kathleen Franklin
The discoverer
An extraterrestrial signal is detected! The discoverer will need to verify the signal several times before revealing to others that it might be a sign of intelligent alien life.
2
Seth Shostak, SETI Institute As director of the SETI Institute, Shostak is likely to be one of the heads of the institutions that are asked to independently verify the signal.
Below: The Allen Telescope Array is an important tool in our hunt for alien life
Source: Wikipedia Commons © LegacyCustoms
where we’ve got excited about something,” Gerry
Source: Wikipedia Commons © Cancillería Argentina
highlighted a key point – there is a huge public clamour for finding extraterrestrial (ET) life, and
3
The president
Once confirmed, national authorities will have to be informed of the signal. In the US that would likely include the president, and in the UK, the prime minister.
4
António Guterres, secretarygeneral of the UN
Broader organisations – including the United Nations – can now start to be told about the groundbreaking new discovery.
5
You
Last, but by no means least, it will be time to publicly and officially inform the world of this amazing discovery – if it hasn’t been leaked by the media already.
43
Alien contact Upcoming projects like the Square Kilometre Array will further our knowledge and bring us closer to a
SETI’s strict protocols usually mean a signal is ruled out as being sent by aliens before the
may very well be some sort of key, or crib, hidden within that can help us decipher it. “If it has a crib, a
discovery that many think is on the horizon.
information is leaked to the public. But one day
directed message, maybe a hello from someone else,
To look for signals, astronomers point telescopes
a signal may very well pass these tests. Despite
then we have a very good chance of deciphering
to distant stars and listen for irregular patterns on a particular frequency, focusing on radio waves. If an
the far-reaching ramifications of this discovery, it will almost certainly be treated like any other
it,” says John Elliott from Leeds Beckett University, who is a member of the UK SETI Research Network
anomaly is found the signal is observed again, and if it disappears it was likely just interference from
scientific finding. Gradually various institutions and organisations will be alerted, and then the fun can
and has spent much of his research career working out how we’d decipher an alien signal. “It’s a bit like
something on Earth, like a satellite. If the signal is heard five times from the same
begin. “It would be a race to see who would be the first to make sense of the signal,” says Harp. “There’s
meeting someone in the Amazon rainforest who is from a tribe that has never had contact from the
point of sky, then things get interesting. At this point the signal would appear to be of alien origin.
a Nobel Prize in unlocking that language.” The first step will be to determine if the signal is
outside world. You’ve only got to point at a tree and say ‘tree’, or point at a rock and say ‘rock’, for them
The SETI Institute uses an automated system to
just generic noise, like the radio transmissions we
to understand that word means that object. That’s
sift through thousands of signals per hour, just ten per cent of which pass the first cut. None of these,
send out daily, or a directed message containing a signal. If it’s the former then the message will serve
what the crib would have to do.” Assuming we could decipher it, then things get
of course, have ever passed the final cut, but there have been an estimated 300 million interesting
simply to tell us that we are not alone, and perhaps we could pick up more errant signals from this
truly interesting. A heated debate is almost certain to spring up on whether we should respond or not.
signals found over the years.
distant civilisation. If it’s the latter, however, there
Many have argued either side of the coin, with some worrying that revealing our presence could
“The question of whether we are alone is arguably one of the greatest unsolved mysteries, and the impact of an answer would be far-reaching”
invite hostile aliens to come here, pillage our land and destroy humanity. Others are more optimistic, noting that the distances involved would likely be too great to travel over. And if we’ve spent so much time discovering we’re not alone, why would we not respond? “I’m firmly in the camp of yes, we should reply,” says Elliott. “I honestly think not to do that would be a waste. The whole point is we want to
© Shutterstock
Above: China’s Fivehundred-meter Aperture Spherical Radio Telescope is a sensitive listening device
44
Alien contact
An alien discovery
How do we know if we’ve made contact?
How the detection of a signal might change life on Earth Politics
Religion
There will be discussions on how humanity should be represented – if we even respond.
Gerry Harp, director of the Center for SETI Research, reveals what we would expect to see
Some religions may deny the discovery. Others may embrace it within their beliefs.
What are we looking for? We’re looking for signals that are clearly artificial. We have lots of ways we communicate using radio on Earth, and in principle ET might use the same. But the interstellar medium – the gas between stars – messes up signals, so we look for narrow-frequency bandwidth signals. How would we verify a signal is real? The signal has to persist. You have to look away and back with telescopes several times, until there have been five cycles. This tells you if it really is from that direction in the sky, or just scattered radiation.
Culture
Have we ever had a promising signal? There has only been one that passed all our automated testing. That was in 2015, and it was exciting. We’re always very sceptical, but we took a look and it was a very interesting signal almost designed to fool our system. It had all the right properties to look like something from outer space, but it was interference.
Conspiracies Science Perhaps the message would contain explanations of advanced scientific concepts, furthering our knowledge.
If people can believe the Moon landings were faked, you can be sure some will not believe this news either.
Golden Record
Our signals into space The primitive attempts we’ve made so far to initiate contact Cosmic Call 1
Teen Age Message
Sent: 1999
Sent: 2001
Sent by: Yevpatoria RT-70 telescope
Sent by: Yevpatoria RT-70 telescope
Sent from a radio telescope in Crimea, the signal targeted four separate Sun-like star systems.
Six Sun-like stars were targeted with a recording of a theremin – an early electronic musical instrument.
Cosmic Call 2 Sent: 2003 Sent by: Yevpatoria RT-70 telescope The second phase of Cosmic Call transmitted photos and multimedia files to five stars.
A Message From Earth
Sent: 1977
Pioneer plaques
Sent by: Voyager 1 and 2
Sent: 1972/1973 Sent by: Pioneer 10 and 11
The two Voyager craft have a vinyl record on board with sounds and images of Earth.
The twin Pioneer spacecraft carried a pair of plaques with information about humanity.
Arecibo message
Across the Universe
Sent: 1974
Sent: 2008
Sent by: Arecibo radio telescope
Sent by: Deep Space Network
A 210-byte image detailing numbers, the chemistry of DNA, the shape of humanity and the Solar System.
The Beatles’ song Across the Universe was sent by NASA towards Polaris, some 430 light years away.
Sent: 2008
RuBisCo Stars
Sent by: Yevpatoria RT-70 telescope
Sent: 2009
A signal was sent to the exoplanet Gliese 581c, which is 20 light years from Earth.
Sent by: Yevpatoria Deep Space Network The genetic code for a protein involved in photosynthesis was sent to three stars.
© Ed Crooks
Discovering that we are not the only life in the universe would likely have a large impact on our culture.
45
Alien contact
In the event of alien contact Certain protocols have been drawn up by the SETI Institute for if an intelligent signal is found 18:30
BREAKING NEWS: SIGNALS FROM SPACE
LIVE: PRESS STATEMENT FROM SETI
1
Verification
While the discovery of a signal will be exciting, the first step is to make sure that the signal is real, and not from Earth-based interference. To do this the discoverer must repeatedly observe the signal five times, and rule out other sources like satellites or terrestrial radio waves. If the signal is continuously seen from the same region of sky when observing from different locations, then the discoverer can move onto the next step.
5
Release and record
© Ed Crooks
All data from the signal – absolutely everything – should now be collected, recorded and stored permanently without any chance of any of the data being lost. All of this data should be given to the aforementioned international institutes, among others, and also released to the wider scientific community so that people can begin studying the signal in earnest. It’s likely that by this point there would be a global race to be the first to decipher the message.
46
2
Get help
6
Block the frequency
The discoverer now needs to inform other international observatories and institutions about the discovery. These need to all independently confirm the discovery themselves, and again verify that the signal is coming from another star, and not some sort of terrestrial interference. At this point there should not yet be a formal public announcement, but national authorities should be informed of the discovery.
Assuming the detection was made via electromagnetic signals, steps should be taken to block and protect the frequency that the discovery was made on. This would stop other people from broadcasting on it while discussions were held across the world about what to do next. It’s not entirely clear how this frequency will be blocked, but SETI recommends “convening an Extraordinary Administrative Radio Conference” to make the necessary arrangements.
3
Prepare the world
7
Consider a response
Now it’s time to tell some of the bigwigs, who can prepare public announcements. The discoverer needs to open the findings to all observers around the world and reveal the discovery to the secretary-general of the UN. SETI then lists the institutions who should be informed, such as the International Telecommunication Union, the International Astronautical Federation and the International Institute of Space Law.
The world will now be debating whether to send a response or not, so SETI recommends that international talks should begin. Stephen Hawking argued against responding in case the aliens are hostile, but there are many who will want to reply. After all, what’s the point in making contact if we aren’t going to respond? The distances involved will likely be so large that any conversation will take place across generations, with little hope of either race visiting the other.
4
Tell everyone
8
Th
Now it’s time to publicly release the find. It should be noted that the discovery is already likely to have been leaked to the media through one form or another. Nonetheless, this is the formal point where the public can be told everything. The discoverer should be given the privilege of making the announcement. They’ve just made the most important discovery in history – they should get some recognition for it!
ath
The final step is to create an international committee to serve as the main focal point for the analysis of the signal. This will include experts from around the world and “such other members as the committee may deem necessary,” according to SETI. As for SETI itself, the signal would turn it from a fringe science into the most popular activity on Earth. Huge amounts of money would likely be poured into the endeavour to study this signal, and perhaps find alien life.
© NASA
Alien contact When will we make contact?
2030 Douglas Vakoch METI International “My best guess for when we’ll detect extraterrestrial life – if, in fact, we make contact in my lifetime – is by 2030, a decade from now.”
2040 Seth Shostak SETI Institute
know if somebody’s out there. We hope they are. And you shouldn’t stay silent when you see the evidence. It just doesn’t sit right for me.” One group also in this camp is METI (Messaging Extraterrestrial Intelligence) International, who think we should be constantly sending out directed messages in the hope of a response, rather than waiting on the off chance that we hear something. “If we began transmitting to nearby stars in earnest, targeting all the stars within 50 light years from Earth and waiting for a reply, 100 years from now we could be hearing back from any of a couple of thousand stars whose inhabitants had received our signal,” Douglas Vakoch, president of METI, tells All About Space. But if an attempt at two-way communication is made, the distance of the planet will dictate what sort of conversation we can have. If it’s nearby, within 50 light years, we could talk over generations. If it is much further, into the thousands of light years, then messages would only be sent back and forth over millennia. Maybe the messages would develop a sort of grand religion around them as people waited eons for a response. “Perhaps there would be little cults or something,” says Harp. But then what? The question of whether we are alone is arguably one of the greatest unsolved mysteries, and the impact of an answer would be far-reaching. Perhaps it would change life as we know it forever, or perhaps it wouldn’t change much at all. We’ve got no way of knowing for sure. As for SETI itself, it would turn from a fringe science into the hottest subject on Earth. “The detection would be like winning the lottery,” says Harp. “But there’s a good chance it would destroy the SETI Institute, and other scientific institutions [would take over].”
But despite evidence suggesting there should be plenty of habitable worlds out there, we still haven’t heard anything. Maybe the route to evolving into sentient beings is tough, and others haven’t done it yet. Earth has actually formed relatively early in the universe – about 10 billion years into its existence – if you consider the universe will stick around for a few trillion years. That’s not to say there isn’t something out there, though. “Making contact is incredibly likely,” says Elliott. “There are many places that could support life, even in our own Solar System. Not intelligent life, but life nonetheless.” Maybe we just haven’t looked hard enough yet. There could be others out there either waiting to hear from us, or looking on until we reach a more technically advanced stage. But maybe we truly are alone. Considering the numbers that seems unlikely, and it’s not an opinion widely shared in SETI circles. “I used to be a lot more confident there was something out there,” says Harp. “I would say that in 100 years we could start examining a fair fraction of the galaxy with bigger and better radio telescopes. And if we don’t find intelligent life we will have to start looking in other galaxies. It would be disappointing, but I think we’ll know a lot more by then.” It’s easy to be optimistic, though. Surely there’s someone else out there… and when we find them, we’d better be ready.
Above: NASA’s Kepler space telescope has revealed far more exoplanets than we thought possible
“Redd dwaarfs make up 80 per centt of thee staars in the sky, andd they look like theey might be haabitaable to life”
“I’ve bet everyone a cup of coffee that we’ll find a signal within two decades. If not, I’ll have the opportunity to buy a lot of brew.”
2050 John Elliott UK SETI Research Network “In 30 years I think we’ll have the dish capacity, techniques and computing power, as well as the knowledge of where is best to target.”
2070 Andrew Siemion Berkeley SETI Research Center “If we haven’t detected evidence of intelligent life beyond Earth in 50 years, it is likely that we are essentially alone in the visible universe.”
2120 Gerald Harp Berkeley SETI Research Center “My firm prediction is 100 years from now. I’m very confident, since I will be dead by then.”
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