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ASTRONAUT TERRY VIRTS INTERVIEW
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TM
BACK MOON
INSIDE
TO THE
The fleet of missions that will land humankind on the lunar surface – To stay
IS THERE LIFE AROUND BLACK HOLES?
ISSUE 118
Samples from titan the vomit comet Mysteries from uranus
Everything you need to know about
PLANETS
NEW RESEARCH IMPACT THAT KILLED THE DINOSAURS
5
issue highlights
Col. Terry Virts The retired astronaut reveals the lessons he learned in Earth orbit 26
The planets with no sun Worlds without the warmth of a host star do exist. But what are they like? 30
On board the Vomit Comet What’s it like to ride in zerogravity? We lift the lid on the amusingly named craft 38
Life at the event horizon
WELCOME
Researchers are hunting for life forms around black holes – but could there be anybody out there? 42
Issue 118
This month marks 52 years since humankind landed on the surface of the Moon for the very first time. A little over five decades later and we’ve not sent humans back since Apollo – but that’s not to say the likes of NASA and the ESA, alongside a selection of private space companies, aren’t once again shooting for our natural satellite. So where are we in our plans to return to the lunar surface, stepping into the boot prints of Neil Armstrong and Buzz Aldrin? Turn to our cover feature for the plans, spacecraft and logistics that’ll see us go back, this time with intention to stay. Elsewhere in the issue, we return to the extinction of the dinosaurs: was it really an asteroid that wiped them out, or another kind of object from outer space? Reveal the worlds that wander around our galaxy without a sun, discover what it’s like to board the infamous ‘Vomit Comet’ and uncover whether life could really exist around black holes. There’s plenty to keep you entertained this month. If you’re looking for more reading material to read in the sunshine – now that the warmer weather is finally here in the Northern Hemisphere – then turn to page 95 for your free eBooks. And don’t forget to check out our sister title, How It Works, for more science and tech!
Ask Space Your questions answered by our team of experts 74
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INSIDE
BACK MOON TO THE
The fleet of missions that will land humankind on the lunar surface – this time to stay
95
claim Your free E books
60 Second Science, Book of Space & Save the World
“This critical step puts humanity on a path to sustainable lunar exploration” Kathy Lueders 4
issue 118
INSIDE launchpad
06
News from around the universe
Neutron stars might be bigger than
52
What killed the dinosaurs?
58
Remembering the Space Shuttle
The object that caused Earth’s last mass extinction may not have been an asteroid
expected, while Perseverance is busy snapping away on Mars
Future Tech
24
Titan sample return A new NASA Institute of
Advanced Concepts study is looking at the surprising advantages of a Titan
Exactly a decade ago, NASA’s reusable low-Earth orbital spacecraft’s time came to an end. All About Space relives the best moments
sample return
Moon profile
interview
64
26
Colonel Terry Virts
All About Space speaks with the former NASA astronaut about his time in space and his newfound ‘cosmic perspective’
30
The Vomit Comet
You’d better have a strong stomach: in space, everyone can hear you spew
36
Worlds without suns
68
Mimas This small, oddly shaped and icy
moon continues to baffle scientists
68
Why are X-rays coming from Uranus?
26
Stargazer 78 What’s in
the sky?
When X-rays were detected from the ice giant for the first time, a team of astronomers began to look into their origin
82 Month’s
74
85 Naked eye
planets 84 Moon tour
Ask Space
& binocular targets
Your questions answered by our panel of experts
86 Deep sky
Astronomers are still on the hunt for rogue planets, but what can they tell us about the layout of our cosmos?
challenge 88 The Northern
Hemisphere
Focus On
90 Astroshots
42
Cleaning a space station
92 Telescope
44
Could life exist around black holes?
review
Astronauts have to keep the space station clean to keep microbes under control
They warp time and space, but could they also nurture life?
96 In the shops
WIN! CELESTRON NEXSTAR EVOLUTION 8
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LAUNCH PAD YOUR FIRST CONTACT WITH THE UNIVERSE
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11 May 2021
A Martian rover’s view of ‘Santa Cruz’
© NASA/JPL-Caltech
NASA’s Perseverance rover snapped this profound photo using its dual-camera Mastcam-Z imager while inside Jezero crater. Here we can see Santa Cruz, a large hill standing proud amid the rugged Martian landscape, located approximately 2.5 kilometres (1.5 miles) away from the rover. Beyond Santa Cruz on the horizon is the faint dusty rim of Jezero crater. This image is presented as a preliminary calibrated version of a natural-colour composite, meaning the colours displayed are similar to how they would look to a person standing on Mars.
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LAUNCH PAD YOUR FIRST CONTACT WITH THE UNIVERSE
26 April 2021
The exquisite and aptly named Necklace Nebula, officially PN G054.2-03.4, is located 15,000 light years away in the constellation of Sagitta (the Arrow). This celestial jewel was forged approximately 10,000 years ago by two doomed Sun-like stars locked in a very tight orbit. One of the ageing stars proceeded to consume its smaller companion, creating what astronomers call a ‘common envelope’ – gas that contains a binary star system. This process caused the expulsion of vast quantities of gas and dust, which now forms the ring that gives the Necklace Nebula its famous shape.
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© ESA/Hubble & NASA
Star-studded necklace
10 May 2021
Magenta mist
© ESO
This captivating image exhibits a purple cloud of ionised hydrogen known as DG121, a HII region located in the constellation of Puppis (the Stern). This type of emission nebula is produced when newly formed stars release vast quantities of ultraviolet energy, ionising the surrounding gas cloud. The dazzling star towards the centre of the image is HD 60068, the brightest in the region. This stunning scene was captured by the FORS 2 (FOcal Reducer and low dispersion Spectrograph) instrument on the Very Large Telescope (VLT) in the Chilean Atacama Desert.
2 May 2021
© NASA
Rare nocturnal splashdown This impressive drone image shows the recovery of the SpaceX Crew Dragon Resilience’s passengers after they splashed down in the Gulf of Mexico off the coast of Panama City, Florida, in the early hours of the morning on 2 May 2021. This was the first nighttime splashdown with American astronauts since the Apollo era, signifying the completion of SpaceX’s first full-fledged crewed mission to the ISS. Working under cover of darkness, recovery crews successfully retrieved NASA astronauts Mike Hopkins, Victor Glover and Shannon Walker and JAXA astronaut Soichi Noguchi.
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LAUNCH PAD YOUR FIRST CONTACT WITH THE UNIVERSE
17 April 2021
This Hubble image presents galaxy cluster ACO S 295 surrounded by a bustling crowd of celestial objects. This jam-packed menagerie of galaxies of varying size and shape shows some virtually head-on, like the spiral galaxy in the centre, while others are edge-on, appearing as thin slithers of light. Due to the significant mass of the galaxy cluster in the centre of the image, gravitational lensing has distorted the background galaxies, causing them to look warped.
© ESA/Hubble & NASA
Galactic soup
25 February 2021
This friendly face is the product of two colliding galaxies, and doesn’t Mrk 739 look rather pleased with itself? It should be, as such mergers are rare in our galactic neighbourhood, and Mrk 739 is helping scientists better understand these colossal events. Due to its relatively close proximity at 425 million light years away, scientists are able to keep a watchful eye on Mrk 739 using instruments such as the Multi Unit Spectroscopic Explorer (MUSE) on the VLT. This provides information on the motions of galaxies, the age of their stars and what they’re made of.
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© ESO
Say cheese!
10 May 2021
Every cloud has a silver lining
© ESA/Hubble
This wispy emission nebula, NGC 2313, is located 3,756 light years away, lying in the constellation of Monoceros. The ionised cloud of dust emits its own light, and while the left-hand side of the image depicts a shimmering, silvery veil, the righthand side is shrouded by a dense cloud of dust. At the heart of this image lies a bright, young star, V565. When stars like this were accompanied by bright fans of gas, as seen here, they were known as cometary nebulae, though this term is now no longer used within the scientific community.
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Neutron stars may be bigger than expected thanks to an outer shell
City-size neutron stars may actually be bigger than we thought Words by Tereza Pultarova
neutron stars.
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have more neutrons. Some of these neutrons are squeezed in the nucleus together with the protons, but not all of them fit. The rest are pushed out to the edge of the nucleus, forming what physicists call the neutron skin. The most common isotope of lead, Pb-208, which is frequently used for experiments, contains 82 protons and 126 neutrons. Physicists know that the size of the skin correlates with the size of the atom. Piekarewicz believes the same can be assumed about the much bigger and denser neutron stars. “The dimensions of that skin, how it extends further, is something that correlates with the size of the neutron star,” said Piekarewicz, though he added that his estimates were rather preliminary. More work and advancements in technology would be needed for scientists to really get a proper grasp of neutron stars.
“There is no experiment that can probe the structure of the neutron star”
© NASA
S
“There is no experiment that we can carry out in the laboratory that can probe the structure of the neutron star,” said Jorge Piekarewicz, a nuclear physicist at Florida State University. “A neutron star is such an exotic object that we have not been able to recreate it in the lab, so anything that can be done in the lab to constrain or inform us about the properties of a neutron star is very helpful.” The researchers probed lead atoms with electron beams and found that the neutron skin of the lead isotope Pb-208 is 0.28 femtometres (0.28 trillionths of a millimetre) thick, about double the thickness predicted. Atoms generally contain positively charged protons, negatively charged electrons and neutrons with no charge. Protons are squeezed inside the atom’s nucleus, while electrons make up its outer shell. With neutrons, it’s a bit more complex. Heavier atoms, such as lead, usually
z
cientists have found neutron stars – the densest known objects in the universe aside from black holes – have a radius of between 13.25 and 14.25 kilometres (8.2 and 8.9 miles). Previously it was believed these stars, leftovers of huge supernova explosions, have a slightly smaller radius of up to 12 kilometres (7.5 miles). Within this relatively small radius – whichever one you look at – an amount of matter that equals 1.4 times the mass of the Sun is squeezed. The Sun, in comparison, has a radius of 695,508 kilometres (432,169 miles). These estimates were made not by measuring neutron stars directly, but by looking at the so-called ‘neutron skin’, or an outer layer of neutrons, surrounding the nucleus of a lead atom. But what does lead have to do with the size of neutron stars? Lead is one of the densest materials that can be naturally found on Earth. Even though lead is nowhere near as dense as neutron stars, scientists assume that the physical principles governing the structure of lead atoms must be similar to those behind the structure of
© NASA
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Scientists ponder how to get samples from Saturn’s weird moon Titan
Words by Tereza Pultarova
A sample-return mission to Saturn’s moon Titan
just like astronauts returning to Earth. With the
could discover unexpected forms of life and bring back chemical compounds that cannot be found on
landing out of the way, the next big challenge would be to get the sample up to space, on its way
Earth. A team of engineers from the NASA Glenn Research Center in Cleveland, Ohio, has recently
back to Earth. For that, the Glenn team envisions, the surface lakes of methane will come in handy.
received a $125,000 (£88,000) NASA Innovative Advanced Concepts (NIAC) grant to look into the
“Producing rocket fuel on Titan wouldn’t require chemical processing – you just need a pipe and a
feasibility of bringing a sample of material from this intriguing world to Earth.
pump,” said Oleson. “The methane is already in a liquid state, so it’s ready to go.” The Compass
“We expect landing on Titan to be relatively easy,” said Steven Oleson, head of the Compass Lab at Glenn. “Titan has a thick atmosphere of nitrogen – 1.5 times the atmospheric pressure of Earth – which can slow the lander’s velocity with an aeroshell and a parachute for a soft landing,
Lab team will now investigate how to effectively produce liquid oxygen to enable the fuel to burn. Although the sample-return concept may never fly, Titan can expect a robotic visitor soon. Dragonfly is an eight-bladed rotorcraft scheduled to begin the eight-year journey to the Saturn system in 2027.
Astronauts may finally start cleaning their space underwear, using microbes
Above: Titan’s conditions are favourable for landing a craft
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Below: Astronauts wear this one piece under their spacesuits when they go out on spacewalks
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spaceflight textiles,” said ESA material engineer Malgorzata Holynska.
PRINT & ITA
© NASA
We can all agree that sharing your unwashed underwear with another person isn’t ideal. But for astronauts on the International Space Station (ISS), performing a spacewalk requires that they share not only the spacesuits, but also a next-to-the-skin piece of clothing that’s worn underneath, known as the Liquid Cooling and Ventilation Garment (LCVG). Access to a freshly laundered LCVG isn’t an option on the ISS, but technicians with the European Space Agency (ESA) are taking steps to improve the antimicrobial properties in LCVG materials to keep these shared garments clean and fresh for longer. In a new project called Biocidal Advanced Coating Technology for Reducing Microbial Activity, ESA researchers are collaborating with the Vienna Textile Lab, a biotechnology company that produces fabric dyes from bacteria. Compounds generated by these bacteria can make textile fibres more resistant to certain types of microbes. Astronauts on the ISS keep their hands and bodies clean with no-rinse cleaning solutions and dry shampoo, but laundering clothes – including underwear – would require too much water and is simply not possible. Nor is there enough room on the ISS for astronauts to pack a fresh change of clothes for every day of their mission. Scientists were already investigating materials for upgrading outer spacesuit layers, so this “is a useful complement, looking into small bacteria-killing molecules that may be useful for all kinds of
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Firefly Aerospace picks SpaceX rocket to launch Blue Ghost moon lander in 2023
Europe unveils plans to bring ‘GPS’ and Skype to the Moon with satellites
Words by Rahul Rao
The ESA has kicked off development of a satellite constellation that will orbit the Moon and provide
A mission called the Lunar Pathfinder is already in the works, which will test the novel GNSS
navigation and telecommunication services to lunar explorers. If all goes according to plan, the
receiver in orbit around the Moon. The satellite, built by the UK-based Surrey Satellite Technology
new system could be in place in the late 2020s.
(SSTL), is scheduled to launch in 2024. SSTL also
The ESA believes that Earth’s celestial companion
leads one of the consortia that will develop the
is set to become a busy destination, with commercial companies and nations from across the
proposal for the new constellation. The other is headed by Italy’s Telespazio.
world all wanting a slice of the ‘eighth continent’. The new constellation, called Moonlight, will make it easier and cheaper for a fledgling lunar economy to blossom. For now contracts have been awarded to two European industrial consortia to study the feasibility of such an undertaking over the next year and a half and propose technical solutions for the ESA to choose from.
The constellation will likely consist of three or four satellites. Additional satellites might be added to beef up the communications aspect of the offering. The ESA expects the constellation will be operated by the private sector, which will sell the service to the agency and other customers in a similar fashion to how SpaceX sells service missions and crew launches to the ISS.
© ESA
Words by Tereza Pultarova
Space launch company Firefly Aerospace announced that when its Blue Ghost lander launches to the Moon in 2023, it will
Above: The satellites will improve lunar navigation
do so on a SpaceX Falcon 9. The Falcon 9 will be able to carry Blue Ghost to the Moon without forcing the lander to expend much of the fuel it might need for the actual touchdown, said Shea Ferring, Firefly’s senior vice president of spacecraft. Firefly has yet to launch anything, though in June the Texas company hopes to begin testing its own rocket for small launches: Firefly Alpha. Nonetheless, the company has been active in designing lunar landers, and it’s paid off. In February NASA awarded Firefly a contract to deliver Blue Ghost to the Moon. Blue Ghost is part of NASA’s Commercial Lunar Payload Services (CLPS) program, which contracts private-sector firms to land science experiments and other assorted cargo on the Moon. The first CLPS missions could launch as soon as this year.
Metals found in the atmospheres of comets surprise scientists
the 425 degrees Celsius (800
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SO ©E
Metal atoms have surprisingly been discovered in the frigid atmosphere of the first known interstellar comet to visit our Solar System. Astronomers have also detected metal in the cold halos surrounding comets local to the Solar System, which suggest our Solar System comets and the interstellar visitor may have similar origins. Scientists often deduce the composition of comets by examining the clouds of gas and dust known as comas that surround the hearts of comets. Scientists do not typically detect metals such as nickel in the comas of comets, since their surfaces are usually too cold for metal to vaporise. Exceptions to this rule are comets passing near or plunging into the Sun, where temperatures can readily exceed
degrees Fahrenheit) needed for nickel vapour to form. Now scientists have detected nickel atoms in the coma of the first known interstellar comet, 2I/Borisov. First discovered in 2019, its speed and trajectory revealed it was a rogue comet from interstellar space, making it the first known interstellar comet and the second known interstellar visitor after the cigar-shaped rock 1I/2017 U1, or ’Oumuamua. The discovery was unexpected – when astronomers first saw these nickel atoms in January using the Very Large Telescope in Chile, 2I/Borisov was far from the Sun, with an estimated temperature of -93 degrees Celsius (-135 degrees Fahrenheit). It remains uncertain how comets like 2I/ Borisov can generate metal at such cold temperatures.
Left: Nickel vapour has been identified in cometary coma Right: Blue Ghost will be Firefly’s first launch
© Firefly
Words by Charles Q. Choi
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The Moon
TO THE to the Moon to explore and mine it Report Rep orted ed by Ian Pa Parke rke er
16
The Moon
The missions to land on the Moon NASA’s Artemis and China and Russia’s ILRS program are attracting the support of many other nations © NASA
NASA’s Artemis
S
ince the first humans evolved in east Africa about 3 million years ago, people have been conflicted
between the pressures of dealing with problems at home and the excitement and
© NASA
possibilities offered by exploration. There will always be problems at home, but it’s not a good enough reason for staying put, so people venture forth, often reaping the benefits. There is much historical evidence to show that exploration produces solutions which can be employed back home. Columbus struggled to fund his expeditions because few could see any benefit. But after Europeans reached the Americas they brought back potatoes, which became a hugely important crop, feeding millions because they thrive where other crops fail. Discoveries are made not only at the destination, but along the way, too. When sailors began to explore the world’s oceans, they needed a way of determining longitude, something which requires accurate timings. Since pendulum clocks are wildly inaccurate on rolling ships, major scientific and engineering advances were made in coming up with a timepiece solution. Your wristwatch, albeit probably electronic, is a direct descendant of that. We discuss all of this for a reason. Since moonwalkers Gene Cernan and Harrison Schmitt splashed down on Earth along with Command Module pilot Ronald Evans (and five mice) on 19 December 1972, humans have never again put boots on the Moon. Several return programs have been proposed and aborted, with none
being successful because of funding problems
Above: 12 people have and a lack of enthusiasm from the public and walked on the politicians. Earthbound problems have been seen Moon, and all as more pressing. of them were But times are changing. Despite the ravages of American. COVID-19 on health and budgets, space agencies That should change in the are getting serious about returning astronauts to next decade Earth’s only natural satellite. And one fact that the pandemic has reinforced is that there is not a fixed amount of money on Earth: governments can create it in an economic process called quantitative easing. President Joe Biden is planning a trilliondollar stimulus package for the US economy, and it’s paving the way for exploration. This time around, NASA astronauts heading for the Moon are likely to include a woman and a person of colour for the first time, reversing the discriminatory wrongdoings of the past, which is an important part of many government policies. But a return to the Moon is nevertheless being seen as a stepping stone for other, perhaps more ambitious missions. Buzz Aldrin, the second human to walk on the Moon’s surface, supports a manned mission to Mars, and NASA is not alone in looking skywards. As it stands, there’s an internal fight going on within the wider space industry, and an argument about whether we should be sending people at all. Having humans in space, or on another celestial body such as the Moon, is much more expensive than sending unmanned craft. Consider the great success that the Mars 2020 mission’s helicopter Ingenuity has recently enjoyed. There’s a strong argument that money is far better spent on unmanned spacecraft and landers. Even so, NASA is getting ready to send astronauts to explore more of the Moon as part of the Artemis program, and the agency has selected SpaceX to continue development of the first commercial human lander that will carry the next two American astronauts to the lunar surface.
Stepping stone to Mars First woman on the Moon First person of colour on the Moon Collaboration with commercial partners Aims to build sustainable elements on the surface Artemis currently has three missions planned, starting with the test of an unmanned Orion spacecraft. The second will be manned and fly around the Moon. The third will touch down.
China and Russia’s International Lunar Research Station A proposed joint-venture research facility Open to all interested countries and international partners Either built on the lunar south pole or in orbit Human presence will follow a robotic stage The ESA is interested, although it’s signed an agreement with NASA Human exploitation of the Moon may well involve mining, so samples will be important. The Chinese and Russian ILRS – which will focus on water and mineral resources – could lead the way to this.
Tap here to play
In Greek mythology, Artemis was the daughter
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Returning to the Moon
s bacck on the Moon be befo fore ore f in internattio iona nall pa part rtne ners rs
2021
1 October 2021
4 November 2021
German aerospace company PTScientists is looking to launch the world’s first-ever private Moon landing. It will use the Autonomous Landing and Navigation Module, which will deploy two rovers.
ncy Roscosmos is aiming to alled d own n y on’s south pole.
ht o dy ion whiich h bit around the Moon.
of Zeus and Leto, and the Moon was among her
© NASA
charges. Her twin brother was Apollo, a name which has already graced lunar missions. The agency’s powerful Space Launch System (SLS) rocket will launch four astronauts aboard the Orion spacecraft for a multi-day journey to lunar orbit. Once there, two crew members will transfer to SpaceX’s Human Landing System (HLS) for the final leg of their journey to the surface of the Moon. After approximately a week exploring the surface, they will board the lander for their short trip back to orbit, where they will return to Orion and their colleagues before heading back to Earth. The firm, fixed-price, milestone-based contract total award value is $2.89 billion (£2.05 billion).
Top: Spacesuit engineer Kristine Davis wears a prototype Exploration Extravehicular Mobility Unit (xEMU) suit, which will be used for spacewalks
© NASA
Left: An Artemis base camp is being developed to support longer expeditions on the lunar surface
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January 2022 Japan’s space agency JAXA is looking to send a lunar lander called the Smart Lander for Investigating Moon (SLIM). It will be the country’s first attempt to land on the surface.
“With this award, NASA and our partners will complete the first crewed demonstration mission to the surface of the Moon in the 21st century as the agency takes a step forward for women’s equality and long-term deep-space exploration,” says Kathy Lueders, NASA’s associate administrator for human exploration and operations mission directorate. “This critical step puts humanity on a path to sustainable lunar exploration and keeps our eyes on missions farther into the Solar System, including Mars.” “This is an exciting time for NASA, and especially the Artemis team,” says Lisa WatsonMorgan, program manager for the HLS at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “During Apollo, we proved that it is possible to do the seemingly impossible: land humans on the Moon. By taking a collaborative approach in working with industry while leveraging NASA’s proven technical expertise and capabilities, we will return American astronauts to the Moon’s surface once again, this time to explore new areas for longer periods of time.” SpaceX’s Starship HLS, designed to land on the surface of the Moon, leans on the company’s tested Raptor engines and flight heritage of the Falcon and Dragon vehicles. Starship includes a spacious cabin and two airlocks for astronaut moonwalks. The Starship architecture is intended to evolve to a fully reusable launch and landing system designed for travel to the Moon, Mars and other destinations in the Solar System. With the powerful new SLS rocket, the Orion capsule, Starship HLS and the Gateway lunar outpost all planned, NASA and its commercial and international partners are returning to the Moon for scientific discovery, economic benefits and inspiration for a new generation.
The Moon
2022
August 2023
2023
October 2024
2024
The Indian Space Research Organisation is planning its third lunar exploration mission, called Chandrayaan-3. It will involve a lander and small rover, but not an orbiter.
Artemis II will be crewed. Those on board NASA’s Orion spacecraft will perform a flyby of the Moon before returning to Earth from beyond low-Earth orbit for the first time in 51 years.
Japanese billionaire Yusaku Maezawa is set to fly up to eight space tourists on a SpaceX Starship on a sixday tour around the Moon. Maezawa aims to fly to the ISS in December 2021.
NASA’s Artemis III is due to land astronauts on the Moon in the south polar region. Two astronauts will be on the surface for about a week – but will the scheduled date be met?
The Lunar Gateway is an international attempt to put a small space station in lunar orbit to make it easier to explore the Moon – and beyond – and carry out scientific experiments.
Eight countries initially signed the Artemis Accords, a set of guidelines surrounding the crewed exploration of the Moon. The UK, Italy, Australia, Canada, Japan, Luxembourg, Ukraine, the United Arab Emirates and the US are now all participants in the project, which aims to return humans to the Moon by 2024 and establish a crewed lunar base by 2030. Strangely, one NASA illustration of Gateway shows a Russian element. Last year Japan said it will recruit astronauts for the first time in 13 years. Japan’s Education and Science minister Koichi Hagiuda said the aim is to have a Japanese national on the Moon for the first time in the latter half of the 2020s. Japan has seven astronauts in the Japan Aerospace Exploration Agency (JAXA), and three of them have already been to space. The Japanese government will seek applications in the latter part of 2021, and the selected group of astronauts may be part of Artemis. It’s the first time since 2008 that Japan will be recruiting astronauts. “We will solicit applications around every five years from now on to maintain a group of astronauts,” Hagiuda says. The project seeks to establish a “set of principles for space exploration, including lunar resource extraction”. African and South American countries are so far absent, although Brazil has expressed an intent to join Artemis. Their economies may prevent their
Right: NASA’s Volatiles Investigating Polar Exploration Rover (VIPER) will be sent to the south pole of the Moon, where it will be able to sample water ice ahead of a human landing
© NASA
“NASA will complete the first crewed demonstration mission to the surface of the Moon in the 21st century” Kathy Lueders
Tap here to play 19
The Moon 3 2
1
1
Artemis: Manned mission to the Moon
We have liftoff 4
NASA will use a super-heavylift launch vehicle called the Space Launch System to send a reusable space capsule called Orion to the Moon.
2
separation
It takes 90 seconds for the rocket to reach the period of greatest atmospheric force. The rocket boosters, fairings and launch abort systems are jettisoned. The core stage engine shuts down and separates away.
5
3
Orbiting Earth
The spacecraft must orbit Earth before it leaves the planet and heads for the lunar surface. As it does, the solar arrays and Interim Cryogenic Propulsion Stage are deployed.
6
4
Deploying CubeSats
© Adrian Mann
A total of 13 small satellites called CubeSats will be deployed as part of the flight. They will carry out missions such as detecting yeast, imaging Earth’s plasmasphere and seeking lunar water ice.
5
Entering DRO
Orion will shift into a high, stable orbit around the Moon called a distant retrograde orbit (DRO). No spacecraft has used a DRO yet. It will entail Artemis 1 performing up to 1.5 revolutions of the Moon.
7 8
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The Moon
“During Apollo, we proved that it is possible to do the seemingly impossible: land humans on the Moon” Lisa Watson-Morgan © NASA
AR SCAN HERE 6
Returning to Earth
The spacecraft will leave DRO and head back to our planet, with the crew module separating from the service module ahead of entry into Earth’s atmosphere.
7
on the Moon. China is very keen to promote its international achievements and find a place in
A lunar outpost
A small space station called Gateway is going to be put into orbit around the Moon. Not only will it allow for deep-space exploration, it’ll make it easier to journey to the surface.
space. The nation’s economy is going from strength to strength, and it wants to follow on from its successful robotic lunar rovers. The new Chinese project has been named the International Lunar Research Station (ILRS). The European Space Above: Phase 1 early Gateway with Power and Propulsion Element (left), Habitation and Logistics Outpost (centre foreground), and cargo spacecraft (centre background)
Beyond 2024, when a crew will have already landed, the idea is that there will be a base camp on the lunar surface, hosting four astronauts at the south pole for up to a week at a time.
9
Below: An artist’s rendition of an Artemis astronaut wearing the xEMU spacesuit and xPLS life-support backpack during an EVA on the Moon
Artemis IV
Artemis IV would dock at the Gateway and allow surface expeditions to take place thereafter as more infrastructure is added over time to aid sustainable exploration.
Agency (ESA) is also reported to be interested in collaborating with China. The ESA’s international relations administrator Karl Bergquist says: “We are following the Chinese lunar exploration plans very closely in order to see where our respective programmatic interests could meet, primarily the Chang’e-6, 7 and 8 missions, but also the ILRS initiative.” Jan Wörner, the recently retired director general of the ESA, has previously suggested that many countries could collaborate to create a ‘Moon village’, perhaps the ESA nations, the US, China, Russia, India and Japan, which all have vibrant space initiatives. In March, the heads of the Chinese and Russian space agencies signed a memorandum of understanding on cooperative construction of the ILRS. Zhang Kejian, head of the China National Space Administration (CNSA), and Dmitry Rogozin, general director of Roscosmos, signed the document during a virtual meeting on 9 March. The ILRS is described as a comprehensive scientific experiment base built on the lunar surface or in lunar orbit that can carry out
© NASA
8
program despite its challenging economy, and may join, as Ukraine has recently done. But the US is not the only country with its eyes
9
Base camp
participation, however. India has a major space
21
The Moon multi-disciplinary and multi-objective scientific research activities, including exploration and utilisation, lunar-based observation, basic scientific experiments and technical verification and longterm autonomous operation. Statements from both Roscosmos and the CNSA underline that the project will be “open to all interested countries and international partners”. If on the surface, the ILRS will likely be constructed at the lunar south pole.
RETURN TO THE MOON BY NUMBERS
China and Russia have previously signed © NASA
agreements for cooperation on the Chang’e-7 and Luna 27 missions and a joint data centre for lunar
and 3D-printing technology tests, as well as life science related to potential long-term stays on the Moon. These missions will form the robotic basis
This falls under international space law, but do lawmakers have the teeth to control the exploitation of the Moon? If mining becomes very profitable, which nations get to benefit, and how much? Will it be a lunar ‘gold rush’? Russia has
of the ILRS before expansion into a more long-term base. Meanwhile, Russia is preparing to launch
already criticised Artemis as being too US-centric,
its Luna 25, Luna 26 and Luna 27 lander missions
The International Space Station has been a technical and political success since construction
across the 2020s. The early stage ILRS would appear to consist of a number of discrete spacecraft, in contrast to a more complex, integrated program such as the International Space Station (ISS). China is also developing capabilities for deep-space human spaceflight. In May 2020 China tested a new spacecraft, and is also developing two separate super-heavy-lift launchers for space infrastructure and crewed missions. The Chinese space station Tiangong, with construction to begin soon, is planned to bring China expertise and experience in human spaceflight operations ahead of potential crewed lunar missions. The return to the Moon could become a race with two factions – the China and Russia-led ILRS and the US-led Artemis program involving many other nations – in direct competition. But this time it’s not just for glory and publicity, it’s for mining rights, and that’s where things get difficult.
MISSIONS
Artemis I, II and III will put astronauts back on the Moon
and deep-space exploration. Chang’e-6, a polar sample-return mission, is scheduled for some point in 2023 or 2024. The later Chang’e-8 mission will be designed for in-situ resource utilisation
3
and the next space race could be one for profit.
began, but will present-day international politics permit one multi-country base on the Moon? It’s a distinct possibility if the funding can be defended. Or will we have two competitive bases? Such programs may be easier in command economies than democratic ones. The space community will try again to bring the people of the world together, as it has for decades on smaller scales. Future moonwalkers may look back on Earth, our only home so far, and intensify the philosophy that we need to learn how to share it and look after it, provided national or regional greed does not take hold.
Above: Testing of craft and systems is well underway at NASA Below: A return to the Moon could see a resurgence of old technology, like Moon buggies
9 Number of countries who have signed the Artemis Accords
18
NASA has announced the Artemis astronaut group, called ‘The Turtles’
8.8 MILLION Thrust in pounds of NASA’s Space Launch System
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Ian Parker
BILLION
Space science writer Ian has been writing about space since 1985. He has reported on missions from the Kennedy Space Center, French Guiana and Kazakhstan.
Price tag of Artemis in USD
250,000
Tap here to play
miles to the Moon
2
© NASA
Artemis and ILRS programs may be competitive, or merged if politics allow
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Future tech Sample return from Titan
SAMPLE RETURN FROM TITAN
1
A new NASA Institute of Advanced Concepts study is looking at the surprising advantages of a mission to Saturn’s moon e’ve launched missions across
Though not expected to have surface life, it’s
the Solar System and studied
an example of a prebiotic planetary surface, deep
be taken to Titan in the first place, but it’s with
an increasing number of diverse targets, from gas giants to asteroids.
frozen for posterity. Titan also has a subsurface water ocean, which like Europa and Enceladus
propellant supply that Titan really shines. On Mars methane must be formed out of the
But so far we’ve only brought physical samples back from the Moon and a couple of asteroids,
offers the possibility of harbouring simple life in the depths. But it’s not an easy place to reach.
atmosphere, but on Titan rocket fuel is actually falling from the sky and lying around in pools,
with a Mars sample return a long-held ambition for NASA. However, Titan has such good resource
Pioneer 11 and Voyagers 1 and 2 have performed Saturn flybys, and the Cassini orbiter spent 13
ready to be pumped into fuel tanks. For oxygen, water ice doesn’t need to be
options it may make sample return surprisingly easy for such a distant target.
years in orbit after a journey of almost seven years. Cassini also brought the Huygens lander,
carefully filtered from the soil, as it constitutes the whole planetary crust. A prospective mission
Titan is arguably the most interesting target in the Solar System. It’s the tenth-largest body and has a dense atmosphere of mostly nitrogen and methane. A similar effect that makes the surface pressure of Venus crushingly high gives this small body an atmospheric pressure just slightly greater than Earth’s, making it the only surface beyond Earth where you wouldn’t need a spacesuit. The other thing this dense, cold atmosphere enables is a surface liquid cycle, giving Titan rain, rivers, lakes and seas like we see on our home planet, but rather than water they are methane.
which touched down on Titan in January 2005. But despite the distance, Titan has a selection of attributes which could make sample return surprisingly feasible, starting with landings. This year saw NASA perform another dramatic crane landing with Perseverance. NASA is forced to employ such a complex system because Mars has a thin atmosphere. It’s enough to get in the way and generate entry heating, but not thick enough to significantly slow spacecraft down. Titan’s thick atmosphere would enable a lander to shed orbital speed through atmospheric drag and make a soft landing with a parachute.
could melt the ice with waste heat from a radioisotope thermoelectric generator before splitting it into hydrogen and oxygen, releasing the hydrogen and storing up the oxygen. On Titan oxygen and methane can even be stored as liquids without refrigeration. When it comes to launching home, potentially with samples collected by NASA’s nuclear-powered Titan quadcopter Dragonfly, the surface gravity is only 14 per cent of Earth’s, making access to space somewhat easier. It may be some time before Titan samples are coasting back to Earth, but it could be sooner than you might think.
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All this serves to reduce the mass that must
Sample return from Titan
1
Saturn
Titan is the largest moon of Saturn, and the iconic Ringed Planet will loom large – clouds permitting – in Titan’s sky.
Dense Dragonfly SampleLowSampleWater ice 2 methane 4 5 6 7 8 lakes atmosphere mission return temperature return 3 launch pad storage vehicle Titan’s unique advantage is that methane exists on Titan as water does on Earth, so there are huge reserves of liquid methane handy for filling tanks.
While methane takes the place of water on Titan, water ice takes the place of rock. The crust is formed of ice, which can be melted and split to produce oxygen.
Titan’s atmosphere is made up of nitrogen, giving the small body slightly more surface pressure than Earth. Combined with low gravity, this makes Titan good for aerobraking and parachute landings.
NASA is also working on the Dragonfly mission for Titan, a nuclearpowered drone to explore the surface. This could bring samples to a samplereturn mission.
The mission will likely consist of a lander, which will take care of the descent and resource collection before serving as the launch pad.
Titan’s lowtemperature and highpressure environment means both methane and oxygen can be stored at ambient temperatures without refrigeration.
Samples would be loaded into an aerodynamically shaped launcher to cope with Titan’s atmospheric drag, despite its low gravity.
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© Adrian Mann
7
AR SCAN HERE 25
BIO
Colonel Terry Virts
© Robert Markowitz/NASA
Former NASA astronaut Virts has spent over seven months in space on the ISS, where he captured the reality of his experience through photography. Virts has famously taken more photos from space than any other human, having taken over 300,000 spectacular images. He is also the author of the National Geographic photography book View From Above, as well as his latest book, How to Astronaut.
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Colonel Terry Virts
COLONEL TERRY VIRTS
“IT’S THE BIGGEST PROBLEM THAT WE’RE NOT WRITING ABOUT”
All About Space speaks with the former NASA astronaut about his time in space and his newfound ‘cosmic perspective’ Interviewed by Daisy Dobrijevic
What was your least favourite part of your astronaut training? Learning the Russian language was probably the hardest thing, but I loved it. I hated it and then I got over the hill and I loved it. The NBL [Neutral Buoyancy Laboratory] can be really fun and satisfying, and it can also be torture. I used to joke that it’s the torture chamber, this giant building right in Ellington Field in Houston. The pool can not be fun because the suits are so bulky. In the early days it was really awful, then towards the end when I got good at it and I knew what I was doing it got a lot better. I remember after my first run I went and talked to Rex Walheim, the senior
astronaut, and I was like, ‘Rex, this is supposed to be fun?’ He laughed and said, “Yes it sucks. It’s terrible, but eventually it gets better.” Was there anything that your rigorous training didn’t prepare you for in space? It doesn’t prepare you for the view – it’s so spectacular. Words can’t describe what it’s like to see that with your own eyes. I’ve tried. I’ve written two books and I’ve got a kid’s book coming out next year. I also directed a film called One More Orbit last year and helped make the IMAX movie A Beautiful Planet, so I’m trying to describe it and show it, but until you see it, the visual impact of looking out at Earth, it’s really amazing. Have you ever been left feeling that way with a particular view on Earth? Earth is amazing; it’s never-ending and there’s so much to see down there. A place that’s amazing is Antarctica. I had a chance to go there a few years ago, and the mountains are unlike anything I’ve ever seen. The Queen Maud Land mountains are just otherworldly. It’s like you’re on some planet in a different solar system. Tierra del Fuego in southern South America is also an amazing place. The sunset I saw there was
unbelievable. The blues and the pinks, I had never seen colours like that. I thought this can’t be real. Tierra del Fuego was pretty spectacular. There are a lot of spectacular places, but those two views just come to mind right away. Though there’s still a lot of places I need to visit. I want to do a TV show where I go and visit the places that I saw from space. Were you a keen photographer before you went into space? Yes, I was. When I was a kid my parents got me a little Konica SLR camera and I learnt photography
Right: The northern lights seen dancing above Earth from the ISS
© Colonel Terry Virts
At what moment did you decide you wanted to become an astronaut? When I was a little kid. The first book I read in kindergarten was about Apollo. Growing up I had pictures of the very first red white and blue 1974 F16, Space Shuttle Columbia and the Andromeda Galaxy. Those are the kinds of things I had all over my wall when I was a boy. When I was a kid I remember going to the Air and Space Museum and watching an IMAX movie called To Fly! and going: ‘That is amazing. I want to be a pilot and an astronaut.’ That IMAX movie really impacted me.
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INTERVIEW Left: Earth with the blue glow of the atmosphere around it Below (left): Virts snapping photos from the ISS’ Cupola observatory module
© Colonel Terry Virts
© Colonel Terry Virts
© Colonel Terry Virts
Below: A beautiful view of snowy mountains from above
on my own. In college I always had a camera around my neck. I think a lot of astronauts are like that. Some astronauts are camera people, and some are not. Everybody learns how to take pictures and everybody takes pictures in space, but some take lots like me and Don Pettit. I take pictures on Earth too. Just yesterday I was out for a walk and took some photos of some ducks. I just take pictures all the time! Have you had any close shaves in space? Yes, by far the biggest deal was halfway through our mission. On my last flight, we had an ammonia alarm go off. It turned out to be a false alarm, but it was a really big deal for a day as we thought there was an ammonia leak in the station. If there’s a real ammonia leak it actually ends up killing the space station as it’s uninhabitable, so we spent the day on a Russian segment with the hatch closed because they don’t have ammonia. We were
28
just staring at each other thinking, ‘I guess the ISS is done… we’ll hang out here for a few weeks’. By the end of the day they called the station and said, “It was a false alarm, but when you go back to the American segment wear your gas masks just in case, and take some samples just to be sure.” That was probably the biggest close shave. We went through a phase for about a month where every day the alarms were going off with some caution or warning. It was a month of constant errors, and that got kind of old to be honest. In the last year we’ve all been cooped up. Have you got any tips for dealing with isolation from your time on the ISS? A year ago I wrote 10 lessons I learned about being stuck in space. When I was in space we
coming back because they cancelled our return flight on the Soyuz until they could send our replacement crew. But they didn’t want to launch our replacement crew until they figured out why the Progress blew up, because it’s the same Soyuz rocket booster. We were stuck, and we didn’t know for how long. All of a sudden all of our work was done, so we had to add new tasks. We relocated the PMM [Leonardo Permanent Multipurpose Module], which was really fun. That was a really cool task to rearrange the space station. It was a big job too. We weren’t supposed to do that, but we did. The ten lessons I learned were: give yourself a schedule – don’t just get lazy and watch Netflix every night, which is what I’m doing now. Keep on exercising, as exercise is very important. Don’t
had three cargo ships blow up back to back to back: an Orbital Cygnus, Russian Progress and SpaceX Dragon. We didn’t know when we were
watch the news 24/7. Every day we would get together and share what we had heard on the news, but it wasn’t all day long. There’s so much
Colonel Terry Virts
was like, ‘You know what, I’ve got the rest of my life on Earth. I’m going to take advantage of this.’ I took a lot of pictures and I shot a lot of scenes for A
Beautiful Planet. Don’t worry about things you can’t control. I can’t control COVID, so it doesn’t do any good worrying about it. Just focus on what you can do. The most important thing is keep your attitude up. We had a good attitude, and we had a bet going as to when we were going to go back to Earth and when the next guys would launch. We all said ‘we’re here, we have the rest of our lives on Earth, so let’s make the most of it’. Those are a few of my top-ten ways to handle isolation. What was your favourite chapter to write in your book How to Astronaut? The survival chapter was really fun because it brought back a lot of memories. The original chapter was two or three times as long. I started remembering all of these details from when I was 17 years old at the Air Force Academy and when I was 20 years old at the French Air Force Academy. I remembered all of these things from a long time ago that I had forgotten about. It’s really fun to write that down. There’s also a chapter about the effects of carbon dioxide and the competition we had with a paper bag. We were just sitting around breathing into this paper bag, and you’re sweating, you turn purple and your heart starts racing really fast. These are carbon dioxide symptoms and you need to know them. It actually happened to me in space two times: once on the shuttle and once on the station. I got in a carbon dioxide bubble and I had all those symptoms. But it was just funny how it turned into this competition with a paper bag. How did you find writing your new book How to Astronaut differed from your picture book View From Above? I wrote View From Above right after I left NASA. I retired, had my last day and then I was home. I would set the alarm every day, and by 08:00 I was typing away on my laptop. I would write a chapter, then my brain was full. I would go to the pool and have a beer, then set my alarm. Then the next day at 08:00, I was writing again. I wrote a chapter a day and took Sunday off, and I had the whole book written within two weeks. A few years later I wrote How to Astronaut. I was travelling a lot because I was doing a lot of speeches and events for my day job. I couldn’t just set my alarm and start writing because I was always on the road. A lot of that book was written on aeroplanes. I found them to be a great place to write because you’re just stuck for a couple of hours, so I would just get my laptop out and start
writing. Half of How to Astronaut or more was actually written on aeroplanes. I was so happy about that book because I had two goals with it. I wanted people to laugh and
seeing things that are really old, you know, billions of years old. Space photography has changed everything. People like you and me just grew up with it, like
say wow! Whenever I’ve taken part in an interview
that was normal. One of the pictures I had when I
about the book, everybody has had that reaction, so I’m really happy about that.
was younger was from Viking, which was the first American lander on Mars. 100 years ago we barely
Would you say you’ve gained a new perspective
had aeroplanes, so it’s amazing how quickly our perspectives have changed.
of Earth after being in space? I think so, yes. People ask, ‘How did you change?’
Do you think space has commercialised now it
I’ve thought about this, and I think the way it changed me is I’m less of a black-and-white person.
seems that everyone is having a go? The problem is that everyone’s having a go, and
The older you get, the more wisdom you have. You
there are too many satellites being launched into
think that there’s probably two sides to everything, and you really should look at the data before you
orbit. Many of them are never going to come back down, so they’re there permanently as debris.
come to a conclusion. A short film that we made last year was called
It may be fine for the next few years, but a century from now and ten centuries from now
Cosmic Perspective. It was about how space photography has changed humanity. We used to be stuck on Earth. Everything was two dimensional, everything was north, south, east and west, right? Then once we started flying, all of a sudden there was this third dimension. Now that we have Hubble and these telescopes that are really looking in four dimensions, they’re not only seeing things that are far away, they’re
they’re still going to be in orbit. Talk about leaving climate change, we’re leaving the space environmental problem for generations to come, and I don’t think that’s cool. I think that’s something that needs to be addressed, and no one’s talking about it. It’s a problem for astronomers, it’s a problem for humanity. It’s the biggest problem that we’re not writing about.
The most important thing is keep your attitude up
Right: Virts floating above Earth on one of his three extravehicular activities
© Colonel Terry Virts
bad news right now, and so you have to moderate the news intake. Do something creative. For me, I
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© Tobias Roetsch
Rogue planets
30
Rogue planets
WORLDS Astronomers are still on the hunt for rogue planets, but what can they tell us about the layout of our cosmos? Reported by Colin Stuart
W
hen we think about planets, a star usually comes as part of the
package. After all, where would Earth be without the Sun? Imagine Luke Skywalker’s home planet of Tatooine without its twin suns, or Superman without Rao, the red supergiant around which Krypton spun. Yet you’d be wrong to imagine that planets are never starless. Astronomers have already found swarms of rogue planets – worlds wandering the open chasm of space alone. As far as we know, planets always start off with stars. They are the leftover fragments from star formation, the offcuts that you’d throw away in a skip if you were building a house. A cloud of gas and dust that was otherwise minding its own business may begin to contract if it’s hit by a shock wave from an exploding star. As the cloud compresses, gravity takes over and bundles it into an ever-smaller space until fledgling stars ignite inside. The shrinking cloud begins to spin faster and faster, flinging leftover gas and dust into discs around new stars. Gravity continues its work here, too. Dust grains merge into lumps the size of golf balls, which continue to snowball until they reach a kilometre or so across. Astronomers call these planetary building blocks planetesimals. Close to the star they are made of metals – the only materials with high enough melting points to stay solid in the face of the inferno. Further out – beyond an imaginary
boundary called the ice line – temperatures plummet below freezing and the planetesimals take the form of frigid lumps of water, ammonia and methane ices. That’s why we have rocky planets close to the Sun and ice giants the furthest out. Looking at the Solar System today, it seems a somewhat serene place. Yet this relative calmness belies the cataclysmic pinball machine that it used to be. Jupiter formed further from the Sun before migrating inwards, scattering many of the asteroids like a flock of pigeons. Uranus and Neptune moved outwards, and may
How to find a rogue planet Gravitational microlensing Microlensing is the distortion and magnification of a star’s light when another object passes in front of it and bends the path of light passing near it through gravity. It’s been successfully used to find exoplanets orbiting other stars, but can also be used to detect interstellar planets, allowing astronomers to estimate how common they are. Microlensing events by interstellar planets tend to be one-offs, so it’s hard to learn much about the planets themselves.
Microlensing at work Orbiting planet
Distant starlight
Distorted light
Magnified image
Direct imaging The direct detection of interstellar planets relies on long-exposure surveys of large areas of the sky looking for brown dwarfs and other faint objects. Infrared surveys are particularly useful, since many of these objects emit more radiation as heat than they do as light. Surveys often target areas of recent star formation, where objects are likely to be at their youngest, and therefore hottest and brightest.
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as bi To h sc et Ro
Solar System started off in a different configuration before evolving into the set-up we see today. Crucially, when planetary scientists run
Are rogue planets ideal for life? Pretty much all life on Earth is dependent on the Sun to survive, so it might seem strange to imagine life thriving on planets lost in the interstellar darkness. But researchers say we shouldn’t write off rogue planets. As early as 1999, David J. Stevenson of the California Institute of Technology argued that even small rogue planets expelled from their solar systems could sustain a hydrogen-rich atmosphere and a warm surface for long enough for life to evolve, thanks to the radiation of energy left over from their formation. This idea is clearly confirmed by the discovery of gas giants like PSO J318.5-22, which pumps out enough energy to vaporise iron. Of course, any life that evolved in the hot atmosphere of a rogue gas giant would be very different from what we see on Earth – conditions might prevent life from gaining a foothold at all, and would almost certainly stop it at the level of bacteria-like organisms that could float among the clouds. But more solid Earth-like worlds with geological activity driven by escaping heat could also have the potential to sustain life on or beneath their surfaces, perhaps similar to the bacteria associated with ‘hot rocks’ and subterranean water channels on Earth. With photosynthesis out of the question due to a lack of sunlight, the ‘primary producers’ at the base of any alien food chain would have to find another chemical means of generating energy, perhaps by consuming carbon from the rock itself. Perhaps the most promising home for life in interstellar space, however, would not be on a rogue planet itself, but on its moons. Here tidal forces might create an environment similar to those seen on several moons in our own Solar System, with a deep ocean of liquid water, heated from below by volcanic activity and shielded from space by a solid, icy crust. Such an interstellar ocean could offer hospitable conditions for the development of fairly advanced aquatic life forms.
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computer simulations of the Solar System’s evolution, they recreate the modern planetary set-up more often when they include a fifth giant planet from the outset. There’s more evidence for
planets trekking through the void. Though given
extra planets, too. We already think, for example, that a Mars-sized planet called Theia careened
their relatively small size, considerable distance from us and the fact they are not illuminated by a
into the Earth just after our planet formed. The resulting surge of debris into space eventually
star, it’s a wonder we’ve been able to spot them at all. It’s only possible thanks to a clever technique
coalesced to form the Moon.
called gravitational microlensing. We often think of gravity as a pull – that the
But if there really was a fifth giant planet patrolling the Solar System where did it go? After all, there are clearly only four giant planets now. Astronomers conveniently say that it was discarded in a gravitational tussle with its siblings, or perhaps picked off by the gravitational pull of a star that buzzed close by. Maybe it ended up marooned in the darkest depths of the Solar
Below: Another planet slammed into Earth when it was young, an event thought to have formed the Moon
to have lost one from our own Solar System bolsters the argument. Stars could also lose their gravitational grip on outer planets as they die. The Sun will one day become a red giant and lose mass as it sheds its outer layers. This could cut the invisible tether to Neptune, irretrievably sending it out into the universe like a child accidentally letting go of a helium balloon. It’s therefore no surprise that there are vagrant
System. That would certainly fit with recent ideas about a so-called Planet Nine lurking far beyond Pluto, the dwarf planet that we used to regard as the ninth planet. Yet it could have been ejected from the Solar System entirely. It’s a notion that once may have seemed far-fetched, but is gaining significant ground. After all, we’ve recently seen jettisoned visitors from other solar systems in the form of ‘Oumuamua and Comet Borisov. While it would take considerably more force to orphan an entire planet, the fact that we seem
Sun pulls on the Earth, and that’s why we orbit around it. It’s certainly the way Isaac Newton thought about gravity. Yet over a century ago Albert Einstein replaced this simple notion with the idea that gravity is the result of curved space. A heavy object like the Sun warps the fabric of space around it, creating a divot in the universe that astronomers call a gravitational well. Earth is caught in this cosmic trap, which is why we’re stuck in orbit around the Sun. Any light travelling across the universe will be forced to alter its path if it encounters the curved space around a local heavy object. Rays of light are bent around it, just as a lens in a telescope bends light. The result is the same: the light gets magnified. If an otherwise-invisible rogue planet passes in front of a distant light source, we can tell it’s there by the way it temporarily amplifies that background light.
© Tobias Roetsch
©
have even swapped order. At least that’s according to the Nice model, which is named after the city in France where it was devised. It says that the
Rogue planets
How rogue worlds are made
Astronomers have put forward a variety of theories to explain how planets could end up drifting through interstellar space
Not all planetary systems are as neatly ordered as our own, and they all evolve over time. If a Jupiter-mass planet had a close encounter with a neighbour, the smaller planet could find itself ejected from orbit around its star.
3
They’re thrown out by a collision with a star or black hole
Close encounters and collisions of stars and stellar remnants, such as black holes, are inevitable over astronomical timescales, happening often in the densely packed clusters where stars are born. Even if the stars survive the encounter, the orbits of their planets would likely be disrupted.
2
They’re ejected by a supernova explosion
4
They form alone from a disc of dust and gas
When the most massive stars reach the end of their lives, a spectacular explosion sheds most of their mass and drastically reduces their gravity, potentially cutting loose any orbiting planets to fly off into interstellar space.
Computer models and observations both show that planet-like objects with more mass than Jupiter, but less mass than a brown dwarf, can form independently out of knots of gas and dust in the same stellar nurseries as stars. Perhaps some rogue planets never had a host at all.
“Jupiter formed further from the Sun before migrating inwards, scattering many of the asteroids”
© Tobias Roetsch
1
They’re kicked out of their system in a planetary collision
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Rogue planets
Wandering worlds we’ve found so far OTS 44
Distance away: 529 light years
Distance away: 7.27 light years
Distance away: 80 light years
Distance away: 130 light years
Distance away: 554 light years
Discovery method: Direct observation
Discovery method: Direct observation
Discovery method: Direct observation
Discovery method: Direct observation
Discovery method: Direct observation
Constellation: Chamaeleon
Constellation: Hydra
Constellation: Capricornus
Constellation: Aquarius
Constellation: Chamaeleon
Discovered in 2004, Cha 110913-773444 has the mass of about eight Jupiters, making it a candidate interstellar planet. Infrared observations show that it is surrounded by a faint disc of planet-forming material – perhaps moons in formation?
Discovered in 2014 using the Wide-field Infrared Survey Explorer, this small object is a little over seven light years away. With a low surface temperature, it’s either a cold, low-mass brown dwarf or an interstellar planet on our cosmic doorstep.
PSO J318.5-22 is the best studied rogue planet so far, with a tightly constrained mass and age that indicates it’s undoubtedly a planet rather than a brown dwarf. It is about 80 light years away and was discovered in 2013.
CFBDSIR 2149-0403 seems to be part of the AB Doradus Moving Group, a group of stars 50 to 120 million years old. With a surface temperature of 430 degrees Celsius (806 degrees Fahrenheit), its mass is likely four to seven Jupiters.
This faint, young object has a mass between 6 and 17 Jupiters, putting it on the boundary between brown dwarf and planet. Excessive infrared radiation from its surroundings suggests it’s shrouded by a disc of planetforming material.
© NASA © NASA
© Michael Osadciw/University of Rochester
© NASA
© MPIA
CFBDSIR 2149-0403
© ESO
PSO J318.5-22
© MPIA
WISE 0855-0714
© NASA/JPL-Caltech
Cha 110913-773444
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Left: A star passing close to another solar system could rip out a rogue planet Bottom left: Planetarymass lenses could also be miniature black holes instead of rogue planets
The technique does have its drawbacks, however. The alignment between the rogue planet – the lens – and the background light source is always temporary and fleeting. It typically lasts between a few hours and a few days. After that we’re never going to see it again, and so we only have that single measurement to go on. Fortunately, the duration of the event does tell us something important: mass. The lighter the lens, the shorter the magnification spike lasts. It’s been over ten years since Japanese scientists used the Optical Gravitational Lensing Experiment (OGLE) to find rogue planets. They observed 50 million stars in the Milky Way and found just 474 microlensing events. Only ten turned out to be consistent with objects with planetary masses. But just because an object has the same mass as a planet doesn’t make it a planet – it could be a miniature black hole with the same mass. More plausibly it could be a failed star called a brown dwarf. They start off with a mass considerably
Once you get down to objects with masses more similar to Earth’s, it’s harder to argue that they aren’t rogue planets. In September 2020, for example, astronomers announced the discovery of the smallest ever rogue planet candidate – one with a mass roughly equal to Earth. We may even have found rogue planets in other galaxies. In 2018 astronomers at the University of Oklahoma looked at a galaxy that was lensing light from the distant quasar RX J1131-1231. Irregularities suggested the presence of an enormous number of objects with masses between the Moon’s and Jupiter’s. The total number of such objects in that galaxy could top 1 trillion. While some could be black holes or brown dwarfs, it’s likely that a significant proportion are rogue planets. Even in our own galaxy there could be as many as 50 billion starless planets, according to a 2019 study that looked into how frequently worlds get kicked out of their home solar systems. That’s why finding rogue planets is about more than
higher than Jupiter’s, but could cool and shrink.
just collecting cosmic curiosities. Working out the
© NASA
Rogue planets
What if a rogue planet entered our Solar System? If a new Jupiter-mass world wandered through the plane of the planets, the results could be catastrophic
1 is an important part of understanding how solar systems form and evolve. Soon there will be a step change in our ability to complete this celestial survey. In 2025, NASA plans to launch the Nancy Grace Roman Space Telescope.
The outer ice giants might be most vulnerable to having their orbits disrupted, perhaps drifting away into interstellar space or falling into orbit around the rogue visitor.
Above: The Roman telescope, due for launch in 2025, will search for rogue planets
When Roman reaches space, it will carry with it a mirror 2.4 metres (7.9 feet) in diameter, equal in size to the Hubble Space Telescope’s. However, it will have a field of view much greater than its cousin, allowing it to observe an area one hundred times wider than Hubble can. Roman is designed for many purposes, including helping to decipher the twin puzzles of dark matter and dark energy – the mysterious entities that bind a galaxy together and push galaxies apart respectively. Yet it will also be able to use microlensing to search for rogue planets – or freefloating planetary-mass objects, to give them their full name. Roman is sensitive enough to discover rogue planets that range in mass from Mars, at ten per cent of Earth’s mass, all the way up to 100 Earth masses. In doing so it will provide an estimate of the number of rogue planets in the Milky Way that is ten times more accurate than the data we currently have. Only then will we have the tools to understand how our Solar System came to look the way it does, telling us something important about what kinds of planetary systems to search for if we want to find other life-supporting planets in this vast and complicated universe.
2 Earth
If Earth’s orbit became more elliptical, it would present a severe danger to life. Sunlight reaching the surface would become more variable, and seasons more extreme.
3 Mercury
4 Venus
Mercury’s orbit is tightly bound by solar gravity. It would likely survive more or less unchanged.
Venus might find its almost perfectly circular orbit disrupted into an ellipse. This could upset its slow rotation period.
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Asteroid Belt
The countless small bodies orbiting between Mars and Jupiter would undoubtedly be disrupted. Some might even be thrown out of the Solar System entirely.
Colin Stuart
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Science and technology journalist Colin holds a degree in astrophysics, has written over 17 books on space and has an asteroid named in his honour: 15347 Colinstuart.
“Working out the ratio of vagabond worlds to stars in the Milky Way is an important part of understanding how solar systems form”
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Mars
If the orbit of Mars was nudged closer to the Sun, surprisingly Mars might become more hospitable as its ice caps melted and its atmosphere thickened.
Jupiter
Jupiter’s gravity would draw in many of the comets falling in from the edge of the Solar System.
8 Saturn
Saturn‘s ring system might not withstand the disruption of the rogue planet’s gravity.
© Tobias Roetsch
ratio of vagabond worlds to stars in the Milky Way
Uranus and Neptune
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