The star system of Trappist-1 is home to the largest group of Earth-like planets ever discovered elsewhere in the Universe by astronomers. This means that investigating these seven rocky worlds gives us a good idea of how common exoplanets with similar compositions to our own are in the Milky Way and the wider cosmos.
New research has revealed that these planets, which orbit the Trappist-1 star 40 light-years away from Earth, all have remarkably similar compositions and densities. Yet, all are less dense than Earth.
The results could indicate these are worlds with much more water than is found on earth, or possibly even that these planets are composed almost entirely of rust.
This similarity between the exoplanets makes the Trappist-1 system significantly different from our own solar system which consists of planets with radically compositions and densities. Trappist-1’s worlds are dense, meaning they are like the rocky planets in our solar system, Earth, Mars, Venus, and Mercury. The system seems to be lacking larger gas dominated planets like Jupiter, Saturn, Uranus and Neptune.
The finding, documented in a paper published in the Planetary science Journal shows how the system, first discovered in 2016, offers insight into the wide variety of planetary systems that could fill the Universe.
“The new observations allowed us to use transit data from a much longer time span than was available to us for the 2018 calculations,” explains Simon Grimm of the University of Bern, who as well as being involved in the current study, was part of a 2018 team that provided the most accurate calculation of the masses of the seven planets thus far. “With the new data, we were able to refine the mass and density determinations of all seven planets.
“It turned out that the derived densities of the planets are even more similar than we had previously expected.”
Seven Exoplanets with Similar Densities
The similarity in densities observed in the Trappist-1 exoplanets seen by the astronomers hailing from the Universities of Bern, Geneva and Zurich, indicates that there is a good chance they are composed of the same materials at similar ratios.
These are the same materials that we believe form most terrestrial planets, iron, oxygen, magnesium, and silicon. But there is a significant difference between our terrestrial world and the Trappist-1 exoplanets.
The planets in the Trappist-1 system appear to be about 8% less dense than the Earth. This suggests that the materials that comprise them exist in different ratios than they do throughout our home planet.
This difference in density could be the result of several different factors.
One of the possibilities being investigated by the team is that the surfaces of the Trappist-1 exoplanets could be covered with water, reducing their overall density. Combining the planetary interior models with the planetary atmosphere models, the team was able to evaluate the water content of the seven TRAPPIST-1 planets with what Martin Turbet, an astrophysicist at the University of Geneva and co-author of the study describes as “a precision literally unprecedented for this category of planets.”
For the Trappist-1 system’s four outermost planets, should water account for the difference in density, the team has estimated that water would account for 5% of their overall masses. This is considerably more than the 0.1% of Earth’s total mass made up of water.
Rust Nevers Sleeps for the Trappist-1 Planets
Another possibility that could explain why the Trappist-1 exoplanets have lower densities than Earth is the fact that they could be composed of less iron than our planet is–21% rather than the 32% found in the Earth.
It’s also possible that the iron within the seven exoplanets could be bonded with oxygen forming iron oxides–commonly known as rust. This additional oxygen would reduce the planet’s densities.
Iron oxides give Mars its rust-red colour, but they are pretty much confined to its surface. Its core is comprised of non-oxidized iron like the solar system’s other terrestrial planets. If iron-oxide accounts for the seven exoplanet’s lower densities it implies that these worlds are rusty throughout and lacking solid non-oxidized iron cores.
“The lower density might be caused by a combination of the two scenarios – less iron overall than and some oxidized iron,” explains Eric Angol, an astrophysicist at the University of Washington and lead author of the new study. “They might contain less iron than Earth and some oxidized iron like Mars.”
Angol also points out that the Trappist-1 planets are likely to have a low-water content, an idea supported by previous research. “Our internal and atmospheric structure models show that the three inner planets of the TRAPPIST-1 system are likely to be waterless and that the four outer planets have no more than a few per cent water, possibly in liquid form, on their surfaces,” says Turbet.
This seems to favour the theory that the lower density of the Trappist-1 planets is a result of one or both of the iron scenarios suggested by the researchers.
There’s Still a Lot to Learn from Trappist-1
Since its discovery in 2o16, the Trappist system has been the subject of a wealth of observations made by both space and ground-based telescopes alike. Before it was decommissioned at the start of January 2020 the team used the Spitzer Space Telescope to collect their data. This telescope, operated by NASA’s Jet Propulsion Laboratory, alone has clocked in more than 1,000 hours of targeted observations of the exoplanets.
This new study demonstrated the importance of studying systems such as Trappist-1 for extended periods of time.
Caroline Dorn, an astrophysicist at the University of Zurich also highlights the fact that studying systems like this could answer questions about the habitability of exoplanets and the possibility of life elsewhere in the Universe.
“The TRAPPIST-1 system is fascinating because around this one star we can learn about the diversity of rocky planets within a single system,” concludes Dorn. “And we can actually learn more about an individual planet by studying its neighbours as well, so this system is perfect for that.”
“The night sky is full of planets, and it’s only been within the last 30 years that we’ve been able to start unravelling their mysteries, also for determining the habitability of these planets.”
Agol. E., Dorn. C., Grimm. S. L., et al, ‘Refining the transit timing and photometric analysis of TRAPPIST-1: Masses, radii, densities, dynamics, and ephemerides,’ Planetary Science Journal, [https://arxiv.org/abs/2010.01074]
We have all, at some point, stared at the stars and dreamed lazily of other worlds, but, fortunately, for many of us, dreaming alone was not enough. These people set about building a toolkit stocked with instruments and techniques to find planets outside our solar system — exoplanets. In turn, these tools help us better understand our place in the Universe.
In October the Nobel Committee awarded the 2019 Nobel Prize in Physics to Michel Mayor, Professor at the Observatory of the Faculty of Science of the University of Geneva (UNIGE), Switzerland, and his doctoral student Didier Queloz for their discovery of 51 Pegasi b in 1995 — which marked the first discovery of an exoplanet orbiting a Sun-like star. The award marked the first time that exoplanet research has scooped what is, arguably, the most prestigious prize in science. Quite fitting as even though 51 Pegasi b was not the first exoplanet to be discovered — that honour goes to Astronomers Aleksander Wolszczan and Dale Frail who discovered an exoplanet around a neutron star in 1992 — it was Mayor and Queloz’s breakthrough that really spurred on the science of exoplanet investigation.
As extraordinary as it sounds, before the 1990s, it wasn’t entirely certain that other stars actually possessed planets of their own. Whilst there was technically no reason to suspect that the solar system was unique, the 1980s had proved a frustrating time for exoplanet hunters. By the turn of that decade, many potential candidates had come and gone evading positive confirmation.
Despite early setbacks, since 1995, the catalogue of exoplanets has soared, with over 4,000 examples now in NASA’s catalogue. And with technology only improving, that collection is set to soar. This animation and sonification from SystemSounds is a stunning representation of how the field has exploded since the 1990s. Created by SYSTEM Sounds (Matt Russo, Andrew Santaguida)
We are becoming so confident in the discovery of exoplanets, that we are now turning our attention to much more detailed examinations of previously discovered examples. For example, many researchers are now focusing on the investigation of exoplanet atmospheres, attempting to discover if they contain traces of chemicals such as carbon monoxide and other organic and complex molecules, and, of course, water. Should these elements be observed it constitutes a clue, a tiny hint, that life may not be unique to our planet.
Thus far, searches for exoplanets have been more effective in finding gas giants, planets similar to Jupiter. But new advances such as the James Webb Space Telescope and the Extremely Large Telescope have researchers salivating at the idea of finding and examining smaller, rocky planets. Planets just like Earth. And of course, the discovery of the Trappist-1 system — containing seven Earth-like rocky planets, three in the so-called ‘habitable zone’ capable of harbouring liquid water — has shown that these planets are definitely out there waiting for us to find them.
As such, exoplanet research stands on the cusp of providing an answer to the question we have all pondered at some point whilst staring at the stars, are we alone in the universe?
Of course, the fact that it took so many years of fruitless searching to begin to successfully spot exoplanets illustrates, these blighters are extremely difficult to observe. This means that astronomers have had to develop extremely precise and sensitive methods of exoplanet detection. These techniques are numerous, each with its own strengths and weaknesses.
It goes without saying that before we spotted the first exoplanet, our experience of observing other planets was restricted to our neighbours in the solar system. This was done exclusively through direct imaging, but this technique becomes much more difficult as the distance to an object increases.
The hindrances imposed on direct imaging increase exponentially when we consider the effect of attempting to spot a dim object next to a much bright one — exactly the scenario faced when attempting to spot a distant planet orbiting its parent star. But, this proximity to an extremely bright object is not always a hindrance to exoplanet detection. In fact, many methods of spotting these planets absolutely depend on it. If a dim object can have an effect of the extremely bright object — then the ability to observe this bright object is a benefit.
This interference arises from the fact that stars with planets orbiting them demonstrate a ‘wobble’ in their motion. This arises from the fact, that despite common belief, planets don’t actually orbit stars. In fact, planets and stars orbit a mutual centre of mass— or barycentre —its location based on the masses of the planets and stars involved. As the usual set-up of a planetary system involves a star that is tremendously more massive than its planets, this mutual point of orbit is usually closer to the star centre of mass — often within the star’s surface.
This huge disparity in mass means that this ‘wobble’ is tiny. As an example, consider our own solar system. As the Sun constitutes more than 99.9% of the total mass of the solar system, the barycentre for our planetary system is located very close to our star’s centre of mass. The most significant gravitational influence on the Sun arises as a result of the solar system’s most mass planet — Jupiter.
Let’s imagine, for simplicity’s sake, that Jupiter is the only planet orbiting the Sun. An observer viewing this reduced solar system and Jupiter’s 12-year orbit from the nearest planetary system — Alpha Centauri, 4.4 light-years away — would see the Sun as a mere point of light. The shift in its position caused by Jupiter would be just 3.7 milliarcseconds. To put this shift into perspective, consider that one pixel in an image from the Advanced Camera for Surveys aboard the Hubble Space Telescope represents 50 milliarcseconds — one pixel! Thus you can see, this ‘wobble’ caused by Jupiter is a tiny, barely perceptible amount of movement, less than 1/10 of a pixel from the nearest star!
Two further things to consider in this hypothetical situation, Jupiter is the most massive planet in the solar system, the wobble caused by Earth viewed from the same position would be smaller by a factor of at least 300. Also, many of the exoplanets that we are attempting to spot are much further afield than 4.4 light-years. That means that any method using this wobble must be incredibly sensitive and precise. Incredibly, despite this tiny effect, the wobble has spawned several methods of exoplanet detection.
One of these methods is astrometry — very effective for detailing high-mass planets in wide orbits around relatively low-mass stars, and thus not well suited to tracking down Earth-like, rocky planets. For an indirect observation method, astrometry is pretty good at pinning down characteristics like mass, and orbital period, shape and width. Unfortunately, it isn’t great at actually identifying planets.
Thankfully there are other indirect techniques that have helped astronomers help find exoplanets — one of which combines a star’s ‘wobble’ with a phenomenon familiar to drivers and pedestrians everywhere.
Sirens, soundwaves and stars. The Doppler Wobble
I’m sure everyone reading this has been in a situation in which an ambulance with sirens blaring has raced towards them, passed their position and continued on its journey. You’ll have likely noticed that as the vehicle approaches the sound of its siren is higher pitched, switching to a lower pitch as it moves away.
This is because as the soundwaves are emitted by the approaching ambulance they are compressed and shorter wavelength sound waves mean a higher-pitched sound. As the siren recedes, the soundwaves are stretched out — resulting in a lower pitch.
This is the Doppler effect, and the key thing for astronomers is, it applies to any kind of wave emitted by a moving object — even light which propagates as a wave. Just as the wavelengths of soundwaves correspond to different pitches, the wavelengths of light correspond to different colours. Longer wavelengths producing a reddening, shorter wavelengths produce bluer light. This is referred to as redshift and blueshift— a crucial phenomenon in astronomy.
Instead of an ambulance, let’s think about a star moving towards us, as the light waves emitted are compressed — causing the light signature of the star to be shifted towards the blue end of the spectrum. As the star moves away, the light is stretched out again — shifting the light signature towards the red end of the electromagnetic spectrum.
If this is the case, why do the lights atop the ambulance as it recedes not appear redder than they were on their approach? This is because the amount of red and blue shift is determined by an object’s speed divided by the speed of light c. As c is so large, an object would have to be moving at tremendous speeds to result in a significant enough change in colour for us to notice.
You might be wondering how exactly scientists can tell that a star’s signature has shifted towards either end of the electromagnetic spectrum. This is because stars don’t emit light in a constant ‘smear’ across the spectrum. There are notable dark bars where light is not emitted — referred to as the absorption spectrum. It is by tracing the shift of these bars that researchers can see if a star is wobbling and by how much, thus inferring the presence of exoplanets.
Of course, you may well have noticed a flaw with this technique. It’s only useful in detecting exoplanets that are causing their star to wobble towards and away from Earth. This gives rise to the method’s alternative name — the radial-velocity method. In addition to this blind-spot in glimpsing planets moving perpendicular to Earth, the Doppler-wobble technique can also only tell us what a planet’s minimum mass is.
But, knowledge of the light signature of a star gives rise to another tool in the exoplanet hunter’s arsenal, one which depends on planets crossing — or transiting — their parent star. The photometry technique.
Don’t cross me!
The photometry technique measures the dip in brightness of a star caused as a planet crosses in front of it, thus allowing us to infer the presence of an exoplanet and even collect details about a few of its characteristics. The method clearly requires searching for rare eclipse events where a planet blocks some of its parent star’s light.
You may be unsurprised to learn that like the other methods detailed above, the photometry technique has to be incredibly sensitive. In this case, that is because the disparity in size between a star and a planet orbiting it is so huge in the star’s favour that the light obscured by this transit is minuscule.
To illustrate this, take a look at this image of Mercury transiting the Sun seen from within the solar system.
This speck, highlighted below, is Mercury. Now imagining the tiny fraction of light this would have obscured. When you’ve done that, imagine viewing this scene from millions of light-years away!
Returning to the example of Jupiter, the largest planet in our solar system, when it transits the Sun it blocks just 1% of the star’s light — making the Sun appear 1% fainter for a period of 12 hours. As small as it is, in comparison to the phenomena exploited by the two methods above this effect is massive.
And again, like its fellow methods of exoplanet detection, the photometric technique has significant limitations that define the situations in which it can be employed. Many planets don’t transit their parent stars and those that do have to be orientated ‘just right’ for the photometry method to work. Also, transits that do occur are incredibly brief, so it takes a lot of good fortune to catch one. That means that the vast majority of exoplanets that we believe exist out there in the depths of space can’t be spotted by this method.
The Earth’s atmosphere and the ‘twinkling effect’ it has on stars is also a major hindrance to the photometry method. This results in its reliance on space-based telescopes. By taking the atmosphere out of the equation, it is possible to not just improve the precision of our measurements but also allows for the continuous monitoring of a star’s brightness without the agony of something as mundane as a rainy-day ruining data.
The future of exoplanet research is extremely bright
With all the limits and drawbacks I’ve listed it may seem like searching for exoplanets is something of a hopeless task, like searching for a needle in a haystack. Except there are 100 billion ‘haystacks’ or stars outside of our analogy in each galaxy. Clearly its a tribute to our advances in science that we have found 4000 or so ‘needles’ thus far.
The astrometry technique, the first tool we examined in the exoplanet hunter’s toolkit isn’t particularly useful, but the second, the doppler technique has been a real boon. It kickstarted exoplanet-hunting as a viable scientific field in the ’90s and provided the majority of discoveries right up into the 2000s. Despite this, its the transit technique — photometry — the last piece of equipment that we turned over, that holds the most promise for the future.
It was a slow starter for sure, reaching maturity much later than the previous two methods mentioned. But, as the use of automated and space-based telescopes has become more prevalent, the ability to keep thousands of stars under constant observation is making the photometry technique the exoplanet-hunting tool that promises to push the boundaries of our understanding of planets elsewhere in the universe.
As our catalogue of exoplanets expands, researchers also now begin to look beyond just spotting these other worlds. The CHEOPS telescope will launch this week (17/12/19) with its mission to spot exoplanets close-by that warrant further investigation. And it is the James Webb Space Telescope, launching in 2021, that will really delve into these selected planets.
Researchers will then use some of the methods I’ve listed above to examine the atmospheres of these planets, a ‘deep-dive’ that would have seemed like little more than a pipe-dream in 1995 when Michel Mayor and Didier Queloz spotted 51 Pegasi b.
Exoplanet research, in many ways, represents one of the ultimate expressions of the drive to perform science. For its pioneers, the men and women that stocked our toolkit, it simply wasn’t enough to lie back staring at the stars, dreaming of other worlds.
Exoplanet researcher Ignas Snellen — a professor in astronomy at the University of Leiden in the Netherlands — has collected the 2019 Hans Sigrist prize for his innovative work in the field of exoplanet research. The award of the prize to Snellen comes at the conclusion of a year which also marked the Nobel Committee’s recognition of the first observation of an exoplanet orbiting a Sun-like star, awarding its discoverers Michel Mayor and Didier Queloz the 2019 Nobel Prize in Physics.
The message from the scientific community seems to be clear, exoplanet research is a field to watch. With the launch of the CHEOPS satellite, later this month and the James Webb Space Telescope set to launch in 2021, applied science is finally catching up to aspirations held by astronomers for decades–the discovery of more and more diverse worlds outside our solar system.
In addition to this, the tantalizing possibility of catching a fleeting glimpse of a clue that we are not alone in the universe seems closer than ever to realization.
But as Snellen explains, things could have been very different for him, falling into exoplanet research was something of a happy accident: “I was doing very different research, working with galaxies,” he says. “I didn’t really know where my research was going. That’s when I was asked to present a workshop on extrasolar planets.”
Despite the serendipity at play, Snellen says he recognised the potential growth for the young field almost immediately. “I thought ‘wow, what an amazing field!'”
And Snellen’s decision to pursue exoplanet research relates indirectly to Nobel prize winners Mayor and Queloz. “This was in 2001, so exoplanet research was still in its infancy, but the first transiting exoplanet had been discovered as well as a few others.”
Despite the fact that only a handful of exoplanets had been discovered when Snellen began his research in the field less than two decades ago, NASA’s catalog of extrasolar planets now numbers in excess of 4,000. Clearly, this is a stunning illustration of just how rapidly the field has advanced in this relatively short period of time.
Snellen’s work focuses on assessing the atmospheric composition of exoplanets. This possible to do when a planet passes in front of–or ‘transits’– its parent star. The planet’s atmosphere absorbs light from the star at certain wavelengths. As chemical elements absorb and emit light at certain frequencies, the resulting light spectrum forms a distinct ‘fingerprint’ by which they can be identified.
This method of transit spectroscopy holds great promise in terms of identifying potential ‘biomarkers’ such as molecular oxygen, water and carbon monoxide.
As the Hans Sigrist Prize is specifically designated to recognize scientists in the midst of their careers rather than acting as a ‘lifetime achievement’ type award, it is only fitting that its recipient should very clearly have their eyes on future goals. And, fortunately, the future is bright for exoplanet research.
The ESO’s CHEOPS telescope launches on 17th December with its mission to identify nearby, small rocky exoplanets. Snedden points out the mission’s role as an important first step in the exoplanet research, helping select targets for researchers to further investigate.
But the two projects that Snellen is most excited for and the launch of the James Webb Telescope in 2021 and the completion of the aptly named 39-meter diameter Extremely Large Telescope (ELT) scheduled for completion in 2025.
“At the moment we can only observe the atmospheres of large Jupiter-like gas giants,” he explains. “The James Webb will finally allow us to start examining the atmospheres of smaller, rocky, more Earth-like exoplanets.”
These planets will still differ quite a bit from Earth, elaborates Snellen, explaining that they will, for example, be much hotter than our planet. “The exciting thing is, we don’t yet know if these small rocky planets can actually hold an atmosphere,” Snellen says.
The researcher concludes by pointing out that the seven Earth-like planets of the Trappist-1 system are very likely the first targets for further investigation. An exciting prospect, given that at least three of these planets are believed to exist in that system’s ‘habitable zone’–an area where water can exist as a liquid, a key ingredient for life.
One of the most promising prospects for discovering liquid water in the Trappist-1 system is Trappist-1e, an exoplanet that is slightly denser than Earth. As liquid water requires a temperature that is not too hot and not too cold, and also a certain amount of pressure–the fact that Trappist-1e receives roughly the same amount of radiation from its star as Earth and its gravitational influence exerts a similar pressure, it seems a safe bet to predict liquid water will be found there.
Of course, the concept of discovering liquid water amongst the stars and drawing comparisons to Earth leads, inevitably to the question could any of these planets also host life?
Snellen urges caution, remarking that even if these biomarkers are found, it is still a long way from confirming the ‘Holy Grail’ of exoplanet research: the presence of extraterrestrial life.
“It would be a major clue,” Snellen points out. “But it’s too simple to say ‘OK we have molecular oxygen, this is a sign of life.’ As molecular oxygen is difficult to detect though, by the time we can identify it, we should also be able to see lots of other gases.”
The Hans Sigrist Prize was established in 1994 to recognise mid-career scientists who still have a significant time left in their careers to make further major contributions to their field. Thus far, two of the previous recipients have gone on to become Nobel Prize Laureates later in their careers.
In connection with the prize, Snellen will receive 100,000 CHF–around $100,000–to help further his research. Accepting his prize, Snellen first thanked the team of researchers that have supported him in his research over the past decade.
The solar system with seven potentially habitable planets is much older than our own.
This illustration shows what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Credits: NASA/JPL-Caltech
TRAPPIST-1, with the much less attractive technical name 2MASS J23062928-0502285, is an ultra-cool brown dwarf just slightly larger than Jupiter. Despite its small size and low temperature, it’s one of the most interesting stars we’ve discovered out there. In February this year, NASA announced the discovery of seven Earth-sized planets around the star, all in the habitable zone — the so-called Goldilocks area where it’s just the right temperature for liquid water to exist. To make things even more exciting, this solar system is a ‘mere’ 40 light years away. It’s far enough to be inaccessible for the foreseeable future, but given the sheer immensity of our galaxy, 40 light years is just peanuts.
But having an Earth-like figure and being located in the habitable zone isn’t nearly enough to support life. That’s why astronomers at NASA have been studying the system assiduously, trying to learn more about it and establish its conditions. Now, for the first time, they’ve put an age on it — or rather, an age range. TRAPPIST-1 is between 5.4 and 9.8 billion years old. This makes it a very old system compared to our own, which is ‘just’ 4.5 billion years old.
It’s indeed a very broad range, but at least it enables us to say that the system is old, though we’re not yet sure how old. Also, while it’s a broad constraint, it’s still a constraint. When it was first discovered, we only knew that the star had to be older than 0.5 billion years, since that’s how long it takes for these stars to contract. It could have been almost as old as the universe itself.
“Our results really help constrain the evolution of the TRAPPIST-1 system, because the system has to have persisted for billions of years. This means the planets had to evolve together, otherwise the system would have fallen apart long ago,” said Adam Burgasser, an astronomer at the University of California, San Diego, and the paper’s first author.
The system overlaid over the habitable zone. Image credits: NASA/JPL.
It’s not clear exactly what this means for the habitability of the planet. It’s known that older stars tend to flare less than younger stars, thus having less of a chance of wiping out potential life. But this also means that the planets have absorbed billions of years of high-energy radiation, which might imply that their atmospheres have boiled off. A decent analogy here is Mars, which once hosted an atmosphere which has since been wiped off by radiation.
But there are more aspects to consider. TRAPPIST-1 planets have lower densities than Earth, which makes it more likely for them to hold vast reservoirs of volatile molecules, which could generate thick atmospheres, strong enough to protect the planets from radiation. Especially the two outer planets, planet g and planet h might have been lucky enough to escape with an atmosphere.
But if any life exists on these planets, it’s almost certainly way more hardy than that on Earth.
“If there is life on these planets, I would speculate that it has to be hardy life, because it has to be able to survive some potentially dire scenarios for billions of years,” Burgasser said.
TRAPPIST-1 is an ultra-cool dwarf star in the constellation Aquarius, and its seven planets orbit very close to it, which puts them in the Goldilocks area. Credits: NASA/JPL-Caltech
Future observations will focus on identifying potential atmospheres around these planets. If such an atmosphere exists, then it likely existed for billions of years, which makes the possibility of extraterrestrial life significantly more likely. The observations will also help astronomers better understand other similar systems form and develop.
“These new results provide useful context for future observations of the TRAPPIST-1 planets, which could give us great insight into how planetary atmospheres form and evolve, and persist or not,” said Tiffany Kataria, exoplanet scientist at JPL, who was not involved in the study.
If there’s any life in the Trappist-q system, it’s likely that it won’t be limited to only one planet, a study from Harvard University says.
An artist’s impression of planets transiting in front of Trappist-1. Image credits NASA, ESA, and G. Bacon (STScI) / Wikimedia.
With NASA’s announcement of the seven exoplanets in the Trappist-1 system, three of which lie in the habitable Goldilocks zone and could have liquid water on their surface, the hope of witnessing the discovery alien life got re-ignited for a lot of people.
And we might get more new friends than we’ve thought: a new study published by Manasvi Lingam and Avi Loeb at Harvard University suggests that the habitable planets in the Trappist-1 system are close enough that microbes could hitch a ride from one world to the others via rocks.
Their theory is that when meteorites or other space bodies hit one of these three habitable worlds, the force of the impact could propel material into space which might find its way to one of the neighbors. Microbes sheltering in these chunks of rock could then ‘seed’ life on its new planet, a process referred to as panspermia. It may sound far-fetched, but it’s actually one of the ways we think life could have appeared on Earth — through microbes blown over from Mars in the wake of a huge impact.
To test their theory, the team created digital models of how life could move between the planets starting from patterns in species immigration between different islands on Earth. Their results suggest that between the habitable planets in Trappist-1, life has a 1,000 times greater likelihood of transfer compared to that estimated between Earth and Mars. It’s mostly thanks to the fact that the planets are tidally locked in tight orbits around the stars — meaning a short commute for germs between them. Once life settles on one planet, it’s very likely to spread on the others, the authors say.
“These planets are similar to islands on the surface of the Earth, and there are studies of the immigration of species from one island to another,” Loeb explained for Gizmodo.
“We used the same model to illustrate that the likelihood is very high for transfer of life.”
Comparison between the Solar and Trappist-1 systems. Image credits NASA/JPL-Caltech.
The final check for the theory of panspermia on Trappist-1 will be to find atmospheres around the habitable planets. In the absence of atmospheric cover water won’t stay liquid on the surface, making it unlikely that life could evolve on the planet and almost impossible for it to immigrate from the neighbours. Loeb says that the next order of business is to monitor the planets as they transit in front of the star and measure the dip in light to see if it’s indicative of atmospheres. After that, finding out the atmospheres’ composition to see if they have what we consider the “building blocks of life” — such as oxygen or CO2.
“We can roll the dice three times in this system compared to Earth, which is the only planet where we know life exists in the solar system,” Loeb said. “So at least you have three chances.”
The full paper “Enhanced interplanetary panspermia in the TRAPPIST-1 system” has been published in the journal Astrophysics.
Remember the Boaty McBoatface incident? Well, the Internet is trying its digital hand at naming things again, and this time it’s for NASA’s latest exciting discovery: the 7 new exoplanets of the Trappist system. Twitter users have come up with a wonderful mix of suggestions ranging from trollish or tongue-in-cheek, all the way to some that might actually have some merit as potential names for the planets.
Image credits NASA.
The Internet doesn’t have the best track record when it comes to naming things. Just last March, UK’s Natural Environment Research Council (NERC) invited people to vote on what name their newest arctic research vessel should be christened with. NERC went with RRS Sir David Attenborough in recognition to the world famous UK naturalist and broadcaster — but that’s not what the public voted for. Oh no.
After former BBC Radio Jersey presenter James Hand jokingly suggested the council should go with Boaty McBoatface, the suggestion picked up a huge number of votes, quickly becoming the most popular name. Thankfully for the NERC, they announced from the beginning that the poll was non-binding in nature so they could opt for what they considered a “more appropriate” name.
Just last month, NASA announced the discovery of seven exoplanets in the Trappist system, three of which lie in the Goldilocks zone of potential habitability. Currently named Trappist-1b to h, the planets’ permanent nomenclature will be decided by the International Astronomical Union — but the opportunity to name them was too good for the collective creativity of the Internet to pass up on, and people are tweeting their ideas under the hashtag 7NamesFor7NewPlanets. Some suggestions are simply funny, we’ve seen some nods to cultural references, and some names that actually sound pretty good. And surely enough, “Planet McPlanetface” made it in the suggestions.
Here are some of the highlights, starting with the funnies.
There’s also a lot of cultural referencing going on, with the names of great houses from Game of Thrones being suggested, the dwarfs’ names in Snow White, as well as nods to the Harry Potter books. But this one I enjoyed the most:
Some users view the christenings as an opportunity to those who have sacrificed in humanity’s efforts to reach for the stars — several tweets call for the planets to be named for the seven astronauts who lost their lives aboard the Challenger in 1986.
So will these suggestions actually make it on the star charts? Probably not.
“The TRAPPIST #7NamesFor7NewPlanets was a trending hashtag that was started by Twitter users, and we were simply joining an existing conversation by posting the current scientific names with the hashtag. We are not collecting suggestions, and we rely on the IAU’s process for the naming of these planets,” NASA’s Social Media Manager John Yembrick told me in an e-mail.
Seeing the generally light-hearted and humorous way these names are being suggested on Twitter, it’s unlikely that the IAU will actually go with any of them. But there are some good contenders tweeted under the hashtag, so the union may still surprise us in the end. Which means there’s still a tiny hope for Pluto.
Author’s note: Corrected the article after receiving NASA’s Social Media Manager John Yembrick’s email. Initially, it stated NASA started the hashtag to ask for suggestions for the new names; 1:50 am EET.