In the first issue of this volume of the Muse, I wrote an article on the discovery of Proxima b, a rocky, earth-like planet found to be orbiting the habitable zone of Proxima Centauri, the closest star to our own sun, praising it as a huge find that should have a lot of people very excited.
Thus I feel I would be remiss if I didn’t take this chance to provide you with a Muse Space Update™ on the latest amazing news in astronomy—a discovery so fantastic you might call it “out-of-this-world!”
By now a lot of you have probably heard this news from the NASA press conference held last week on February 22, but I’m here to provide some more details for those interested in learning more about our newly-discovered stellar neighbours.
The star that the seven planets orbit around is a small, ultra-cool dwarf star called TRAPPIST-1. It is named for the satellite that was used by the team at the University of Liège in Belgium to study star system – the Transiting Planets and Planetesimals Small Telescope—and for the Catholic order of cloistered monastics the satellite’s acronym takes its moniker from. According to the team’s calculations, TRAPPIST-1 is approximately 8 per cent of the mass of our own sun and 11 per cent its radius, similar in size to Jupiter, though about 80x its mass, and lies about 40 light years away. TRAPPIST-1 is about 10x the distance of Proxima b, but is infinitesimal compared to the greater than 100,000 light year diameter of the Milky Way.
The researchers were able to calculate, using a lot of complex space math, the mass, radius and orbital period of all seven planets except for the outermost, for which only one transition was observed. The planets are named as follows, in order of their distance from the orbiting star: TRAPPIST-1b, the innermost, which orbits only 0.011 AU from the star—or 0.011% the distance from the Sun to the Earth – and circles it every 1.51 days, c, d, e, f, g and h, their orbital periods range from 2.42 to about 20 days. All of them are a similar size to Earth, ranging from 0.76 to 1.13 times our planet’s radius, and have a rocky, terrestrial composition like our own inner four planets. Being so close to their parent star, it’s highly likely all the planets are also tidally locked, meaning the same side always faces towards it.
Because TRAPPIST-1 is so cool and dim, its habitable zone, the area in which liquid water can exist on a planet’s surface without boiling away or freezing, is much closer than our own solar system. According to the team’s calculations, the planets e, f and g all orbit the habitable zone and are thus potentially capable of supporting liquid oceans on their surface.
Of course it’s far too soon to know if any of these planets host any sort of life, but it’s certainly not out of the realm of possibility. Follow-up observations are already underway, and a website has been set up at trappist.one to help eager science fans monitor future progress—I know I’ve already got it bookmarked. It’s quite possible that we could know whether or not life exists on one of these planets very soon by studying the molecular compositions of their atmospheres via spectral analysis of the light of the star passing through them as the planets transit in front of it.
If it turns out that life has evolved on any of these worlds though, chances are that it might not look very much like Earth-born life considering the local conditions. For starters, according to the researchers, the star itself would appear salmon-coloured in the sky, the light being about 200x dimmer than our own sun since most of the solar radiation it emits being infrared, which would still warm the planet, but not be visible to our own eyes. As well, research suggests that cool, dim stars like this emit frequent and powerful solar flares, meaning that any life on planets so close to the star would have to have some way of resisting this detrimental phenomenon. Although the authors of the study detailing these findings, published this month in Nature, say that this particular start is fairly quiet and some research suggests that such frequent stellar activity could actually help to replenish an atmosphere rather than destroying it.
Whether or not any of the planets actually end up having life on them, this still represents a truly amazing discovery being the largest number of Earth-sized planets we’ve ever found in a single system, and a relatively close one at that. Be sure to keep your eyes out for more news coming from TRAPPIST-1 in the coming months/years, and as always, keep watching the skies… *X-Files music plays during a fade out to black*