This artist’s impression shows an imagined view of the three planets orbiting TRAPPIST-1, 40 light years from Earth,via ESO/M. Kornmesser/N. Risinger (skysurvey.org)
Astronomers have found three planets that may be habitable ‘just’ 40 light years away, orbiting an ultracool dwarf star called TRAPPIST-1.
Named after the telescope that astronomers are using to monitor its system (TRAnsiting Planets and PlanetesImals Small Telescope), TRAPPIST-1 is about one-eighth the size of our sun. It’s far weaker and radiates far less. However, that means the three planets orbiting it every 1.5, 2.4 and 73 days could support life.
An international team of astronomers from MIT and the University of Liège in Belgium estimate that, given the size of TRAPPIST-1 and its three orbiting planets, each may have regions with temperatures well below 400 kelvins, making them suitable for sustaining water and life.
This artist’s impression shows an imagined view from the surface one of the three planets orbiting TRAPPIST-1, via ESO/M. Kornmesser
Move over Earth 2.0
The three each have similar sizes to either Earth or Venus and, given the previously heralded Earth 2.0 is a whopping 1,400 light years away, expect growing interest in these nearby neighbours. Of course, 40 light years is still a phenomenally large distance. To put that into perspective, Pluto is only five light hours away.
“You and I probably won’t be travelling to these planets, but our children’s children’s children could be,” NASA’s Jeff Coughlin said of last summer’s discovery. Maybe worth bringing that time estimate back a generation?
TRAPPIST-1 is what’s called an ultracool dwarf star — it is much cooler and redder than the sun and barely larger than Jupiter. These types of stars are very common, but never has evidence of orbiting planets emerged. Until now.
Despite its relative closeness to us, you need a specialised telescope to see TRAPPIST-1 from Earth. It lies in the constellation of Aquarius (The Water Carrier).
This picture shows the sun and the ultracool dwarf star TRAPPIST-1 to scale. The faint star has only 11pc of the diameter of the sun and is much redder in colour, via ESO
Just like home
“With such short orbital periods, the planets are between 20 and 100 times closer to their star than the Earth to the sun,” said Michaël Gillon, author of the research paper on the discovery, published in Nature. “The structure of this planetary system is much more similar in scale to the system of Jupiter’s moons than to that of the solar system.”
The discovery was an odd one. TRAPPIST was built by Gillon and Emmanuel Jehin, both of the University of Liège, to specifically hone in on a handful of very faint stars, 60, in total.
“It’s not looking at 100,000 stars at a time, like the Kepler Space Telescope,” de Wit said. “It’s a few of them that you’re spending time on, one at a time. And one paid off.”
“Now we have to investigate if they’re habitable,” de Wit said. “We will investigate what kind of atmosphere they have, and then will search for biomarkers and signs of life.
“We have facilities all over the globe and in space that are helping us, working from UV to radio, in all different wavelengths to tell us everything we want to know about this system. So many people will get to play with this [system].”
