About the image. The star and its seven planets are drawn in their correct order, but not to scale: at true scale the planets would be specks. JWST has found little or no atmosphere on the two innermost planets.
4.1×as wide as our Sun looks from Earth
65%of the light Earth gets
Likely tidally locked: the star stays put
The sky from TRAPPIST-1
TRAPPIST-1 would look 4.1× as wide as the Sun does from Earth, and the planet gets 65% of the light Earth gets from the Sun.
Its colour comes from its surface temperature of 2 566 K (2 290 °C); the Sun's is about 5 772 K (5 500 °C).
At their closest, planets d and f would each look about 1.0× as wide as the Sun does from Earth: as large as our Moon appears.
Planet e is likely tidally locked, though pulls from its neighbours may keep its spin chaotic: one side always faces the star.
There are no sunrises. Where you stand decides where the star hangs, overhead on the day side, low at the edge, gone on the night side.
Apparent size = star radius ÷ orbit; light = size² × (temperature ÷ 5 772 K)⁴. Both from the values on this page. The landscape is imagined.
TRAPPIST-1 is a red dwarf only slightly larger than Jupiter, with about 9% of the Sun’s mass. Around it circle seven planets, all roughly the size of Earth, all on orbits that would fit well inside Mercury’s. The outermost goes around in under 19 days.
How they were found
The star was catalogued in 1999. In 2016 a team led by Michaël Gillon used the small TRAPPIST telescope at La Silla in Chile, which gave the system its name, to find planets crossing in front of it. Further analysis in 2017 brought the count to seven, the largest number of planets known in any star’s habitable zone at the time. Depending on the model, three or four of them could receive the right amount of light for liquid water.
A clockwork system
Neighbouring planets’ years form simple ratios: 8:5, 5:3, 3:2, 3:2, 4:3 and 3:2. Each set of three is locked in a resonance, and the orbits are almost perfectly circular and flat. Systems like this are thought to form slowly and survive only if nothing disturbs them.
What JWST sees
The James Webb Space Telescope has looked at the two innermost planets. TRAPPIST-1b appears to have no atmosphere or only a very thin one. For TRAPPIST-1c, Venus-like and carbon-dioxide-rich atmospheres are ruled out, although some thinner atmospheres are still possible. The planets farther out, the ones in the habitable zone, are still waiting their turn.
Its orbit, to scale
Seven planets, from 1.5 days to 19 days per orbit, all closer in than Mercury. The whole view is tiny on Solar System scale: Mercury orbits the Sun about 6 times farther out than the outermost orbit shown here.
TRAPPIST-1: TRAPPIST-1e, equilibrium temperature. Logarithmic scale from 100 K to 10 000 K. Reference values: NASA, IAU.
How long to get there?
TRAPPIST-1 is about 40.5 light-years away.
Light299 792 km/s41 years
Breakthrough Starshotplanned light sail, 20% of light speed203 years
Parker Solar Probefastest spacecraft so far, 192 km/s63 237 years
Voyager 1leaving the Solar System, 17 km/s714 210 years
At Voyager 1's speed the trip would take about 8 928 human lifetimes of 80 years. Bars are on a logarithmic scale. Speeds: NASA, Breakthrough Initiatives.
Your weight on TRAPPIST-1e
On TRAPPIST-1e
Gravity there is about 0.82× Earth's. Calculated from the measured mass and radius.
Gallery
Artist's impressions rendered from the same model as the view at the top of this page.
Timeline
1999The star is identified in a survey of nearby ultra-cool dwarfs (published 2000).
2016The TRAPPIST telescope finds the first planets.
2017The count rises to seven.
2023JWST finds little or no atmosphere on TRAPPIST-1b.
Questions people ask
How many planets does TRAPPIST-1 have?
Seven confirmed planets, b to h. An eighth candidate has been reported but not confirmed.
Which TRAPPIST-1 planets could be habitable?
Depending on the model, three or four: usually e, f and g, sometimes d.
How old is TRAPPIST-1?
About 7.6 billion years, older than the Solar System.