was made by TRAPPIST - the TRAnsiting Planets and Planetesimals Small Telescope. It is located at ESO's Observatory of La Silla in Chile. Additional observations were conducted by UKIRT (Hawai'i), the VLT (Atacama), and the HCT (Himalaya).

Three planets with sizes similar to the Earth were identified when they transited the ultra-cool dwarf star, TRAPPIST-1, 40 light years away from Earth. The characteristics and proximity of TRAPPIST-1 means that its planets will be the first Earth-like worlds whose atmospheres will be remotely explored. Part of the planets' surfaces may be habitable. Soon we will be able to verify this empirically.


The initial announcement for the discovery of the TRAPPIST-1 system was published in Nature (vol. 533, issue 7602, p221-224)

Additional news about the system, a timeline of the exploration of the systems, related press releases, and scientific publications will be collected in our news section.


TRAPPIST-1 was discovered by a prototype to a more ambitious project called SPECULOOS (a Search for Planets EClipsing ULtracOOl Stars)

SPECULOOS consists of four 1-metre robotic telescopes, installed at Cerro Paranal. We will survey 10 times more red dwarfs than TRAPPIST did, and expect to discover a dozen systems similar to TRAPPIST-1. We will explore the diversity of atmospheres and climates for Earth-like worlds.

Small is Beautiful!

The star at the centre of the TRAPPIST-1 system is 8% of the Sun's mass, and 12% of its radius.

It is astonishing that this small a star could produce more Earth-sized worlds than our Sun! Its unique characteristics have helped us detect planets as small as Earth. This will also help us study their atmospheres remotely.

star's mass 0.08 M
star's radius 0.12 R
star's temperature 2550 K
star's luminosity 0.0005 L
distance 12pc -- 40 light years
constellation Aquarius


Current innermost planet, TRAPPIST-1b was also the first to be identified.

orbital period 1.51 days
planet's mass unknown at this stage
planet's radius 1.11 ± 0.04 R
equilibrium temperature 285 -- 400 K
semimajor axis 0.011 AU
orbital eccentricity unknown at this stage


TRAPPIST-1c receives as much light from its star than our Venus does. Are they similar? We will know soon.

orbital period 2.42 days
planet's mass unknown at this stage
planet's radius 1.05 ± 0.05 R
equilibrium temperature 242 -- 342 K
semimajor axis 0.015 AU
orbital eccentricity unknown at this stage


Identified from two transit events, only a range of orbital periods is currently known for TRAPPIST-1d. Many of those are compatible with the habitable zone.

orbital period 4.55 -- 72.8 days
planet's mass unknown at this stage
planet's radius 1.17 ± 0.07 R
equilibrium temperature 75 -- 280 K
semimajor axis 0.022 -- 0.146 AU
orbital eccentricity unknown at this stage


Are there more planets in the TRAPPIST-1 system?

This is possible. The current orbital inclinations of the planets implies that if more bodies orbit this tiny star, they are likely to transit too.

Check the news


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