Planetary system · 7 known planets · Aquarius

TRAPPIST-1

Its star: above the horizon after darkHighest after dark 23:08 · south · 34°

Join the waitlistSkyMate is coming to iPhone

Where is TRAPPIST-1?

Times for LondonChange city

Look south, about 34° up at 23:08 in Aquarius.

Rises: 17:31
Highest: 23:10
Sets: 04:48
Best after dark: 23:08 · 34°

Can I see TRAPPIST-1?

No. The planets of TRAPPIST-1 can’t be seen with the eye, binoculars or any amateur telescope: they are lost in their star’s light. What you can do is point toward the star.

From London tonight, the star TRAPPIST-1 is above the horizon after dark. It’s highest after dark at 23:08, in the south at 34°.

Why is TRAPPIST-1 interesting?

TRAPPIST-1 has 7 known planets, discovered between 2016 and 2017 by the primary transit method.

All of them are close to Earth’s size or mass, based on the catalog values.

What can you see?

Eyes

Direction only

Not visible. The star is around magnitude 18.8 in visible light.

Binoculars

Not visible.

Telescope

Beyond visual reach in nearly all amateur telescopes. Imagers with large telescopes and cameras can record the star as a faint red dot. The planets themselves can’t be seen with any backyard telescope.

What you’re likely to see, not what a space telescope photographs.

About

TRAPPIST-1 is a small, cool red dwarf star about 40 light-years away with seven known planets, all roughly the size of Earth. It is the largest set of Earth-sized planets found around a single star.

The whole system is remarkably compact: all seven planets orbit closer to their star than Mercury is to the Sun, with years lasting from about 1.5 to 19 days. Because the star is so dim, several of them receive amounts of energy similar to the inner planets of our Solar System, and three or four lie in the zone where liquid water might be possible.

The planets were found by watching the star dim slightly as each one passed in front of it. The James Webb Space Telescope is now probing them for atmospheres; early results suggest the two innermost planets do not have thick ones.

You can point toward TRAPPIST-1, but you can’t see its planets. Even the star itself is extremely faint in visible light.

The TRAPPIST-1 system

Known planets of TRAPPIST-1 (catalog values from exoplanet.eu)
Planet	Mass	Radius	Orbit	From star	Found	Method
TRAPPIST-1 b	1.37 M⊕	1.12 R⊕	36.3 h	0.0115 AU	2016	Primary Transit
TRAPPIST-1 c	1.30 M⊕	1.10 R⊕	2.42 days	0.0158 AU	2016	Primary Transit
TRAPPIST-1 d	0.38 M⊕	0.79 R⊕	4.05 days	0.0223 AU	2016	Primary Transit
TRAPPIST-1 e	0.70 M⊕	0.92 R⊕	6.10 days	0.0293 AU	2017	Primary Transit
TRAPPIST-1 f	1.05 M⊕	1.04 R⊕	9.21 days	0.0385 AU	2017	Primary Transit
TRAPPIST-1 g	1.33 M⊕	1.13 R⊕	12.4 days	0.0468 AU	2017	Primary Transit
TRAPPIST-1 h	0.32 M⊕	0.76 R⊕	18.8 days	0.0619 AU	2017	Primary Transit

M⊕ / R⊕ = Earth masses / radii; M♃ / R♃ = Jupiter. Masses from radial velocity are often minimum masses. Data: The Extrasolar Planets Encyclopaedia, exoplanet.eu (CC BY 4.0).

Questions

Can I see the TRAPPIST-1 planets?

No. They are far too small, faint and close to their star. Astronomers detect them from the tiny dips in starlight as they pass in front.

Could any TRAPPIST-1 planets have life?

No one knows. A few are at distances where liquid water might be possible, but whether any have atmospheres or water is still being studied.

Can I see the star TRAPPIST-1?

Not by eye or with typical amateur telescopes. It is very faint in visible light, though brighter in infrared.

Another planetary systemTau Ceti Another planetary systemEpsilon Eridani GuideStargazing for beginners ToolMoon phase & visibility tool Browse allExoplanets What's up tonightTonight

Sources: The Extrasolar Planets Encyclopaedia (CC BY 4.0); star chart: Wikidata (CC0). Positions computed for your place and time with astronomy-engine. Data & Licences