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TRAPPIST-1 – Star system · Seven Earth-sized planets
Image: NASA, ESA, CSA, J. Olmsted (STScI) · CC BY 4.0
🌍 Exoplanets · Other Worlds

TRAPPIST-1

Star system · Seven Earth-sized planets

TRAPPIST-1 is a small, cool star with seven rocky planets, all roughly the size of Earth, packed closer to their star than Mercury is to the Sun. Three of them are in the zone where liquid water might be possible.

  • 40.7 light-years awayEven light – the fastest thing there is – needs 40.7 years to get here.
  • 7 rocky worldsPlanets
  • 3 of themIn the habitable zone
🔭 Find it in the sky

Take a closer look

Barely bigger than Jupiter

The star TRAPPIST-1 is only a little wider than Jupiter and less than a tenth as heavy as the Sun. Its surface is around 2,300 °C, so it glows a deep red and gives off much of its energy as invisible infrared light. It will keep shining for trillions of years.

Planets in rhythm

The seven planets go round their star in a neat pattern, a bit like musicians keeping a beat. For example, while one planet makes two orbits, its neighbour makes almost exactly three. Scientists think this chain of rhythms helps keep the crowded system stable.

A name with a story

TRAPPIST stands for “TRAnsiting Planets and PlanetesImals Small Telescope”, a robotic telescope run by Belgian astronomers. The name is also a nod to the monks of Belgium’s Trappist monasteries, famous for their beer – and the system’s planets got the same family name.

How we found out

  1. 2016

    Michaël Gillon’s team uses the TRAPPIST telescope in Chile to find three planets.

  2. 2017

    With NASA’s Spitzer Space Telescope, the team reveals there are seven – a record for Earth-sized planets around one star.

  3. 2023

    The James Webb Space Telescope measures the two innermost planets and finds no sign of thick atmospheres. The outer ones are still being studied.

🤔 Something to wonder about

Could there be life in the TRAPPIST-1 system?

See it yourself

The star is far too faint for your eyes. Point your phone to know where it is, in Aquarius.

Got it?

Mark TRAPPIST-1 as explored to earn 10 XP.