The TRAPPIST-1 System

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Are we alone?

Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with NASA’s Universe of Learning partners: Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, NASA Jet Propulsion Laboratory, and Sonoma State University
  • Illustration of full system with star and seven planets visible, some transiting the star: 
  • Illustration of planets orbiting star: 
  • Image of the TRAPPIST Telescope:
  • Graph showing data from NASA’s Spitzer Space Telescope, which studied the star by recording tiny dips in the star’s brightness, caused by orbiting planets passing in front of it.
  • Image comparing sizes of TRAPPIST system and planets to the inner planets of our solar system.
  • Illustration of TRAPPIST planets, to scale by volume:
  • Illustration of TRAPPIST-1b and 1c, the very hot planets:
  • Illustration of TRAPPIST-1h, the very cold planet:
  • Illustrations of TRAPPIST-1d, 1e, 1f, and 1g, which could be either water worlds or worlds mixing water and rocky land: 


 A view of a planet from space. 

Text, Where could life exist? 

Is there anything out there? 

The questions are underlined. 

Text, Are we alone? 

A star surrounded by planets. Text, Illustration. 

NASA has helped unveil the largest family of Earth-size planets around a single star. 

A planetary system that could harbor water-bearing worlds suitable for life. 

Colorful rings show orbit patterns. 

Text, The planets orbit a small, cool, red dwarf star, about the size of Jupiter, located 40 light-years away. 

The system is called TRAPPIST-1, after the ground-based observatory that first studied it and announced the detection of three orbiting planets in 2016. 

A photo of the observatory in the bottom right corner. A graph. 

Text, NASA's Spitzer Space Telescope studied the star by recording tiny dips in the star's brightness, caused by orbiting planets passing in front of it. 

Relative Brightness of Star, Day of Observation. 

The data revealed a total of seven circling planets. 

All of the planets are approximately the size of Earth and mostly made of rock. 

TRAPPIST-1 System, Inner Solar System. 

Follow-up observations by the Spitzer, Kepler, and Hubble Space Telescopes have increased our understanding of the planets. 

Orbits enlarged 25 times. 

Some could be up to 5 percent water by mass. The form of that water depends on how much heat they receive. 

Planets labeled, B, C, D, E, F, G, and H. 

Text, These circumstances create intriguing possibilities, illustrated in these artist's conceptions of the planets. 


The innermost planets may have hot, steamy surfaces under thick clouds. 

TRAPPIST-1 H -- Illustration. 

The outermost planet may be an icy world across its entire globe. 

A water planet. Text, Illustration. 

The middle temperate planets may be covered with a planet-wide ocean of liquid water. 

Text, Or may be a mix of rocky land and water, similar to our own Earth. 

A land and water planet. 

A sunset behind water. 

Text, Such watery worlds may have conditions suitable for life to develop. 

We can at present only imagine what life on such worlds may be like. 

A satellite in space. 

Text, Astronomers are conducting follow-up observations of this system using both space- and ground-based telescopes. Some of these studies have given us clues to whether or not the atmospheres could support life. 

More satellites appear. A planet in space. Text, Illustration. 

These studies will be an important step in the human quest to answer the age-old question. Are we alone? 

It may hasten the day when we find the first truly Earth-like world. 

Answering that question once and for all.