The 7 Earth-sized Planets of TRAPPIST-1

Precise measurements reveal that the exoplanets have remarkably similar densities, which provides clues about their composition.

Measuring the mass and diameter of a planet reveals its density, which can give scientists clues about its composition. Scientists now know the density of the seven TRAPPIST-1 planets with a higher precision than any other planets in the universe, other than those in our own solar system

A planets density is determined by its composition as well as its size: Gravity compresses the material a planet is made of, increasing the planets density. Uncompressed density adjusts for the effect of gravity and can reveal how the composition of various planets compare.

Three possible interiors of the TRAPPIST-1 exoplanets. The more precisely scientists know the density of a planet, the more they can narrow down the range of possible interiors for that planet. All seven planets have very similar densities, so they likely have a similar compositions.

Detailed measurements of the physical properties of the seven rocky TRAPPIST-1 planets and the four terrestrial planets in our solar system help scientists find similarities and differences between the two planet families.

In the year since NASA announced the seven Earth-sized planets of the TRAPPIST-1 system, scientists have been working hard to better understand these enticing worlds just 40 light-years away. Thanks to data from a combination of space- and ground-based telescopes, we know more about TRAPPIST-1 than any other planetary system besides our solar system.

This illustration shows the seven Earth-size planets of TRAPPIST-1. The image does not show the planets' orbits to scale, but highlights possibilities for how the surfaces of these intriguing worlds might look.

This artist's concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets' diameters, masses and distances from the host star, as of February 2018.

This artist's concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets' diameters, masses and distances from the host star, as of February 2018.

This chart shows, on the top row, artist concepts of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, radii, masses, densities and surface gravity as compared to those of Earth.

All seven planets discovered in orbit around the red dwarf star TRAPPIST-1 could easily fit inside the orbit of Mercury, the innermost planet of our solar system. In fact, the proportions of the TRAPPIST-1 system look more like Jupiter and its moons.

This graph presents known properties of the seven TRAPPIST-1 exoplanets (labeled b thorugh h), showing how they stack up to the inner rocky worlds in our own solar system.

Since 2017, we knew the TRAPPIST-1 system had seven earth-sized planets. Now in 2018, a study using new data--including extensive observations by NASA's Spitzer and Kepler space telescopes--has provided more information about this amazing system. We now know more about TRAPPIST-1 than any planetary system apart from our own.

This video shows artist's concepts of the seven Earth-sized planets of TRAPPIST-1, an exoplanet system about 40 light-years away, based on data current as of February 2018. Each planet is shown in sequence, starting with the innermost TRAPPIST-1 b and ending with the outermost TRAPPIST-1 h.

NASA's Spitzer Space Telescope has revealed the first known system of seven Earth-size planets around a single star. Three of these planets are firmly located in the habitable zone, the area around the parent star where a rocky planet is most likely to have liquid water.

This artist's conception shows what the TRAPPIST-1 planetary system may look like, based on available data about their diameters, masses and distances from the host star.

The TRAPPIST-1 star, an ultra-cool dwarf, has seven Earth-size planets orbiting it. This artist's concept appeared on the cover of the journal Nature in Feb. 2017 announcing new results about the system.

Imagine standing on the surface of the exoplanet TRAPPIST-1f. This artist's concept is one interpretation of what it could look like.

This illustration shows the seven TRAPPIST-1 planets as they might look as viewed from Earth using a fictional, incredibly powerful telescope. The sizes and relative positions are correctly to scale: This is such a tiny planetary system that its sun, TRAPPIST-1, is not much bigger than our planet Jupiter, and all the planets are very close to the size of Earth.

This data plot shows infrared observations by NASAs Spitzer Space Telescope of a system of seven planets orbiting TRAPPIST-1, an ultracool dwarf star. Over 21 days, Spitzer measured the drop in light as each planet passed in front of the star. Spitzer was able to identify a total of seven rocky worlds, including three in the habitable zone where liquid water might be found.

This chart shows, on the top row, artist conceptions of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, radii and masses as compared to those of Earth. The bottom row shows data about Mercury, Venus, Earth and Mars.

All seven planets discovered in orbit around the red dwarf star TRAPPIST-1 could easily fit inside the orbit of Mercury, the innermost planet of our solar system. In fact, they would have room to spare. TRAPPIST-1 also is only a fraction of the size of our sun; it isnt much larger than Jupiter. So the TRAPPIST-1 systems proportions look more like Jupiter and its moons than those of our solar system.

The TRAPPIST-1 system contains a total of seven planets, all around the size of Earth.Three of them -- TRAPPIST-1e, f and g -- dwell in their stars so-called habitable zone. The habitable zone, or Goldilocks zone, is a band around every star (shown here in green) where astronomers have calculated that temperatures are just right -- not too hot, not too cold -- for liquid water to pool on the surface of an Earth-like world.

The first observations of the TRAPPIST-1 system reported in 2016 revealed three planets orbiting a small, red-dwarf star, though the exact location of the outermost one, was not well-determined (yellow band, top image). Follow-up observations with NASA's Spitzer Space Telescope, as well as ground-based telescopes, dramatically changed our understanding of this system, revealing a total ofseven planets in Earths size range.

This video details a system of seven planets orbiting TRAPPIST-1, a discovery of the Spitzer Space Telescope, operated by NASA's Jet Propulsion Laboratory in Pasadena, California.

This video details a system of seven planets orbiting TRAPPIST-1, an ultra-cool dwarf star. Over 21 days, Spitzer measured the drop in light as each planet passed in front of the star. Spitzer was able to identify a total of seven rocky worlds, including three in the habitable zone where liquid water might be found.

This video depicts artist's concepts of each of the seven planets orbiting TRAPPIST-1, an ultra-cool dwarf star. Over 21 days, NASA's Spitzer Space Telescope measured the drop in light as each planet passed in front of the star.

This video details a system of seven planets orbiting TRAPPIST-1, an ultra-cool dwarf star. Over 21 days, Spitzer measured the drop in light as each planet passed in front of the star. Spitzer was able to identify a total of seven rocky worlds, including three in the habitable zone where liquid water might be found.