The TRAPPIST-1 system is home to seven planets that are about the size of Earth and potentially just the right temperature to support life. So how would life on these alien worlds be different than life on Earth? Here are some of the major differences. Perhaps one of the most dramatic things that visitors to the TRAPPIST-1 system would notice is the view of the other six planets in the sky. In some cases, a neighboring planet might appear twice as large as the full moon seen from Earth.
All seven of the known planets in the TRAPPIST-1 system orbit closer to their star than Mercury orbits the sun. The innermost planet and the outermost planet are almost 30 times closer together than Earth and Venus at their largest separation. The reason these seven planetary siblings can fit into such tight orbits is because their parent star is an ultracool dwarf star. It’s about 2,000 times dimmer than the sun, and only slightly larger than the planet Jupiter.
Three of the known planets orbit the star in what’s known as the “habitable zone,” or the region around a star where the planet could have a surface temperature right for liquid water. The position of the habitable zone is different around each star — on a very dim star like TRAPPIST-1, which radiates significantly less heat than the sun, the habitable zone lies much closer to the star. But there’s no guarantee that a planet in the habitable zone of TRAPPIST-1 can host liquid water on its surface. Without an atmosphere, water won’t remain a liquid in space. For example, on comets (which don’t have atmospheres), water ice sublimates directly into a vapor when it is heated by the sun.
Quote from: SPACE.COM
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