The orbits of all seven Earth-size planets in the TRAPPIST-1 system are now known.
Astronomers have nailed down the path of TRAPPIST-1h, the outermost planet in the system, finding that this world takes just under 19 Earth days to complete one lap around its small, faint host star.
The new result suggests that TRAPPIST-1h is too cold to host life as we know it, and it confirms that all seven TRAPPIST-1 worlds circle their star in a sort of gravitational lockstep with one another, study team members said. [Exoplanet Tour: Meet the 7 Earth-Size Planets of TRAPPIST-1]
"It's incredibly exciting that we're learning more about this planetary system elsewhere, especially about planet h, which we barely had information on until now," Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate at the agency's headquarters in Washington, DC, said in a statement.
"This finding is a great example of how the scientific community is unleashing the power of complementary data from our different missions to make such fascinating discoveries," Zurbuchen added.
TRAPPIST-1 is a dim, dwarf star just 8 percent as massive as the sun that lies about 40 light-years from Earth. In May 2016, astronomers using the TRAPPIST (Transiting Planets and Planetesimals Small Telescope) instrument in Chile announced the discovery of three roughly Earth-size planets in the system. That number jumped to seven with further observation by NASA's Spitzer Space Telescope, TRAPPIST and other ground-based telescopes.