Scientists use Kepler telescope data to uncover details about TRAPPIST-1 planet
Data collected by NASA’s exoplanet-hunting Kepler Space Telescope has enabled scientists to uncover orbital information for the outermost planet of the unusual TRAPPIST-1 planetary system.
First discovered in 2016 via the ground-based Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, the unusual system has seven Earth-sized planets in close orbits around a cool, dim red dwarf star that has a mass just eight percent that of the Sun. Three of those planets are located in the star’s habitable zone, where temperatures could allow liquid water to exist on their rocky surfaces. TRAPPIST-1 is located approximately 40 light-years from Earth in the constellation Aquarius.
NASA’s Spitzer Space Telescope discovered that the system, initially thought to have three planets, actually has seven. Follow-up observations to determine the composition of the planets’ atmospheres are currently being conducted with the Hubble Space Telescope and will be done with the James Webb Space Telescope when it launches in 2018.
While the Spitzer data confirmed the planets all orbit in a mathematical pattern known as an orbital resonance, it was not enough for scientists to uncover details about the orbit of the outermost planet – TRAPPIST-1h.
The Kepler data confirmed a pattern in the orbits of all seven planets, enabling scientists to determine TRAPPIST-1h orbits its star every 18.77 Earth-days and is likely far too cold to host life on its surface.
Orbiting at a distance of about six million miles (10 million kilometers) from the star, TRAPPIST-1h receives about the same energy from the star as the dwarf planet Ceres – located between Mars and Jupiter in the Solar System – receives from the Sun.
“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,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington. “This finding is a great example of how the scientific community is unleashing the power of contemporary data from our different missions to make such fascinating discoveries.”
Kepler observed the region of the sky where the TRAPPIST-1 system is located during the period between Dec. 15, 2016, and March 4, 2017, tracking even the smallest changes in the star’s brightness as its planets transited in front of it.
When raw data from these observations was released to scientists worldwide on March 8, astronomers around the world took less than two hours to determine the orbital period of TRAPPIST-1h.
“Pulling results out of data is always stimulating, but it was a rare treat to watch scientists across the world collaborate and share their progress in near-real time on social media as they analyzed the data and identified the transits of TRAPPIST-1h,” said Jessie Dotson, project scientist for Kepler’s extended K2 mission at NASA’s Ames Research Center in California.
Video courtesy of NASA’s Ames Research Center
Planets in orbital resonances exert gravitational tugs on one another at regular intervals, pulling back any somehow nudged out of their orbits.
Three of Jupiter’s Galilean moons – Io, Europa, and Ganymede – have resonant orbits that keep them stable. For every orbit of Ganymede, the most distant Galilean moon, Europa orbits Jupiter twice and Io orbits it four times. This pattern is known as a 1:2:4 resonance.
Before the discovery of the TRAPPIST-1 system, the two record holders for the number of planets in such resonances were Kepler-80 and Kepler-223, each with four planets in resonant orbits.
Rodrigo Luger of the University of Washington in Seattle, and the lead author of a paper on the discovery published in the journal Nature Astronomy, said that the orbital resonances date back to the time the planetary system had formed.
“The resonant structure is no coincidence and points to an interesting dynamical history in which the planets likely migrated inward in lock-step,” Luger said. “This makes the system a great laboratory for planet formation and migration theories.”
Video courtesy of NASA Spitzer
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.