The seven Earth-sized exoplanets orbiting the star TRAPPIST-1 generated a lot of excitement when their discovery was announced last month. This is the largest collection of Earth-sized worlds in one planetary system found so far, and some of them are well within the star's "habitable zone" where temperatures could allow liquid water to exist on their surfaces. Little else is known about the actual conditions on these planets so far, but NASA's Kepler Space Telescope has also been observing TRAPPIST-1 in recent weeks.
The original findings were made by NASA's Spitzer Space Telescope, but now Kepler has been conducting its own follow-up observations.
"Scientists and enthusiasts around the world are invested in learning everything they can about these Earth-size worlds," said Geert Barentsen, K2 research scientist at NASA's Ames Research Center at Moffett Field, California. "Providing the K2 raw data as quickly as possible was a priority to give investigators an early look so they could best define their follow-up research plans. We're thrilled that this will also allow the public to witness the process of discovery."
Kepler observed the TRAPPIST-1 system for 74 days, from Dec. 15, 2016 to March 4, 2017, as part of its K2 mission. This is the longest, nearly continuous set of observations of TRAPPIST-1 yet obtained. It collected data on the tiny changes in brightness of the star due to the transiting planets. This will help astronomers better refine the data from Spitzer's previous observations, including measurements of six of the planets and the mass and orbital period of the seventh outermost planet, as well as magnetic activity of the star itself.
Astronomers are also preparing proposals this month to use Earth-based telescopes next winter to further examine the TRAPPIST-1 planetary system. There is even a chance of finding more as-yet undiscovered planets.
The new raw data set from Kepler is available here.
TRAPPIST-1 as seen by Kepler
"We were lucky that the K2 mission was able to observe TRAPPIST-1. The observing field for Campaign 12 was set when the discovery of the first planets orbiting TRAPPIST-1 was announced, and the science community had already submitted proposals for specific targets of interest in that field," said Michael Haas, science office director for the Kepler and K2 missions at Ames. "The unexpected opportunity to further study the TRAPPIST-1 system was quickly recognized and the agility of the K2 team and science community prevailed once again."
The new measurements from Kepler will also help astronomers when they observe TRAPPIST-1 later on with the upcoming James Webb Space Telescope, due to launch in 2018.
JWST will be able to study the atmospheres of the planets and determine their composition, including searching for possible water and biomarkers - gases which could be indicative of possible life, such as oxygen, nitrogen or methane. All seven planets are close to the Earth in size, and thought to be rocky. With at least three of them in the habitable zone, scientists are very interested in studying them further as part of the search for evidence of alien life. They all orbit closer to their star than Mercury orbits our Sun, but because the star is much smaller and cooler than our Sun, at least some of them are still at distances where temperatures could be Earth-like, depending on other surface or atmospheric conditions.
According to James Webb Program Director Eric Smith, when JWST looks at one of the planets, “What [the JWST] will do is determine what are the major components of the planet’s atmosphere,” Smith says. “If it has a lot of water, a lot of oxygen, a lot of methane, it will be able to find those things in the atmosphere. We can see if it has an atmosphere similar to Earth or different from Earth.”
By studying planetary systems such as TRAPPIST-1 with Kepler and JWST, astronomers will be another step closer to perhaps finding the first evidence for life beyond Earth.