1. The lighter green indicates optimistic regions of the habitable zone and the darker green denotes more conservative limits.
Credit: University of Oklahoma
2. This artist’s impression displays TRAPPIST-1 and its planets reflected in a surface. Image credit: NASA / R. Hurt / T. Pyle.
3. The TRAPPIST-1 system contains a total of seven Earth-size planets. Three of them — TRAPPIST-1e, f and g — dwell in their star’s so-called ‘habitable zone.’ Image credit: NASA
A University of Oklahoma post-doctoral astrophysics researcher, Billy Quarles, has identified the possible compositions of the 7 planets in the TRAPPIST-1 system. Using thousands of numerical simulations to identify the planets stable for million of years, Quarles concluded that 6 of the 7 planets are consistent with an Earth-like composition. The exception is TRAPPIST-1f, which has a mass of 25% water, suggesting that TRAPPIST-1e may be the best candidate for future habitability studies.
“The goal of exoplanetary astronomy is to find planets that are similar to Earth in composition and potentially habitable,” said Quarles. “For thousands of years, astronomers have sought other worlds capable of sustaining life.” Numerical simulations for this project were performed using the Pleiades Supercomputer provided by the NASA High-End Computing Program through the Ames Research Center and at the OU Supercomputing Center for Education and Research.
TRAPPIST-1 planets are more tightly spaced than in Kepler systems, which allow for transit timing variations with the photometric observations. These variations tell the researchers about the mass of the planets and the radii are measured through the eclipses. Mass and radius measurements can then infer the density. By comparing Earth’s density (mostly rock) to the TRAPPIST-1 planets, Quarles can determine what the planets are likely composed of and provide insight into whether they are potentially habitable.
TRAPPIST-1f has the tightest constraints with 25% of its mass in water, which is rare given its radius. The concern of this planet is that the mass is 70% the mass of Earth, but it is the same size as Earth. As the radius is so large, the pressure turns the water to steam, and it is likely too hot for life as we know it. The search for planets with a composition as close to Earth’s as possible is key for finding places that we could identify as being habitable. Quarles said he is continually learning about the planets and will investigate them further in his studies.
TRAPPIST-1 is a nearby ultra-cool dwarf about 40 light-years away from Earth and host to a remarkable planetary system consisting of seven transiting planets. The 7 planets are known as TRAPPIST 1b, c, d, e, f, g and h. http://www.ou.edu/content/publicaffairs/archives/OUAstrophysicistIdentifiesCompositionofEarth-SizePlanetsinTRAPPIST-1System/
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