Which Earth-Size Planets are Habitable?

A University of Oklahoma
post-doctoral astrophysics researcher, Billy Quarles, has identified the possible
compositions of the seven planets in the TRAPPIST-1 system. Using thousands of
numerical simulations to identify the planets stable for millions of years,
Quarles concluded that six of the seven planets are consistent with an
Earth-like composition. The exception is TRAPPIST-1f, which has a mass of 25
percent 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.”

The Earth seen from space, by NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans [Public domain or Public domain], via Wikimedia Commons
Quarles, a researcher in the
Homer L. Dodge Department of Physics and Astronomy, OU College of Arts and
Sciences, collaborated with scientists, E.V. Quintana, E. Lopez, J.E. Schlieder
and T. Barclay at NASA Goddard Space Flight Center on the project. 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 percent of its mass in water, which is rare given its
radius. The concern of this planet is that the mass is 70 percent the mass of
Earth, but it is the same size as Earth. Because 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 seven planets are known as
TRAPPIST 1b, c, d, e, f, g and h.

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Posted on June 12, 2017, in Useful Information. Bookmark the permalink. Leave a comment.

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