Researchers searching the galaxy for planets
that could pass the litmus test of sustaining water-based life must find
whether those planets fall in what’s known as a habitable zone. Using
the latest data, a Penn State Department of Geosciences team has
developed an updated model for determining whether discovered planets
fall within a habitable zone – where they could be capable of having
liquid water and thus sustaining life. The work builds on a prior model
by James Kasting, Evan Pugh
Professor of Geosciences at Penn State, to offer a more precise
calculation of where habitable zones around a star can be found. In the
new model, Earth appears to be situated at the very edge of the
habitable zone, but the model doesn’t take into account feedback from
clouds, which reflect radiation away from the earth and stabilize the
climate.
Comparing the new estimates with the previous model, the team found that
habitable zones are actually farther away from the stars than
previously thought.
“This has implications for finding other planets with life on them,”
said post-doctoral researcher Ravi Kumar Kopparapu, a lead investigator
on the study.
For the paper, Kopparapu and graduate student Ramses Ramirez used updated absorption databases of greenhouse gases (HITRAN
and HITEMP). The databases have more accurate information on water and
carbon dioxide than previously was available and allowed the research
team to build new estimates from the groundbreaking model Kasting
created 20 years ago for other stars.
Using that data and super computers at Penn State and the University
of Washington, the team was able to calculate habitable zones around
other stars. In the previous model, water and carbon dioxide were not
being absorbed as strongly, so the planets had to be closer to the star
to be in the habitable zone.
The new model has already found that some extrasolar planets
previously believed to be in habitable zones may, in fact, not be.It
could also help scientists with research that is already under way. For
example, the model could be used to see if planets the NASA Kepler mission
discovers are within a habitable zone. The Kepler mission has found
more than 2,000 potential systems that could be investigated.
The data could assist with the Habitable Zone Planet Finder that a
team of scientists in the Department of Astronomy and Astrophysics in
Penn State’s Eberly College of Science is building. In 2011, that team
received a National Science Foundation grant to develop an instrument to
find planets in habitable zones. The precision spectrograph, which is
under construction, will help scientists find Earth-sized planets in the
Milky Way that could sustain liquid water.
In the future, the model could also be useful for research done with Terrestrial Planet Finder telescopes, which would guide users of the supersized telescopes on where to look.
Support for the research comes from NASA Astrobiology Institute’s Virtual Planetary Laboratory. An interactive calculator to estimate Habitable Zones is online at depts.washington.edu/naivpl/content/hz-calculator.
The paper is available online at http://arxiv.org/abs/1301.6674
Source: The Daily Galaxy via Penn State University
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