Scientists redefine ‘habitable zone;’ Earth booted out of ‘Goldilocks zone’

Scientists redefine the habitable zone for exoplanets.

By Max Sonnenberg, The Space Reporter
Wednesday, January 30, 2013

Scientists redefine ‘habitable zone;’ Earth booted out of ‘Goldilocks zone’

Researchers from Penn State University have redefined the “habitable zone” for exoplanets. Interestingly, this new definition has delivered a major hit to Earth’s habitability rating.

An updated model for identifying whether newly discovered exoplanets fall within a habitable zone has been created by the Penn State Department of Geosciences team using the latest data, according to a news release from Penn State. The updated model will help researchers tasked with combing the galaxy for planets that could be capable of having liquid water and sustaining life.

According to the research team, their work is based on a prior model developed by James Kasting, Evan Pugh Professor of Geoscience at Penn State. The updated model will offer researchers a more accurate calculation of where habitable zones around a star can be found.

Comparing new data from the updated model to old estimates made by the previous model, researchers discovered 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 Ravi kumar Kopparapu, a lead investigator on the study, in a statement.

For the study, Kopparapu and graduate student Ramses Ramirez used updated absorption databases of greenhouse gases. The databases have more precise information on water and carbon dioxide than previously was available and let the researchers create new estimates from the innovative model Kasting developed 20 years ago.

With the help of super computers at Penn State and the University of Washington, researchers were able to calculate habitable zones around other stars. They note that in Kasting’s model, water and carbon dioxide were not being absorbed as strongly, so the model estimated that the planets had to be closer to the star to be in the habitable zone.

Some planets thought to be in habitable zones may actually be outside the habitable zone, according to estimates from the updated model.

Researchers believe that the model could be used to determine whether any of the planets spotted by the NASA Kepler mission are within a habitable zone. For example, the Kepler missions has already discovered more than 2,000 exoplanets that could be examined.

The new model is expected to help scientists in Penn State’s Department of Astronomy and Astrophysics with the development of their Habitable Zone Planet Finder. The precision spectrograph will help the team discover Earth-sized planets in the Milky Way that could hold liquid water.

The new model could also help researchers using the Terrestrial Planet Finder telescopes, which would point users of the giant telescopes in the right direction for finding exoplanets.

The updated model nearly boots the Earth’s orbit out of the new “Goldilocks zone,” according to Geekosystem. The website says that the Goldilocks zone is a narrow belt around a star where an orbiting planet would be warm enough to support life. Of course, the Earth doesn’t have to be in the center of the habitable zone to support life, that location is simply where the best conditions for sustaining life can be found.

According to the New Scientist, while Earth used to be right in the middle of our Sun’s habitable zone, it is now approximately a million kilometers away from the warm edge.

Before you consider packing up your bags and finding another planet, keep in mind that the updated model doesn’t take into consideration feedback from clouds, which reflect radiation away from the Earth and stabilize the climate. In other words, the clouds are keeping the Earth from being overheated.

The study’s findings were recently published in the Astrophysical Journal.


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