MIT scientists and their Danish peers have found that small explanets follow a circular orbit during their complete revolution around a host star just like our planet does. If that is the norm, scientists may have found another parameter to look for when searching for alien life.
Astronomers explained that habitable planets do not only need to have a reduced size and rocky structure, but they also require a circular orbit in order to offer the best conditions for life to thrive.
Other exoplanets have elongated orbits, so they usually either get too close to their star so the surface temperatures become unbearable or they move too far from their sun so they become ice-cold. Such climate extremes do not favor life, astronomers explained.
However, elongated or eccentric orbits are a common feature of giant exoplanets. But until now, scientists weren’t too sure whether smaller exoplanets could also have eccentric orbits.
The new finding suggests that small rocky planets usually follow a circular route around their star. The discovery is based on data collected on 74 exoplanets located hundreds of light-years away from our solar system.
The exoplanets were discovered by NASA’s Kepler space telescope during its regular survey of the skies in search of extraterrestrial life.
Astrophysicists learned that the 74 exoplanets moved around 28 stars in a circular orbit just like the planets in our solar system do.
Vincent Van Eylen from the Aarhus University in Denmark and one of the study’s authors noted that two decades ago, when there was only data available on our solar system, everybody thought that planets located outside it may have circular orbits as well.
But studies on super giant exoplanets proved scientists that they were wrong. The larger the planet, the more elongated its orbit seemed to be. Researchers, however, had harder times in setting an orbital rule for smaller exoplanets. Yet, the new findings suggest that small planets usually move in circular orbits.
And that is a very good news for alien life search. If elongated orbits were the rule for small, rocky planets with great potential for life, the weather extremes over the course of one year would have reduced their chances of hosting life to zero, the team explained.
On the other hand, the new findings were contested by other scientists. For instance, Prof. David Kipping from the Harvard-Smithsonian Center for Astrophysics, noted that the evidence to support such conclusions was particularly “tentative.” By evidence he meant the 74 exoplanets and 28 stars out of more than 145,000 new stars identified by Kepler to this date.
Image Source: MIT.edu