Astronomers have found that circular orbits of planets around their host stars are not a distinctive feature of our solar system solely. Instead 74 exoplanets, or planets located outside our solar system, share the common trait.
Planets with circular orbits usually follow a regular route and maintain the same distance from the sun. Circular paths are a must-have for any habitable planet because they shield the planet from extreme climate patterns that would make it impossible for life to thrive.
Astrophysicists said that their new find suggested that orbital regularity was the rule, not the exception at least in our galaxy when it comes to small planets such as Earth. A paper on the discovery was published last week in the Astrophysical Journal.
The 74 exoplanets, which are located light-years away from our sun, orbit about 30 suns and have the approximate size of our planet.
Usually, larger exoplanets have elongated obits that either draw them really close to their host star or push them really far away from it. These odd orbits are called eccentric orbits.
Over the past two decades, as scientists started finding more and more giant exoplanets with eccentric orbits, they wondered whether those elongated orbital paths would also occur in smaller planets. So, their new discovery points out that “for small planets, circular is probably the norm.”
Authors of the find argued that circular orbits were another requirement for habitable planets. First they have to be really dense and compact like the Earth is, so they can also have a rocky structure.
Second, they need a circular orbit so their climate remains stable throughout the year. In elongated orbits, climate swings are so dramatic that hardly any life form could inhabit those planets, scientists explained.
“If eccentric orbits are common for habitable planets, that would be quite a worry for life, because they would have such a large range of climate properties,”
During their research, astronomers from MIT’s Department of Physics and Aarhus University in Denmark sifted through the orbital data on 74 Earth-like exoplanets gathered by NASA’s Kepler telescope over the past four years. Kepler’s main mission is to monitor the sky in search for planets with great potential for hosting life.
The data contained info on abut 145,000 stars, but 28 of them caught the team’s attention. Those stars’ mass and radius had been measured through a method that focuses on star’s pulsations, also known as asteroseismology. By taking into account the star’s mass and radius, astronomers were able to estimate their orbiting planets’ transit durations.
As a follow-up, the team now plans to analyze the orbits of more exoplanets to see whether circular orbits are a universal trait of smaller planets, or a common feature of the small sample of 74 exoplanets alone.
Image Source: Astrowatch
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