Extra Solar Planet with Surface Temperatures conducive to life

https://phys.org/news/2020-06-mirror-image-earth-sun.html

A mirror image of Earth and sun:

Among the more than 4,000 known exoplanets, KOI-456.04 is something special: less than twice the size of Earth, it orbits a sun-like star. And it does so with a star-planet distance that could permit planetary surface temperatures conducive to life. The object was discovered by a team led by the Max Planck Institute for Solar System Research in Göttingen. Its host star, called Kepler-160, actually emits visible light; the central stars of almost all other exoplanets, on the other hand, emit infrared radiation, are smaller and fainter than the sun and therefore belong to the class of red dwarf stars.

Space telescopes such as CoRoT, Kepler, and TESS have allowed scientists the discovery of about 4000 extrasolar planets (planets around distant stars) within the past 14 years. Most of these planets are the size of the gas giant planet Neptune, about four times the size of the Earth, and in relatively close orbits around their respective host stars. But scientists have also discovered some exoplanets as small as the Earth that could potentially be rocky. And a handful of these small planets are also at the right distance to their host star to potentially have moderate surface temperatures for the presence of liquid surface water—the essential ingredient for life on Earth. "The full picture of habitability, however, involves a look at the qualities of the star too," explains MPS scientist and lead author of the new study Dr. René Heller. So far, almost all exoplanets less than twice the size of Earth that have a potential for clement surface temperatures are in orbit around a red dwarf.

Red dwarf stars are known for their extremely long lifetimes. Life on an exoplanet in orbit around an old red dwarf star could potentially have had twice as much time than life on Earth to form and evolve. But the radiation from a red dwarf star is mostly infrared rather than visible light as we know it. Many red dwarfs are also notorious for emitting high-energy flares and for frying their planets, which would later become habitable, with enhanced stellar luminosities as long as these stars are young. Moreover, their faintness requires any habitable planet to be so close to the star that the stellar gravity starts to deform the planet substantially. The resulting tidal heating in the planet could trigger fatal global volcanism. All things combined, the habitability of planets around red dwarf stars is heavily debated in the scientific community.

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The other factor of course for "life as we know it" is tha presence of an atmosphere and what that atmosphere consists of.
In the relatively short time that we have been able to detect extra solar planets, we already have numbers of around 4000. Considering a couple of decades ago, we had no evidence whatsoever of any planet beyond our own solar system.

 

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