An unexpected discovery is upending theories about habitable planets. Astronomers have just proven that super-Earths are not rare... and that they are hiding much further from their star than we imagined.
Super-Earths are rocky exoplanets that are larger than Earth, but less imposing than giants like Neptune. Until now, it was thought that they only existed at a short distance from their star, where telescopes like Kepler were used to spotting them. But a team of researchers, whose work was published in the journal Science, has just proven that these worlds are also present in very distant orbits, up to ten times the distance that separates our planet from the Sun. This change of perspective opens a new chapter in the search for habitable worlds.
The discovery is based on a rare observation technique, gravitational microlensing, which makes it possible to spot otherwise invisible planets. By analyzing an event called OGLE-2016-BLG-0007, researchers detected a super-Earth in distant orbit. By expanding their calculations, they estimate that a third of stars could harbor this type of planet. In other words, these worlds could be much more widespread than expected, including in areas previously considered uninteresting.
These distant super-Earths could be located in habitable zones
These distant planets could be located in so-called habitable zones, where water can exist in liquid form. If the star is hotter than the Sun, a super-Earth as far away as Saturn could very well be at the right temperature. This is reminiscent of the exoplanet LHS 1140 b, detected by the James Webb telescope, which could harbor a temperate ocean at 20°C. This type of discovery reinforces the idea that life could develop in very different places than what was previously imagined.
Beyond their interest in the search for life, these planets also shake up our understanding of the formation of stellar systems. Astronomers now distinguish two main families: rocky planets like super-Earths, and gas giants like Jupiter. Their frequency at great distances suggests more varied formation mechanisms than previously thought. Thanks to the KMTNet network, which allows continuous observation of the sky from three continents, researchers hope to expand their catalog and perhaps discover even more surprising worlds.
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