These three exoplanets are actually…stars!

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[EN VIDÉO] exoplanets
What are exoplanets, where are they located and why are they so interesting? Video answer!

In 1995 astronomers announced that they washed the planet in orbit around a star other than ours Sun. Shot thunder! Since then, scientists have discovered many more. About 5000 in our galaxy. But rather 5000 minus 3 – even minus 4. Because researchers from Massachusetts Institute of Technology (MIT, USA) today reports that three exoplanets maybe even four, identified thanks to Kepler space telescopeare actually likely to be very small stars.

Recall that there is a mass limit that allows you to distinguish a planet from a star. “Twice mass of Jupiterit’s starting to look suspicious.”comments Prajwam Niraula, lead author of the study, in press release from the Massachusetts Institute of Technology . Since over this mass the temperature and pressure at the heart of the object are such reactions thermonuclear reactioninitiated. Then a star lights up. Thus, an estimate of the size and mass of an object appears to be critical in confirming that it is an exoplanet.

Astronomers from the Massachusetts Institute of Technology were alerted primarily by the strange signal returned by Kepler-854b. What they were looking for was to identify systems showing signs of tidal distortion, which occurs when the gravitational pull of one object causes another close to it to form an egg. “This gives an idea of ​​the mass of the smallest object under consideration”Prajwam Niraula says. So he literally stumbled upon Kepler-854b. “The object is a huge ellipsoidal signal. Almost immediately, we realized that this could not have come from the planet.”explains Avi Sporer, a researcher at the Massachusetts Institute of Technology.

Updated catalog of exoplanets

So the team did some testing. When Kepler-854b was identified in 2016, the available stellar data was not as accurate as what we have today, thanks in part to the Gaia mission. The size of the object was estimated based on the then known size of its parent star. By method transits . It consists in determining the size of an object by falling brightnessrecorded for the star in the background. But new data available to astronomers now show that Kepler-854b reaches a size on the order of three times that of Kepler-854b. Jupiter . “It’s impossible toUniversecould create a planet of this size.”, says Avi Sporer. What was thought to be an exoplanet is actually just a small star orbiting a larger one.

The surprise passed, the researchers wanted to know if there was catalog of exoplanets, other possible errors of this kind. To find the answer, they set off in search of stars whose size had been revised thanks to measurements from the Gaia mission. They found three. With putative planets in orbit that end up being two to four times the size of Jupiter. Kepler-840b and Kepler-699b have left the ranks of exoplanets and joined the ranks of small stars.

Doubts about Kepler-747b persist. The size of the object has indeed been overestimated and is now 1.8 times the size of Jupiter. So close to the famous star-planet boundary. But leaning a priori more on the exoplanet side. However, astronomers note that Kepler-747b is orbiting very far from its intended orbit. host star. Too far away to be such a big planet.

The corrections made by the MIT researchers will be useful, in particular, to those who rely on the list of exoplanets to study the population as a whole. In order to provide them with correct results, it is better to avoid intruders. But what “false positives” slippage into data should happen less and less, we are assured. Thanks to the sensitivity of the instruments, which continues to progress.

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