This planet is getting dangerously close to its dying star

It could be a preview of what’s coming to Earth next. When its host star dies, an exoplanet gets dangerously close to it, a phenomenon called orbital regression. At this rate, a collision would occur in less than three million years, which would destroy the planet.

The event occurs at about 2629 light yearslight years from here. a starstarnamed Kepler-1658, has run out of fuel for Nuclear fusionNuclear fusion, and became a dying star. It was discovered in 2009 by Kepler Space TelescopeIt has continued to be studied since then, to the point where it was discovered exoplanetexoplanet Announced in 2019! and last, a Hot JupiterHot Jupiter Called Kepler-1658b, it appears to be gradually approaching its star. This is what scientists discovered and reported in a study in the journal Astrophysical Journal Letters.

with one collectivecollective 5.9 times larger than Jupiter, Kepler-1658b orbitorbit very close to the host star. Kepler-1658 completes a full rotation in just 3.85 days and is eight times closer to its star than Mercury. SunSunhence the nickname, Hot Jupiter ! And if it continues to approach its star at the same rate, it will collide with it in less than three million years.

Tidal forces bring Kepler-1658b closer to its star

This approach of Kepler-1658b toward its star is called an “orbital regression.” This phenomenon has also been observed among Neptune and its moon Io, or between Mars and its moon Phobos. It can have several causes, but in the study it mainly has to do with tidal effects. When two bodies orbit a common center of gravity, as is the case in these planetary systems, they exert a gravitational forcegravitational force one over the other. However, the force exerted will be more intense at the level of the parts closest to the center of gravity, and less at the level of the farther places.

But the tidal forces, alone, would not be sufficient to modify Kepler-1658b’s orbit, otherwise the same phenomenon would apply to all similar systems! This is the direction of rotation of the two starsstars which determines the outcome of this phenomenon. In the case of the Earth-Moon system, they force rotation synchronoussynchronous : The Moon is locked by tidal effects, and simultaneously makes a revolution around the Earth and rotates around itself. So much so that he always shows us the same face!

In the case of Kepler-1658b, the a movementa movement Retrograde: the planet rotates in the opposite direction to that of its star. This is what causes the convergence that the researchers noticed! Or at least partially. Because the star Kepler-1658 also turned out to be unusual! With 1.45 solar masses but a diameter more than three times that of the Sun, the star is currently in the “supergiant” phase: having used up all of its fuel, the star’s core contracts, and nuclear fusion reactions kick in at a slightly longer interval. outer layer. The result is a swelling of the star, and thus its diameter three times its own Sun !

A glimpse of what lies ahead in 5 billion years

Thanks by checking out the star Kepler-1658 and its planet transit method Almost 13 years ago, researchers observed a decrease in its orbit time of 131 milliseconds per year, a first around this type of star! “We’ve already detected evidence of exoplanets sucked into their stars, but we’ve never seen such a planet around an evolving star.”Shreyas Visapragada said in A communicationW., first author of the study AstrophysicistAstrophysicist to me Harvard-Smithsonian Center for Astrophysics. The theory predicts that evolving stars are very efficient at extracting energy from the orbits of their planets, and now we can test these theories through observations. »

An opportunity to learn more about this star and phenomenon. Because the same fate awaits our planet, when the Sun passes into the sub-giant stage, and then into red giantred giant. But do not panic, this phenomenon will not happen for 5 billion years, and the sun is only in the middle of its life! “Now that we have evidence of an absorbing planet around an evolving star, we can really start to improve our models physicalphysical Tides S. Vissapragada excited. “The Kepler-1658 system can serve as a celestial laboratory in this way for years to come, and we hope there will be more such laboratories soon.”