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Astronomers have come across an exoplanet with a bleak future, spiraling closer to its host star until it is eventually obliterated.
The exoplanet, called kepler-1658bwas identified in 2019, a decade after the Kepler space telescope discovered it as a planet candidate.
The planet is considered as ahot jupiter”, or a type of exoplanet similar in size to Jupiter, but with a searing temperature. Kepler-1658b closely orbits its aging star, completing a single orbit every 3.85 days.
But the orbit is decaying, bringing the planet ever closer to its star. Finally, this movement will lead to a collision and the destruction of the planet. The Astrophysical Journal Letter published a study detailing the findings on Monday.
“We have previously detected evidence of exoplanets inhaling towards their stars, but we have never seen such a planet around an evolved star before,” said the study’s lead author, Shreyas Vissapragada, a member of 51 Pegasi b. at the Harvard & Smithsonian Center for Astrophysics, in a statement.
“Theory predicts that evolved stars are very effective at extracting energy from the orbits of their planets, and now we can test those theories with observations.”
After years of observations with Using both space and ground-based telescopes, the researchers calculated that the planet’s orbit is declining at a rate of 131 milliseconds per year. The telescopes observed dips in the star’s brightness as the planet passed in front of it. The intervals between these dips, called transits, have steadily decreased as the orbit has decayed.
Tidal interactions, or the gravitational relationship between Kepler-1658b and its star, are to blame for the planet’s inward pull. Astronomers are still learning about the gravitational interactions between orbiting bodies, like Earth and the Moon, but this planetary system could shed light on those dynamics.
The new research also helped the researchers potentially explain why Kepler-1658b appears even hotter and brighter than expected. The same gravitational pull between the planet and its star may also be releasing extra energy from the planet.
“What we realized during this study is that the planet could be bright because it is much hotter than previously predicted, which could happen if the same effects that cause the planet’s orbit to decay are also warming it,” he said. Vissapragada in an email. “I am excited to further study this possibility: are we witnessing the last gasp of a doomed planet?”
It’s not unlike Jupiter’s moon Io, the most volcanic place in our solar system. Jupiter’s strong gravitational influence is melting Io’s interior, causing lava to erupt from hundreds of volcanoes on the moon’s surface. The Juno mission will carry out multiple flybys of Io in the next year and a half to learn more about this volatile relationship.
Meanwhile, the aging star orbiting Kepler-1658b is expanding and entering its subgiant phase before becoming a red giant, a dying star in the final stages of life. The findings could potentially anticipate the fate of planets in our own solar system that may one day find themselves too close to the sun.
“In about five billion years, the sun will become a red giant star,” Vissapragada said. “It seems certain that Mercury and Venus will be engulfed in this process, but what happens to Earth is less clear.”
Researchers believe that more exoplanets are in danger of dying out in the fiery light of their respective host stars, and observations of them may be just around the corner using TESS, or the Transiting Exoplanet Survey Satellite, which studies the light from nearby stars.
“The Kepler-1658 system may serve as a celestial laboratory in this way for years to come,” Vissapragada said, “and with any luck, there will be many more of these laboratories soon.”
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