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Astronomers have discovered an exoplanet with a dark future, moving closer to its host star until it was finally obliterated.
The exoplanet, called Kepler-1658b, was identified in 2019, a decade after the Kepler space telescope discovered it as a candidate planet.
The planet is considered a “hot Jupiter”, or a type of exoplanet similar in size to Jupiter – but hot in temperature. Kepler-1658b orbits its aging star tightly, completing a single orbit every 3.85 days.
But the orbit breaks down, causing the planet to gradually move closer to its star. Finally, this movement will result in a collision and the obliteration of the planet. The Astrophysical Journal Letter published a study on Monday detailing the findings.
“We have already detected evidence of exoplanets inspiring towards their stars, but we have never seen such a planet around an evolved star,” said study lead author Shreyas Vissapragada, 51 Pegasi Fellow. b. at the Astrophysics Center | Harvard & Smithsonian, in a statement.
“The theory predicts that evolved stars are very efficient at extracting energy from the orbits of their planets, and now we can test these theories with observations.”
After years of observations with Space and ground telescopes, researchers have calculated that the planet’s orbit is shrinking at a rate of 131 milliseconds per year. Telescopes monitored the star’s dips in brightness as the planet passed in front of it. The intervals between these troughs, called transits, have steadily decreased as the orbit has deteriorated.
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 the Earth and the Moon, but this planetary system could shed light on such dynamics.
The new research also helped researchers explain why Kepler-1658b looks even hotter and brighter than expected. The same gravitational tug between the planet and its star can also release additional energy from the planet.
“What we realized during this study is that the planet could be bright because it is much hotter than expected, which could happen if the same effects causing the decay of the planet’s orbit were also warming it,” Vissapragada said in an email. “I’m excited to investigate this possibility further: 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. The strong gravitational influence of Jupiter melts the interior of Io, causing lava to erupt from hundreds of volcanoes on the surface of this moon. The Juno mission will conduct several flybys of Io over the next year and a half to learn more about this volatile relationship.
Meanwhile, the aging star around which Kepler-1658b extends and enters its subgiant phase before becoming a red giant, a dying star in the later stages of life. The findings could potentially predict the fate of planets in our own solar system that may one day end up too close to the sun.
“In about five billion years, the sun will evolve into a red giant star,” Vissapragada said. “It seems certain that Mercury and Venus will be swallowed up during this process, but what happens to Earth is less clear.”
Researchers think more exoplanets are at risk of dying in the fiery light of their respective host stars, and their sightings could be imminent using TESS, or the Transiting Exoplanet Survey Satellite, which studies light from nearby stars.
“The Kepler-1658 system can serve as a celestial laboratory in this way for years to come,” Vissapragada said, “and hopefully there will be many more such laboratories soon.”
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