Astronomers have identified for the first time a planet spiraling toward a cataclysmic collision with the aging Sun, potentially offering a glimpse of how Earth could one day end. In a new study published Monday, a team of mostly US researchers said they hope the doomed exoplanet Kepler-1658b can help shed light on how worlds die as their stars age. Kepler-1658b, which is 2,600 light-years away from Earth, is known as the “hot Jupiter” planet.
Although the planet is similar in size to Jupiter, it orbits its host star at an eighth of the distance between our Sun and Mercury, making it much hotter than the gas giant in our own solar system. Kepler-1658b’s orbit around its host star takes less than three days — and shortens by about 131 milliseconds a year, according to a study published in The Astrophysical Journal Letters. “If it continues to spiral toward its star at the observed rate, the planet will collide with its star in less than three million years,” said Shreyas Vissapragada, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics and lead author of the study.
“This is the first time we have observed direct evidence that a planet is spiraling towards its evolved star,” he told . An evolved star has entered the “subgiant” stage of the stellar life cycle, when it begins to expand and become brighter. Kepler-1658b’s orbit is shortened by tides, a process similar to how Earth’s oceans rise and fall each day. This gravitational push-and-counter can work both ways – for example, the Moon very slowly spirals away from Earth. – Earth’s ‘final adios’? –
So could Earth be headed for a similar doom?
“Death after a star is a fate that awaits many worlds and could be Earth’s final adios in billions of years as our Sun ages,” the Center for Astrophysics said in a statement. Vissapragada said that “in five billion years the Sun will evolve into a red giant star”. While the tidal-driven processes observed on Kepler-1658b “will drive the decay of Earth’s orbit toward the Sun,” the effect could be balanced by the Sun’s mass loss, he said.
“The ultimate fate of the Earth is somewhat unclear,” he added. Kepler-1658b was the first ever exoplanet observed by the Kepler space telescope, which launched in 2009. But it took nearly a decade before the planet’s existence was confirmed in 2019, the Center for Astrophysics said. Over the course of 13 years, astronomers were able to observe a slow but steady change in the planet’s orbit as it crossed the face of its host star. One “big surprise” was that the planet itself is quite bright, Vissapragada said. It was previously thought that this was because it was a planet with a special reflectivity, he said. But now scientists believe that the planet itself is much hotter than expected, likely due to the same forces driving it toward its star.
