In 6 billion years, the sun will expand into a red giant. That process should consume Mercury, and maybe Venus. For a long time, we have thought it might incinerate Earth, too.
But perhaps all is not doomed for Earth, although it may be a world that will have long since become uninhabitable.
Scientists have found a rocky world orbiting another star that already went through its red giant phase. This planet now orbits a white dwarf, the smaller stellar body that remains after a star burns out.
Crucially, the planet looks like it once orbited the star in the same position Earth now travels around our sun, and did so until it was pushed to a more distant orbit, twice the Earth-sun distance, sometime before the dying giant could eat it. This makes it the first potential rocky world to be observed orbiting a white dwarf.
“We don’t know if Earth can survive,” said Keming Zhang, an astrophysicist at the University of California, San Diego, who led the work published in the journal Nature Astronomy. “If it does, it’ll end up somewhere like this system.”
The planet is about 4,000 light-years away from us. It was discovered in 2020 with a Korean telescope network. The Korean team had watched as the planet’s star passed in front of another star, which from the background magnified the amount of light heading toward the telescope by 1,000 times.
This specific occurrence was a one-off event, limiting chances for detailed follow-up observations. But Zhang’s team was able to do additional work at the Keck Observatory in Hawaii last year and identify the star as a white dwarf.
The data the researchers managed to gather allowed them to calculate that there were at least two objects orbiting the white dwarf.
One was a suspected brown dwarf, a failed star that never ignited with nuclear fusion, situated at a very great distance away from the star. But the other object was a planet about 1.9 times the mass of Earth orbiting much closer to the star, suggesting it was a rocky planet. — JONATHAN O’CALLAGHAN/NYT
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