“Doomed fate of planets: Researchers observe planet being swallowed by dying star”

For the first time, a research team is able to observe how a planet is being swallowed up by its dying star – a fate that also awaits Earth.

Boston – Stars like the sun fuse hydrogen into helium in their hot core – until the hydrogen runs out. The star then begins to fuse helium into carbon, expanding into a red giant star in the process. A star can expand to 100 to 1000 times its original size – bad news for the planets orbiting the star: If they are too close, they can be swallowed up by their star in the process.

Research assumes that in the Milky Way alone, a few planets are wiped out from their star in this way every year. So far, planets have been observed that came dangerously close to their star and stars that were swollen and must have swallowed their planets. “What we couldn’t do was catch the star in the act when a planet met that fate in real time,” explains Kishalay De of the Masachusetts Institute of Technology (MIT) in Boston. De is lead author of a new study reporting for the first time a planet being swallowed by a star. It was published in the specialist journal Nature. “We have seen the final stage of swallowing,” explains the researcher.

Dying star brightens a thousand times in a week

For a long time, however, the researchers involved had no idea what they had seen. In data from the Zwicky Transient Facility (ZTF) telescope, De made the discovery that would lead to the study: “One night I noticed a star that got brighter by a factor of 100 over the course of a week, out of nowhere,” recalls he himself in one communication from his university. “It was unlike any stellar outburst I had seen before.”

Data from the Keck Telescope in Hawaii showed that the star was ejecting neither hydrogen nor helium – an unexpected discovery for the researcher. Instead, De saw evidence of molecules that can only exist at very low temperatures. “You can only see these molecules in stars that are very cold. And when a star gets brighter, it usually gets hotter. Low temperatures and brightening stars don’t go together,” says De, explaining his mysterious find.

Surprising discovery: dying star is devouring its planet

An observation in the infrared range gave De’s research team a helping hand, because in the infrared range the researchers were able to discover something that De “let fall off his chair”, as he says himself. “The source was incredibly bright in the infrared,” the scientist recalls. Apparently the star threw cold material into space. The research team suspected that the star might be merging with another star – but there was not enough material that the star released into space.

“Whatever merged with the star had to be 1,000 times smaller than any star we’ve seen so far,” De explains his team’s finding. “And by a happy coincidence, the mass of Jupiter is exactly one hundred-thousandth that of the Sun. Then we understood: It was a planet crashing into its star.”

Puzzle solved: dying star puffs up and devours planets

With this finding, the research group was able to piece the puzzle together: the bright flash that caught De’s attention was the final moment in a Jupiter-sized planet crashed into a bloated, dying star. The star’s outer layers were then blasted away and settled as cold dust over the course of the year.

Science is sure that one day a similar fate will befall the planets Mercury, Venus and Earth. “We see the future of the earth,” emphasizes De. “If another civilization were to watch us from 10,000 light-years away as the sun engulfs the earth, they would see the sun suddenly brighten as it ejects some material, then forms dust around itself before becoming that again.” what it was,” says the researcher.

Good news: the sun won’t expand for five billion years

But there is also good news: There is still a lot of time until this dramatic end of the earth. The sun’s nuclear fusion isn’t expected to end for another five billion years, when the sun will balloon out and engulf the inner planets of the solar system, including Earth. (tab)