A star swallows a planet

This artist’s interpretation shows a star so swollen that it is engulfing a doomed planet.
K. Miller/R. Hurt (California Institute of Technology/IPAC

  • Astronomers have detected a distant star swallowing a planet for the first time ever.
  • It’s a glimpse into the future: In 5 billion years, the Sun will swell up to engulf the Earth.
  • This star swallowed a planet the size of Jupiter and left nothing but dust. The death of the Earth will be no less tragic.

A distant Jupiter-sized planet found itself in serious trouble when its star began to die – the same fate Earth would eventually face.

As the space star burned up the last of its hydrogen fuel, it swelled to 100 times its original size, and its atmosphere bulged outward toward the planet it orbits. Meanwhile, this world was getting closer and closer to the bulging star with each orbit.

Finally, the dying star’s atmosphere engulfed the planet, drawing it into its core. Swallowing the entire planet produced a blast of energy that ejected the star’s outer layers, causing it to rapidly expand and brighten.

The gas from the star’s ejected layers then cooled and condensed into a cloud of dust – the only remaining evidence that a planet ever existed there.

This is what astronomers determined after watching the star, 12,000 light-years away, suddenly explode with hot white light, getting 100 times brighter in just 10 days, before quickly fading and turning colder.

This is exactly how the Earth will die. In about 5 billion years, when the Sun burns up and swells, it will devour all the inner planets: Mercury, Venus, and Earth.

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The Sun, with flares of plasma erupting from its surface.
NASA/SDO

“We see the future of Earth,” Kechalai D, a postdoctoral fellow at MIT’s Kavli Institute for Astrophysics and Space Research who led the discovery, said in a press release. “If another civilization were watching us from 10,000 light-years away as the sun swallowed the earth, they would see the sun suddenly rise as it ejected some material, then form dust around it, before settling back to where it was.”

Dee and colleagues at Harvard University, Caltech, and other institutions published Their findings appear in the journal Nature on Wednesday.

The swallowing of the Earth would be a “minor” act in relation to the Sun

Sunbeams begin to illuminate Earth’s atmosphere as the International Space Station flies into a tropical sunrise.
NASA

Scientists believe that most planets will die this way. This is the first time they’ve seen it happen live, thanks to the lucky timing and sheer size of the planet.

Even for this giant world, D said at a briefing with reporters Tuesday, it was “almost like a star ate up that planet and completely forgot about it.”

Except for a speck of dust, the star looked pretty much the same as before, one year after it devoured its planet.

For the sun, swallowing the earth would be less important. The distant planet whose star had just been sucked in was the size of Jupiter, more than 1,300 Earths.

Jupiter, captured by NASA’s Juno spacecraft as it made a close pass of the gas giant planet.
NASA/JPL-Caltech/SwRI/MSSS/Kevin M

It’s possible that Mercury, Venus, and Earth have “really minor perturbations in the sun’s energy production,” said Morgan MacLeod, a postdoctoral researcher at the Harvard-Smithsonian Center for Astrophysics and co-author of the new study. in the briefing.

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“When the sun evolves and engulfs the planets of the solar system, this future sun may not be disturbed at all,” he said.

Fortunately, humans – and perhaps all other forms of life – will not be around to see that. At that point, Earth would be inhospitable for tens of thousands of years. As the sun bulges toward it, all of the planet’s water would likely evaporate and become too hot for life as we know it.

Three clues point to the first glimpse of a star absorbing a planet

Dee first spotted the dying star while researching supernovae—stars that devour so much gas from a nearby star that they cause a nuclear explosion, and erupt thousands of times brighter in a period of just weeks.

A nova explodes in space, while one star is feeding on another.
NASA Goddard

In search of any possible novae he spotted, he looked again with the Keck Observatory in Hawaii, which refracts wavelengths of light emitted by a star, to determine its chemical composition.

That’s when he started scratching his head around this lonely star 12,000 light-years away. It was full of particles that can only exist in extremely cold temperatures. This was the first clue that something was unusual about this star.

“That’s when we realized it was nothing like a nova at all,” Dee said.

The nova should be surrounded by hot gas. This star was sitting in cool gas – it’s bright in infrared light. So Di and his colleagues pointed an infrared camera at the star.

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There was clue number 2: It was startlingly bright in the infrared, indicating that the star was surrounded by dust. She must have expelled this dust as part of the bright explosion that first caught Dee’s attention.

How long has the dust been there? NASA’s infrared space telescope, NEOWISE, will have a record of it. So De went back through his data.

This is where they found the third clue: dust had been circulating around the star for several months before its bright outburst. This was definitely not a star eating another star. (It later turned out that the pre-eruptive dust was material from the planet skimming off the star’s atmosphere as it closely orbited.)

They calculated the total energy released by all that dust and gas expelled from the star, and determined that the object the star was eating must be about 1,000 times smaller than the star—about the size of a planet.

“Since we knew there were planets around other stars, it was almost an inevitable expectation that the stars should swallow their planets as they evolved,” Di said. “What we hadn’t really seen before was the effect of ingestion itself. And that was the missing piece to this whole puzzle.”

This article has been updated. Originally published on May 3, 2023.

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