For the first time ever, a group of scientists caught a sun-like star devouring a planet. Unfortunately, the discovery may also foreshadow Earth's fate in about five billion years. In a study published Wednesday in Nature, a team at MIT, Harvard University, Caltech and multiple other institutions detailed that over the course of 10 days in May 2020, they observed a Jupiter-sized planet spiral closely to a dying star that was 1,000 times its size until it was finally engulfed in the star's core.
The scientists said the star continued to expand and grew 100 times brighter in just 10 days before quickly fading away and returning to its normal state once the meal was over. The planetary demise took place in our galaxy, some 12,000 light-years away near the eagle-like constellation Aquila. "We were seeing the end-stage of the swallowing," said Kishalay De, the study's lead author and postdoctoral student at MIT, in a news release.
It's a sobering reality of what many astronomers believe will also likely befall Earth in the far off future when our own Sun runs out of fuel, balloons and consumes any matter—including the solar system's inner planets—in its wake. Luckily, humans likely won't be around for the event. "We are seeing the future of Earth," De said. "If some other civilization was observing us from 10,00 light-years away while the sun was engulfing the Earth, they would see the sun suddenly brighten as it ejects some material, then form dust around it, before settling back to what it was."
The team reportedly stumbled upon the discovery by accident. De was looking at data from the Zwicky Transient Facility at Caltech's Palomar Observatory for signs of eruptions of binary star systems, in which two stars orbit one another, with one periodically brightening as it pulls mass from the other. "One night, I noticed a star that brightened by a factor of 100 over the course of a week, out of nowhere," De said. "It was unlike any stellar outburst I had seen in my life."
The rendering shows the gas giant meeting its demise as it spiraled into its parent star. Ultimately, the planet plunged into the core of the star, which triggered the star to expand and brighten.
K. Miller/R. Hurt (Caltech/IPAC)Additionally, De noticed that the source produced molecules that only exist at cold temperatures, meaning it was not likely to be a binary system. "Low temperatures and brightening stars do not go together," De said. With additional observations taken with an infrared camera at the Palomar Observatory, the team was able to confirm the presence of cold material that appeared to spill out from the source over the next year.
Following further measurements taken by NASA's infrared space telescope NEOWISE, the team realized the source of the cool outburst after learning that the total energy released by the star since it brightened was only 1/1,000th the magnitude of any previously observed stellar mergers. "That means that whatever merged with the star has to be 1,000 time smaller than any other star we've seen," De said. "That's when we realized: This was a planet, crashing into its star."
The scientists concluded that the initial outburst—the bright, hot flash—was likely the final moments of the planet being pulled into the dying star's expanded atmosphere. As the planet was drawn into the star's core, the outer layers of the star blasted away, settling out as a cold dust.
De said that for decades, scientists have only been able to see when planets are still orbiting very close to their star and after when a planet has already been engulfed and star is giant. "What we were missing was catching the star in the act, where you have a planet undergoing this fate in real-time," he said. "That's what make this discovery really exciting."
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