Astronomers have spotted a star devouring one of its planets for the first time. It’s a stunning insight into the fate of our own planet, when in about 5 billion years Earth will likely be engulfed by our rapidly expanding sun as well.
A distant planet met its bloody demise 13,000 light-years from Earth around a star that rapidly exploded to a thousand times its original size. Astronomers witnessed the death of the unfortunate planet as a distinct white flash of light that grew in intensity over 10 days.
By studying the light from the explosion, as well as chemical signatures from the material ejected from the planet-eating star, scientists identified the consumed planet as a gas giant at least 30 times the size of Earth. We see the future of Earth,” lead author Kishalay De a postdoctoral fellow at the Kavli Institute for Astrophysics and Space Research at the Massachusetts Institute of Technology.
“If any other civilization were to observe us from 10,000 light-years away while the Sun was engulfing the Earth, they would see the Sun suddenly brighten as it ejects some material, then create dust around it before settling back to what it was.”
For most of their lives, stars burn by fusing hydrogen atoms into helium. However, once they exhaust their hydrogen fuel, they begin fusing helium, leading to a massive increase in energy output that causes them to swell to hundreds or even thousands of times their original size engulfing their inner planets as they transform into giant stars called red giants.
Scans the sky for sudden changes in star brightness
Astronomers first spotted the strange flash of light using the Zwicky Transient Facility, an astronomical survey that scans the sky for sudden changes in star brightness using the California Institute of Technology’s Palomar Observatory.
That’s when they discovered the flash, designated ZTF SLRN-2020, which began as a bright beam of light and grew 100 times stronger over the next 10 days. The light was on for 100 days before it erupted.
To investigate what might have caused the flash, scientists turned to the Keck Observatory in Hawaii and used a spectrograph to break the light into individual wavelengths to determine its chemical composition. At first, scientists suspected they were spotting a nova a dying binary pair that brightens suddenly when the shell of one star (a white dwarf) steals some fire from its red giant the chemical signatures didn’t match.
The molecules the researchers saw “are only seen in stars that are very cool,” De said. “And when a star brightens, it usually warms up. So cold temperatures and brightening stars don’t go together.”
Using NASA’s NEOWISE infrared space telescope, scientists found the final clue to the mystery the energy released by the flash was tiny, about 1,000 times less bright than any previous star merger. Astronomers realized they had captured the final moments of a Jupiter-sized planet being engulfed by its star, burning in a blazing flame as it fell towards the red giant’s core before turning to dust.
Evidence of stars consuming their planets has long been observed in chemical signatures around stars, but this is the first direct observation ever. Scientists say it provides a crucial insight into what the rest of the universe will see when Earth, along with Mercury and Venus, have a deadly rendezvous with our star in about 5 billion years.
“I think there’s something quite remarkable about these results that speaks to the transience of our existence,” co-author Ryan Lau an astronomer at NOIRLab, said in a statement. “After the billions of years that span the lifetime of our Solar System, our own end stages are likely to complete a final flare lasting only a few months.”
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