There’s a planet 140 light years from Earth that is rapidly disappearing right before astronomers’ eyes. An immense amount of intense heat is to blame.
Although the planet is about the size of Mercury, its orbit is about 20 times closer to its star than Mercury is to our sun. Its year passes in about 30.5 of our hours, they report in the The Astrophysical Journal Letters.
Astronomers suspect the planet’s proximity has raised its temperature to about 3,000 degrees Fahrenheit, and rendered its surface in magma that is boiling off into space. As the hot planet orbits, it throws of a massive amount of surface minerals, which evaporate into space. To the astronomers observing it, the planet looks like a huge comet with a long tail of debris. That tail stretches nearly 6 million miles long, encircling about half the planet’s entire orbit.
Finding a Disintegrating Planet
The astronomers found what they named BD+05 4868 Ab while hunting for exoplanets. When doing so, they look for short dips in starlight brightness that occur whenever an exoplanet passes it. They saw such a signal from the comet-like planet, with one key difference. The “dip” in brightness changed with every orbit — not exactly a planetary sign of stability.
“We weren’t looking for this kind of planet,” Marc Hon, an MIT research fellow an an author of the paper, said in a press release. “We were doing the typical planet vetting, and I happened to spot this signal that appeared very unusual.”
In planetary terms, BD+05 4868 Ab is disintegrating rapidly. It loses the equivalent of Mt. Everest in material every time it circles its star. Given its size and the speed of its orbit, astronomers estimate it will be completely gone in about 1 million to 2 million years.
“We got lucky with catching it exactly when it’s really going away,” Avi Shporer, an MIT collaborator on the discovery and a co-author of the study said in a press release. “It’s like on its last breath.”
Read More: 6 Exoplanets in our Universe That Could Support Life Other Than Earth
Relatively Short Planet Life Left
Indeed, this planet is incredibly rare. Astronomers have discovered nearly 6,000 planets so far — but only three other similarly disintegrating ones. The other three also possess comet-like tails, but BD+05 4868 Ab has the longest tail and the deepest transits out of the four such planets.
“That implies that its evaporation is the most catastrophic, and it will disappear much faster than the other planets,” Hon said.
This summer, astronomers will take a closer look BD+05 4868 Ab with the James Webb Space Telescope. “This will be a unique opportunity to directly measure the interior composition of a rocky planet, which may tell us a lot about the diversity and potential habitability of terrestrial planets outside our solar system,” Hon said.
And now that they know what a signal for such a planet looks like, other astronomers are sure to be on the lookout for more.
Read More: 5 Planets with Extreme (and Weird) Weather Patterns in Our Solar System
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
The Astrophysical Journal Letters. A Disintegrating Rocky Planet with Prominent Comet-like Tails around a Bright Star
Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
