Planet collapses to 140 light-years of dust

In the Pegasus of the constellation, a tiny world disappears before the eyes of astronomers. MIT scientists have discovered a planet the size of mercury that actually evaporated as it orbits its star, leaving behind spectacular traces of planetary debris that stretched millions of kilometers in space.

The doomed planet is designated BD+05 4868 AB, and the stars are circled every 30.5 hours at temperatures reaching 1,600 degrees Celsius, which is enough to boil surface minerals into space. Even more strikingly, the dying world describes researchers as an unprecedented proportion of “comet-like tail.”

“The tail range is Gargantuan, which is 9 million kilometers long, about half the entire orbit,” said Marc Hon, a postdoctoral fellow at the MIT Kavli Institute of Astrophysics and Space Studies.

Astronomers used NASA’s Exoplanet Survey Satellite (TESS), a MIT-led mission to watch Telltale Dips in nearby stars in a spinning planet. What caught the researchers’ attention was a special transit signal, with each orbit fluctuating in depth.

The demise of the earth is happening at an alarming rate. Each orbit emits material equivalent to Mount Everest, completely disintegrating within 1 to 2 million years – only in the blink of an astronomical timescale.

“When it really fades away, we were lucky to be able to catch it accurately,” noted Avi Shporer, a collaborator at Tess Science office. “It’s like a last breath.”

BD+05 4868 AB was not discovered through targeted studies, but in routine analysis of TESS data. “We’re not looking for such a planet,” Hon explained. “We’re doing a typical planetary review, and I happened to find this signal, which looks very unusual.”

Unlike typical exoplanet signatures that show a brief and even tilt in starlight, the planet’s transit pattern reveals something strange: brightness takes longer to return to normal, suggesting trailing structures, and each orbit changes with each orbit, indicating variable blockage of starlight.

“The shape of the transit is typical of a long-tail comet,” Horn said. “Except for this kind of tail is unlikely to contain volatile gases and ice like a real comet – they won’t survive close proximity to the host star.”

The low mass of the Earth – between Mercury and our moon – creates a deadly feedback loop. As the minimum intensity of gravity holds itself together, it keeps losing matter, further weakening its gravity.

“It’s a very tiny object with very weak gravity, so it’s easy to lose a lot of mass and then further weaken its gravity, so it loses more mass,” Shporer explained. “It’s a process that is out of control, and for the earth, it’s just getting worse.”

Of nearly 6,000 confirmed exoplanets, only three other disintegrating worlds were discovered by NASA’s Kepler telescope a decade ago. BD+05 4868 AB stands out in this rare group with the longest tail and the deepest transit.

“This means its evaporation is the most disastrous and its disappearance will be much faster than other planets,” Hon noted.

The scientific team plans to use NASA’s James Webb space telescope this summer to view the system, hoping to determine the mineral composition of the dust tail. Hon suggests that these observations can provide unprecedented insights: “This will be a unique opportunity to directly measure the composition of rocky planets, which may tell us a lot about the diversity and potential habitability of terrestrial planets outside the solar system.”

Meanwhile, researchers will continue to search for more examples of these rare disappearing worlds through Tess data. “Sometimes, food brings an appetite, and we are now working to start searches for these objects,” Shporer said.

The study will be published in the Journal of Astrophysics letter with the support of NASA.