A Planet 140 Light-Years Away Is Shedding Itself Into Space, One Mountain at a Time

Every orbit, it loses the equivalent of Mount Everest. Minerals boiling off the surface, cooling into a tail of cosmic dust stretching 9 million kilometers behind it — roughly half its own orbital path. A planet disintegrating in plain sight.

BD+05 4868 Ab sits in the constellation Pegasus, 140 light-years away, roughly Mercury-sized, orbiting its star every 30.5 hours at 20 times Mercury's proximity to our sun. Surface temperature: around 1,600 degrees Celsius (2,900 degrees Fahrenheit). At those temperatures, rock does not stay rock.

The feedback is what makes this singular. Shedding mass weakens gravity, which causes more mass to escape in a runaway loop with no corrective mechanism. MIT astronomers who found it using NASA's TESS give it 1 to 2 million years before it's gone entirely. Three other such planets are known. This one has the longest tail and deepest transits of all four.

JWST observations are planned. The mineral composition of that tail — the planet's own interior, scattered into space — is still unknown.

Read the full story at MIT News, April 22, 2025.

Hot Take: A runaway feedback loop with only one possible outcome, unfolding on a schedule we can actually calculate. The universe is rarely this legible about its intentions.