More than a decade ago, Fomalhaut b was considered one of the first exoplanets to be directly imaged — but now it’s vanished, and scientists suspect it was actually nothing more than a huge cloud of dust created by a cosmic smashup.
- The disappearing act in the Fomalhaut star system, 25 light years away in the southern constellation Piscis Austrinus, was chronicled by the Hubble Space Telescope between 2004 and 2014. In 2004, the object known as Fomalhaut b was a bright spot in the dusty disk surrounding the star, but by 2014, its brightness had faded to below Hubble’s observational limit.
- For a while, scientists referred to Fomalhaut b half-jokingly as a “zombie planet” because they expected it to rise from the grave. But today in the Proceedings of the National Academy of Sciences, astronomers declare Fomalhaut b to be really most sincerely dead.
- They say the best explanation for the Hubble observations starts with a collision between two 125-mile-wide planetesimals. The result would be an expanding cloud of dust that eventually widened to span the size of Earth’s orbit around the sun — and dimmed as it did so. “This is a blueprint of how planets destroy each other,” the University of Arizona’s George Rieke said today in a news release.
Rieke and Andras Gaspar of the University of Arizona’s Steward Observatory are co-authors of the study in PNAS, titled “New HST Data and Modeling Reveal a Massive Planetesimal Collision Around Fomalhaut.”