Hubble solves the mystery of the bizarre disappearing exoplanet

One of the interesting things about science is that knowledge is constantly being updated. This week, for example, images from the Hubble Space Telescope have led astronomers to question the nature of what was thought to be one of the first exoplanets ever imaged, Fomalhaut b.

First announced in 2008, Fomalhaut b was assumed to be an exoplanet because it was seen to be moving in Hubble images taken between 2004 and 2006. However, there were some oddities about it. It was bright in the visible light spectrum, but it didn’t have an infrared heat signature. And it seemed to be moving along a strange orbit.

Now, in the latest Hubble observations, Fomalhaut b has apparently disappeared.

This makes astronomers think that the object is not in fact a planet, but is actually a cloud of dust particles caused by a tremendous collision of two icy asteroids orbiting the star Fomalhaut. This is even more exciting than an exoplanet, as such collisions are not often observed. The scientists estimate that such an event only occurs in the Fomalhaut system once every 200,000 years.

Visualisation of Fomalhaut and Fomalhaut b
Data from the NASA/ESA Hubble Space Telescope have revealed an expanding cloud of dust produced in a collision between two large bodies orbiting the bright nearby star Fomalhaut. This is the first time such a catastrophic event around another star has been imaged. ESA/NASA, M. Kornmesser

“These collisions are exceedingly rare and so this is a big deal that we actually get to see one,” András Gáspár of the University of Arizona said in a statement. “We believe that we were at the right place at the right time to have witnessed such an unlikely event with the Hubble Space Telescope.”

“Our study, which analyzed all available archival Hubble data on Fomalhaut b, including the most recent images taken by Hubble, revealed several characteristics that together paint a picture that the planet-sized object may never have existed in the first place,” he continued.

Researchers believe that the collision must have occurred only shortly before the first observations were taken in 2004. When it happened, a cloud of dust was thrown out which looked like a planet. By the time of the latest observations, the dust had dispersed enough to no longer be visible.

To learn more about this system, astronomers plan to study it with the upcoming James Webb Space Telescope, set to launch next year.

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