This Exoplanet Disappeared From Hubble Observations. Now, We Finally Know Why

In 2004 and 2006, the Hubble Area Telescope captured anything incredible. There appeared to be a earth orbiting a star identified as Fomalhaut 25 light-several years away, and it was right detectable in seen light: exceptionally rare for exoplanets, which are generally far too small and faint to be viewed.


The item, formally named Fomalhaut b or Dagon, was introduced in 2008, and confirmed in 2012, assumed to be a fuel huge on a 1,seven-hundred-12 months, hugely elliptical orbit all around its host star.

But whilst examining previously unpublished Hubble photographs taken back again in 2014, astronomers acquired a shock. The putative earth hadn’t just changed. It wasn’t that its orbit was not as expected.

Dagon had vanished altogether.

dagon planet(NASA, ESA, P. Kalas/UC Berkeley)

In its area was… very little, foremost astronomers to the summary that the spot was never an exoplanet at all. In its place, they now believe that the vibrant spot seen in people early Hubble photographs was an even rarer sight – the aftermath of a collision concerning two asteroid-sized planetesimals.

“These collisions are exceedingly rare and so this is a large deal that we truly get to see one,” claimed astronomer András Gáspár of the College of Arizona. “We believe that that we had been at the right area at the right time to have witnessed these kinds of an unlikely occasion with the Hubble Area Telescope.”

The identification of Dagon as an exoplanet was never challenge cost-free. Fomalhaut is rather a youthful star, all around 440 million several years old, and nonetheless surrounded by an icy ring of dust and fuel, the remnants of a circumstellar disc.


That signifies any planets orbiting the star should also be rather youthful, and as a result heat, emitting infrared radiation – however no infrared radiation was detected emitting from Dagon. It was also unusually vibrant in blue optical wavelengths, which isn’t really consistent with our types of earth development. 

To reveal these peculiarities, astronomers proposed that the earth was shrouded by a large ring or cloud of dust, most likely as the end result of collisions with other objects, or a smaller earth with a large ring technique. Some even proposed that Dagon may be a neutron star.

But none of these explanations had been conclusive, and there was another large challenge: Dagon’s orbit appeared to cross the ring of debris all around the star without having disturbing it gravitationally, as a earth should. So astronomers have ongoing to look at the technique.

dagon smear(NASA, ESA, and A. Gáspár and G. Rieke/College of Arizona))

“Our examine, which analysed all available archival Hubble facts on Fomalhaut b, such as the most current photographs taken by Hubble, unveiled a number of qualities that jointly paint a picture that the earth-sized item may never have existed in the first area,” Gáspár claimed.

When they uncovered Dagon’s astonishing absence in the 2014 Hubble facts, Gáspár and his colleague, astronomer George Rieke of the College of Arizona, scurried to reexamine the prior observations.


And they identified, astonishingly, that the item looks to have been fading over time – which right contradicts that 2012 examine that validated Dagon’s exoplanet position by acquiring no change in the object’s brightness concerning observations.

“Clearly, Fomalhaut b was accomplishing factors a bona fide earth should not be accomplishing,” Gáspár claimed.

Centered on their examination of the facts, Gáspár and Rieke believe that that the collision took area not extended prior to that first Hubble image in 2004. The two objects would have every been all around two hundred kilometres (one hundred twenty five miles) throughout, and most likely built up of rock and ice, like Solar Procedure comets.

The two objects arrived jointly in a colossal smash-up that was briefly seen, but has been increasing and dissipating over time. By now, the particles will be considerably far too small to be picked up by Hubble, so tracking it further more would not genuinely be feasible.

On the other hand, dependent on the facts, the team was capable to ascertain that Dagon – or what’s left of it – isn’t really orbiting the star following all. Instead, it is really on an escape trajectory away from Fomalhaut.

“A recently designed huge dust cloud, suffering from appreciable radiative forces from the central star Fomalhaut, would be placed on these kinds of a trajectory,” Gáspár explained. “Our product is obviously capable to reveal all impartial observable parameters of the technique: its expansion price, its fading and its trajectory.”

The investigation has been released in PNAS.