NASA finds 'most luminous' galaxy

The WISE telescope has discovered the brightest galaxy ever found, shedding new light on the supermassive black holes commonly found at their centre.

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Artist's depiction of the newly-discovered galaxy; the most luminous ever found in the Universe.
Image credit: NASA/JPL-Caltech

The most luminous galaxy discovered to date, shining with the brightness of 300 trillion Suns, has been found using NASA’s Wide-field Infrared Survey Explorer (WISE).

The galaxy belongs to a class known as extremely luminous infrared galaxies (ELRIGs), which have been recently discovered by WISE.

It is thought that this latest, named WISE J224607.57-052635.0, could have a massive black hole at its centre that is feeding on gas. When this happens, supermassive black holes suck gas and matter into a disk surrounding them, heating the gas to temperatures of millions of degrees and emanating high energy, ultraviolet X-ray light. This light heats up surrounding dust, creating an infrared glow.

Light from this black hole has travelled 12.5 billion years to reach us, meaning the black hole was already billions of times the mass of the Sun when the Universe was only a tenth of its age.

Three theories have been posited as to why black holes in ELIRGs are so massive. The first suggests that the ‘seeds’ of the black holes might have been bigger than currently thought possible.

The second suggests that the black hole may have broken its feeding limit, called the Eddington limit. As a black hole sucks in matter, the gas on which it ‘feeds’ heats up, emanating light. But the pressure of this light pushes the gas away, meaning there is a limit to how fast the black hole can feed on the matter. Theoretically, the Eddington limit could be broken, which would see the black hole balloon in size. However, for this theory to work, the black hole would have to repeatedly break the limit in order to grow so big.

The third theory sees the black hole simply bending the Eddington limit.

“Another way for a black hole to grow this big is for it to have gone on a sustained binge, consuming food faster than typically thought possible,” says Chao-Wei Tsai of NASA’s Jet Propulsion Laboratory in Pasadena, California, lead author of the report. “This can happen if the black hole isn’t spinning that fast. We are looking at a very intense phase of galaxy evolution.”

“The massive black holes in ELIRGs could be gorging themselves on more matter for a longer period of time,” says Andrew Blain of the University of Leicester, a co-author of the report. “It’s like winning a hot-dog-eating contest lasting hundreds of millions of years.”

The team will now attempt to better determine the masses of central black holes in order to shine a light on their history and evolution.


 

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