NASA's WISE Spacecraft Discovers Most Luminous Galaxy in Universe

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NASA's WISE Spacecraft Discovers Most Luminous Galaxy in Universe
Jet Propulsion Laboratory
May 21, 2015

A remote galaxy shining with the light of more than 300 trillion suns
has been discovered using data from NASA's Wide-field Infrared Survey
Explorer (WISE). The galaxy is the most luminous galaxy found to date
and belongs to a new class of objects recently discovered by WISE -- extremely
luminous infrared galaxies, or ELIRGs.

"We are looking at a very intense phase of galaxy evolution," said Chao-Wei
Tsai of NASA's Jet Propulsion Laboratory in Pasadena, California, lead
author of a new report appearing in the May 22 issue of The Astrophysical
Journal. "This dazzling light may be from the main growth spurt of the
galaxy's black hole."

The brilliant galaxy, known as WISE J224607.57-052635.0, may have a behemoth
black hole at its belly, gorging itself on gas. Supermassive black holes
draw gas and matter into a disk around them, heating the disk to roaring
temperatures of millions of degrees and blasting out high-energy, visible,
ultraviolet and X-ray light. The light is blocked by surrounding cocoons
of dust. As the dust heats up, it radiates infrared light.

Immense black holes are common at the cores of galaxies, but finding one
this big so "far back" in the cosmos is rare. Because light from the galaxy
hosting the black hole has traveled 12.5 billion years to reach us, astronomers
are seeing the object as it was in the distant past. The black hole was
already billions of times the mass of our sun when our universe was only
a tenth of its present age of 13.8 billion years.

The new study outlines three reasons why the black holes in the ELIRGs
could have grown so massive. First, they may have been born big. In other
words, the "seeds," or embryonic black holes, might be bigger than thought
possible.

"How do you get an elephant?" asked Peter Eisenhardt, project scientist
for WISE at JPL and a co-author on the paper. "One way is start with a
baby elephant."

The other two explanations involve either breaking or bending the theoretical
limit of black hole feeding, called the Eddington limit. When a black
hole feeds, gas falls in and heats up, blasting out light. The pressure
of the light actually pushes the gas away, creating a limit to how fast
the black hole can continuously scarf down matter. If a black hole broke
this limit, it could theoretically balloon in size at a breakneck pace.
Black holes have previously been observed breaking this limit; however,
the black hole in the study would have had to repeatedly break the limit
to grow this large.

Alternatively, the black holes might just be bending this 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,"
said Tsai. "This can happen if the black hole isn't spinning that fast."

If a black hole spins slowly enough, it won't repel its meal as much.
In the end, a slow-spinning black hole can gobble up more matter than
a fast spinner.

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

More research is needed to solve this puzzle of these dazzlingly luminous
galaxies. The team has plans to better determine the masses of the central
black holes. Knowing these objects' true hefts will help reveal their
history, as well as that of other galaxies, in this very crucial and frenzied
chapter of our cosmos.

WISE has been finding more of these oddball galaxies in infrared images
of the entire sky captured in 2010. By viewing the whole sky with more
sensitivity than ever before, WISE has been able to catch rare cosmic
specimens that might have been missed otherwise.

The new study reports a total of 20 new ELIRGs, including the most luminous
galaxy found to date. These galaxies were not found earlier because of
their distance, and because dust converts their powerful visible light
into an incredible outpouring of infrared light.

"We found in a related study with WISE that as many as half of the most
luminous galaxies only show up well in infrared light," said Tsai.

JPL manages and operates WISE for NASA's Science Mission Directorate in
Washington. The spacecraft was put into hibernation mode in 2011, after
it scanned the entire sky twice, thereby completing its main objectives.
In September 2013, WISE was reactivated, renamed NEOWISE and assigned
a new mission to assist NASA's efforts to identify potentially hazardous
near-Earth objects.

For more information on WISE, visit:

http://www.nasa.gov/wise


Media Contact

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, California
818-354-4673
whitney...@jpl.nasa.gov

Felicia Chou
NASA Headquarters, Washington
202-358-0257
felici...@nasa.gov

2015-173