Astronomers using NASA’s Wide-Field Infrared Survey Explorer (WISE) have discovered the most luminous galaxy ever found.
This artist’s concept depicts the extremely luminous infrared galaxy WISE J2246-0526. Image credit: NASA / JPL-Caltech
The galaxy, catalogued as WISE J224607.57-052635.0 (WISE J2246-0526), belongs to a recently discovered class of objects – extremely luminous infrared galaxies (ELIRGs).
WISE J2246-0526 is smaller than our home Milky Way Galaxy, yet puts out 10,000 times more energy (equal to more than 300 trillion suns).
Astronomers think that the galaxy may have a behemoth black hole at its belly, gorging itself on gas. As the gas is dragged toward the black hole, it heats up and blasts out visible, UV and X-ray light.
The dust swaddling WISE J2246-0526 absorbs this light and heats up, radiating longer-wavelength, infrared light. The dust also blocks our view of shorter, visible-light wavelengths, while letting longer-wavelengths through.
In fact, over 99% of the light escaping from this dusty galaxy is infrared. As a result, it is much harder to see with optical telescopes.
Because light from WISE J2246-0526 has traveled 12.5 billion years to reach Earth, astronomers are seeing the galaxy as it was in the distant past. During this epoch, galaxies would have been more than five times closer together than they are now. This is due to the expansion of space – space itself and the galaxies in it are stretching apart from each other at ever-increasing speeds.
WISE J2246-0526’s black hole was already billions of times the mass of our Sun when the Universe was only a 1/10 of its present age of 13.8 billion years.
“The massive black holes in ELIRGs could be gorging themselves on more matter for a longer period of time. It’s like winning a hot-dog-eating contest lasting hundreds of millions of years,” said Prof Andrew Blain of the University of Leicester, UK, a co-author of the paper accepted for publication in the Astrophysical Journal (arXiv.org preprint).
Prof Blain and co-authors report a total of 20 new ELIRGs, including WISE J2246-0526. These galaxies, which are even more luminous than the ultraluminous infrared galaxies (ULIRGs) reported before, were not found earlier because of their distance, and because dust converts their powerful visible light into an incredible outpouring of infrared light.
The astronomers have plans to better determine the masses of the central black holes in ELIRGs. 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.
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Chao-Wei Tsai et al. 2015. The Most Luminous Galaxies Discovered by WISE. ApJ, in press; arXiv: 1410.1751
