With New Year's resolutions abound from people who pigged out during the holiday season, it looks like galactic black holes can shed weight too. Astronomers found a galaxy 1 billion light years away with two black holes, and one of them is "skinny" or "naked".
Black holes are massive structures in space that are usually surrounded by millions or billions of stars. This black hole discovered by scientists who used observations from the Hubble Space Telescope and NASA's Chandra X-ray Observatory do not have the expected number of starts surrounding it.
Scientists from the University of Colorado in Boulder found the "naked" black hole at the merger of two galaxies. With two galaxies coming together, they found two black holes - one massive as usual and the other one looking "naked" because of being deprived of the expected number of stars.
"One black hole is starved of stars, and has 500 times fewer stars associated with it than the other black hole," Julie Comerford, lead researcher and an assistant professor in CU-Boulder, Department of Astrophysical and Planetary Sciences said in a news release.
"The question is why there's such a discrepancy," she added.
The findings, presented at the annual meeting of the American Astronomical Society (AAS) held at Kissimmee, Florida, could shed light in the evolution and behavior of black holes in space. The bizarre black hole is located around 1 billion light years from Earth in SDSS J1126+2944, a merger of two galaxies.
Middle-sized black holes, unlike bigger and massive ones, have been predicted by astrophysics but have never been seen by any observers until now. In the past, astronomers only found supermassive black holes at the centers of all massive galaxies like the one where the solar system is found: the Milky Way.
Comerford added that the "naked" black hole could have emerged during the turmoil of the merger millions of years ago and extreme gravity and tidal forces stripped the smaller black hole of its stars. It might have also started with just a few stars because it is a different type of black hole.
Another theory the scientists have speculated is that the merger reveals a very rare "intermediate" black hole with a mass between 100 and 1 million times of that of the sun. This type of black hole is predicted to occur in the center of dwarf galaxies, hence having fewer stars to begin with. These intermediate black holes, however, can grow into supermassive black holes, which are common today in space.
"This unusual galaxy may provide a rare glimpse of one of these intermediate mass black holes," Scott Barrows, postdoctoral researcher at CU-Boulder, said.
The study was published online in Astrophysical Journal. It is publicly available [PDF] at arXiv.