A study carried out using NASA's Swift satellite and the Chandra X-ray Observatory has discovered a second super-sized black hole lying at the heart of an "unusual" galaxy near the Milky Way.

The new black hole is believed to exist in the Markarian 739 -- also known as NGC 3758 -- galaxy. Markarian 739 is believed to lie around 25 million light-years away toward the constellation Leo. The new black hole is the second to be discovered in the region.

New studies suggest that the two black holes are only separated by 11,000 light-years -- around a third of the distance separating the solar system from the center of the Milky Way. The two black holes' close proximity has since led to speculation about what would happen should they collide.

"If two galaxies collide and each possesses a supermassive black hole, there should be times when both black holes switch on as AGN," commented the study's coauthor Richard Mushotzky, professor of astronomy at UMCP. "We weren't seeing many double active galactic nuclei (AGN), so we turned to Chandra for help."

Active galactic nuclei are galaxies whose centres display unusual characteristics, such as atypical spectral line emissions or very strong radio emissions.

Only about 1 per cent of "monster black holes" are currently classified as "powerful AGN." The newly discovered black hole in Markarian 739 belongs to the even rarer binary AGN class, making it the second identified within half a billion light-years of Earth.

A study exploring the newly discovered AGN is set to appear in a forthcoming issue of The Astrophysical Journal Letters. The AGN's discovery comes just after NASA released data from the Swift satellite showing a sun being eaten by a black hole.