Article Posted on : - Sep 06, 2011

Composite image of spiral galaxy NGC 3393. Photo: NASA

WASHINGTON (BNS): Astronomers have discovered the first pair of supermassive black holes in a spiral galaxy similar to the Milky Way, according to NASA.

The black holes are approx 160 million light years from Earth and they were discovered by using NASA's Chandra X-ray Observatory.

The black holes are located near the center of the spiral galaxy NGC 3393 and separated by only 490 light years from each other. They are likely the remnant of a merger of two galaxies of unequal mass a billion or more years ago.

According to the report, previous observations in X-rays and at other wavelengths indicated that a single supermassive black hole existed in the center of NGC 3393. However, a long look by Chandra allowed the researchers to detect and separate the dual black holes.

When two equal-sized spiral galaxies merge, astronomers think it should result in the formation of a black hole pair and a galaxy with a disrupted appearance and intense star formation. A well-known example is the pair of supermassive black holes in NGC 6240, which is located about 330 million light years from Earth, it said.

Both of the supermassive black holes are heavily obscured by dust and gas, which makes them difficult to observe in optical light. Because X-rays are more energetic, they can penetrate this obscuring material. Chandra's X-ray spectra show clear signatures of a pair of supermassive black holes.