Astronomers have discovered an extremely massive, mysterious dark object inside two colliding galaxies that could be a black hole much more massive than ever thought possible.

If the object is indeed a black hole, it is at least 40 billion times more massive than the Earth's sun and 10 to 100 times more massive than any black hole previously believed possible.The object could also be a dormant quasar, from which galaxies are believed to have been born more than 10 billion years ago, astronomers speculated.

But scientists are uncertain what the object is and hope to learn more by studying it further, including observing the object with the Gamma Ray Observatory, which was launched by the space shuttle Atlantis on Sunday.

The object was discovered by Andrew Wilson of the University of Maryland at College Park, Joss Bland-Hawthorn of Rice University in Houston and Brent Tully of the University of Hawaii. Their work is described in an article in Friday's issue of The Astrophysical Journal.

The astronomers discovered the object while mapping a galaxy called NGC 6240, which is about 300 million light years from Earth.

The astronomers used a powerful three-dimensional light-measuring instrument and an 88-inch telescope on an observatory perched on the 14, 000-foot-high extinct Mauna Kea volcano in Hawaii.