A supermassive black hole was discovered by NASA in what is believed to be one of the smallest galaxies known to man.

According to NASA, the supermassive black hole was seen by its astronomers using the Hubble Space Telescope on Wednesday, when they found the small galaxy known as M60-UCD1.

The dwarf galaxy reportedly "crams 140 million stars within a diameter of about 300 lightyears, which is only 1/500th" of the diameter of the Milky Way galaxy.

"It is the smallest and lightest object that we know of that has a supermassive black hole," said University of Utah astronomer Anil Seth.

"We believed this once was a very big galaxy with maybe 10 billion stars in it, but then it passed very close to the center of an even larger galaxy, M60, and in that process all the stars and dark matter in the outer part of the galaxy got torn away and became part of M60," Seth explained. "That was maybe as much as 10 billion years ago. We don't know."

"Eventually, this thing may merge with the center of M60, which has a monster black hole in it, with 4.5 billion solar masses - more than 1,000 times bigger than the supermassive black hole in our galaxy. When that happens, the black hole we found in M60-UCD1 will merge with that monster black hole," he added.

In an interview with ABC News Australia, Seth explained how a black hole works, saying "In a black hole, even if you launch yourself at the speed of light, which is the fastest you can go, you can't get out of a black hole."

The existence of the supermassive black hole is reportedly rare as such conditions have only been previously seen in larger galaxies and prompts researchers to believe that there is a chance that there are more black holes in the Milky Way than previously discovered.