Washington, Sep 18 :
Astronomers including an Indian-origin scientist have found an unlikely object in an improbable place – a monster black hole lurking inside one of the tiniest galaxies ever known.
If you lived inside this dwarf galaxy, the night sky would dazzle with at least 1 million stars visible to the naked eye.
Our nighttime sky as seen from Earth’s surface shows 4,000 stars.
The black hole is five times the mass of the one at the center of our Milky Way galaxy.
“We do not know of any other way you could make a black hole so big in an object this small,” said astronomer Anil Seth from University of Utah.
“It is inside one of the densest galaxies known to date — the M60-UCD1 dwarf galaxy that crams 140 million stars within a diameter of about 300 light-years, which is only 1/500th of our galaxy’s diameter,” added the team that used data from NASA’s Hubble Space Telescope and ground observation.
The finding implies there are many other compact galaxies in the universe that contain supermassive black holes.
The observation also suggests dwarf galaxies may actually be the stripped remnants of larger galaxies that were torn apart during collisions with other galaxies rather than small islands of stars born in isolation.
Seth’s team of astronomers used the Hubble Space Telescope and the Gemini North 8-meter optical and infrared telescope on Hawaii’s Mauna Kea to observe M60-UCD1 and measure the black hole’s mass.
The sharp Hubble images provide information about the galaxy’s diameter and stellar density. Gemini measures the stellar motions as affected by the black hole’s pull. These data are used to calculate the mass of the black hole.
The black hole at the center of our Milky Way galaxy has the mass of four million suns.
As heavy as that is, it is less than 0.01 percent of the Milky Way’s total mass.
By comparison, the supermassive black hole at the center of M60-UCD1, which has the mass of 21 million suns, is a stunning 15 percent of the small galaxy’s total mass.
“That is pretty amazing, given that the Milky Way is 500 times larger and more than 1,000 times heavier than the dwarf galaxy M60-UCD1,” Seth noted.
The international study of the dwarf galaxy was published in the journal Nature.