Scientists discover massive but peaceful black...
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Feb 19, 2016  |  Vote 0    0

Scientists discover massive but peaceful black hole

Black hole with mass 21 billion times that of the Sun detected in galaxy pictured by Hubble Space Telescope about 300 million light years from Earth

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Astronomers have detected a supermassive black hole with a mass about 21 billion times larger than that of the Sun in a galaxy some 300 million light-years from Earth.

But don’t fret, the gigantic black hole is “napping quietly as it waits for its next celestial snack,” researchers said earlier this month.

And despite its size, the environment of the black hole is so peaceful that stars are forming and orbiting it undisturbed.

An elliptical galaxy known as NGC 4889, astronomers working with images from the Hubble Space Telescope said, “harbours a dark secret.”

“At its heart lurks one of the most massive black holes ever discovered,” a post on the Hubble website reads.

Black holes cannot be directly detected. In this case, scientists measured the velocity of stars moving within the NGC 4889 galaxy, which is influenced by the mass of the object they orbit, to determine the mass of the black hole.

“A black hole is essentially the remnants of a very large star that is near the end of its life,” explained Randy Attwood, executive director of the Astronomical Society of Canada.

Much larger than the Sun, that original star is “always in a tug of war” between the gravitational force pulling material in and the nuclear energy at its centre producing light and heat and pushing out, Attwood explained.

When the star collapses due to its gravitational force taking over — a phenomenon that also causes it to explode as a supernova — it becomes a black hole.

“That’s what we call a black hole — not because it is a hole, but because it is so dense — and the gravitational force from that black hole is so dense — it cannot reflect light. That’s why it appears dark,” Attwood told the Star.

The event horizon — the point around a black hole at which light cannot escape the gravitational pull — of this particular, supermassive black hole measures 130 billion kilometres in diameter.

That is 15 times the diameter of Neptune’s orbit from the Sun, the Hubble Space Telescope website explained.

“If you were to get close to it, everything gets pulled in, including light. The event horizon being 130 billion kilometres . . . that’s huge — much, much bigger than other event horizons that they’ve seen around black holes,” Attwood said.

By comparison, the diameter of the event horizon of the supermassive black hole at the centre of the Earth’s galaxy, The Milky Way, is one-fifth Neptune’s orbit and its mass is four million times that of the Sun.

The NGC 4889 black hole may help astronomers better understand the early formation of “mysterious and elusive objects” known as quasars, extremely luminous object believed to surround a black hole, the Hubble post explained.

“It’s just a better understanding of the evolution of stars and galaxies that sort of helps you understand the whole history of the universe,” Attwood said.

Toronto Star

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