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Existing theories on the relationship between the size of a galaxy and its central black hole are wrong according to a new Australian study.

The discovery by Dr Nicholas Scott and Professor Alister Graham, from Melbourne’s Swinburne University of Technology, found smaller galaxies have far smaller black holes than previously estimated.

Central black holes, millions to billions of times larger than the Sun, reside in the core of most galaxies, and are thought to be integral to galactic formation and evolution.

However astronomers are still trying to understand this relationship.

Scott and Graham combined data from observatories in Chile, Hawaii and the Hubble Space Telescope, to develop a data base listing the masses of 77 galaxies and their central supermassive black holes.

The astronomers determined the mass of each central black hole by measuring how fast stars are orbiting it.

Existing theories suggest a direct ratio between the mass of a galaxy and that of its central black hole.

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Black holes are surrounded by many mysteries, but now researchers from the Niels Bohr Institute, among others, have come up with new groundbreaking theories that can explain several of their properties. The research shows that black holes have properties that resemble the dynamics of both solids and liquids.

Black holes are extremely compact objects in the universe. They are so compact that they generate an incredibly strong gravitational pull and everything that comes near them is swallowed up. Not even light can escape, so light that hits a black hole will not be reflected, but will be entirely absorbed, as a result, they cannot be seen and we call them black holes.

“But black holes are not completely black, because we know that they emit radiation and there are indications that the radiation is thermal, i.e. it has a temperature,” explains Niels Obers, a professor of theoretical particle physics and cosmology at the Niels Bohr Institute at the University of Copenhagen.

Researchers know that the black holes are very compact, but they do not know what their quantum properties are. Niels Obers works with theoretical modelling to better understand the physics of black holes. He explains that you can look at a black hole like a particle. A particle has in principle no dimensions. It is a point. If you give a particle an extra dimension, it becomes a string. If you give the string an extra dimension, it becomes a plane. Physicists call such a plane a ‘brane’ (the word ‘brane’ is related to ‘membrane’ from the biological world).

“In string theory, you can have different branes, including planes that behave like black holes, which we call black branes. The black branes are thermal, that is to say, they have a temperature and are dynamical objects. When black branes are folded into multiple dimensions, they form a ‘blackfold’,” explains Niels Obers, who worked out this new way of looking at black branes with associate professor in theoretical physics at the Niels Bohr Institute, Troels Harmark, back in 2009.

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Astronomers have discovered a new, enormous black hole that could change our understanding of how galaxies evolve.

Holding the mass of 17 billion suns, the black hole at the centre of the NGC 1277 galaxy may be the largest discovered to date. It is 250 million light-years from the Earth.

Most supermassive black holes are contained within very large galaxies. But the NGC 1277 galaxy is remarkably small compared to the black hole at its centre.

The researchers, who reported their findings in Nature today, say black holes usually take up 0.1% of a galaxy’s “stellar bulge” (the collection of stars at its centre). It’s thought this black hole comprises 59% of its galaxy’s stellar bulge mass, and 14% of the galaxy’s mass overall.

For this reason, the black hole has been described as “overmassive” rather than simply supermassive.

In its entirety, it is thought to be 11 times wider than Neptune’s orbit of the sun.

“This is a really oddball galaxy,” team member Karl Gebhardt of The University of Texas said in a statement. “It’s almost all black hole.”

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Astronomers have found the best evidence yet that the dormant gravitational monster that lies at the centre of the Milky Way — a supermassive black hole known as Sagittarius A* — recently emitted a pair of γ-ray jets.

As they feed on stars and clouds of gas that stray too close, black holes at the centres of other galaxies create bright jets that can be seen across cosmic distances. But the Milky Way’s black hole shows no signs of such activity. Now, the Fermi Gamma-ray Space Telescope has picked up some faint γ-ray signals that suggest that Sagittarius A* has not always been so tranquil. The black hole could even have been active as recently as 20,000 years ago, after gulping down a gas cloud with a mass about 100 times that of the Sun, says Douglas Finkbeiner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

“If these features truly are γ-ray jets from Sagittarius A*, it would tell us that our Galactic supermassive black hole has not always been as feeble as we currently observe it to be,” says Fred Baganoff of the Massachusetts Institute of Technology in Cambridge. And that would solve an enduring puzzle, he notes. Sagittarius A* is growing about 1,000 times too slowly for it to have reached its current mass of about four million solar masses since the Galaxy formed about 13.2 billion years ago. “If confirmed, the existence of γ-ray jets would provide the strongest evidence to date for the existence of higher activity in the past,” he says.

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Scientists may have found the smallest black hole yet by listening to its X-ray “heartbeat.”

The black hole, if it truly exists, would weigh less than three times the mass of the sun, putting it near the theoretical minimum mass required for a black hole to be stable.

The researchers can’t directly observe the black hole, but they measured a rise and fall in X-ray light coming from a binary star system in our Milky Way galaxy that they think signals the presence of a black hole.

Until now, this X-ray pattern, which is similar to a heartbeat registered on an electrocardiogram, has been seen in only one other black hole system.

NASA’s Rossi X-ray Timing Explorer (RXTE) spacecraft measured this X-ray heartbeat in a star system in the direction of the constellation Scorpius, at a distance between 16,000 and 65,000 light-years away (a light-year is the distance light travels in a single year, about 6 trillion miles (10 trillion kilometers).

Researchers think the system, officially called IGR J17091-3624, includes one normal star with a companion black hole. Mass would stream off this normal star and fall toward the black hole, forming a flattened disk around it. As friction in the disk heats the gas to millions of degrees, the disk would emit high-energy X-rays that can be seen across the galaxy.

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