A new way to weigh giant black holes

July 16, 2008
A composite image from NASA's Chandra X-ray Observatory (shown in purple) and Hubble Space Telescope (blue) shows the giant elliptical galaxy NGC 4649. By applying a new technique, scientists used Chandra data to measure the black hole at its center to be about 3.4 billion times more massive than the Sun. The value from this X-ray technique is consistent with a more traditional method using the motions of stars near the black hole. NGC 4649 is now one of only a handful of galaxies for which the mass of a supermassive black hole has been measured with two different methods. Credit: X-ray: NASA/CXC/Univ. of California Irvine/P.Humphrey et al.; Optical: NASA/STScI

How do you weigh the biggest black holes in the universe? One answer now comes from a completely new and independent technique that astronomers have developed using data from NASA's Chandra X-ray Observatory.

By measuring a peak in the temperature of hot gas in the center of the giant elliptical galaxy NGC 4649, scientists have determined the mass of the galaxy's supermassive black hole. The method, applied for the first time, gives results that are consistent with a traditional technique.

Astronomers have been seeking out different, independent ways of precisely weighing the largest supermassive black holes, that is, those that are billions of times more massive than the Sun. Until now, methods based on observations of the motions of stars or of gas in a disk near such large black holes had been used.

"This is tremendously important work since black holes can be elusive, and there are only a couple of ways to weigh them accurately," said Philip Humphrey of the University of California at Irvine, who led the study. "It's reassuring that two very different ways to measure the mass of a big black hole give such similar answers."

NGC 4649 is now one of only a handful of galaxies for which the mass of a supermassive black hole has been measured with two different methods. In addition, this new X-ray technique confirms that the supermassive black hole in NGC 4649 is one of the largest in the local universe with a mass about 3.4 billion times that of the Sun, about a thousand times bigger than the black hole at the center of our galaxy.

The new technique takes advantage of the gravitational influence the black hole has on the hot gas near the center of the galaxy. As gas slowly settles towards the black hole, it gets compressed and heated. This causes a peak in the temperature of the gas right near the center of the galaxy. The more massive the black hole, the bigger the temperature peak detected by Chandra.

This effect was predicted by two of the co-authors -- Fabrizio Brighenti from the University of Bologna, Italy, and William Mathews from the University of California at Santa Cruz -- almost 10 years ago, but this is the first time it has been seen and used.

"It was wonderful to finally see convincing evidence of the effects of the huge black hole that we expected," said Brighenti. "We were thrilled that our new technique worked just as well as the more traditional approach for weighing the black hole."

The black hole in NGC 4649 is in a state where it does not appear to be rapidly pulling in material towards its event horizon, nor generating copious amounts of light as it grows. So, the presence and mass of the central black hole has to be studied more indirectly by tracking its effects on stars and gas surrounding it. This technique is well suited to black holes in this condition.

"Monster black holes like this one power spectacular light shows in the distant, early universe, but not in the local universe," said Humphrey. "So, we can't wait to apply our new method to other nearby galaxies harboring such inconspicuous black holes."

These results will appear in an upcoming issue of The Astrophysical Journal.

Source: Chandra X-ray Center

Explore further: Black hole is 30 times expected size

Related Stories

Black hole is 30 times expected size

September 24, 2015

The central supermassive black hole of a recently discovered galaxy is far larger than should be possible, according to current theories of galactic evolution. New work, carried out by astronomers at Keele University and ...

Milky Way's black hole shows signs of increased chatter

September 23, 2015

Three orbiting X-ray space telescopes have detected an increased rate of X-ray flares from the usually quiet giant black hole at the center of our Milky Way galaxy after new long-term monitoring. Scientists are trying to ...

11-year cosmic search leads to black hole rethink

September 24, 2015

One hundred years since Einstein proposed gravitational waves as part of his general theory of relativity, an 11-year search performed with CSIRO's Parkes telescope has failed to detect them, casting doubt on our understanding ...

Recommended for you

What happens when your brain can't tell which way is up?

October 13, 2015

In space, there is no "up" or "down." That can mess with the human brain and affect the way people move and think in space. An investigation on the International Space Station seeks to understand how the brain changes in ...

Hubble sees an aging star wave goodbye

October 12, 2015

This planetary nebula is called PK 329-02.2 and is located in the constellation of Norma in the southern sky. It is also sometimes referred to as Menzel 2, or Mz 2, named after the astronomer Donald Menzel who discovered ...

What are white holes?

October 9, 2015

Black holes are created when stars die catastrophically in a supernova. So what in the universe is a white hole?


Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (1) Jul 16, 2008
This method, which apparently only requires one observation, sounds like it's WAY faster than measuring star motions, which requires multiple observations. I'd bet we'll suddenly start hearing about the masses of all kinds of black holes, and the records of the biggest and smallest will soon be broken.
3 / 5 (2) Jul 16, 2008
This might change their views?

1 / 5 (1) Jul 16, 2008
Baloney. The HSK is good science!!!
1 / 5 (1) Jul 17, 2008
weight and temperatures do not distinguish between a blackhole and many stars orbiting each other.
not rated yet Jul 28, 2009
how could the research done by Evan Scannapieco and Marcus Brüggen (http://www.physor...07.html) on the turbulence created by black holes as cooler gas is drawn toward its center then pushed out by its jets, affect this method of determining the mass of a black hole??

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.