Scientists find black hole bonanza

25.06.2013 02:25

You're in no danger of falling in,

but a large group of possible cosmic vacuum

cleaners have just been identified.

Researchers have come upon 26 possible

black holes in Andromeda, a galaxy near our


This is the largest number of possible black

holes found in a galaxy outside the Milky

Way, but that may be because of

Andromeda's relative proximity to our galaxy.

It's probably easiest for Earth-based

scientists to find black holes outside the

Milky Way there, said Robin Barnard of the

Harvard-Smithsonian Center for Astrophysics

in Cambridge, Massachusetts.

Combining this discovery with previous

observations of nine other black hole

candidates, scientists can say that

Andromeda has a total of 35 possible black

holes. The research is published in The

Astrophysical Journal.

NASA's Chandra X-ray Observatory made

more than 150 observations over the course

of 13 years to identify these black hole


Seven of the new potential Andromeda black

holes reside within 1,000 light years of the

center of that galaxy. This supports earlier

research showing that, near the center of

Andromeda, there are an unusual number of

X-ray sources.

Black holes can't be seen directly. But

astronomers can detect material falling into

them when they interfere with other stars.

A black hole is a dense region of space that

has collapsed in on itself in such a way that

nothing can escape it, not even light.

In a binary system of this nature, a black

hole and a star orbit each other closely.

Material from the star falls into the black

hole and "as it spirals in, it gets hotter and

hotter, and faster and faster, and eventually

it gives off X-rays, so we see lots and lots of

X-rays coming out of it," Barnard said.

The material as it has been swallowed gets

incredibly hot, up to about 10 billion degrees.

Because of the tremendous amount of energy

released, some of the brightest objects in the

universe are black holes.

It's hard for scientists to distinguish distant

black holes from neutron stars, however.

When a star explodes in a supernova, its fiery

death leaves behind either a neutron star or

a black hole, which is a more extreme version

of a neutron star.

If our own sun were a neutron star, it would

be only about 10 kilometers, or 6.2 miles,

across, Barnard said. By comparison, as a

black hole our sun might be only 2 kilometers

across. Black holes of the kind that scientists

may have spotted in Andromeda have masses

that are typically five to 10 times that of the


Neutron stars have a surface, so falling

material pounds onto it, Barnard said.

Material rains down at enormous speeds,

causing huge explosions and energy


Billions of years from now, the Milky Way and

Andromeda galaxies will collide, marking the

end of the galaxy as we know it .