Almost but not quite in time for
Halloween, astronomers announced on Friday that they had discovered the closest
known black hole. It is huge, a shell of yawning emptiness 10 times as massive
as the sun, orbiting as far from its own star as the Earth is from ours.
اضافة اعلان
Not to worry, however: This black hole is 1,600
light-years away, in the constellation Ophiuchus. The next nearest known black
hole is about 3,000 light-years away in the constellation Monoceros. What sets
this new black hole apart from the 20 or so others already identified in our
Milky Way galaxy, besides its proximity, is that it is not doing anything — not
drawing the nearby star to its doom, not gravitationally consuming everything
nearby. Rather, the black hole is dormant, a silent killer waiting for the
currents of space to feed it.
Black holes are objects so dense that, according to
Einstein’s theory of general relativity, not even light can escape them. This
makes them the most intriguing and violent phenomena in nature; when they feed,
they can become the most brilliant objects in the universe as gas, dust, and
even smaller stars are ripped and heated to incandescence, spewing energy as
they approach the gates of eternity.
Most every galaxy has a supermassive black hole
millions of billions of times more massive than the sun. And scientists are not
sure where they come from. Smaller black holes are thought to form from massive
stars that have reached the ends of their thermonuclear lives and collapsed.
There are probably millions of black holes in the Milky Way. They typically
make themselves known by the X-rays they spit out as they strip gas from their
companions in double-star systems.
But what about dormant holes, those that are not
currently coughing fire? Kareem El-Badry, an astrophysicist at the
Harvard-Smithsonian Center for Astrophysics, has been searching for such hidden
demons for four years. He found this black hole by scrutinizing data from the
European Space Agency’s GAIA spacecraft, which has been tracking with exquisite
precision the positions, motions, and other properties of millions of stars in
the Milky Way.
El-Badry and his team detected a star, virtually
identical to our sun, that was jittering strangely, as if under the
gravitational influence of an invisible companion. To investigate further, the
researchers commandeered the Gemini North telescope atop Mauna Kea in Hawaii,
which could measure the speed and period of this wobble and thus determine the
relative masses of the objects involved. The technique is identical to the
process by which astronomers analyze the wobbles of stars to detect the
presence of orbiting exoplanets — except this time the quarry was far bigger.
Their results and subsequent calculations were
consistent with a black hole of 10 solar masses being circled by a star similar
to our own. They named it Gaia BH1.
“Take the solar system, put a black hole where the
sun is and the sun where the Earth is, and you get this system,” El-Badry said
in a news release from the National Optical and InfraRed Laboratory, which runs
the Gemini North Telescope.
“This is the
nearest known black hole by a factor of three, and its discovery suggests the
existence of a sizable population of dormant black holes in binaries,” he and
his co-authors wrote in a paper published last week in the Monthly Notices of
the UK’s
Royal Astronomical Society.
Astronomers said that the new discovery raised
questions about their presumed knowledge of how such binary star systems
evolved. The progenitor of this black hole must have been a star of about 20
solar masses. According to the leading theories, the star’s death and the
subsequent black hole formation would have involved a supernova explosion and
other processes that would have severely disrupted the other, smaller star in
the system. So why does the other star appear so normal?
“It poses many questions about how this binary
system was formed,” El-Badry said in the news release, “as well as how many of
these dormant black holes there are out there.”
Read more Odd and Bizarre
Jordan News
.jpg)
.jpg)
