SEATTLE - The
discovery of three distant supermassive black holes in proximity to one another is giving astronomers a glimpse into the chaotic early years of the
universe.
Known as quasars,
these incredibly bright objects are thought to be powered by gas
falling into enormous black
holes situated in the centers of galaxies.
Although smaller than our solar
system, a single quasar can outshine an entire galaxy of a hundred billion stars.
Roughly
100,000 quasars have been observed in recent years, some of them double
quasars. But this is the first time that three quasars have been found so
near one another. The three quasars are separated by about 100,000 to 150,000
light years--about the width of our Milky
Way [image].
"Quasars
are extremely rare objects. To find two of them so close together is very
unlikely if they were randomly distributed in space," said study leader
George Djorgovski, an astronomer at Caltech. "To find three is unprecedented."
The
discovery, made using the European Space Observatory's Very Large Telescope and
the W.M. Keck Observatory Hawaii, was reported here today at the 209th
meeting of the American Astronomical Society. A science paper on the research
has been submitted to Astrophysical Journal Letters.
One of the
quasars in the triplet, called LBQS 1429-008, was discovered in 1989 by a team
of astronomers led by Paul Hewett of the Institute of Astronomy in Cambridge,
England.
Hewett's
team later spotted what appeared to be a faint companion to their quasar, but
they dismissed it as a visual illusion created by gravitational
lensing, whereby light traveling towards Earth from distant galaxies is bent by
the gravity of massive objects--such as star
clusters, dark
matter clumps or other galaxies--in their path. Sometimes, this can create
mirror images of a galaxy in one or more different places in the sky.
But the new
observations have revealed a third, even fainter companion to Hewett's quasar
duo and, equally important, the lack of any galaxy that could possibly serve as
a lens. This makes it highly unlikely that gravitational lensing is
responsible, the researchers say.
"We
just could not reproduce the data," said study team member Frederic
Courbin of Ecole Polytechnique Federale de Lausanne in Switzerland. "It is
essentially impossible to account for what we see using reasonable
gravitational lensing models."
The team
also observed small differences in the properties of the three quasars that are
best explained if the quasars are physically distinct objects.
Double
quasars are thought to form when two galaxies, each containing their own supermassive
black holes, merge together. While the amalgamation of two black holes is
thought to just create a larger black hole, the merger of three black holes is
expected to be more violent and interesting.
"Three
is so much better than two because the dynamics of three gravitationally
interacting bodies is chaotic, as opposed to the much more regular motion of
two bodies simply orbiting each other," said Frederic Rasio of
Northwestern University in Illinois.
Rasio was
not involved in the triple quasar observations, but his team has done recent
theoretical work showing that interactions between three supermassive black
holes might occur as frequently as a few times per year within the observable
universe.
Rasio's
work also predicts that triple quasar encounters could eject one or more of the
bright objects straight out of the host galaxy. These "naked" quasars
are then destined to wander alone through the universe.
The triple
quasar discovery provides astronomers with a rare glimpse into an early, and
much more chaotic, period of the universe. The quasar trio is located about
10.5 billion light years away in the Virgo constellation [image].
This means light from those quasars that astronomers now see were emitted when
the universe was just over 3
billion years old. During that early epoch, the universe was a much smaller
space; galaxies were also smaller and collided much more frequently.
"Quasars
are believed to be powered by gas falling into supermassive black holes,"
Djorgovski said. "This process happens very effectively when galaxies
collide or merge, and we are observing this system at the time in the cosmic
history when such galaxy interactions were at a peak."
Editor's
Note: All
week, SPACE.com is providing complete
coverage of the 209th meeting of the American Astronomical Society.
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