Astronomers
have looked under the hoods of quasars, the brightest objects in the universe,
and found some of the best evidence yet for the black
holes that are thought to power them.
The new
study, presented today at the meeting of the American Astronomical Society
(AAS) High Energy Astrophysics Division in San Francisco, lends further
confirmation to the idea that quasars are anchored by supermassive black holes
and the flattened disks of material spiraling into them.
Astronomers
have puzzled over quasars
for decades before deciding each is a very active and developing galaxy most
likely containing supermassive black
holes that formed billions of years ago. This cosmic yin-yang between the
darkest and brightest space objects has made understanding quasars difficult.
Black holes
are so dense that nothing, not even light, can escape their gravitational
clutches, making them impossible to observe directly. And even though quasars, or quasi-stellar radio sources, are the universe's most powerful
sources of constant light, they are billions of light-years away. So even with the most
powerful telescopes they appear as pinpoints of light. On top of that, the dust
and gas lit up by a quasar makes seeing inside one a great challenge.
The
researchers led by Xinyu Dai and Christopher Kochanek of Ohio State University
were only able to view the interior structures of the two quasars, named
RXJ1131-1231 and Q2237+0305, when a galaxy lined up between them and the Earth,
magnifying their light--a phenomenon called gravitational
microlensing. Like a Sumo wrestler rolling over and deforming a soft mat,
the weighty galaxy dented, or curved, the fabric of space-time, rerouting and
in this case focusing light from the quasars behind it.
The
magnification allows astronomers to see quasars that would otherwise have
remained invisible.
"Luckily
for us, sometimes stars and galaxies act as very high-resolution
telescopes," Kochanek said. "Now we're not just looking at a quasar,
we're probing the very inside of a quasar and getting down to where the black
hole is."
With NASA's
Chandra X-Ray Observatory, coupled with measurements from optical telescopes,
the astronomers were able to measure the size of the so-called accretion disk
inside each quasar, one of which spanned about 14 astronomical units (AU),
where one AU is the distance from Earth to the sun.
"It's the
first time anyone has measured the size of the disk around one of these black
holes," Kochanek told SPACE.com.
The disks
each surrounded an area that was emitting X-rays, a telltale sign that the
material at the disk's center is being heated up as it speeds up prior to
falling into the black
hole.
The
astronomers are currently studying 20 such lensed quasars, and they hope to
gather X-ray data on all of them.
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