Quasar light variability linked to black hole mass (Forwarded)

News Bureau
University of Illinois at Urbana-Champaign
Champaign, Illinois

Contact:
James E. Kloeppel, Physical Sciences Editor
217-244-1073

Released: 1/8/07

Quasar light variability linked to black hole mass

CHAMPAIGN, Ill. -- Quasars are some of the most luminous and distant
objects in the universe -- and appear to have something in common with
ordinary light bulbs, say researchers at the University of Illinois at
Urbana-Champaign and at the National Center for Supercomputing
Applications.

Quasars were discovered 40 years ago, when astronomers noticed that these
objects -- thought at the time to be stars -- were emitting far more radio
waves than expected. Researchers found, upon further inspection, that
these objects represented a new class of extremely energetic astronomical
object.

Astronomers now believe quasars are young galaxies powered by supermassive
black holes at their centers. These black holes can be millions or
billions of times more massive than our sun.

"With such enormous sources of energy, quasars are among the brightest
objects in the universe, some giving off thousands of times more light
than our own Milky Way galaxy from a region slightly larger than our solar
system," said Brian Wilhite, an astronomer at Illinois and a researcher at
NCSA. "Astronomers have also determined that quasars are incredibly
variable, with some quasars quadrupling in brightness in the span of just
a few hours."

Although rarely that dramatic, variability in light output is seen in
nearly all quasars, with average quasars changing in brightness by 10 to
15 percent over the course of one year, Wilhite said. Astronomers have yet
to pin down the exact mechanism that drives these changes.

Recently, Wilhite and other researchers at Illinois and NCSA found that
this variability is related to both the mass of the black hole at the
center of the quasar, and to the efficiency of the quasar at converting
gravitational potential energy into light energy.

Using data obtained by the Sloan Digital Sky Survey, the researchers
monitored the brightness and estimated the central black hole mass of more
than 2,500 quasars, observed over a period of four years. They found that,
for a given brightness, quasars with large black hole masses are more
variable than those with low black hole masses.

"Quasars with more massive black holes have more gravitational energy that
can potentially be extracted, which we would see in the optical as light,"
said Wilhite, who will present the team's findings at the American
Astronomical Society meeting in Seattle on Monday (Jan. 8).

"If two quasars have the same brightness, the one with the larger black
hole mass is actually less efficient at converting this gravitational
energy into light," Wilhite said. "We have found that these less-efficient
quasars have more variable light output. It could be a little like
flickering light bulbs -- the bulbs that are the most variable are those
that are currently the least efficient."

The researchers' findings mark the first time that changes in light output
of quasars have been related to their efficiency, and could prove useful
in helping astronomers decipher the underlying physics that causes quasars
to vary so wildly.

Collaborators on the project include astronomy professor Robert Brunner at
Illinois and NCSA, Illinois undergraduate student Catherine Grier, and
other members of the Sloan Digital Sky Survey collaboration. The study
uses public data from the Sloan Digital Sky Survey, which is managed by
the Astrophysical Research Consortium for the participating institutions,
which are listed on the SDSS Web site.

This work was funded by NASA and the U. of I.

Editor's note: To reach Brian Wilhite, call 217-244-1325.

Graphics are available at
http://hunter.astro.uiuc.edu/PR

Andrew Yee wrote:
News Bureau
University of Illinois at Urbana-Champaign
Champaign, Illinois

Contact:
James E. Kloeppel, Physical Sciences Editor
217-244-1073

Released: 1/8/07

Quasar light variability linked to black hole mass

CHAMPAIGN, Ill. -- Quasars are some of the most luminous and distant
objects in the universe -- and appear to have something in common with
ordinary light bulbs, say researchers at the University of Illinois at
Urbana-Champaign and at the National Center for Supercomputing
Applications.

Quasars were discovered 40 years ago, when astronomers noticed that these
objects -- thought at the time to be stars -- were emitting far more radio
waves than expected. Researchers found, upon further inspection, that
these objects represented a new class of extremely energetic astronomical
object.

Astronomers now believe quasars are young galaxies powered by supermassive
black holes at their centers. These black holes can be millions or
billions of times more massive than our sun.

"With such enormous sources of energy, quasars are among the brightest
objects in the universe, some giving off thousands of times more light
than our own Milky Way galaxy from a region slightly larger than our solar
system," said Brian Wilhite, an astronomer at Illinois and a researcher at
NCSA. "Astronomers have also determined that quasars are incredibly
variable, with some quasars quadrupling in brightness in the span of just
a few hours."

Although rarely that dramatic, variability in light output is seen in
nearly all quasars, with average quasars changing in brightness by 10 to
15 percent over the course of one year, Wilhite said. Astronomers have yet
to pin down the exact mechanism that drives these changes.

Recently, Wilhite and other researchers at Illinois and NCSA found that
this variability is related to both the mass of the black hole at the
center of the quasar, and to the efficiency of the quasar at converting
gravitational potential energy into light energy.

Using data obtained by the Sloan Digital Sky Survey, the researchers
monitored the brightness and estimated the central black hole mass of more
than 2,500 quasars, observed over a period of four years. They found that,
for a given brightness, quasars with large black hole masses are more
variable than those with low black hole masses.

"Quasars with more massive black holes have more gravitational energy that
can potentially be extracted, which we would see in the optical as light,"
said Wilhite, who will present the team's findings at the American
Astronomical Society meeting in Seattle on Monday (Jan. 8).

"If two quasars have the same brightness, the one with the larger black
hole mass is actually less efficient at converting this gravitational
energy into light," Wilhite said. "We have found that these less-efficient
quasars have more variable light output. It could be a little like
flickering light bulbs -- the bulbs that are the most variable are those
that are currently the least efficient."

The researchers' findings mark the first time that changes in light output
of quasars have been related to their efficiency, and could prove useful
in helping astronomers decipher the underlying physics that causes quasars
to vary so wildly.

Collaborators on the project include astronomy professor Robert Brunner at
Illinois and NCSA, Illinois undergraduate student Catherine Grier, and
other members of the Sloan Digital Sky Survey collaboration. The study
uses public data from the Sloan Digital Sky Survey, which is managed by
the Astrophysical Research Consortium for the participating institutions,
which are listed on the SDSS Web site.

This work was funded by NASA and the U. of I.

Editor's note: To reach Brian Wilhite, call 217-244-1325.

Graphics are available at
http://hunter.astro.uiuc.edu/PR


Dear Andrew Yee

Can you please let me know
(i) How much energy is emitted is emitted by QUASAR.
(ii) How much mass is annihilated in the process?
(iii) Is E=mc2 is used to estimate relationship between
'mass annihilated' and 'energy emitted'.

AJAY SHARMA
www.ajayonline.us

" wrote in message ups.com...
|
| Andrew Yee wrote:
| News Bureau
| University of Illinois at Urbana-Champaign
| Champaign, Illinois
|
| Contact:
| James E. Kloeppel, Physical Sciences Editor
| 217-244-1073
|
| Released: 1/8/07
|
| Quasar light variability linked to black hole mass
|
| CHAMPAIGN, Ill. -- Quasars are some of the most luminous and distant
| objects in the universe -- and appear to have something in common with
| ordinary light bulbs, say researchers at the University of Illinois at
| Urbana-Champaign and at the National Center for Supercomputing
| Applications.
|
| Quasars were discovered 40 years ago, when astronomers noticed that these
| objects -- thought at the time to be stars -- were emitting far more radio
| waves than expected. Researchers found, upon further inspection, that
| these objects represented a new class of extremely energetic astronomical
| object.
|
| Astronomers now believe quasars are young galaxies powered by supermassive
| black holes at their centers. These black holes can be millions or
| billions of times more massive than our sun.
|
| "With such enormous sources of energy, quasars are among the brightest
| objects in the universe, some giving off thousands of times more light
| than our own Milky Way galaxy from a region slightly larger than our solar
| system," said Brian Wilhite, an astronomer at Illinois and a researcher at
| NCSA. "Astronomers have also determined that quasars are incredibly
| variable, with some quasars quadrupling in brightness in the span of just
| a few hours."
|
| Although rarely that dramatic, variability in light output is seen in
| nearly all quasars, with average quasars changing in brightness by 10 to
| 15 percent over the course of one year, Wilhite said. Astronomers have yet
| to pin down the exact mechanism that drives these changes.
|
| Recently, Wilhite and other researchers at Illinois and NCSA found that
| this variability is related to both the mass of the black hole at the
| center of the quasar, and to the efficiency of the quasar at converting
| gravitational potential energy into light energy.
|
| Using data obtained by the Sloan Digital Sky Survey, the researchers
| monitored the brightness and estimated the central black hole mass of more
| than 2,500 quasars, observed over a period of four years. They found that,
| for a given brightness, quasars with large black hole masses are more
| variable than those with low black hole masses.
|
| "Quasars with more massive black holes have more gravitational energy that
| can potentially be extracted, which we would see in the optical as light,"
| said Wilhite, who will present the team's findings at the American
| Astronomical Society meeting in Seattle on Monday (Jan. 8).
|
| "If two quasars have the same brightness, the one with the larger black
| hole mass is actually less efficient at converting this gravitational
| energy into light," Wilhite said. "We have found that these less-efficient
| quasars have more variable light output. It could be a little like
| flickering light bulbs -- the bulbs that are the most variable are those
| that are currently the least efficient."
|
| The researchers' findings mark the first time that changes in light output
| of quasars have been related to their efficiency, and could prove useful
| in helping astronomers decipher the underlying physics that causes quasars
| to vary so wildly.
|
| Collaborators on the project include astronomy professor Robert Brunner at
| Illinois and NCSA, Illinois undergraduate student Catherine Grier, and
| other members of the Sloan Digital Sky Survey collaboration. The study
| uses public data from the Sloan Digital Sky Survey, which is managed by
| the Astrophysical Research Consortium for the participating institutions,
| which are listed on the SDSS Web site.
|
| This work was funded by NASA and the U. of I.
|
| Editor's note: To reach Brian Wilhite, call 217-244-1325.
|
| Graphics are available at
| http://hunter.astro.uiuc.edu/PR
|
|
| Dear Andrew Yee
|
| Can you please let me know
| (i) How much energy is emitted is emitted by QUASAR.
| (ii) How much mass is annihilated in the process?
| (iii) Is E=mc2 is used to estimate relationship between
| 'mass annihilated' and 'energy emitted'.

You've got to learn to walk before you can run.

"scu" == sciencecool@yahoo co uk writes:

Quasar light variability linked to black hole mass

CHAMPAIGN, Ill. -- Quasars are some of the most luminous and
distant objects in the universe -- and appear to have something in
common with ordinary light bulbs, say researchers at the University
of Illinois at Urbana-Champaign and at the National Center for
Supercomputing Applications.
[...]
scu Can you please let me know (i) How much energy is emitted is
scu emitted by QUASAR.

Quasars have a range of luminosities. To quote a typical value, a
quasar's luminosity would be 10^{40} Watts.


scu (ii) How much mass is annihilated in the process?

It is thought to be zero. Rather, the luminosity is the result of
matter falling into a supermassive black hole. Matter falling from a
long distance into a black hole gains an enormous amount of energy.
If only a fraction of this energy is extracted as light, there is
plenty to power a quasar.

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html