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NSF PR 00-06 - February 18, 2000
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Newfound Quasar Wins Title: "Most Distant in
If Guinness had a Book of Cosmic Records, a newly discovered
quasar in the constellation Cetus would make the front
page. This distant quasar easily skates past the previous
record holder, placing it among the earliest known
structures ever to form in the Universe.
A team of astronomers identified the candidate after
nights of deep (long-exposure) imaging at the California
Institute of Technology's 200-inch (5-meter) Hale
Telescope at Palomar Observatory, Calif., and at the
National Science Foundation's 157 inch (4-meter) Mayall
Telescope at Kitt Peak, Ariz. A spectral analysis
of the quasar′s light was then completed at the Keck
Observatory in Hawaii.
"As soon as we saw the spectrum, we knew we had
something special," said Dr. Daniel Stern of
NASA's Jet Propulsion Laboratory, Pasadena, Calif.,
who played a key role in the discovery. "In images,
quasars can look very much like stars, but a spectral
analysis of a quasar′s light reveals its true character.
This quasar told us that it was 'an ancient' -- one
of the universe's first structures."
Quasars are extremely luminous bodies that were more
common in the early universe. Packed into a volume
roughly equal to our solar system, a quasar emits
an astonishing amount of energy -- up to 10,000 times
that of the whole Milky Way galaxy. Scientists believe
that quasars get their fuel from super-massive black
holes that eject enormous amounts of energy as they
consume surrounding matter.
A quasar's "redshift" measures how fast the object
is moving away from us as the Universe expands, and
is a good indicator of cosmic distances. The faster
it moves away, the more its light shifts to the red
part of the spectrum (toward longer wavelengths),
which means the faster an object appears to move,
the farther away it is. At a redshift of 5.50, light
travelling from Stern's quasar has journeyed about
13 billion years to get here. That means the quasar
existed at a time when the universe was less than
8 percent of its current age.
"The odds against us finding a quasar at a redshift
of 5.5 were fairly large, especially when you consider
how small a portion of the sky we were observing --
10 by 10 arcminutes. To get an idea of how small that
is, try holding a dime at arms length against the
night sky; it's roughly the size of FDR's ear," said
Stern. Until very the last few years, no one had discovered
an object that came close to a redshift of 5.0.
High-redshift quasars are vitally important to understanding
one of the biggest mysteries confronting scientists:
how the universe went from the smooth uniformity of
its youth to the clumpy, galaxy-strewn formations
we observe today. Astronomers believe that the young
universe began in a hot, dense state shortly after
the Big Bang. Matter in the universe was ionized back
then, meaning that electrons were not bound to protons.
As the universe aged, matter cooled enough for electrons
and protons to combine, or to become neutral. As the
first stars and galaxies formed, they reheated matter
between galaxies, creating the ionized intergalactic
medium we see today in our local universe. The million-dollar
question for today's cosmologists is when this second
transition from neutral to ionized gas occurred.
Analyzing the spectrum of the new quasar will be very
useful for testing whether the universe was neutral
or ionized at redshift 5.50. As a quasar's light makes
its journey toward us, the light is absorbed by any
matter that lies in its path. Scientists have learned
that clouds of neutral hydrogen absorb more than half
of a quasar's light at high redshift (in the early
universe). That finding is central to understanding
when and how super-massive black holes, quasars, and
other structures condensed from large, high-density
clouds of hydrogen soon after the Big Bang. The new
quasar will also shed light on how matter was distributed
at earlier stages of cosmic history.
"Finding a quasar at this distance is like turning
on a flashlight at the edge of the universe,"
said Stern, "Because quasars are more luminous
than distant galaxies at the same redshift, they act
as the brightest flashlights, allowing us to study
everything that has ever developed between us and
The recent findings will be presented in an upcoming
issue of the Astrophysical Journal Letters. The team
included Daniel Stern and Peter Eisenhardt of JPL;
NSF-supported researcher Hyron Spinrad, Steve Dawson,
and Adam Stanford of the University of California;
Andrew Bunker of Cambridge University; and Richard
Elston of the University of Florida. Images can be
found at: http://www.jpl.nasa.gov/pictures/quasar