Donald Savage
Headquarters, Washington, DC
February 18, 2000
(Phone: 202/358-1547)
Amber Jones
National Science Foundation, Arlington, VA
(Phone: 703/306-1070)
Michelle Viotti
Jet Propulsion Laboratory, Pasadena, CA
(Phone: 818/354-8774)
RELEASE: 00-30
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 in California and at the National Science Foundation’s
157-inch (4-meter) Mayall Telescope at Kitt Peak, AZ. 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, CA, 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 5.5, 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 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 5.5. 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
quasar.”
The recent findings will be presented in an upcoming issue of
the Astrophysical Journal Letters. The paper was written by
Daniel Stern and Peter Eisenhardt of JPL; 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:
The Palomar Observatory, near San Diego, CA, is owned and
operated by Caltech. Kitt Peak National Observatory is a division
of the National Optical Astronomy Observatory (NOAO), which is
operated by the Association of Universities for Research in
Astronomy, Inc., under Cooperative Agreement with the National
Science Foundation. The W.M. Keck Observatory, atop Mauna Kea on
the island of Hawaii, is managed by a partnership among Caltech,
the University of California, and NASA. JPL is a division of
Caltech, Pasadena, CA.
