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National Radio Astronomy Observatory
P.O. Box O
Socorro, NM 87801
http://www.nrao.edu

Contacts:
Dave Finley, NRAO Public Information Officer, Socorro, NM
(505) 835-7302, dfinley{at}nrao.edu

Bill Steigerwald, NASA Goddard Space Flight Center
(301) 286-5017, William.A.Steigerwald{at}nasa.gov

EMBARGOED For Release: 10:00 a.m., CDT, May 27, 2003

VLBA Reveals Dust-Enshrouded "Supernova Factory"

Using the National Science Foundation's Very Long Baseline Array
(VLBA) radio telescope, astronomers have discovered a newly-exploded
star, or supernova, hidden deep in a dust-enshrouded "supernova
factory" in a galaxy some 140 million light-years from Earth.

"This supernova is likely to be part of a group of super star
clusters that produce one such stellar explosion every two years,"
said James Ulvestad, of the National Radio Astronomy Observatory
(NRAO) in Socorro, NM. "We're extremely excited by the tremendous
insights into star formation and the early Universe that we may gain
by observing this 'supernova factory,'" he added.

Ulvestad worked with Susan Neff of NASA's Goddard Space Flight Center
in Greenbelt, MD, and Stacy Teng, a graduate student at the
University of Maryland, on the project. The scientists presented
their findings to the American Astronomical Society's meeting in
Nashville, TN. 

"These super star clusters likely are forming in much the same way
that globular clusters formed in the early Universe, and thus provide
us with a unique opportunity to learn about how some of the first
stars formed billions of years ago," Neff said.

The cluster is in an object called Arp 299, a pair of colliding 
galaxies, where regions of vigorous star formation have been found in 
past observations. Since 1990, four other supernova explosions have
been seen optically in Arp 299.

Observations with the NSF's Very Large Array (VLA) earlier showed a 
region near the nucleus of one of the colliding galaxies which had
all the earmarks of prolific star formation. The astronomers focused
on this region, prosaically dubbed "Source A," with the VLBA and the
NSF's Robert C. Byrd Green Bank Telescope in 2002, and found four
objects in this dusty cloud that are likely young supernova remnants.
When they observed the region again in February 2003, there was a
new, fifth, object located only 7 light-years from one of the
previously detected objects.

More observations on April 30-May 1, 2003, showed that this new
object has typical characteristics of a supernova explosion by a
young, massive star.

"This supernova is exploding in a very dense environment, quite 
different from the environments of supernova explosions that can be
seen in visible light," Teng said. "This is the kind of dense
environment in which stars likely formed in the early Universe," she
added. 

The astronomers believe the super star cluster in Arp 299 saw its
most recent peak of star formation some 6-8 million years ago, and
now its massive stars, 10-20 times (or more) as massive as the Sun,
are ending their lives in supernova explosions. Super star clusters
typically contain up to a million stars, which is why the scientists
think Source A will see frequent supernova explosions.

"We plan to keep watching this region, and hope that we can study 
numerous supernovae, and gain important new information about the 
processes of star formation, both in the early Universe and at the 
present time," Neff said.

"Because of the dust and the distance, only a radio telescope with
the VLBA's ability to see fine detail can find the supernovae in this
region," Ulvestad said.

The VLBA is a continent-wide system of ten radio-telescope antennas, 
ranging from Hawaii in the west to the U.S. Virgin Islands in the
east, providing the greatest resolving power, or ability to see fine
detail, in astronomy. Dedicated in 1993, the VLBA is operated from
the NRAO's Array Operations Center in Socorro, New Mexico.

The VLBA has made landmark contributions to astronomy, including
making the most accurate distance measurement ever made of an object
beyond the Milky Way Galaxy; the first mapping of the magnetic field
of a star other than the Sun; "movies" of motions in powerful cosmic
jets and of distant supernova explosions; the first measurement of
the propagation speed of gravity; and long-term measurements that
have improved the reference frame used to map the Universe and detect
tectonic motions of Earth's continents.

The National Radio Astronomy Observatory is a facility of the
National Science Foundation, operated under cooperative agreement by
Associated Universities, Inc.

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