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Office of Public Affairs
Yale University

CONTACT:
Jacqueline Weaver, 203-432-8555 #166

For Immediate Release: May 26, 2003

Yale Astronomer Sees New Gravitational Lens

New Haven, Conn. -- Using a snapshot technique, a Yale astronomer has
discovered a bright new gravitational lens.

The gravitational lens was observed on April 25 by Nicholas Morgan, a 
post-doctoral fellow at the Yale Center for Astronomy and
Astrophysics, using the 3.5-meter WIYN Telescope at the Kitt Peak
National Observatory near Tucson, Arizona. The lens is located near
the constellation Hercules and is officially known as SDSS 1650+4251.

Gravitational lenses are images of bright but extremely distant
galaxies known as quasars. The light from these distant quasars is
deflected by the gravitational fields of fainter foreground galaxies,
distorting the background quasar into multiple copies of itself.
Sometimes as many as four copies of the single quasar are possible.
About 70 of these systems have been discovered since the first
sighting in 1979. How distorted the images become and how many copies
are made depends on the alignment between the foreground galaxy and
the more distant quasar.

"You need exquisite alignment," said Morgan.

The value of finding a gravitational lens, he said, is that it can
help in deducing the age of the universe by watching how the light
from the quasar changes with time. Finding several lenses can also
help in calculating the expansion rate of the universe, whether it is
decelerating or accelerating, and if the universe will eventually
collapse or expand forever. 

The snapshot technique used by Morgan involves taking pictures of
multiple targets. He looked at over 200 targets during the two nights
of observations, taking a picture every few minutes. Astronomers
generally look at only a handful of targets in the same period.

"You look at as many distant quasars as possible," he said. "For
each, you have about a one percent chance of finding a gravitational
lens. Sometimes you get lucky."

Ideal conditions are also dependent on the weather and the
performance of the telescope.

Morgan said SDSS 1650+4251 appears as a relatively small system with
a separation between its two images of about one arcsecond. One
arcsecond is about the size a dime would appear if held two miles
away. The largest gravitationally lensed quasars currently known are
slightly larger than six arseconds. 

The WIYN Observatory is owned and operated by the WIYN Consortium,
which consists of the University of Wisconsin, Indiana University,
Yale University, and the National Optical Astronomy Observatories.

# # #

EDITORS: A photo of the gravitational lens is available at
http://www.yale.edu/opa/assets/images/releases/20030520_lens.jpg

after 3 P.M. EST, on May 26, 2003. It is an I-band image of the new 
gravitationally lensed quasar SDSS taken with the WIYN 3.5-meter
telescope in 0.3-arcsecond seeing at Kitt Peak National Observatory
near Tucson, Arizona. PHOTO CREDIT: NOAO/KPNO/N. D. Morgan.

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