Steve Roy

Marshall Space Flight Center

Huntsville, AL

Phone: 256-544-6535

Deborah Halber

Massachusetts Institute of Technology

Cambridge, MA

Phone: 617-258-9276,

Dr. Wallace Tucker

Chandra X-ray Observatory Center

Harvard-Smithsonian Center for Astrophysics

Cambridge, MA

Phone: 617-496-7998

For Release: Dec. 14, 1999

RELEASE: 99-296

The End of Days — Chandra Catches X-ray Glow From Supernova

Through a combination of serendipity and skill, scientists have used NASA’s Chandra X-ray Observatory to capture a
rare glimpse of
X-radiation from the early phases of a supernova, one of the most violent events in nature. Although more than a
thousand supernovae have been observed by optical astronomers, the early X-ray glow
from the explosions has been detected in less than a dozen cases.

The Chandra observations were made under the direction of a team of scientists from the Massachusetts Institute of
Technology (MIT) in Cambridge, led by Walter Lewin and his graduate student, Derek Fox. When combined with
simultaneous observations by radio and optical telescopes, the X-ray observations tell about the thickness of the shell
that was blown off, its density, its speed, and how much material was shed by the star before it exploded.

Chandra observed an X-ray glow from SN1999em with the total power of 50,000 suns. Ten days later it observed the
supernova for another nine hours, and found that the X-rays had faded to half their previous intensity. The optical
luminosity, which had the brightness of 200 million suns, had faded somewhat less. No radio emission was
detected at any time.

With this information, the MIT group and their colleagues are already piecing together a picture of the catastrophic
explosion. Observations by optical astronomers showed that SN1999em was a Type II supernova produced by the
collapse of the core of a star ten or more times as massive as the sun. The intense heat generated in the collapse
produces a cataclysmic rebound that sends high speed debris flying outward at speeds in excess of 20 million miles
per hour. The debris crashes into matter shed by the former star before the explosion. This awesome collision
generates shock waves that heat expanding debris to three million degrees. The X-ray glow from this hot gas was
detected by Chandra and gives astrophysicists a better understanding of the
dynamics of the explosion, as well as the behavior of the doomed star in the years before the explosion.

“The combination of X-ray detection and radio non-detection is unusual, but may have less to do with the supernova
and more to do with the great sensitivity of Chandra,” said Roger Chevalier of University of Virginia, Charlottesville.
Chevalier explained that the combined observations indicate that SN1999em shed a relatively small amount of matter
before it exploded, compared to other supernovae observed in X-rays. The Chandra observation is important because
it may
represent a more common type of supernova.

The Chandra observation also provides an inside look at the hectic, exciting world of the international “quick
response” network that scientists have set up to track and investigate supernovae.

On Friday, October 29, Alex Fillipenko of the University of California, Berkeley, notified Bob Kirshner at
Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., that his automated supernova search project had a
good candidate in a relatively nearby spiral galaxy, NGC 1637. Nearby in this case means about 25 million light
years from Earth. Wei Dong Li, who is visiting Fillipenko’s group from the Beijing Astronomical Observatory in
China, called his colleagues in Beijing, who confirmed the supernova when the Earth rotated into a position to make
viewing from China possible. The astronomers also notified the International Astronomical Union’s central bureau for
astronomical telegrams in Cambridge, Mass., from which the discovery was broadcast worldwide. Radio astronomers
Christina Lacey and Kurt Weiler at the Naval Research Laboratory in Washington, D.C., Schuyler van Dyk at the
California Institute of Technology, Pasadena and Richard Sramek at the National Radio Astronomy Observatory’s Very
Large Array, Socorro, N.M., were alerted.

Kirshner then got in touch via e-mail with Harvey Tananbaum, director of the Chandra X-ray Center at
Harvard-Smithsonian a little before 11 p.m. on Saturday night. The Chandra operations team replanned the
telescope’s observation activities and by Monday morning, and by Monday morning, Chandra was pointed at the
supernova and observed it for about nine hours.

Lewin, who had been awarded the rights to Chandra’s first observation of a nearby supernova, was ecstatic. “This is a
unique chance that we have been hoping for!!!!” he wrote in an e-mail to Tananbaum.

“I was impressed by how rapid the Chandra response was, ” said Kirshner.

“Supernovae expand quickly and cool quickly, so each day we delay observing the supernova it has changed
irretrievably,” Filippenko said. “We caught this really early, only a day or two after the explosion. We were lucky.”

The Chandra observation was taken with the Advanced CCD Imaging
Spectrometer (ACIS) on November 1 and 2, and 11 and 12, 1999 in two separate observations that lasted
approximately nine hours each. ACIS was built by Pennsylvania State University, University Park, and MIT.

To follow Chandra’s progress, visit the Chandra sites at:


NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. TRW, Inc., Redondo Beach,
Calif., is the prime contractor for the spacecraft. The Smithsonian’s Chandra X-ray Center controls science and flight
operations from Cambridge, Mass.

This image will be available on NASA Video File which airs at noon, 3:00 p.m., 6:00 p.m., 9:00 p.m. and midnight
Eastern Time. NASA Television is available on GE-2, transponder 9C at 85 degrees West longitude, with vertical
polarization. Frequency is on 3880.0 megahertz, with audio on 6.8 megahertz.

High resolution digital versions of the X-ray image (JPG, 300 dpi TIFF) and other information associated with this
release are available on the Internet at:

or via links in

Note to Editors / News Directors: Interviews, photos and video supporting this release are available to media
representatives by contacting Steve Roy of the Marshall Media Relations Department at (256) 544-0034. For an
electronic version of this release, digital images or more information, visit Marshall’s News Center on the Web at: