Astronomers from the University of Massachusetts and Columbia
University have found the “bulls-eye” pulsar in a bright ring of high-energy
particles in a distant supernova remnant. This discovery, made with NASA’s
Chandra X-ray Observatory and the Arecibo Radio Telescope, will help
scientists better understand how neutron stars channel enormous amounts of
energy into particles moving near the speed of light.

Chandra’s image of the supernova remnant SNR G54.1+0.3 reveals a
bright, point-like central source, which is surrounded by a ring and two
jet-like structures in an extended nebula of high-energy particles. The
radio data show that this bright central source is a neutron star, or
pulsar, that is rotating 7 times per second.

“The features Chandra found appear to be due to the energetic flow
of radiation and particles from a rapidly spinning neutron star formed
during a supernova event,” said Fangjun Lu of the University of
Massachusetts at Amherst who led the X-ray research.

Lu and colleagues informed Fernando Camilo of Columbia University in
New York of this detection. Camilo and his collaborators then used the
powerful Arecibo telescope to look for the tell-tale radio pulsations from a
neutron star at the center of the ring. After a search in August 2001 was
aborted by radio-frequency interference, they observed the source again in
April 2002 and found a weak, pulsating radio source. Further observations
indicate the pulsar (and hence the supernova remnant) has an age of
approximately 3000 years. Analysis of 1997 ASCA satellite data confirmed
that the source is pulsing in X-rays as well.

“This discovery is an excellent example of how the superb resolution
of Chandra and the improved capabilities of Arecibo worked together to
quickly resolve an outstanding scientific question,” said Camilo. “We look
forward to continued substantial progress in understanding the properties of
young neutron stars.”

Intense electric fields around the neutron star accelerate particles
to form jets blasting away from the poles and a disk of matter and
anti-matter flowing away from the equator at high speeds. As the equatorial
flow rams into particles and magnetic fields in the nebula, a shock wave
forms. The shock wave then boosts the particles to extremely high energies
causing them to glow in X-rays and produce the bright ring. The particles
continue to stream outward from the ring and the jets to supply the extended
nebula, which spans approximately 6 light years.

The features observed in SNR G54.1+0.3 are very similar to other
“pulsar wind nebulas” found by Chandra in the Crab Nebula, the Vela
supernova remnant, and B1509-58. By analyzing the similarities and
differences between these objects, scientists hope to better understand the
fascinating process of transforming the rotational energy of the neutron
star into extremely high-energy particles with very little frictional heat

Chandra observed SNR G54.1+0.3 on June 6-7, 2001, using the Advanced
CCD Imaging Spectrometer instrument. The radio data on the central pulsar,
known as PSR J1930+1852, were gathered at Arecibo on April 29, 2002. The
results from this work appear in two separate papers in the March 20 and
July 20, 2002 issues of the Astrophysical Journal Letters.

The Arecibo Observatory is part of the National Astronomy and
Ionosphere Center (NAIC), operated by Cornell University under a cooperative
Agreement with the National Science Foundation (NSF). NASA’s Marshall Space
Flight Center, Huntsville, Ala., manages the Chandra program for the Office
of Space Science, Washington, D.C. 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.

Images and additional information about this result are available