X-rays from a rare type of supernova in the Whirpool Galaxy were recently
observed, thanks to the fine resolution of NASA’s Chandra X-ray Observatory.
The team of researchers also detected a large number of point-like X-ray
sources due to black holes and neutron stars in binary star systems.

Chandra’s image highlights the energetic central regions of the two interacting
galaxies, NGC 5194 (center) and its smaller companion (upper left) NGC 5195,
that are collectively called the Whirlpool Galaxy.

The inset contains an expanded image of the central region of NGC 5194.
Extending to the north and south of the bright nucleus are clouds of
multimillion-degree gas, with diameters of about 1500 light years and 500 light
years, respectively. The similarity of these features with ones observed at
radio wavelengths suggests that the gas is heated by high-velocity jets
produced near a supermassive black hole in the nucleus of the galaxy.

On the lower left of the inset image is a faint source identified with a
supernova discovered in 1994 by amateur astronomers in Georgia, and
subsequently determined to be an unusual Type Ic supernova. The massive stars
responsible for these supernovas are thought to have lost their outer layers of
hydrogen and helium gas thousands of years before the explosion, either through
evaporation or transfer to a companion.

In the millennia before a doomed star explodes into a supernova, it loses
mass. X-ray observations of the supernova shock wave provide a method to
sensitively probe into this process. The Chandra data from SN 1994I and its
surrounding area indicate that the progenitor star evaporated material into a
cloud around the star that has a diameter at least 0.2 light years. Further
monitoring over the years will tell just how large the cloud is, and how long
the star was losing mass before it exploded.

Andrew Wilson of the University of Maryland, in College Park, was the principal
investigator for the Chandra observations of M51. Other scientists involved in
the research were Yuichi Terashima of the University of Maryland, and Stefan
Immler of the University of Massachusetts, Amherst.

Images and additional information about this result are available at: