G11.2-0.3: A Textbook Supernova Remnant (Forwarded)

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
(Phone: 617/496-7998)

For Release: January 30, 2007

G11.2-0.3: A Textbook Supernova Remnant
[http://chandra.harvard.edu/photo/2007/g11/]

G11.2-0.3 is a circularly symmetric supernova remnant that contains a dense,
rotating dead star at its center, representing a textbook case of what the
remnant of an exploding star should look like after a couple thousand years.
When a massive star collapses, the outer layers of the star are blown away
in an extremely energetic explosion. Depending on the mass of the original
star, a dense object such as a neutron star or a black hole, can form and be
left behind at the explosion's center. Such a neutron star, known as a
"pulsar" when it rapidly rotates, can be kicked by the thermonuclear shock
wave created when the star exploded, causing it to race through space at
millions of miles per hour.

By combining X-ray and radio observations, astronomers have evidence that
G11.2-0.3 is likely the result of the explosive death of such a massive
star, perhaps witnessed in 386 A.D. Radio observations measure the remnant's
expansion rate, which, in turn, can be used to calculate how long ago the
star exploded. The radio data is consistent with association of the
supernova remnant with the "guest star" reported by Chinese astronomers
nearly 2,000 years ago. Chandra's ability to pinpoint the pulsar at nearly
the very center of G11.2-0.3 also supports the idea that this debris field
could have been created around the time of the Chinese observations.
Surprisingly, the age of the pulsar determined from the X-ray and radio data
differs from the standard pulsar age estimate, usually determined from how
fast it is spinning. In this case, the so-called spin parameters suggest the
G11.2-0.3 is 10 times older than the remnant age. This argues strongly that
young pulsar spin ages can be very misleading and should be considered with
caution.

In Chandra's X-ray image, the pulsar and a cigar-shaped cloud of energetic
particles, known as a pulsar wind nebula, are predominantly seen as
high-energy X-rays (blue). A shell of heated gas from the outer layers of
the exploded star surrounds the pulsar and the pulsar wind nebula and emits
lower-energy X-rays (represented in green and red).