We present the peculiar expanding HI shell GSH 138-01-94, discovered in the
Canadian Galactic Plane Survey (recently expanded into the International
Galactic Plane Survey). This shell is unique because of its unusual location,
in the outermost regions of the Galactic disk. The properties of the shell
are discussed, as well as possible origins. This leads to the interpreattion
that GSH 138-01-94 is probably the remnant of a supernova explosion that
occurred 4.3 million years ago in the outer Galaxy. As such, GSH 138-01-94
is the largest, oldest supernova remnant known to date. We relate the
peculiar properties of this objects to the special environment in which it
was found.
The complete paper is available as electronic preprint
astro-ph/0108368
gzipped postscript
Press Release
The Canadian
Galactic Plane Survey allows a multi-wavelength view of the Galaxy
in unprecedented detail. One of the beautiful structures found in the
survey data is the expanding shell of hydrogen gas GSH 138-01-94. The
name of the shell contains the Galactic coordinates according to guide
lines set by the IAU.
GSH 138-01-94 is a very large shell: diameter 360 parsec, more than
1000 lightyears. At this time, the shell is still expanding
with a velocity of 11.8 km/s.
More about GSH 138-01-94 on the CASCA 2001 poster
 Click on details of the image to learn more Image prepared by Jayanne English |
Colour shades represent observations at different frequencies. Click on a detail in the image to read more about it. The image shows the shell of atomic hydrogen, radio continuum sources, a molecular cloud, and infrared emission from interstellar dust. Animation of the 21-cm line data (JAVA) |
