Discovery of Most Recent Supernova in Our Galaxy
- From: baalke@xxxxxxxxxxxxx
- Date: Thu, 15 May 2008 17:21:08 -0700 (PDT)
May 14, 2008
JD Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@xxxxxxxx
Jennifer Morcone
Marshall Space Flight Center, Huntsville, Ala.
256-544-7199
jennifer.j.morcone@xxxxxxxx
Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998
cxcpress@xxxxxxxxxxxxxxx
RELEASE: 08-126
DISCOVERY OF MOST RECENT SUPERNOVA IN OUR GALAXY
WASHINGTON -- The most recent supernova in our galaxy has been
discovered by tracking the rapid expansion of its remains. This
result, using NASA's Chandra X-ray Observatory and the National Radio
Astronomy Observatory's Very Large Array, will help improve our
understanding of how often supernovae explode in the Milky Way
galaxy.
The supernova explosion occurred about 140 years ago, making it the
most recent in the Milky Way. Previously, the last known supernova in
our galaxy occurred around 1680, an estimate based on the expansion
of its remnant, Cassiopeia A.
Finding such a recent, obscured supernova is a first step in making a
better estimate of how often the stellar explosions occur. This is
important because supernovae heat and redistribute large amounts of
gas, and pump heavy elements out into their surroundings. They can
trigger the formation of new stars as part of a cycle of stellar
death and rebirth. The explosion also can leave behind, in addition
to the expanding remnant, a central neutron star or black hole.
The recent supernova explosion was not seen with optical telescopes
because it occurred close to the center of the galaxy and is embedded
in a dense field of gas and dust. This made the object about a
trillion times fainter, in optical light, than an unobscured
supernova. However, the remnant it caused can be seen by X-ray and
radio telescopes.
"We can see some supernova explosions with optical telescopes across
half of the universe, but when they're in this murk we can miss them
in our own cosmic backyard," said Stephen Reynolds of North Carolina
State University in Raleigh, who led the Chandra study. "Fortunately,
the expanding gas cloud from the explosion shines brightly in radio
waves and X-rays for thousands of years. X-ray and radio telescopes
can see through all that obscuration and show us what we've been
missing."
Astronomers regularly observe supernovae in other galaxies like ours.
Based on those observations, researchers estimate about three explode
every century in the Milky Way.
"If the supernova rate estimates are correct, there should be the
remnants of about 10 supernova explosions that are younger than
Cassiopeia A," said David Green of the University of Cambridge in the
United Kingdom, who led the Very Large Array study. "It's great to
finally track one of them down."
The tracking of this object began in 1985, when astronomers, led by
Green, used the Very Large Array to identify the remnant of a
supernova explosion near the center of our galaxy. Based on its small
size, it was thought to have resulted from a supernova that exploded
about 400 to 1000 years ago.
Twenty-two years later, Chandra observations revealed the remnant had
expanded by a surprisingly large amount, about 16 percent, since
1985. This indicates the supernova remnant is much younger than
previously thought.
That young age was confirmed in recent weeks when the Very Large
Array
made new radio observations. This comparison of data pinpoints the
age of the remnant at 140 years - possibly less if it has been
slowing down - making it the youngest on record in the Milky Way.
Besides being the record holder for youngest supernova, the object is
of considerable interest for other reasons. The high expansion
velocities and extreme particle energies that have been generated are
unprecedented and should stimulate deeper studies of the object with
Chandra and the Very Large Array.
"No other object in the galaxy has properties like this," Reynolds
said. "This find is extremely important for learning more about how
some stars explode and what happens in the aftermath."
These results are scheduled to appear in The Astrophysical Journal
Letters. NASA's Marshall Space Flight Center in Huntsville, Ala.,
manages the Chandra program for NASA's Science Mission Directorate in
Washington. The Smithsonian Astrophysical Observatory controls
Chandra's science and flight operations from the Chandra X-ray Center
in Cambridge, Mass.
Additional information and images about this discovery is available
on
the Web at:
http://www.nasa.gov/chandra
and
http://chandra.harvard.edu
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