DURHAM, N.H. -- A University of New Hampshire space
scientist is among the researchers who have detected the
remnant of one of the closest, most recent supernova
It's also one of the more mysterious, says James Ryan, professor of physics in the university's Institute for the Study of Earth, Oceans and SpaceInstitute for the Study of Earth, Oceans and Space. Ryan and his colleagues used the UNH-directed COMPTEL imaging telescope aboard NASA's Compton Gamma Ray Observatory to study the supernova remnant's titanium gamma ray emissions, a new technique for finding young supernovae remnants (SNRs).
Occurring 680 years ago and a mere 650 light years away (for perspective, our Milky Way galaxy is 50,000 light years wide), the supernova or exploding star was close enough to be seen on Earth, but the question remains, did anyone see it?
There are no written records of a bright light, outshining everything in the night sky except the moon. The supernova explosion certainly was close enough within the Milky Way to be seen by medieval astronomers. And previous supernovae were recorded in the years 1054, 1574 and 1604.
Ryan's colleagues at the Max Planck Institute, the Space Research Organization of the Netherlands and the European Space Agency guess the supernova may have been optically obscured by material between the Earth and the supernova. Another possibility is that the position or time of the event may have been unfavorable; perhaps it was too cloudy to observe the event.
Ryan points out the location of the remnant is minus-45 degrees latitude. So, it could only be well observed by people in the Southern Hemisphere, not in Europe or Asia. "Who was there to see it?" asks Ryan. And would those who did witness the bright light in the sky document it?
Ryan and his team have used data from the COMPTEL to study recent supernovae before, almost all in distant galaxies, millions of light years away. In these cases, COMPTEL analyzed the cobalt emissions from the exploding star, since cobalt decays rapidly and gives off a more intense emission. In other words, it's easier to "see" from a distance.
For this closer SNR, titanium was analyzed. Titanium also is produced in the high energies of a supernova explosion, and as it decays, like cobalt, it emits gamma rays. However, because titanium has a half-life of about 90 years, it is best used to detect SNRs hundreds of years old.
In general, gamma rays can penetrate through the dust and gas associated with supernova explosions, so we can detect these high energy wavelengths more easily than optical wavelengths. Thus, titanium gamma ray emission serves as both a clock and a beacon for observers on Earth.
Ryan says this latest find is significant because it involved a supernova remnant "in the neighborhood," our own galaxy. "There are very few supernovae seen optically in our galaxy," he points out. "And it provides us with dynamic information about the supernova process and the life cycle of a star."
Note: Jim Ryan is unavailable for comment until Friday, Jan. 8. He can be contacted at 862-3510. In the meantime, his colleague, Mark McConnell of the Space Science Center, can provide comment. His number is 862-2047.
By Carmelle Druchniak
UNH News Bureau