Astronomers find supernova remnant being created
COLUMBIA UNIVERSITY NEWS RELEASE
Posted: Feb. 28, 2000
The activity was sighted on Dec. 25, 1999, by a team of Columbia astrophysicists, Stephen Lawrence, Arlin Crotts, Ben Sugerman, and Robert Uglesich, led by Patrice Bouchet of the National Optical Astronomy Observatories' Cerro Tololo Inter-American Observatory (CTIO). A "hot spot" that appeared in the circumstellar ring around the supernova in 1997 was believed to be the first impact of supernova ejecta, but no other activity sites had been observed until the CTIO and Columbia team sighted this one in December. The new hot spot is about the same brightness as the first was when it was originally found. Other, fainter impact sites are present in their observations. The scientists also determined that the original hot spot had brightened significantly since their last observation over a year ago.
"The first collision of ejecta may have been a jet of material striking the circumstellar ring, shocking the gas into emission, much like bullets hitting a target," said Crotts, a Columbia professor of astronomy. "Now the entire ring is beginning to be engulfed with shocked material from the supernova, lighting up the ejecta and circumstellar material as a supernova remnant. We have observed many examples of supernova remnants -- for example, the Crab Nebula -- but all were formed long ago. We have never before seen one in the making in any meaningful degree of detail."
The CTIO observations used an innovative imaging system on a Blanco 4-m telescope that achieved better spatial resolution than is commonly possible from ground-based observatories. The CTIO system tips and tilts the secondary mirror of the telescope to take the "twinkle" out of starlight, producing steadier, sharper images. They also used a novel image processing technique developed by the Columbia team.
Supernova 1987A occurred when the star known as Sanduleak -69 202 ended its life in a gigantic explosion, which was observed on earth on February 23, 1987, and became known as supernova 1987A. While the radiation from that explosion traveled out at the speed of light, material from the star itself was ejected at a much lower speed, some tens of millions of miles per hour. This material is now beginning to catch up and collide with material blown out some twenty thousand years earlier by the star in a relatively gentle, slow, cool stellar wind. This collision of supernova ejecta with the wind material, now forming the circumstellar shell, was predicted to occur sometime between 1995 and 2010.
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