Curent Science at NOAO

Ejecta From Supernova 1987a Lights Up Circumstellar Ring

Patrice Bouchet, CTIO/National Science Foundation; Stephen Lawrence, Arlin Crotts, Ben Sugerman, and Robert Uglesich, Columbia University; Stephen Heathcote, CTIO/NSF

We are about to see, for the first time in history, a supernova remnant in the making.

15 February, 2000  |  Astronomers using the National Science Foundation's Cerro Tololo Inter-American Observatory (CTIO) Blanco 4-meter telescope have observed the first evidence that material from a supernova explosion in 1987 has finally begun to collide with a shell of gas blown out by the star earlier in its lifetime. This collision has been eagerly awaited since its prediction at the time of the initial explosion. It now provides us with a ring-side seat to watch a supernova remnant in the making.

167,000 years ago a star exploded in the Large Magellanic Cloud, a neighbor galaxy to our own Milky Way. The explosion was first seen on Earth in 1987, the light from the explosion taking that long to make the journey. Before the star exploded, it was known to astronomers as Sanduleak -69° 202, a massive star in the Large Cloud. It was given a new designation, SN 1987A, after the explosion.

During its earlier evolution, Sk -69° 202 blew much of its mass back into space in the form of massive stellar winds. The material from these winds formed a dark ring around the star about a light year in diameter. This ring was first detected about six months after the explosion, when it was heated by the intense burst of light from the supernova. Then the ring cooled and faded to invisibility again.

The Crab Nebula, the most famous supernova remnant.

Astronomers have been anticipating that the ring would brighten again once the matter ejected at high speed from the supernova reached the distance of the ring, sometime between 1995 and 2010. The first hint of this occured late in 1997, when the a fast-moving knot of matter encountered the ring, causing a glowing hot spot.

Now, matter from the supernova explosion is encroaching all around the ring, heating the slower-moving gas from the stellar wind, and causing it to glow brightly. Astronomers observing at the Cerro Tololo InterAmerican Observatory have detected new brightenings in the ring at several locations, observations which have since been confirmed and refined by Hubble Space Telescope. Astronomers at CTIO will continue to monitor this birth of a supernova remnant, one of the most beautiful objects in the universe.

For more information see:
   NOAO Nesletter
   NOAO Media Advisory
   IAU Circular 7354

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