Supernova 1987A - Credit: Pete Challis (CfA)
In 1987 the light from an exploding star in the Large Magellanic Cloud reached Earth. Supernova 1987A (SN 1987A) was the closest supernova explosion seen in 400 years. Astronomers have studied closely, watching the debris fade over the years. On June 8, 2011 a team of astronomers led by Josefin Larsson, University of Stockholm, announced that the supernova debris is brightening marking the transition from a supernova to a supernova remnant.
As the image shows, SN 1987A is surrounded by a ring of material. Astronomers say this material blew off the progenitor star thousands of years before it exploded. The ring is about 1 light-year (6 trillion miles) across and inside that ring, the “guts” of the star – released in the supernova explosion seen from Earth in 1987 – are rushing outward in an expanding cloud of debris.
The supernova’s light originates from radioactive decay of the elements created in the explosion fading over time as a result. However, the brightening debris from SN 1987A suggests that a new power source is lighting it.
In other words, the debris of SN 1987A is beginning to impact the surrounding ring, creating powerful shock waves that generate X-rays – observed with NASA’s Chandra X-ray Observatory. Those X-rays are illuminating the supernova debris, and shock heating is making it glow. The same process powers well-known supernova remnants in our galaxy like Cassiopeia A.
Being so young, the remnant of SN 1987A still shows the history of the last few thousand years of the star’s life recorded in the knots and whorls of gas. By studying it further, astronomers may be able to decode that history.
Eventually, that history will be lost when the bulk of the expanding stellar debris hits the surrounding ring and shreds it. Until then, SN 1987A continues to offer an amazing opportunity to watch a cosmic object change over the course of a human lifetime.