New Power Source Lights Up Supernova Six Trillion Light-Years Across — the Closest to Earth in 400 Years


In 1987, light from an exploding star, Supernova 1987A, in a neighboring galaxy, the Large Magellanic Cloud, reached Earth — the closest supernova explosion witnessed in almost 400 years, allowing astronomers to study it in unprecedented detail as it evolves. An international team of astronomers announced that the supernova debris, which has faded over the years, is brightening, and marks the transition from a supernova to a supernova remnant.

"Supernova 1987A has become the youngest supernova remnant visible to us," said Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics (CfA), who leads a long-term study of SN 1987A with NASA's Hubble Space Telescope. Since its launch in 1990, Hubble has provided a continuous record of the changes in SN 1987A.

As shown in the image above, SN 1987A is surrounded by a ring of material that blew off the progenitor star thousands of years before it exploded. The ring is about one light-year (6 trillion miles) across. Inside that ring, the "guts" of the star are rushing outward in an expanding debris cloud.

Most of a supernova's light comes from radioactive decay of elements created in the explosion. As a result, it fades over time. However, the debris from SN 1987A has begun to brighten, suggesting that a new power source is lighting it.

"It’s only possible to see this brightening because SN 1987A is so close and Hubble has such sharp vision," Kirshner said.

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.

Because it's 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 decode that history.

"Young supernova remnants have personality," Kirshner agreed.

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 unprecedented opportunity to watch a cosmic object change over the course of a human lifetime. Few other objects in the sky evolve on such short time-scales.

This research appears in a paper in the June 9, 2011 issue of Nature.

The Daily Galaxy via Harvard-Smithsonian Center for Astrophysics

Image Credit: This HST image of SN 1987A shows the brightening ring of supernova debris. TThe Credit: Pete Challis (CfA)


"The Galaxy" in Your Inbox, Free, Daily