U. COLORADO (US)—Astronomers have been able to measure the velocity and composition of “star guts” being ejected into space following the explosion of a nearby supernova, thanks to a newly refurbished Hubble Space Telescope.

The team detected significant brightening of emissions from Supernova 1987A—the closest exploding star to Earth—which were consistent with some theoretical predictions about how supernovae interact with their immediate galactic environment. Details are reported this week in the journal Science.

Discovered in 1987, Supernova 1987A resides in the nearby Large Magellanic Cloud, a dwarf galaxy adjacent to our own Milky Way Galaxy.

The team observed the supernova in optical, ultraviolet, and near-infrared light, charting the interplay between the stellar explosion and the famous “String of Pearls,” a glowing ring 6 trillion miles in diameter encircling the supernova remnant that has been energized by X-rays.

The gas ring likely was shed some 20,000 years before the supernova exploded, and shock waves rushing out from the remnant have been brightening some 30 to 40 pearl-like “hot spots” in the ring—objects that likely will grow and merge together in the coming years to form a continuous, glowing circle.

“The new observations allow us to accurately measure the velocity and composition of the ejected ‘star guts,’ which tell us about the deposition of energy and heavy elements into the host galaxy,” says Kevin France, lead study author and a research associate at the University of Colorado at Boulder.

“The new observations not only tell us what elements are being recycled into the Large Magellanic Cloud, but how it changes its environment on human time scales.”

Ejected elements
In addition to ejecting massive amounts of hydrogen, 1987A has spewed helium, oxygen, nitrogen, and rarer heavy elements like sulfur, silicon, and iron.

Supernovae are responsible for a large fraction of biologically important elements, including oxygen, carbon and iron found in plants and animals on Earth today, he says. The iron in a person’s blood, for example, is believed to have been made by supernovae explosions.

Thank Hubble
Hubble is the only observatory in the world that can survey the brightening of the String of Pearls in ultraviolet light, says France. Most of the data for the study was gathered by the Space Telescope Imaging Spectrograph, or STIS, which was installed on Hubble in 1997 and was one of the workhorse instruments before its power supply failed in 2004. A faulty circuit board on STIS was replaced by astronauts on the final Hubble repair mission in May 2009.

The team compared STIS observations in January 2010 with Hubble observations made over the past 15 years on 1987A’s evolution. STIS has provided the team with detailed images of the exploding star, as well as spectrographic data—essentially wavelengths of light broken down into colors like a prism that produce unique fingerprints of gaseous matter.

The results revealed temperatures, chemical composition, density, and motion of 1987A and its surrounding environment, says France.

Light years away
Since the supernova is roughly 163,000 light years away, the explosion occurred in roughly 161,000 B.C., says France. One light year is about 6 trillion miles.

“To see a supernova go off in our backyard and to watch its evolution and interactions with the environment in human time scales is unprecedented,” he says. “The massive stars that produce explosions like Supernova 1987A are like rock stars—they live fast, flashy lives and die young.”

France says the energy input from supernovae regulates the physical state and the long-term evolution of galaxies like the Milky Way. Many astronomers believe a supernova explosion near our forming sun some 4 to 5 billion years ago is responsible for a significant fraction of radioactive elements in our solar system today, he says.

“In the big picture, we are seeing the effect a supernova can have in the surrounding galaxy, including how the energy deposited by these stellar explosions changes the dynamics and chemistry of the environment,” says France. “We can use this new data to understand how supernova processes regulate the evolution of galaxies.”

In addition to researchers at Colorado, the international study involved coauthors from 15 other universities and institutes.

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