aug 062013


Astronomers using ALMA, the Atacama Large Millimeter/submillimeter Array, have detected, for the first time, the formation of new molecules in the remains of a star that went supernova. By detecting and mapping the distribution of these molecules, the researchers also have caught a glimpse of the final internal structure of the star, which became “frozen in” to the debris when the star exploded.

In optical light (Hubble: blue color), SN 1987A shows a beautiful three-ring structure. The rings are material expelled from the star in its death throes just before exploding, now lit up by the explosion. The shredded remains of the star’s interior are rapidly expanding but still located within the inner knotty ring, shown here in the green colored image of glowing iron previously formed deep in the star. Emission from cold CO observed with ALMA (red color) is only coming from those stellar remains, proving that the CO is newly forming there. Image Credit: Remy Indebetouw and Bill Saxton, NRAO/AUI/NSF; NASA/Hubble

The astronomers discovered these new molecules in the fading embers of a star that went supernova in 1987, known, conveniently, as SN 1987A. Located in the Large Magellanic Cloud, a nearby satellite galaxy of the Milky Way, supernova 1987A provides a unique opportunity to study how the aftermath of a supernova evolves. Computer models that attempt to recreate the conditions just prior to a supernova suggest that there is powerful and rapid mixing inside the star. This churning, astronomers speculate, is the trigger that sets off the explosion.

Since it’s impossible to peer inside an actual star, astronomers study the debris of a supernova to see how material is distributed and how the remnant of the star evolves over time to infer the conditions just prior to the explosion. Earlier research with infrared telescopes detected a small amount of carbon monoxide (CO) glowing hot within the first 500 days after the explosion. Twenty-five years later, the new ALMA results, which are the first of their kind, reveal a supernova environment filled with ten times the amount of CO detected by the infrared studies.

The astronomers estimate that there is about 10 percent the mass of our Sun in CO and also a significant mass of silicon monoxide (SiO) currently in the supernova remnant. These molecules are forming in areas with abundant atomic carbon, silicon, and oxygen atoms, elements that only form inside the nuclear furnace of a star and get spilled into the cosmos during a supernova explosion. Over time, as they cool, the atoms are able to bond, creating the CO and SiO that is detectable by ALMA. The molecules forming in SN 1987A, or at least their constituent atoms, could someday be incorporated into future planets.

This research was presented in a paper “Carbon Monoxide in the Cold Debris of Supernova 1987A” and was accepted for publication in the Astrophysical Journal Letters.

Source: The ALMA Observatory

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