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article imageStudy discovers methods to find white dwarfs before they explode

By Nancy Houser     Sep 25, 2011 in World
In a Harvard press release, Tuesday, September 6, 2011, a research study by astrophysicist Rosanne Di Stefano has answered numerous questions about the exploding white dwarf stars that are spinning in space and their development into a Type 1a supernova.
The scientific research paper on these “ticking time bombs” has been published in the September 1st issue of Astrophysical Journal Letters.
Previously, it was next to impossible to recognize the white dwarf stars that were ready to explode. The scientific study looked at things that had always been ignored, finding that those were the things that should have been examined all along. It found that massive old stars, called white dwarfs, are held in place by a rapid spin. Once the stars slow down at the ends of their lives, a few will explode into Type la supernovas---with thousands scattered throughout the galaxy.
What was discovered is that the only thing containing their nuclear cores is the rate of their spin in the galaxy. In other words, once the spin slows down, these white dwarf stars will explode into supernovae killers.
"We haven’t found one of these 'time bomb' stars yet in the Milky Way, but this research suggests that we've been looking for the wrong signs," astrophysicist Rosanne Di Stefano of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said in a press release. "Our work points to a new way of searching for supernova precursors."
Exploding white dwarf stars
According to MSNBC, when massive aging stars are in the process of beginning to explode they are hidden many light years away in the galaxy. Scientists are estimating that a few thousand light years away from Earth are dozens of stars on the verge of exploding, merrily twirling away until they slow down.
The problem is being able to identify the stars before they explode, which are followed by the release of a destructive spectrum of radiation for many light years.
When the stars explode, it is to become supernovas that occur at the end of a massive star’s lifetime. The star’s nuclear fuel is completely exhausted and cannot be supported by the fuel’s release. NASA reports that the developing “supernovae are one of the most energetic explosions in nature, equivalent to the power in a 1028 megaton bomb (i.e., a few octillion nuclear warheads).”
The Type 1a supernova
Every thousand years or so inside the Milky Way galaxy, approximately three stars will explode that are categorized as a Type 1a supernova. This means that a carbon-oxygen white dwarf star is growing larger by accumulating matter from a companion star.
This mass piles up so much that the core of the white star reaches a critical density. According to NASA, this causes the star to detonate because of “the runaway fusion of carbon and oxygen in the core of the white dwarf.”
When the destabilized white dwarf star is more massive than five solar masses, the core collapses as it is impossible to prevent the star’s core from falling into itself and forming a black hole. Escape from it will require traveling greater than the speed of light---300,000 km/sec.
"Our work is new because we show that spin-up and spin-down of the white dwarf have important consequences. Astronomers therefore must take angular momentum of accreting white dwarfs seriously, even though it's very difficult science," explained Di Stefano in the Harvard press release.
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