Chuck Bednar for redOrbit.com – @BednarChuck
The discovery of a particular class of Type Ia supernovae could help astronomers learn more about dark energy, the phenomenon behind the acceleration of the cosmos, according to new research published in Friday’s edition of the journal Science.
It’s Supernova to the rescue!
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As researchers from NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California explained, astronomers have long been using Type Ia supernovae (the explosions of dead stars) to determine the distance to galaxies and to calculate the rate at which the universe is expanding.
The method isn’t perfect, and astronomers are constantly looking for ways to improve the data obtained using these techniques. Now, University of California, Berkeley postdoc Patrick Kelly and his colleagues have identified the best type of supernovae in such measurements.
Using archived data from NASA’s Galaxy Evolution Explorer (GALEX), Kelly’s team showed that there is one specific class of Type Ia supernovae that occur near younger stars, and they improve cosmic distance measurements with a precision over twice what was previously possible.
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“We have discovered a population of Type Ia supernovae whose light output depends very precisely on how quickly they fade, making it possible to measure very exact distances to them,” Kelly said. “These supernovae are found close to populations of bright, hot young stars.”
New light on dark energy
In addition to improving measurements, the discovery could shed new light on dark energy, which is believed to be the primary culprit for the acceleration of the cosmos. This acceleration was originally discovered in 1998 as astronomers noticed that galaxies were moving away from each other at increasing speeds. However, the phenomenon itself is shrouded in mystery.
Type Ia supernovae are the key to measuring this acceleration, and thus using the nature of dark energy, according to JPL. The researchers compare them to a series of 60-watt light bulbs lined up along a field. If a person stand at one end of the light bulbs, the one at the opposite end would not appear as bright as the closest one due to its distance, and by knowing how bright that far off light bulb actually is, a person can use the degree of dimming to figure out its distance.
In much the same way, Type Ia supernovae consistently shine with roughly the same amount of light. These explosions occur when the burnt-out core of a white dwarf star explodes, causing its host galaxy to briefly become brighter. However, the explosions can differ considerably based on a variety of different factors, throwing off distance measurements.
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Kelly and his colleagues examined the reliability of this method by analyzing the surroundings of nearly 100 previous Type Ia explosions using data from GALEX, which detects ultraviolet light and can be used to differentiate between young and old star-forming communities. They learned that those supernovae more closely affiliated with the younger, hotter stars were far more reliable at determining distances than the older, cooler types.
By using primarily this specific type of Type Ia supernova in the future, astronomers could be able to make more precise measurements of the size and scale of the universe. In fact, Kelly and his colleagues believe that these supernovae could be accurate to distances of at least six billion light years away, and perhaps even farther than that.
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