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Study: First-generation supernovae were blue

Astronomers have struggled to find a method for differentiating between ancient and modern supernovae.

By
Brooks Hays
A diagram shows the various visual signatures of metal-poor and metal-rich supernovae. Photo by Kavli IPMU
A diagram shows the various visual signatures of metal-poor and metal-rich supernovae. Photo by Kavli IPMU

KASHIWA, Japan, July 12 (UPI) -- Scientists may have found a way to identify the first generation of supernovae. The light curves of the most ancient supernovae are most likely blue, astronomers at Japan's Kavli Institute for the Physics and Mathematics of the Universe determined.

Studying first-generation supernovae can reveal a wealth of information about the early universe and the first galaxies. At first, the universe contained only hydrogen and helium.

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The heavy elements that make life possible were forged by stars and proliferated throughout the universe as exploding stars expelled the new elements. In the context of astronomy, so-called "heavy metals" include all elements heavier than helium.

Astronomers have struggled to find a method for differentiating between ancient and modern supernovae.

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To isolate a discrepancy between the two, astronomers at Kavli modeled the light curves of the explosion of metal-poor stars and metal-rich stars. The scientists detailed their findings in The Astrophysical Journal.

The first generation of stars were all metal poor, and thus produced metal-poor supernovae. Over time, metals become more abundant throughout the universe. More metal-rich stars were born, and thus more metal-rich stars exploded.

"The explosions of first generation of stars have a great impact on subsequent star and galaxy formation," lead study author Alexey Tolstov said in a news release. "But first, we need a better understanding of how these explosions look like to discover this phenomenon in the near future."

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"The most difficult thing here is the construction of reliable models based on our current studies and observations," Tolstov added. "Finding the photometric characteristics of metal poor supernovae, I am very happy to make one more step to our understanding of the early universe."

Simulations showed that the light curves of metal-poor supernova are blue. As such, the color blue could serve as indicator for the first generation of supernovae.

The analysis showed that both metal-rich and metal-poor supernovae feature a similar visual succession -- a peak brightness or flash followed by a plateau and a steady, exponential decline. For metal-poor supernovae, however, each phase is shorter.

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Currently, the expanding universe causes the light of early and distant stars to shift into the infrared, making it difficult for astronomers to pick up the color of a supernova's light curve, but the next generation of powerful radio telescopes is expected solve this problem.

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