Supernova Mystery Found at the Bottom of the Sea

Cassiopeia: A supernova remnant

Excerpt from news.discovery.com


One of the least likely places you might think astronomers would

learn about ancient supernovae is at the bottom of the ocean, but in new

research scientists have done just that.

Through the careful analysis of ocean sediment, tiny particles

that originated from deep space have settled on the seabed, locking the

chemical secrets to supernova processes that would have otherwise

remained a mystery.




“Small amounts of debris from these distant explosions fall on

the earth as it travels through the galaxy,” said lead researcher Anton

Wallner, of the Australian National University. “We’ve analyzed galactic

dust from the last 25 million years that has settled on the ocean and

found there is much less of the heavy elements such as plutonium and

uranium than we expected.”

Supernovae are powerful explosions triggered when massive stars

reach the ends of their lives. During these powerful events, many

elements are forged, including elements that are essential for life to

thrive — such as iron, potassium and iodine.






Wallner and his team studied samples of sediment from the

bottom of a stable area at the bottom of the Pacific Ocean. But when

measuring the quantities of plutonium-244, a radioisotope that is

produced by supernovae, they found something strange in their results —

there was 100 time less plutonium-244 than predicted.

Plutonium-244 has a half-life of 81 million years, making it an

excellent indicator of the number of supernovae that have exploded

nearby in recent galactic history. “So any plutonium-244 that we find on

earth must have been created in explosive events that have occurred

more recently, in the last few hundred million years,” said Wallner.




But the fact that there is less recent deposition of the

heaviest of elements, despite the fact that we know supernovae have

erupted nearby, suggests a different formation mechanism may be

responsible for plutonium-244 and elements like it.

“It seems that these heaviest elements may not be formed in standard

supernovae after all,” concludes Wallner. “It may require rarer and more

explosive events such as the merging of two neutron stars to make

them.”

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Supernova Mystery Found at the Bottom of the Sea