Chuck Bednar for redOrbit.com – Your Universe Online
Extraterrestrial dust on the ocean floor could radically alter our understanding of supernovae, according new research published online Tuesday by the journal Nature Communications.
A supernova is a star that increases in brightness drastically over a period of several days, making it appear as if a “new” star was born (hence the term “nova”). Leftover material from supernovae that took place long ago fell to Earth’s surface, finding its way to the ocean floor.
Analysis of this dust–which is believed to have come from exploding stars far beyond our solar system–has found that the amount of plutonium is much lower than expected. The research is at odds with current theories of supernovae, in which some of the materials essential for human life (including iron, potassium and iodine) are created and distributed throughout space.
“Small amounts of debris from these distant explosions fall on the Earth as it travels through the galaxy,” lead author Dr. Anton Wallner of the Research School of Physics and Engineering at The Australian National University (ANU) explained in a statement. “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.”
Other elements in supernovae dust
Supernovae are also known to create lead, silver and gold, as well as heavy radioactive elements such as uranium and plutonium. Dr. Wallner’s team studied plutonium-244, which behaves like a radioactive clock through the nature of its decay and its 81-million-year half-life.
“Any plutonium-244 that existed when the Earth formed from intergalactic gas and dust over four billion years ago has long since decayed,” he explained. “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.”
Less plutonium?
Dr. Wallner and his colleagues analyzed a 10 centimeter-thick sample of the planet’s crust and represented 25 million years of accretion, as well as deep-sea sediments collected from a stable region at the Pacific Ocean. They found 100 times less plutonium-244 than expected.
“It seems that these heaviest elements may not be formed in standard supernovae after all. It may require rarer and more explosive events such as the merging of two neutron stars to make them,” he noted.
The fact that these heavy elements were present, and uranium and thorium can still be found on Earth, suggest that an explosive event must have taken place nearby when the planet form, Dr. Waller noted.
Since radioactive elements such as uranium and thorium provide much of the heat responsible for continental movement on Earth, he added that they may not have the same type of heat engine inside them.
—–
Follow redOrbit on Twitter, Facebook, Instagram and Pinterest.
Comments