Ancient star explosions revealed in the deep sea

Date:

Share post:

A mystery surrounding the space around our solar system is unfolding thanks to evidence of supernovae found in deep-sea sediments.

Ancient star explosions revealed in the deep sea
Credit: ANU

Professor Anton Wallner, a nuclear physicist at ANU, led the study which shows the Earth has been travelling for the last 33,000 years through a cloud of faintly radioactive dust.

“These clouds could be remnants of previous supernova explosions, a powerful and super bright explosion of a star,” Professor Wallner said.

Professor Wallner conducted the research at the ANU Heavy Ion Accelerator Facility (HIAF). He also holds joint positions at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Technical University Dresden (TUD) in Germany.

The researchers searched through several deep-sea sediments from two different locations that date back 33,000 years using the extreme sensitivity of HIAF’s mass spectrometer. They found clear traces of the isotope iron-60, which is formed when stars die in supernova explosions.




Iron-60 is radioactive and completely decays away within 15 million years, which means any iron-60 found on the earth must have been formed much later than the rest of the 4.6-billion-year old earth and arrived here from nearby supernovae before settling on the ocean floor.

Professor Wallner previously found traces of iron-60 at about 2.6 million years ago, and possibly another at around 6 million years ago, suggesting earth had travelled through fallout clouds from nearby supernovae.

For the last few thousand years the solar system has been moving through a denser cloud of gas and dust, known as the local interstellar cloud, (LIC), whose origins are unclear. If this cloud had originated during the past few million years from a supernova, it would contain iron-60, and so the team decided to search more recent sediment to find out.

Sure enough, there was iron-60 in the sediment at extremely low levels – equating to radioactivity levels in space far below the Earth’s natural background levels – and the distribution of the iron-60 matched earth’s recent travel through the local interstellar cloud. But the iron-60 extended further back and was spread throughout the entire 33,000 year measurement period.




The lack of correlation with the solar system’s time in the current local interstellar cloud seems to pose more questions than it answers. Firstly, if the cloud was not formed by a supernova, where did it come from? And secondly, why is there iron-60 so evenly spread throughout space?

“There are recent papers that suggest iron-60 trapped in dust particles might bounce around in the interstellar medium,” Professor Wallner said.

“So the iron-60 could originate from even older supernovae explosions, and what we measure is some kind of echo.

“More data is required to resolve these details.”

The findings have been published in the Proceedings of the National Academy of Sciences.

Source: Australian National University [August 24, 2020]

ADVERTISEMENT

spot_img

Related articles

Life found in the sediments of an Antarctic subglacial lake for the first time

Evidence of diverse life forms dating back nearly a hundred thousand years has been found in subglacial lake...

NASA releases Kepler Survey Catalogue with hundreds of new planet candidates

NASA's Kepler space telescope team has released a mission catalog of planet candidates that introduces 219 new planet...

Exotic mixtures: X-ray scattering enables closer scrutiny of the interior of planets and stars

Recreating extreme conditions in the lab, like those in the interior of planets and stars, is very complex...

A cosmic barbecue: Researchers spot 60 new ‘hot Jupiter’ candidates

Yale researchers have identified 60 potential new "hot Jupiters" -- highly irradiated worlds that glow like coals on...

Stellar corpse sheds light on origin of cosmic rays

The origin of cosmic rays, high-energy particles from outer space constantly impacting on Earth, is among the most...

Seeking the star stuff that made us

At the 2021 Fall Meeting of the APS Division of Nuclear Physics, two independent research groups will unveil...

Life-producing phosphorus was carried to Earth by meteorites

Scientists may not know for certain whether life exists in outer space, but new research from a team...

Hubble spies newly forming star incubating in IC 2631

Stars are born from clouds of gas and dust that collapse under their own gravitational attraction. As the...