Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Exploding star strafed Earth

12.02.2002


A supernova is the death throes of a large star
© NASA


A supernova may have caused mass extinction two million years ago.

The explosion of a dying star could have ended much of marine life on Earth two million years ago. The supernova could have strafed the Earth’s atmosphere with cosmic rays, severely damaging the ozone layer and exposing living organisms to high levels of the Sun’s hazardous ultraviolet rays, US researchers propose1.

This idea dates back to the 1950s, but now Narciso Benítez of Johns Hopkins University in Baltimore, Maryland, and colleagues have come up with the first plausible evidence. Their proposal remains tentative, but is consistent with what is known about the likelihood of nearby stellar explosions and the telltale signatures of these events on our planet.



Supernovae are the death throes of large stars. When such stars run out of fuel for nuclear fission, they collapse under their own gravity, heat up rapidly and explode, releasing huge amounts of matter and energy. Fortunately for us, such outbursts are rare: the most recent one in our own galaxy was spotted in 1604, and was too far away to pose any risk. Several supernovae have been observed more recently in other galaxies.

One-fifth of all supernovae occur in large groups of relatively young stars that are thought to have coalesced from the same gas cloud. One such cluster in our own galaxy is the Scorpius-Centaurus association, which comprises three subgroups of stars.

Each subgroup would have generated supernovae at different times: about 10, 7 and 2 million years ago, say Benítez’ group. The most recent episode could have included a supernova as little as 130 light years from Earth. This is not close enough to fry our planet. But it would have left a mark that the researchers think has already been found.

Three years ago, scientists in Germany reported high concentrations of iron-60 in two layers of ocean rock, dated at about 0-3 and 4-6 million years old2. Iron-60 is a rare form produced on Earth by nuclear reactions involving cosmic rays, such as those that supernovae generate.

Putting these arguments together, Benítez’ team proposes that the most recently formed iron-60 layer could be the result of a nearby supernova in the Scorpius-Centaurus association around two million years ago. The supernova could have left another signature - in the fossil record.

Two million years ago, many marine creatures, such as bivalve molluscs, died out suddenly all over the planet. As mass extinctions go, this was a mild one. But no one knows what caused it.

Benítez and his colleagues think that a nearby supernova at this time could have showered the Earth with cosmic rays. These charged subatomic particles collide with atoms in the air, initiating chemical reactions. Copious cosmic rays are thought to produce nitrogen monoxide, which can destroy ozone molecules.

The researchers calculate that a supernova 130 light years away could have thinned the ozone layer by up to 60 per cent, exposing marine organisms to ultraviolet rays from the Sun. This could have killed off plankton, and thence the molluscs that live off them.

To support this hypothesis, astronomers now need to find the smoking gun: remnants of ancient supernovae in nearby star clusters.

References
  1. Benítez, N., Maíz-Apellániz, J. & Canelles, M. Evidence for nearby supernova explosions. Physical Review Letters, 83, 081101, (2002).
  2. Knie, K. et al., Indication for supernova produced 60Fe activity on Earth. Physical Review Letters, 83, 18 - 21, (1999).


PHILIP BALL | © Nature News Service

More articles from Physics and Astronomy:

nachricht Unconventional superconductor may be used to create quantum computers of the future
19.02.2018 | Chalmers University of Technology

nachricht Hubble sees Neptune's mysterious shrinking storm
16.02.2018 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Japanese researchers develop ultrathin, highly elastic skin display

19.02.2018 | Information Technology

Dispersal of Fish Eggs by Water Birds – Just a Myth?

19.02.2018 | Ecology, The Environment and Conservation

Studying mitosis' structure to understand the inside of cancer cells

19.02.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>