Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Exploding star strafed Earth


A supernova is the death throes of a large star

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.

  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 'Frequency combs' ID chemicals within the mid-infrared spectral region
16.03.2018 | American Institute of Physics

nachricht Fraunhofer HHI have developed a novel single-polarization Kramers-Kronig receiver scheme
16.03.2018 | Fraunhofer-Institut für Nachrichtentechnik, Heinrich-Hertz-Institut, HHI

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: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>