From UPSC perspective, the following things are important :
Prelims level : Hangenberg Crisis
Mains level : Mass Extinction
The explosion of a nearby star — occurred at between Devonian and Carboniferous periods — could have caused a mass extinction event that took place 359 million years ago.
Try this question from CSP 2018:
Q.The term “sixth mass extinction/sixth extinction” is often mentioned in the news in the context of the discussion of
(a) Widespread monoculture Practices agriculture and large-scale commercial farming with indiscriminate use of chemicals in many parts of the world that may result in the loss of good native ecosystems.
(b) Fears of a possible collision of a meteorite with the Earth in the near future in the manner it happened 65million years ago that caused the mass extinction of many species including those of dinosaurs.
(c) Large scale cultivation of genetically modified crops in many parts of the world and promoting their cultivationin other Parts of the world which may cause the disappearance of good native crop plants and the loss offood biodiversity.
(d) Mankind’s over-exploitation/misuse of natural resources, fragmentation/loss, natural habitats, destructionof ecosystems, pollution and global climate change.
- The Earth suffered an intense loss of species diversity that lasted for at least 300,000 years.
- The event is thought to have been caused by long-lasting ozone depletion, which would have allowed much more of the Sun’s ultraviolet (UV) radiation to reach and harm life on Earth.
- It was called the Hangenberg crisis.
What did researchers find?
- Extensive volcanism and global warming can also rupture the ozone layer but shreds of evidence for these are indefinite as far as the time period is concerned.
- So, they up that one or more supernovae explosions, at a distance of 65 light-years away from the Earth, may have caused a prolonged loss of ozone.
- Betelgeuse, a supernova, around 600 light-years away and present outside the kill distance of 25 light-years poses a danger today.
- Events like gamma-ray bursts, solar eruptions and meteorite collisions end up very soon. As such, they cannot pave the way for gradual ozone depletion that took place at the close of the Devonian aeon.
- A supernova event can be powerful enough to bathe its galaxy in light for days and months alike. It can be spotted across the universe as well.
Why Supernovae are considered dangerous?
- Supernovae (SNe) are quick sources of ionizing photons that include fatal X-rays, UV and gamma rays.
- Over a longer period of time, the bang clashes with the nearby gas, resulting in a shockwave that causes particle acceleration.
- As such, cosmic rays are generated by SNe. These charged particles with high energies get magnetically confined on the inside of SN remains.
- The fossil evidence shows a 300,000-year shrink in biodiversity leading the way to Devonian-Carboniferous Boundary (DCB) mass extinction.
- This puts forward the possibility of multiple catastrophes or multiple supernovae explosions.