ISRO Missions and Discoveries

[pib] What are Wolf–Rayet Stars?


From UPSC perspective, the following things are important :

Prelims level: Wolf–Rayet Stars

Mains level: Not Much

Indian astronomers have tracked a rare supernova explosion and traced it to one of the hottest kind of stars called Wolf–Rayet stars or WR stars.

Space science-related terms these days are often focused on Gravitational waves, Black holes etc. But basic terminologies are very important and need to be taken care of. For example, a layman may hardly find any difference between Novae-Supernovae, Neutron star, Nebula etc. UPSC often tries to bust you with such basic differences.

Wolf–Rayet Stars

  • Wolf-Rayet stars represent a final burst of activity before a huge star begins to die.
  • These stars, which are at least 20 times more massive than the Sun, “live fast and die hard”.
  • Wolf-Rayets stars are divided into 3 classes based on their spectra, the WN stars (nitrogen dominant, some carbon), WC stars (carbon dominant, no nitrogen) and WO where oxygen is in dominant quantities.
  • The average temperature of a Wolf-Rayet star is greater than 25,000 Kelvin, and they can have luminosities of up to a million times that of the Sun.

What have Indian researchers studied?

  • Indian astronomers have conducted the optical monitoring of one such stripped-envelope supernova called SN 2015dj hosted in the galaxy NGC 7371 which was spotted in 2015.
  • They calculated the mass of the star that collapsed to form the supernovae as well as the geometry of its ejection.

Their findings

  • The scientists found that the original star was a combination of two stars – one of them is a massive WR star and another is a star much less in mass than the Sun.
  • Supernovae (SNe) are highly energetic explosions in the Universe releasing an enormous amount of energy.
  • Long-term monitoring of these transients opens the door to understand the nature of the exploding star as well as the explosion properties.
  • It can also help enumerate the number of massive stars.

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