Topic of the Day – AT2018cow

UPSC Exam Preparation: Topic of the Day – AT2018cow

Science and technology is an important part of the UPSC syllabus. In this article, you will read about the celestial object AT2018cow and also some background on the phenomena of Nova and Supernova for IAS exam.

AT2018cow is a bright celestial object seen close to the very small galaxy CGCG 137-068. The celestial object was spotted by the ATLAS telescope.

  • The cow proved to be suitably interesting, because though it was initially thought to be a nova, later analysis showed that it was more like a broadline supernova of the Type Ic.
  • Specifically, a Type Ic supernova is caused by the explosion of an extremely massive star which has lost its outer layers of hydrogen and helium.

AT2018cow and India

  • Indian scientists too are keeping an eye on the mysterious transient AT2018cow using the 2-metre Himalayan Chandra Telescope (HCT) at Hanle, Ladakh.
  • The HCT observations indicate that the transient is steadily fading in all-optical bands.


A nova is defined as “A star that suddenly becomes much brighter and then gradually returns to its original brightness over a period of weeks to years”. A nova is a nuclear fusion on the surface that brightens the star for a while. The gas is heated as it is compressed, and the hydrogen may go up in flames in nuclear reactions that brighten the surface and blow excess gas outward. This type of explosion is called a nova.


A supernova is “a rare celestial phenomenon involving the explosion of most of the material in a star, resulting in an extremely bright, short-lived object that emits vast amounts of energy”. It is basically a procedure when a star is completely destroyed because it is not able to sustain its gravity anymore.

How is Nova different from a Supernova?

  • Supernova releases much more mass than a nova.
  • Supernova destroys its host star; whereas a nova does not.
  • Supernovae cannot occur at the same place more than once.
  • More energy is released in a supernova than in a nova.
  • Supernova lasts longer than a nova.
  • Novae occur more often than supernovae.

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