Fact Box: Hottest Known Planet in Universe

Scientists have discovered the hottest known exoplanet, designated KELT-9b which is warmer than most stars in the universe. The study has been published in the journal Nature.

Exoplanet is a planet that does not orbit the Sun and instead orbits a different star, stellar remnant, or brown dwarf. They are also called as extrasolar planet.

Salient Highlights

  • The planet orbits a massive star KELT-9 every day and a half.
  • The planet’s day-side temperature is 4,326 degree Celsius and is only 926 degree Celsius cooler than the Sun.
  • The planet is located 650 light years from Earth and sports a giant, glowing gas tail like a comet.
  • The ultraviolet radiation experienced by the planet from its star KELT-9 is so fierce that the planet may be evaporating producing a glowing gas tail.
  • The Jupiter-like planet is 2.8 times more massive than Jupiter. However, it is only half as dense as that of the Jupiter.
  • Due to extreme radiation from its host star the atmosphere of the planet has puffed up like a balloon. It has been classified as a planet by considering its mass but its atmosphere is not similar to any other known planet.
  • Due to the bombardment of stellar radiation, the planet is very hot so much so that the  molecules such as water, carbon dioxide and methane can not form there.


The first planet outside our solar system was found out in 1995. With the help of NASA’s Kepler telescope, the discovery of planets has become easier. So far, astronomers have identified 52 potentially habitable planets and around 3,600 planets outside our solar system. With the launch of James Webb Space Telescope (JWST) by NASA in 2018, chances of studying planets and detecting a familiar atmosphere will increase manifold. JWST will succeed the Hubble space telescope.



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