Prelims cum Mains Science & Tech

What is 99942 Apophis? Why are scientists excited?

News Summary

  • 99942 Apophis asteroid will flyby very close to earth on April 13, 2029.
  • The asteroid will flyby at a distance of about 31000km above the surface of the earth.
  • It is the first time that an asteroid of the size of about 340 m wide will flyby so close to earth.
  • The asteroid is named after ancient Egypt’s ‘god of chaos’.



  • Though the asteroid is expected to be harmless, optical and radar telescopes are deployed to study various features important like its size, shape, orbit, composition and possibly even its interior
  • Asteroid’s orbit
    • Since the asteroid will pass through so close, earth’s gravity will have an effect on the asteroid’s orbit.
  • Spin of the asteroid
    • The earth’s gravity will also affect the spin of the asteroid.
    • The change in spin produces avalanches on asteroid which can reveal details on interior of the asteroid.
  • Defense for asteroid collision
    • Studying the orbital behavior of such closely approaching asteroids can help to understand potential solution to ward off threats from similar Potentially Hazardous Asteroids.
  • Note: NASA’s HAMMER Mission is one such effort to ward off threat from closely approaching asteroids.

(HAMMER – Hypervelocity Asteroid Mitigation Mission for Emergency Response vehicle.)


In brief: Asteroids

  • Asteroids are rocky objects within the orbit of Jupiter, most of which orbit the sun in the same direction as the planets. Asteroids are also called minor planets.
  • The largest asteroid, Ceres, has a diameter of about 900 km, followed by Vesta which is about 500 km in diameter.
  • Asteroids orbit the Sun at distances of 2 to 3.5 AU (1 Astronomical Unit = 150 million kilometers, distance between earth and sun).
  • This region of the solar system between the orbits of Mars and Jupiter is called the asteroid belt.
  • The early solar system is thought to have been filled with planetesimals, most of which were incorporated into the planets.
  • The leftover objects that missed out on becoming a planet make up the present-day asteroids.

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