UPSC PRELIMS 2019 : L 98-59b – A new planet discovered

L 98-59b - A new planet discovered

Topic : L 98-59b – A new planet discovered

Topic in Syllabus: Science & Technology



L 98-59b - A new planet discovered

NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered a new planet, the tiniest of its finds so far.


About L 98-59:

  • It is between the sizes of Mars and Earth and orbits a bright, cool, nearby star.
  • The planet is called L 98-59b because it sits in a nearby star system called L 98-59.
  • It is 35 light-years from our solar system in the southern constellation Volans.
  • It  is around 80% of Earth’s size and about 10% smaller than the previous smallest planet discovered by TESS.
  • Apart from L 98-59b, two other worlds orbit the same star.
  • The two other worlds in the system, L 98-59c and L 98-59d.
  • These planets add to humanity’s still-small catalog of exoplanets similar in size to Earth.



  • An exoplanet is a planet that orbits a star other than the Sun.
  • Exoplanets are also called extrasolar planets. Since 1988, more than 3000 exoplanets have been found.


NASA’s Transiting Exoplanet Survey Satellite (TESS) 

  • NASA Transiting Exoplanet Survey Satellite (TESS) mission led by the Massachusetts Institute of Technology (with seed funding from Google) will look for planets orbiting the brightest stars in Earth’s sky.
  • TESS will survey 200,000 of the brightest stars near the sun to search for transiting exoplanets.
  • TESS was launched in 2018, aboard a SpaceX Falcon 9 rocket.


TESS employs the transit method to detect exoplanets:

  • The transit method of detecting exoplanets looks for dips in the visible light of stars and requires that planets cross in front of stars along our line of sight to them.
  • Repetitive, periodic dips reveal a planet or planets orbiting a star.


Sample Question:

Which of the following methods has led to the most discoveries of massive planets orbiting near their parent stars?

A) detecting the starlight reflected off the planet

B) detecting the infrared light emitted by the planet

C) detecting the gravitational effect of an orbiting planet by looking for the Doppler shifts in the star’s spectrum

D) detecting the shift of the star’s position against the sky due to the planet’s gravitational pull


Answer:  C