International Space Agencies – Missions and Discoveries



From UPSC perspective, the following things are important :

Prelims level : Ploonets

Mains level : Not Much

  • Astronomers have defined a new class of celestial objects called “ploonets,” which are orphaned moons that have escaped the bonds of their planetary parents.


  • Astronomers named a new class of theorized objects that begin as moons around large planets, but eventually move out on their own. They call them “ploonets.”
  • The scientists think these objects should exist in solitary orbits around their host stars and could even be discovered in observations from past and present exoplanet-hunting surveys, like Kepler and TESS.

Why such renaming?

  • Earth’s own Moon is slowly spiraling away from our planet; it may also end up as a ploonet in some 5 billion years.

Making of a Ploonet

  • Over the past few decades, astronomers have uncovered more than 4,000 confirmed exoplanets, and nearly as many exoplanet candidates.
  • And one thing astronomers have learned from this sizeable census is that a surprisingly high number of massive exoplanets — called “hot Jupiters” — are located oddly close to their host stars.
  • Although at least part of the reason they detected so many hot Jupiters boils down to observational biases, this significant sample of weird planets still raises questions about how planets form.

Have we already found Ploonets?

  • Although there has yet to be a definite confirmation of a Ploonet orbiting a star, there are at least a few examples that might fit the bill.
  • The evidence for these potential Ploonets comes from perplexing exoplanetary observations that have yet to be adequately explained.
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