Types of Exoplanets
The galaxy contains categories of planet with no direct Solar System equivalent. This matrix places the five headline classes on axes of size and orbital environment, with clear caveats about what each label really means.
Key takeaways
- “Super-Earth” describes size or mass, not habitability.
- Sub-Neptunes are the most common class discovered, yet the Solar System has none.
- Rogue planets are unbound to any star and are detected mainly by microlensing.
- Every label is a starting point, not a final classification.
About this visual
Astronomers classify exoplanets first by size or mass, then by how much stellar energy they receive. The five headline categories cover most of the confirmed catalogue.
- Hot Jupiters — gas giants that orbit their stars in only a few days. They were the first exoplanets found and remain important atmospheric laboratories.
- Warm Neptunes and sub-Neptunes — worlds between Earth and Neptune in size, often with substantial hydrogen-rich atmospheres. The most common class in the catalogue — yet completely absent from our Solar System.
- Super-Earths — rocky planets larger than Earth but smaller than Neptune. The name describes size, not habitability.
- Terrestrial worlds — small rocky planets like Mars, Venus, Earth or the TRAPPIST-1 planets.
- Rogue planets — planetary-mass objects that drift through the galaxy unbound to any star, detected mainly through microlensing events.
The category boundaries are fuzzy
Real planets fall on a continuum. A 2.5-Earth-radius world might be a gas-rich sub-Neptune with a thick atmosphere or a dense stripped rocky core. Only by combining mass, radius, atmosphere and stellar irradiation can astronomers decide.
Labels do not equal habitability
A "super-Earth in the habitable zone" only means the world is somewhat larger than Earth and receives an amount of stellar energy that could, in principle, allow liquid water on a suitable surface. It says nothing about the atmosphere, magnetic field or geology.
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Seven Earth-size planets orbiting a single ultracool dwarf in an extraordinarily compact resonant chain.
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Read more on Universe & Planets
Sources and methodology
Values verified against official mission and archive pages on the updated date shown above. Numeric quantities are cited to the precision typical of introductory astronomy references.