Exoplanet Basics
Learn the fundamental concepts of exoplanets, including what they are, different planet types, size comparisons with Earth, and basic orbital mechanics that govern planetary systems.
Topics Covered:
What are Exoplanets?
An exoplanet (extrasolar planet) is any planet that orbits a star outside our solar system. These worlds come in many forms — some may resemble Earth, while others are completely alien, with extreme temperatures, strange compositions, or unusual orbits.
Planet Types
Scientists classify exoplanets into different types based on their size, composition, and temperature:
Gas Giants
Large planets like Jupiter and Saturn, mostly hydrogen and helium.
Neptunian Planets
Similar to Neptune or Uranus, with thick atmospheres and icy cores.
Super-Earths
Bigger than Earth but smaller than Neptune, possibly rocky and potentially habitable.
Terrestrial Planets
Rocky worlds like Earth or Mars, sometimes found in the "habitable zone."
Size Comparisons
Exoplanets vary enormously in size:
- ●Some are smaller than Mercury, barely detectable.
- ●Others are "Hot Jupiters," so large and close to their stars that they dwarf Earth many times over.
- ●Scientists often use Earth-radius (R⊕) and Jupiter-radius (R♃) units to compare sizes and understand their nature.
Orbital Mechanics
Every exoplanet follows an orbit around its star, defined by key parameters:
Orbital Period (P)
How long it takes to complete one revolution.
Semi-Major Axis (a)
Average distance from the star.
Eccentricity (e)
How circular or stretched the orbit is.
Inclination (i)
Tilt of the orbit as seen from Earth.
These orbital properties are crucial for detecting exoplanets (via transit, radial velocity, etc.) and for predicting whether a planet could sustain life.
Finished this module?
Mark this module as complete to track your progress and celebrate your achievement!
Ready for the Next Module?
Continue your journey through the fascinating world of exoplanets with our other learning modules.
Explore All Modules