What are Exoplanets?
Exoplanets, or extrasolar planets, are planets that orbit stars outside our Solar System. Unlike planets in our system, they are located beyond the Sun’s gravitational influence and are found across the Milky Way galaxy. The first confirmed discovery of an exoplanet orbiting a Sun-like star was made in 1995.
Why are Exoplanets Important?
- Help understand planet formation and evolution
- Expand knowledge of diverse planetary systems
- Key to the search for life beyond Earth
- Improve models of stellar and galactic evolution
Major Types of Exoplanets
- Gas Giants (Hot Jupiters)
- Massive planets similar to Jupiter
- Orbit very close to their stars
- Extremely high surface temperatures
- Neptune-like Planets
- Smaller than gas giants
- Thick atmospheres of hydrogen and helium
- Super-Earths
- More massive than Earth but lighter than Neptune
- Can be rocky or gaseous
- Most commonly discovered type
- Terrestrial (Rocky) Planets
- Earth-like composition
- Potential candidates for habitability
Habitable Zone (Goldilocks Zone)
- Region around a star where liquid water can exist on a planet’s surface
- Neither too hot nor too cold
- Presence in this zone does not guarantee life, but increases possibility
Methods of Detecting Exoplanets
- Transit Method (most successful)
- Detects tiny dips in star brightness when a planet passes in front
- Used by Kepler and TESS missions
- Radial Velocity (Doppler Method)
- Measures star’s wobble due to planet’s gravity
- Helps estimate planet mass
- Direct Imaging
- Photographs planets by blocking starlight
- Effective for large planets far from stars
- Gravitational Microlensing
- Uses light bending due to gravity
- Useful for detecting distant planets
Key Space Missions
- Kepler Space Telescope – First major exoplanet hunter
- TESS (Transiting Exoplanet Survey Satellite) – Ongoing survey of nearby stars
- James Webb Space Telescope (JWST) – Studies exoplanet atmospheres for water, CO₂, methane
Challenges in Exoplanet Study
- Vast interstellar distances
- Atmospheric analysis is complex
- Biosignatures can be ambiguous
