1. Radial Velocity Method (Doppler Spectroscopy):
* How it works: This method measures the slight wobble in a star's motion caused by the gravitational pull of an orbiting planet. As the star moves towards us, its light is blueshifted (wavelengths get shorter). As it moves away, its light is redshifted (wavelengths get longer).
* Advantages: Relatively easy to implement, good for detecting massive planets close to their stars.
* Disadvantages: Only detects planets with a significant gravitational pull on the star, and can be difficult to measure accurately for faint or distant stars.
2. Transit Method:
* How it works: This method observes the slight dimming of a star's light as a planet passes in front of it.
* Advantages: Very sensitive, can detect planets of all sizes, and can determine the planet's size and orbital period.
* Disadvantages: Only works for planets whose orbits are aligned with our line of sight to the star, and doesn't provide information about the planet's mass directly.
3. Astrometry:
* How it works: This method measures the tiny wobble in a star's position in the sky caused by the gravitational pull of an orbiting planet.
* Advantages: Can determine the planet's mass and orbital period, and works for planets at any orbital inclination.
* Disadvantages: Requires extremely precise measurements, and is difficult to implement due to the small size of the wobble.
4. Gravitational Microlensing:
* How it works: This method uses the gravity of a foreground star to bend the light of a more distant star, magnifying it. If a planet is orbiting the foreground star, it can create a separate, smaller magnification event.
* Advantages: Can detect planets at great distances, even those with wide orbits.
* Disadvantages: Events are rare and fleeting, and it's difficult to determine the planet's mass or orbital period.
5. Direct Imaging:
* How it works: This method takes pictures of planets directly, using powerful telescopes and techniques to block out the star's glare.
* Advantages: Can provide detailed information about the planet's atmosphere, size, and temperature.
* Disadvantages: Extremely difficult to achieve, only possible for large planets far from their stars, and often requires sophisticated image processing techniques.
These methods are often used in combination to get a complete picture of an exoplanetary system.
