Detecting Exoplanets
Physics: AQA A Level, topic 9.3.4
Detecting Exoplanets
Detecting planets around stars other than the Sun was a huge development in 20th Century Astrophysics.
Very faint signal
- Exoplanets are very faint compared with their star and are also very close to them.
- Techniques for observing exoplanets are currently in their infancy.
Transit method
- By observing how the light intensity of the star changes over time, sufficiently sensitive detectors can distinguish when an exoplanet passes in front of its star.
- The light intensity dips for a short period in a very regular and periodic way, as shown in the diagram.
Light curve
- This type of diagram known as a light curve.
- It shows how the brightness of a star varies with time.
Radial velocity method
- The presence of a large, closely orbiting exoplanet causes the host star to wobble in a periodic and regular way, changing its radial velocity.
- The wobble causes the light from the star to be affected by Doppler shift.
- Observing the spectral lines of the star and how they shift periodically implies the existence of an exoplanet.
Test yourself on Detecting Exoplanets
What types of exoplanets will cause stars to wobble?