Detecting Exoplanets

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Detecting Exoplanets

Detecting planets around stars other than the Sun was a huge development in 20th Century Astrophysics.

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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.
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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.
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Light curve

  • This type of diagram known as a light curve.
  • It shows how the brightness of a star varies with time.
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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.

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1Measurements & Errors

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6Further Mechanics & Thermal Physics (A2 only)

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