Exoplanet Detection Techniques

-- | January 3, 2013

Question: My question is two-fold and relates to exoplanet detection. Firstly, it seems like the two most successful detection methods, namely the transit and radial velocity methods, rely on exoplanet systems being edge-on relative to our vantage point. Is this correct? And if so, will we forever be limited to edge-on discoveries, or is there any hope for an alternative method that could be as successful as the aforementioned? — Eric

Answer: The answer to the first part of your question is yes.  The radial velocity and transit timing methods of exoplanet detection require that the planet pass along the line-of-sight between us and the star that the planet orbits.  As for the second part to your question, there are several alternate exoplanet detection methods that do not require the observational orientation needed for the radial velocity and transit methods:

  • Direct Imaging: In rare cases where the parent star is not very bright (like when it is a Brown Dwarf) and the exoplanet is very large (Jupiter sized or larger), one can directly detect an exoplanet in such a system.
  • Astrometry: By measuring the gravitational “wobble” of a star as a planet orbits around it we can infer the existence, and mass, of an exoplanet.
  • Polarimetry: Since light that passes through an exoplanet atmosphere gets polarized, one can infer the presence of an exoplanet by measuring the polarization of the star+exoplanet light.

Jeff Mangum