Exoplanets

The study of exoplanets is one of the most vibrant fields of astrophysics today. Precise radial velocity (RV, or Doppler) measurements created the field by discovering the first exoplanets. Although employed for more than 30 years, RV measurements are still relevant today; when used with the transit method it provides the first characterization of exoplanets in terms of its mass, radius, and bulk density. These provide the first clues as to the internal structure of the exoplanet.

In a month when the tally of confirmed exoplanets passed 5,000, it's astonishing to remember that just 30 years ago, the notion of planets outside our own solar system was, well – just a notion. Since the first extrasolar planet was discovered in 1992, a staggering array of other worlds have been identified, including many in solar systems quite unlike our own.