First Discoveries

The first exoplanets' discovery was announced in 1992, although this was unlikely to ever be a system to search for life. It features three planets (called Draugr, Poltergeist and Phobetor) all orbiting a pulsar called PSR B1257+12 (see Figure 1). Since pulsars are rapidly rotating (in this case, around 160 times per second), very dense remnants of supernovae with extremely large magnetic fields, these exoplanets are different to the main population of exoplanets that we now know about. As you might imagine, this exciting discovery opened up a new field of astronomy and was announced in a paper in the Nature journal.

Figure 1: An artist's impression of the PSR B1257+12 planetary system.
Credit: NASA/JPL-Caltech/R. Hurt (SSC)

This discovery was followed in 1995 by the discovery of 51 Pegasi b, the first exoplanet found to be orbiting a normal Sun-like star. The work of Swiss astronomers Michel Mayor and Didier Queloz used the radial velocity technique to prove the existence of the planet orbiting its parent star every 4.23 days. They used the ELODIE spectrograph (see Figure 2) at the Observatoire de Haute Provence in France. 51 Peg b has a similar mass to Jupiter but is much closer to its star, being more than 7 times nearer than Mercury is to our Sun. This affords it the understated designation of a 'hot Jupiter'.

Figure 2: The ELODIE spectrograph which discovered 51 Peg b.
Credit: S. Ilovaisky

It is worth noting that at a time when we have ground-based optical telescopes with mirrors up to 10 metres across, this discovery was made using a telescope with a more modest 1.93 metre mirror. 

The following year, the planet 47 Ursae Majoris b was found orbiting its star at a much greater distance (around twice that of the Earth's distance from the Sun) with an orbital period of 2.95 years.

Read more about the previous studies and missions.