Free Astronomy Magazine July-August 2015

30 JULY-AUGUST 2015 SPACE CHRONICLES ets now known to be relatively com- monplace, which are similar in size and mass to Jupiter, but orbit much closer to their parent stars. Since that landmark discovery, more than 1900 exoplanets in 1200 plane- tary systems have been confirmed, but, in the year of the twentieth an- niversary of its discovery, 51 Pegasi b returns to the ring once more to provide another advance in exoplan- et studies. The team that made this new detection was led by Jorge Martins from the Instituto de Astro- física e Ciências do Espaço (IA) and the Universidade do Porto, Portugal, who is currently a PhD student at ESO in Chile. They used the HARPS instrument on the ESO 3.6-metre telescope at the La Silla Observatory in Chile. Currently, the most widely used method to examine an exoplanet’s atmosphere is to observe the host star’s spectrum as it is filtered through the planet’s atmosphere during transit — a technique known as transmission spectroscopy. An alternative approach is to observe the system when the star passes in First detection of reflected visible light from 51 Pegasi b by ESO T he exoplanet 51 Pegasi b lies some 50 light-years from Earth in the constellation of Pega- sus. It was discovered in 1995 and will forever be remembered as the first confirmed exoplanet to be found orbiting an ordinary star like the Sun (two earlier planetary ob- jects were detected orbiting in the extreme environment of a pulsar). It is also regarded as the arche- typal hot Jupiter — a class of plan- T his zoom video takes the viewer from a broad view of the sky deep into the northern constella- tion of Pegasus (The Winged Horse). The sequence ends with a close-up of 51 Pegasi, which is orbited by 51 Pegasi b, the first exoplanet ever discovered around a normal star. [ESO/Digitized Sky Survey 2/A. Fujii, M. Kornmesser/Nick Risinger (skysurvey.org)]