Helvetios — Star in Pegasus

51 Pegasi is a sun-like G2 IV star about 50 light-years away in the Square of Pegasus, magnitude 5.49. In 1995 it became the first main-sequence star outside the Solar System found to host a planet — 51 Pegasi b, a hot Jupiter orbiting in 4.23 days at 0.05 AU. The discovery launched the modern era of exoplanet astronomy.

Easy naked-eye target from a dark site, simple in binoculars. Once located, the meaning of the star is in your imagination — the planet itself is invisible — but the sense of looking at the first known exoplanet host is unmatched. Best in autumn high in Pegasus.

Michel Mayor and Didier Queloz at Observatoire de Haute-Provence detected the planet via radial-velocity wobble using the ELODIE spectrograph, announcing it on 6 October 1995. The companion's short period and Jupiter-class mass overturned the assumption that giant planets only form far from their stars, and the pair won the 2019 Nobel Prize in Physics.