51 Pegasi [SEP] constellation
51 Pegasi
51 Pegasi (abbreviated 51 Peg), formally named Helvetios , is a Sun-like star located from Earth in the constellation of Pegasus. It was the first main-sequence star found to have an exoplanet (designated 51 Pegasi b, officially named Dimidium, formerly unofficially dubbed "Bellerophon") orbiting it.
Properties.
The star is of apparent magnitude 5.49, and so is visible with the naked eye under suitable viewing conditions.
51 Pegasi was listed as a standard star for the spectral
of core hydrogen fuel and expands into a giant and transfers material to the smaller star.
Twelve star systems have been found to have exoplanets. 51 Pegasi was the first Sun-like star discovered to have an exoplanet companion; 51 Pegasi b (unofficially named Bellerophon) is a hot Jupiter close to its sun, completing an orbit every four days. Spectroscopic analysis of HD 209458 b, an extrasolar planet in this constellation, has provided the first evidence of atmospheric water vapor beyond the solar system, while extrasolar planets orbiting