HD 208527 is a star with an orbiting exoplanet located in the northern constellation of Pegasus. It has a reddish hue and is dimly visible to the naked eye with an apparent visual magnitude of +6.39. The star is located at a distance of approximately 1,080 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +4.8 km/s.It is currently the largest star known to have an exoplanet.
This was once catalogued as a K-type main-sequence star with a stellar classification of K5V, but is now known as an aging red giant with a class of M1III, based on its dimensions and low surface gravity. This indicates that the two-billion year old star has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. It has an estimated 1.6 times the mass of the Sun but has swollen to 58 times the Sun's radius. The star is radiating 729 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,035 K.
From September 2008 to June 2012, the team B.-C. Lee, I. Han and M.-G. Park observed HD 208527 with "the high-resolution spectroscopy of the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO)".
In 2012, a long-period, wide-orbiting exoplanet was deduced by radial velocity variations. This was published in November, gaining the designation HD 208527 b. Along with HD 220074 b this is one of the first two planets proposed around an M-type red giant.