HD 190228 is a star with an orbiting substellar companion in the northern constellation of Vulpecula.
[5] The spectrum of HD 190228 presents as a subgiant star with a stellar classification of G5 IV,[4] indicating it has exhausted the supply of hydrogen at its core and is evolving off the main sequence.
The star is older than the Sun with an age over 5 billion years with a projected rotational velocity of 1.4 km/s.
The star is radiating roughly 4.6 times the luminosity of the Sun from its photosphere at an effective temperature of 5,311 K.[6] In 2000, it was announced that a giant exoplanet was orbiting the star with a minimum mass of 5 Jupiter masses, designated HD 190228 b.
[3] A 2011 study using astrometric measurements from Hipparcos found that, with 95% confidence, HD 190228 b is in fact a brown dwarf of 49.4±14.8 Jupiter masses in a nearly face-on orbit.