HR 8799

HR 8799 is a young main sequence star with a debris disk and four known giant extra-solar planets. It is one of the first systems in which the exoplanets were discovered (or confirmed) by direct imaging and the clearest view of so much of a planetary system. The planets are giant planets that are a substantial distance from their host. HR 8799 characteristics:

• Pegasus - constellation.
• 23h07m28.7157s - right ascension.
• +21deg08m03.311s - declination.
• +5.964 - apparent magnitude (V).
• 133.3 ly - distance.
• F0 - spectral type based upon effective temperature: it also has atypical spectral features indicated appending more types.
• 1.43 - mass(solar).
• 5.05 - luminosity(solar).
• 1.44 - radius(solar).
• +0.234 - B-V color index.
• 42 million years - age.

(R_J and M_J are Jupiter's radius and mass.) The planet temperatures are effective temperatures, and the mass and radius determinations use this along with the host star's age and evolutionary models of such objects. Some determinations of the star's age are much greater and if so, evolution models would show the orbiting objects to be more massive, in the brown-dwarf range.