HD 210277

HD 210277 is a single[8] star in the equatorial constellation of Aquarius. It has an apparent visual magnitude of 6.54,[2] which makes it a challenge to view with the naked eye, but it is easily visible in binoculars. The star is located at a distance of 69.5 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −20.9 km/s.[5]

An early classification of this star was a G0 dwarf,[10] and some sources still use this value.[11] More modern classification surveys list it as G8V,[3] matching a late G-type main-sequence star.[8] It is older than the Sun with a very low level of chromospheric activity [3] and is spinning with a projected rotational velocity of 1.9 km/s. The star has a slightly higher mass and larger radius than the Sun.[7]

In 1999 it was announced that a dust disk orbiting HD 210277, similar to that produced by the Kuiper Belt, had been imaged, lying between 30 and 62 AU from the star.[12] However, observations with the Spitzer Space Telescope failed to detect any infrared excess at 70 micrometres or at 24 micrometres wavelengths.[13][14] Subsequent measurements by the Herschel Space Observatory did detect an excess at 100 and 160 micrometres. A model fit to the emission matches a disk orbiting at 160 AU with a mean temperature of 22 K.[15]

The only known exoplanet was discovered using 34 radial velocity measurements taken from 1996 to 1998 at W. M. Keck Observatory. It has a minimum mass greater than Jupiter orbiting the star in 442 days.[8] The high eccentricity (ovalness) of the exoplanet's orbit means it is unlikely that there is a companion planet co-orbiting the star at a trojan point.[11]