Magnitude 6.09 Apparent magnitude (V) 6.09 | ||
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HD 166 or V439 Andromedae (ADS 69 A) is a 6th magnitude star in the constellation Andromeda, approximately 45 light years away from Earth. It is a variable star of the BY Draconis type, with a variation in brightness smaller than 0.2 magnitude. This is a G-type main sequence star like the Sun, yet cooler and dimmer, having a stellar classification of G8V and an effective temperature of 5,327 kelvin. It appears within one degree of the star Alpha Andromedae.
The star has a proper motion of 0.422 arcsecond per year (114.1° from north). It has an estimated visual luminosity of 61% of Sol. It has a diameter that is about 0.9 × Sol and has a radial velocity of -6.6 km/s. Age estimates range from as low as 200 million years old based on its chromospheric activity, up to 9.6 billion years. X-ray emission has been detected from this star, with an estimated luminosity of 8.5 × 1028 erg s−1.
An infrared excess has been detected around this star, most likely indicating the presence of a circumstellar disk at a radius of 7.5 AU. The temperature of this dust is 90 K.