羽林军廿五

Tau¹ Aquarii is a solitary star in the equatorial constellation of Aquarius. Its name is a Bayer designation that is Latinized from τ¹ Aquarii, and abbreviated Tau¹ Aqr or τ¹ Aqr. With an apparent visual magnitude of 5.66, it is a faint naked eye target that requires dark suburban skies for viewing. Parallax measurements yield a distance estimate of approximately 357 light-years (109 parsecs) from the Sun. The star is drifting further away with a radial velocity of +15 km/s. It is a candidate member of the Pisces-Eridanus stellar stream.

The stellar classification of τ¹ Aquarii is B9 V; at the borderline between a B- and A-type main sequence star. This is a candidate silicon star; a type of Ap star of class CP2 that shows a magnetic field. It is around 100 million years old and is spinning rapidly with a projected rotational velocity of 185 km/s. The star has 2.8 times the mass of the Sun and 2.56 times the Sun's radius. It is radiating 87 times the luminosity of the Sun from its photosphere at an effective temperature of 10,560 K. When examined in the infrared band, it displays an excess emission that is a characteristic of s…