HD 21278

HD 21278 is a binary star system in the constellation Perseus, located within the Alpha [Persei Cluster]. It has a blue-white hue and is visible to the naked eye with a combined apparent visual magnitude of 4.99. The system is located at a distance of approximately 570 light years from the Sun based on parallax, and it is drifting further away with a radial velocity of +1.20 km/s.
The binary nature of this star was announced in 1925 by Otto Struve. It is a double-lined spectroscopic binary with an orbital period of 21.685 days and an eccentricity of 0.138.
The primary component is a B-type main-sequence star with a stellar classification of B5V, indicating it is generating energy through core hydrogen fusion. The star is spinning with a projected [rotational velocity] of 53 km/s. It has 5.381 times the mass of the Sun and about 3.75 times the Sun's radius. HD 21278 A is radiating 940 times the luminosity of the Sun from its photosphere at an effective temperature of 16,410 K.
The secondary component is also a B-type main-sequence star, with a spectral class B9V. It has 3.353 times the mass of the Sun and an effective temperature of 11,120 K.