Tags: Star.
21 Persei is an star in the constellation Perseus. Its apparent magnitude is 5.10. Located around 98.03 parsecs (319.7 ly) distant it is an hot blue star of spectral type B9. The star is an Alpha2 Canum Venaticorum variable meaning that the star has a strong magnetic field chromium silicon and strontium spectral lines. 21 Persei’s period is approximately 2.88 days