Star profile
21 Persei
Variable starWhat is 21 Persei
21 Persei is a variable star that pulses slowly some three hundred and twenty light-years away, within the hero who brandishes Medusa's head. Its B type places it among the young and hot, and its brightness shifts in subtle rhythms that only patient photometry can capture. In Perseus, neighbour to famous Algol —the Gorgon's eye that blinks every three days—, it is not the only star that breathes with light.
Where it is and when to see it
21 Persei lies in the northern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is November: the Sun sits at the opposite point of the sky and the star culminates around midnight. How high it climbs above the horizon depends on the latitude you watch from.
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The signature wall
Stelvia's sky works like a signature wall: anyone can leave their name and a message on a real star, and that signature goes up on the map for everyone to read. Signing is free.
A signature without a lock can be replaced by someone else's. The lock makes the signature permanent and lets you choose a symbolic name for the star, always shown next to the star's catalogue identifier. How the lock works
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A public signature from a real person. The chosen name is a symbolic denomination within Stelvia, with no official standing or IAU recognition: the sky is not for sale and belongs to no one.
Astronomical data for 21 Persei
- Constellation
- Perseus
- Apparent magnitude
- 5.10
- Distance
- 319.8 light years
- Coordinates (J2000)
- RA 44.322° · Dec 31.934°
- Catalogue
- HIP 13775 · HD 18296
A symbolic commemorative gift: neither the signature nor the chosen name implies ownership of the star or recognition by the IAU.
Other stars in Perseus
Perseus has 99 stars in Stelvia's catalogue. Here are a few of them.
- MirfakAlpha Persei1.79
- AlgolBeta Persei2.09
- Zeta Persei2.84
- 4 Persei4.99
- HIP 152195.04
- 31 Persei5.05
- 42 Persei5.14
- 9 Persei5.16