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, when it culminates around midnight.
- From London it culminates about 70° above the horizon.
- From New York it culminates about 81° above the horizon.
- From Sydney it culminates about 24° above the horizon.
It can be seen from anywhere north of 58° S.
It ranks no. 43 in brightness among the 99 stars of Perseus in our catalogue. To find it, start from Mirfak, the brightest: it lies about 19° away (a fist at arm's length covers about 10°).
The light you see today left it about 320 years ago.
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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
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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