Star profile
21 Sagittarii
What is 21 Sagittarii
21 Sagittarii is a pair of bright K2 giants some 410 light-years away, set against the dense skies of the Archer. The system's estimated mass is around eight times the Sun's, and both components drift gently toward us at roughly twelve kilometres per second. Beyond astronomy, the BBC turned it into the setting of its 2022 docu-drama «First Contact: An Alien Encounter», imagining an extraterrestrial artefact arriving precisely from here.
Where it is and when to see it
21 Sagittarii lies in the southern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is June: 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 Sagittarii
- Constellation
- Sagittarius
- Apparent magnitude
- 4.81
- Distance
- 410.3 light years
- Coordinates (J2000)
- RA 276.338° · Dec -20.542°
- Catalogue
- HIP 90289 · HD 169420
A symbolic commemorative gift: neither the signature nor the chosen name implies ownership of the star or recognition by the IAU.
Other stars in Sagittarius
Sagittarius has 117 stars in Stelvia's catalogue. Here are a few of them.
- Kaus AustralisEpsilon Sagittarii1.79
- NunkiSigma Sagittarii2.05
- AscellaZeta Sagittarii2.60
- TerebellumOmega Sagittarii4.70
- 4 Sagittarii4.74
- HIP 987614.77
- 60 Sagittarii4.84
- HIP 919184.86