Garnet star
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Triple garnet star (μ cep) |
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| Observation data epoch : J2000.0 |
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| AladinLite | ||
| Constellation | Cepheus | |
| Astrometry | ||
| Radial velocity | +19.3 km / s | |
| Proper movement | ||
| Rec. Share: | 5.24 mas / a | |
| Dec. portion: | −2.88 mas / a | |
| Individual data | ||
| Names | Garnet star , μ Cep B , μ Cep C | |
| Observation data: | ||
| Right ascension | Garnet star | 21 h 43 m 30.5 s |
| μ Cep B | 21 h 43 m 27.8 s | |
| μ Cep C | 21 h 43 m 25.6 s | |
| declination | Garnet star | + 58 ° 46 ′ 48.2 ″ |
| μ Cep B | + 58 ° 46 ′ 45 ″ | |
| μ Cep C | + 58 ° 47 ′ 08 ″ | |
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Apparent brightness |
Garnet star | 3.68 to 5.0 m |
| μ Cep B | 12.3 m | |
| μ Cep C | 12.7 m | |
| Typing: | ||
| Spectral class | Garnet star | M2 Iae |
| μ Cep B | M0 | |
| μ Cep C | A. | |
| BV color index | Garnet star | 2.26 |
| μ Cep B | ||
| μ Cep C | ||
| UB color index | Garnet star | 2.42 |
| μ Cep B | ||
| μ Cep C | ||
| Astrometry: | ||
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Absolute visual brightness M vis |
Garnet star | −7.3 mag |
| μ Cep B | 0.92 mag | |
| μ Cep C | 1.32 mag | |
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Absolute bolometric brightness M bol |
Garnet star | −8.5 mag |
| μ Cep B | like | |
| μ Cep C | like | |
| Physical Properties: | ||
| Dimensions | Garnet star | 25 M ☉ |
| μ Cep B | 2–5 M ☉ | |
| μ Cep C | ~ 2.5 M ☉ | |
| radius | Garnet star | 1420 R ☉ |
| μ Cep B | 24 R ☉ | |
| μ Cep C | ~ 2.5 R ☉ | |
| Luminosity | Garnet star | 350,000 (bol.) L ☉ |
| μ Cep B | 36.58 L ☉ | |
| μ Cep C | 25.34 L ☉ | |
| Effective temperature | Garnet star | 3,450 K |
| μ Cep B | 3,850 K | |
| μ Cep C | ~ 9,000 K | |
| Rotation time | Garnet star | 1,250 d |
| μ Cep B | 15.2 d | |
| μ Cep C | 0.5 d | |
| Designations and catalog entries | ||
| Bayer-Bez. | μ Cep | |
| Bonn diam. | BD +58 2316 | |
| Bright Star Cat. | HR 8316 | |
| HD catalog | HD 206936 | |
| SAO catalog | SAO 33693 | |
| Tycho catalog | TYC 3979-1616-1 | |
| Hipparcos catalog | HIP 107259 | |
| WDS catalog | WDS J21435 + 5847A | |
| ADS catalog | ADS 15271 | |
| Other names |
Erakis • Herschel's garnet star • 2MASS J21433045 + 5846480 | |
| The garnet star is the prototype of the My Cephei stars . | ||
Garnet Star is the name of the star μ Cephei in the constellation Cepheus .
The name “garnet star” comes from Wilhelm Herschel , because μ Cephei appears garnet red due to its spectral class M2. μ Cephei is a semi-regularly variable star and was the prototype of the no longer used class of My Cephei stars . My Cephei is today assigned to the SRc stars and its apparent visual brightness fluctuates between +3.7 mag and +5.0 mag with periods of 850 and 4400 days.
The garnet star is orbited by two relatively faint companions about which little is known. With apparent magnitudes of 12.3 mag and 12.7 mag, they are only visible in larger telescopes. μ Cephei B was assigned to the spectral class M0; further details regarding mass, luminosity and radius are still very uncertain and are only based on estimates and results from simulations.
Web links
- Variable Star of the Month: Mu Cephei - A Most Beautiful Object
- The Largest Stars (English) ( Memento from August 10, 2007 in the Internet Archive )
- The Brightest Stars (English) ( Memento of 10 August 2007 at the Internet Archive )
- Historical Archive Photometry of µ Cephei (English)