S Monocerotis
Monoceros . | ||
| Observation data Epoch J2000 Equinox J2000 | ||
|---|---|---|
| Constellation | Monoceros
| |
| A | ||
| Right ascension | 06h 40m 58.656s[1] | |
| Declination | +09° 53′ 44.71″[1] | |
| Apparent magnitude (V) | 4.66[2] (4.62 - 4.68[3]) + 5.90[2] | |
| B | ||
| Right ascension | 06h 40m 58.566s[1] | |
| Declination | +09° 53′ 42.20″[1] | |
| Apparent magnitude (V) | 7.830[1] | |
| Characteristics | ||
| Spectral type | O7V((f))zvar[4] + O9.5Vn[5] + B2V[6] | |
| U−B color index | −1.034[7] | |
| B−V color index | −0.261[7] | |
| Variable type | Ia[3] | |
| Absolute magnitude (MV) | −5.21[10] | |
| B | ||
Distance | 2,110 ± 50 ly (650 ± 20 pc) | |
Argument of periastron (ω)(secondary) | 63±4° | |
| Details | ||
| Aa | ||
Myr | ||
BD +10°1220 | ||
| Database references | ||
| SIMBAD | data | |
| ARICNS | data | |
Christmas Tree Cluster
(upside down in this image) with S Monocerotis at the very top of the image (and the base of the Christmas tree)S Monocerotis, also known as 15 Monocerotis, is a massive
Christmas Tree open cluster in the area catalogued as NGC 2264
.
S Monocerotis is found within an open cluster and the
arcseconds away. It is classified as B2 main sequence star with a mass of 7.31 M☉. Designated component C is an 11th-magnitude B8V star.[6]
The cluster contains another dozen or so 9th and 10th magnitude stars and many fainter stars.
S Monocerotis A is a
spectrum of this star has served as the MK standard for O7 by which other stars are classified.[19] It is also an irregular variable star with a range of less than a tenth of a magnitude. The orbital parameters can be used to derive the masses of the two stars, giving 31 M☉ and 11 M☉.[6]
The distance to S Monocerotis and NGC 2264 has been derived in various ways, including dynamical parallax and isochrone fitting. These consistently give estimates of 700 - 900 parsecs, although this is double the likely distance derived from the
mas
and 1.5 mas respectively, consistent with the expected distance to the cluster.
References
- ^ ISBN 0333750888.
- ^ ].
- ^ Bibcode:2009yCat....102025S.
- S2CID 119248206.
- ^ .
- ^ .
- ^ Bibcode:1985A&AS...61..331O.
- S2CID 119387088.
- ^ S2CID 18759600.
- Bibcode:1986A&A...159..223F.
- ^ .
- ^ .
- ^ S2CID 247759810.
- ^ Bibcode:1992A&A...261..209H.
- S2CID 5272305.
- Bibcode:1970CoAsi.239....1B.
- S2CID 111387483.
- .
- Bibcode:1993AAS...183.1710G. Archived from the originalon 2019-06-25. Retrieved 2012-02-04.
External links
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