R Doradus
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Dorado |
Right ascension | 04h 36m 45.59127s[1] |
Declination | −62° 04′ 37.7974″[1] |
Apparent magnitude (V) | 4.8–6.6[2] 5.40[3] |
Characteristics | |
Evolutionary stage | AGB |
Spectral type | M8III:e[4] |
Apparent magnitude (J) | −2.6[5] |
Apparent magnitude (K) | −4.2[5] |
U−B color index | +0.86[1] |
B−V color index | +1.58[1] |
Variable type | SRb[2]
|
Details | |
Gyr | |
Database references | |
SIMBAD | data |
R Doradus (HD 29712 or P Doradus) is a
Variability
The
It is classified as a semiregular variable star of type SRb, indicating giants with slow poorly-defined variations, often alternating between periodic and irregular brightness changes.[2] Some studies show it alternating between periods of about 175 and 332 days, and a period of 117.3 days has also been identified.[12] It has been likened to a Mira variable when its variations are relatively regular, although its amplitude of only 1.5 magnitudes is smaller than Mira variables.[13]
Angular diameter
The angular diameter of R Doradus is easily measured using
The angular diameter of R Doradus is larger than any other measured star other than the Sun. The angular diameter of the next-largest star, Betelgeuse, is around 45 mas.[14]
Properties
The
The
Comparison of its properties with theoretical evolutionary tracks gives an age of between 6 and 14 billion years, with a current mass of between 0.7 and 1.0 M☉. Its initial mass would have been between 1 and 1.25 M☉. It is on the asymptotic giant branch having exhausted its core helium.[12]
The radius of 298 R☉ means that the diameter of R Doradus is 415 million km (2.77
R Doradus has a projected equatorial
R Doradus figures almost at the western limit of Dorado, next to Reticulum (map to be held, as standard, upwards, with south horizon in front of viewer). Like Alpha Reticuli, which outshines it, it is a little south of a line between the bright stars Canopus and Achernar, as is the narrow kite-shaped asterism of Reticulum. |
References
- ^ S2CID 18759600.
- ^ a b c "GCVS Query=R Dor". General Catalogue of Variable Stars @ Sternberg Astronomical Institute, Moscow, Russia. Retrieved 2012-08-22.
- Bibcode:1978A&AS...34....1N.
- doi:10.1086/149317.
- ^ S2CID 18913331.
- Bibcode:1953GCRV..C......0W.
- ^ S2CID 201103617.
- ^ S2CID 52088412.
- ^ "* P Dor". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2015-03-05.
- S2CID 15358667. Retrieved 2 January 2022.
- doi:10.1086/129124.
- ^ S2CID 15358380.
- S2CID 15358667.
- ^ S2CID 15438522.