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) | 5.40[2] |
| Characteristics | |
| Spectral type | M8 III |
| U−B color index | +0.86[1] |
| B−V color index | +1.58[1] |
| Variable type | Mira variable |
| Astrometry | |
| Radial velocity (Rv) | +26.1[3] km/s |
| Proper motion (μ) | RA: -69.36[1] mas/yr Dec.: -75.78[1] mas/yr |
| Parallax (π) | 18.31 ± 0.99[1] mas |
| Distance | 178 ± 10 ly (55 ± 3 pc) |
| Details | |
| Mass | 1.2[4] M☉ |
| Radius | 370 ± 50[5] R☉ |
| Luminosity | 6,500 ± 1400[5] L☉ |
| Temperature | 2,740 ± 190[5] K |
| Rotation | 340 days |
| Other designations | |
| Database references | |
| SIMBAD | data |
R Doradus (also called HD 29712) is the name of a red giant Mira variable star in the far-southern constellation Dorado, although visually it appears more closely associated with the constellation Reticulum. Its distance from Earth is 178 ± 10 light-years (55 ± 3.1 parsecs).[1] Having a uniform disk diameter of 0.057 ± 0.005 arcsec,[6] and given its distance, it is currently believed to be the star with the second largest apparent size as viewed from Earth (right after the Sun). The estimated diameter of R Doradus is 515 ± 70 million km (3.46 AU) or 370 ± 50[5] times the diameter of the Sun. If placed at the centre of the Solar System, the orbit of Mars and most of the main asteroid belt would be contained within the star.
The visible magnitude of R Doradus varies between 4.8 and 6.6, which makes it usually just visible to the naked eye, but in the infrared it is one of the brightest stars in the sky and its total luminosity is 6500 ± 1400 times that of the Sun.[7]
[edit] An anomaly?
 |
This section may contain original research. Please improve it by verifying the claims made and adding references. Statements consisting only of original research may be removed. More details may be available on the talk page. (February 2012) |
The finding that this star has the largest angular measurement presented by the ESO[7] appears to contradict the results of typical methods of calculating the total luminosity and radius of a star. The star is approximately 200 light years away and has a maximum apparent magnitude 5.73, which seems to imply an absolute magnitude of 1.75 and hence a radius 18 times that of the Sun rather than 350 times. The discrepancy arises because of the very cool surface temperature of the star, which results in most of its radiation being emitted in the infrared rather than at visible wavelengths. Applying the appropriate bolometric correction reveals that its true total luminosity is about 6500 times that of the Sun, rather than 17 times, as estimated from the visual brightness alone.
[edit] References
- ^ a b c d e f g h van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, Bibcode 2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- ^ Nicolet, B. (1978). "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System". Astronomy and Astrophysics Supplement Series 34: 1–49. Bibcode 1978A&AS...34....1N.
- ^ Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Washington: Carnegie Institution of Washington. Bibcode 1953QB901.W495......
- ^ Jacob, A. P. et al. (March 2004), "Multiwavelength visibility measurements of Miras: observations of R Dor and R Leo with MAPPIT", Monthly Notices of the Royal Astronomical Society 349 (1): 303–312, Bibcode 2004MNRAS.349..303J, doi:10.1111/j.1365-2966.2004.07503.x
- ^ a b c d Bedding, T. R. et al. (April 1997), "The angular diameter of R Doradus: a nearby Mira-like star", Monthly Notices of the Royal Astronomical Society 286 (4): 957–962, arXiv:astro-ph/9701021, Bibcode 1997MNRAS.286..957B
- ^ Richichi; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431: 773–777, Bibcode 2005A&A...431..773R, doi:10.1051/0004-6361:20042039
- ^ a b "The Biggest Star in the Sky" (Press release). European Southern Observatory. 1997-03-11. http://www.eso.org/outreach/press-rel/pr-1997/pr-05-97.html. Retrieved 2006-09-05.
[edit] External links
- Swinburne Astronomy Online; information about R Doradus
- Variáveis Binoculares
- The 3µ spectrum of R Doradus observed with the ISO-SWS
|
|||||||||||
