W Hydrae
Variable star in the constellation Hydra
From Wikipedia, the free encyclopedia
W Hydrae is a Mira-type variable star in the constellation Hydra. The star is nearly located within the Solar neighborhood, at 320 light years from the Solar System. It has a visual apparent magnitude range of 5.6 to 10. In the near-infrared J band it has a magnitude of -1.7,[4] is the 7th brightest star in the night sky, and is even brighter than Sirius.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 13h 49m 01.998s |
| Declination | −28° 22′ 03.49″ |
| Apparent magnitude (V) | 7.7 - 11.6[2] |
| Characteristics | |
| Spectral type | M7.5e-M9ep[3] |
| Apparent magnitude (J) | -1.7[4] |
| Variable type | Mira |
| Astrometry | |
| Parallax (π) | 10.18±2.36 mas[5] |
| Distance | 320+98 −59 ly (98+30 −18 pc)[5] |
| Details | |
| Mass | 2.14+1.07 −0.71[6] M☉ |
| Radius | 436+134 −80[7][a] R☉ |
| Luminosity | 9,290+2,460 −1,940[6] L☉ |
| Temperature | 3,000[6] K |
| Other designations | |
| W Hya, CCDM J13491-2822A, HD 120285, RAFGL 1650, CPD-27° 4792, HIP 67419, SAO 181981, AAVSO 1343-27, IRAS 13462-2807, GC 18659, TYC 6728-19-1. | |
| Database references | |
| SIMBAD | data |
Water masers and dust
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The star also shows signs of intense water emissions, indicative of the presence of a wide disk of dust and water vapour.[8] Such emissions cover a zone spanning between 10.7 Astronomical Units (within Saturn's orbital zone) and 1.2 parsecs (or nearly 247,500 Astronomical Units, as far away as the Oort Cloud in Solar System).
Notes
- Radius calculated using a distance of 98+30
−18 parsecs and an angular diameter of 41.4 milliarcseconds (0.041 arcsec). 98 • 0.041 = diameter of 4.06 AU, which is multiplied by 107.5 to convert from AU to R☉.
