W Hydrae

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W Hydrae
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[1]
Spectral type M7.5IIIe
Apparent magnitude (J) -1.7[2]
Variable type Mira-type
Parallax (π) 9.59 ± 1.12 mas
Distance 374.9 ly
(115 pc)
Mass >1 M
Radius 562 R
Luminosity 11,050[3] L
Temperature 2,500[3] 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

W Hydrae is a Mira-type variable star in the constellation Hydra. The star is nearly located within the Solar neighborhood, between 75 and 120 parsecs, likely at 375 light years from the Sun. 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,[2] is the 7th brightest star in the night sky, and is even brighter than Sirius.

Water and dust masers[edit]

The star also shows signs of intense water emissions, indicative of the presence of a wide disk of dust and water vapour.[3] 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).


  1. ^ "GCVS Query=W Hya". General Catalogue of Variable Stars @ Sternberg Astronomical Institute, Moscow, Russia. Retrieved 2012-08-22. 
  2. ^ a b "V* W Hya". SIMBAD Astronomical Database. Retrieved 2012-08-21. 
  3. ^ a b c Zubko & Elitzur, Moshe (2000). "Water and Dust Emission from W Hydrae". The Astrophysical Journal. 544 (2): 137–140. Bibcode:2000ApJ...544L.137Z. arXiv:astro-ph/0009440Freely accessible. doi:10.1086/317317. 

Coordinates: Sky map 13h 49m 01.998s, +28° 22′ 03.49″

External links[edit]