W Hydrae

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Star
W Hydrae
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Water snake
Right ascension 13 h 49 m 2 s
declination -28 ° 22 ′ 3.5 ″
Apparent brightness 7.7 (5.6 to 9.6) mag
Typing
B − V color index (1.27) 
Spectral class M7e-M9ep
Variable star type M. 
Astrometry
Radial velocity (42.3 ± 2) km / s
parallax (6.09 ± 0.82)  mas
distance (530 ± 80)  ly
(160)  pc
Proper movement 
Rec. Share: (−51.77 ± 1.30)  mas / a
Dec. portion: (−59.69 ± 1.26)  mas / a
Physical Properties
radius (230)  R ☉
Luminosity

(4500)  L ☉

Effective temperature (3100)  K
Other names
and catalog entries
Cordoba Survey CD −27 ° 9429
Henry Draper Catalog HD 120285 [1]
Hipparcos catalog HIP 67419 [2]
SAO catalog SAO 181981 [3]
Tycho catalog TYC 6728-19-1 [4]
2MASS catalog 2MASS J13490199-2822034 [5]
Other names W Hydrae, FK5 5220

W Hydrae is a variable star ( Mira star ) in the constellation of Hydra , about 115 parsecs (about 375 light years ) from the Sun according to Hipparcos' catalog . Its visual apparent brightness fluctuates between 5.6 and 9.6. In the near infrared (J band), its apparent brightness is −1.6, so it appears as the seventh brightest star in this area (for example, brighter than Sirius ).

Water and dust

The star also shows intense emissions from the water, indicating the existence of an extensive disk of dust and gaseous water. The source of such emissions spans an area between 0.182 ″ and 36 ′ in diameter. At the above distance, this corresponds to a disk of dust with an inner radius of about 10.5 astronomical units (about the distance of Saturn from the Sun) and an outer radius of about 2 light years (i.e. about 125,000 astronomical units, i.e. slightly more than the extent of the Oort cloud in the solar system).

Web links

Individual evidence

  1. ↑ a b c d e f g W Hya. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed September 9, 2018 .
  2. ↑ a b c W Hya. In: VSX. AAVSO, accessed September 9, 2018 .
  3. ^ A b c E. De Beck, L. Decin, A. De Koter, K. Justtanont, T. Verhoelst, F. Kemper, KM Menten: Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles . II. CO line survey of evolved stars: Derivation of mass-loss rate formulas . In: Astronomy and Astrophysics . 523, 2010, p. A18. arxiv : 1008.1083 . bibcode : 2010A & A ... 523A..18D . doi : 10.1051 / 0004-6361 / 200913771 .
  4. ^ A b Zubko & Elitzur, Elitzur, Moshe: Water and Dust Emission from W Hydrae . In: The Astrophysical Journal . 544, No. 2, 2000, pp. 137-140. arxiv : astro-ph / 0009440 . bibcode : 2000ApJ ... 544L.137Z . doi : 10.1086 / 317317 .