R Hydrae

from Wikipedia, the free encyclopedia
Star
R Hydrae
Image and illustration of the bow shock wave of the star R Hydrae.
Image and illustration of the bow shock of the star R Hydrae.
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Water snake
Right ascension 13 h 29 m 42.77 s
declination -23 ° 16 ′ 52.7 ″
Apparent brightness 4.97 (3.5 to 10.9) mag
Typing
B − V color index (1.61) 
U − B color index (0.68) 
R − I index (2.42) 
Spectral class M6e-M9eS (Tc)
Variable star type M. 
Astrometry
Radial velocity (−10.0 ± 0.6) km / s
parallax (4.47 ± 0.89)  mas
distance (730   +180−130)  Ly
(220)  pc
Proper movement 
Rec. Share: (−46.66 ± 1.45)  mas / a
Dec. portion: (7.98 ± 1.51)  mas / a
Physical Properties
radius (630)  R ☉
Luminosity

(7400)  L ☉

Effective temperature (2100)  K
Other names
and catalog entries
Bonn survey BD −22 ° 3601
Cordoba Survey CD −22 ° 9961
Bright Star Catalog HR 5080 [1]
Henry Draper Catalog HD 117287 [2]
Hipparcos catalog HIP 65835 [3]
SAO catalog SAO 181695 [4]
Tycho catalog TYC 6713-24-1 [5]
2MASS catalog 2MASS J13294277-2316514 [6]
Other names IRAS 13269-2301

R Hydrae ( R Hya ) is a variable star of the Mira type in the eastern part of the constellation Water Snake .

The brightness of R Hydrae fluctuates between +3.5 and +10.9 m with a period that is currently 389 days . The period of R Hydrae changes slowly. It was 500 days at the beginning of the 18th century and has been decreasing slowly since then.

The period from maximum to minimum is 198 days, and that from minimum to maximum is 191 days.

During the maximum brightness, the star can be easily seen with the naked eye, while at least a telescope with an objective aperture of at least 5 centimeters is required for observation.

R Hydrae is about 730 light years away and belongs to the spectral class M. The star has about 2,100 K a very low surface temperature .

Web links

Individual evidence

  1. ↑ a b c d e f g h R Hya. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed September 9, 2018 .
  2. ↑ a b c d R Hya. In: VSX. AAVSO, accessed September 8, 2018 .
  3. ^ A b c d 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. ↑ Mira Predictions - 2019. In: britastro.org. 2019, accessed June 22, 2019 .