R Hydrae

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R Hydrae
Hydra constellation map.svg
Red circle.svg
Location of R Hydrae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hydra
Right ascension  13h 29m 42.77203s[1]
Declination −23° 16′ 52.6972″[1]
Apparent magnitude (V) 3.5 to 10.9 (variable)[2]
Spectral type M6e/M9e:[3]
B−V color index 1.317±0.254[4]
Variable type Mira[2] (period 388.87 days)
Radial velocity (Rv)−10.0±0.6[5] km/s
Proper motion (μ) RA: −46.660[1] mas/yr
Dec.: +7.984[1] mas/yr
Parallax (π)4.4682 ± 0.8942[1] mas
Distanceapprox. 700 ly
(approx. 220 pc)
Absolute magnitude (MV)+0.95[4]
Mass2[6] M
Radius460[6] - 631[7] R
Luminosity7,375[7] - 10,000[6] L
Temperature2,128[7] - 2,830[6] K
Other designations
R Hyd, BD−22° 3601, HD 117287, HIP 65835, HR 5080, SAO 181695[8]
Database references
The bow shock around R Hya [9]

R Hydrae, also known as R Hya,[2] is a Mira-type variable star in the constellation Hydra.[2][8]

The magnitude of R Hydrae varies over a period of 389 days, between 3.5 and 10.9. The period of R Hydrae changes slowly.

At maximum brightness the star can be seen with the naked eye, while at minimum a telescope of at least 5 cm is needed.

R Hydrae is approximately 700 light years from Earth, its spectral class is M6e/M9e:.[8]


  1. ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. ^ a b c d AAVSO
  3. ^ Keenan, Philip C.; Garrison, Robert F.; Deutsch, Armin J. (1974). "Revised Catalog of Spectra of Mira Variables of Types ME and Se". Astrophysical Journal Supplement. 28: 271. Bibcode:1974ApJS...28..271K. doi:10.1086/190318.
  4. ^ a b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  5. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  6. ^ a b c d Zijlstra, A. A.; Bedding, T. R.; Mattei, J. A. (2002). "The evolution of the Mira variable R Hydrae". Monthly Notices of the Royal Astronomical Society. 334 (3): 498. arXiv:astro-ph/0203328. Bibcode:2002MNRAS.334..498Z. doi:10.1046/j.1365-8711.2002.05467.x.
  7. ^ a b c De Beck, E.; Decin, L.; De Koter, A.; Justtanont, K.; Verhoelst, T.; Kemper, F.; Menten, K. M. (2010). "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 formulae". Astronomy and Astrophysics. 523: A18. arXiv:1008.1083. Bibcode:2010A&A...523A..18D. doi:10.1051/0004-6361/200913771. A18.
  8. ^ a b c "V* R Hya". SIMBAD. Centre de données astronomiques de Strasbourg.
  9. ^ Spitzer Science Center Press Release: Red Giant Plunging Through Space Archived 2007-05-13 at the Wayback Machine

External links[edit]