Star in the constellation Hydra
Phi2 Hydrae ,Latinized fromφ2 Hydrae , is astar in theconstellation Hydra . It originally received theFlamsteed designation of1 Crateris before being placed in the Hydra constellation.[ 10] parallax shift of 4.31 mas as seen from Earth, it is located roughly 760 light years from theSun . The star is faintly visible to thenaked eye with anapparent visual magnitude of 6.09.[ 3] φ1 Hydrae and the brighterφ3 Hydrae , betweenμ Hydrae andν Hydrae .
Pulsations[ 6] Period Amplitude 11.0 0.008 110.3 0.012 153.6 0.015
This is anevolved red giant star with astellar classification of M1 III.[ 11] asymptotic giant branch ,[ 11] semiregular variable that undergoes changes in luminosity according to three pulsation periods.[ 6] [ 8] Sun's luminosity from itsphotosphere at aneffective temperature of 3,791 K.[ 8]
Phi2 Hydrae has a faint visual companion: a magnitude 12.20 star at anangular separation of 3.50 arc seconds along aposition angle of 280°, as of 1959.[ 12]
^ EAS (1997)."The HIPPARCOS and TYCHO catalogues" .Astrometric and Photometric Star Catalogues Derived from the ESA Hipparcos Space Astrometry Mission . ESA SP Series.1200 . Noordwijk, Netherlands: ESA Publications Division.Bibcode :1997HIP...C......0E .ISBN 9290923997 . Retrieved14 December 2024 . ^a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction",Astronomy and Astrophysics ,474 (2):653– 664,arXiv :0708.1752 Bibcode :2007A&A...474..653V ,doi :10.1051/0004-6361:20078357 ,S2CID 18759600 . ^a b c de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project",Astronomy & Astrophysics ,546 : 14,arXiv :1208.3048 Bibcode :2012A&A...546A..61D ,doi :10.1051/0004-6361/201219219 ,S2CID 59451347 , A61. ^ Houk, Nancy; Smith-Moore, M. (1978),Michigan catalogue of two-dimensional spectral types for the HD stars , vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan,Bibcode :1988mcts.book.....H . ^a b Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)",Catalogue of Eggen's UBV Data ,SIMBAD ,Bibcode :1986EgUBV........0M . ^a b c Tabur, V.; et al. (2009), "Long-term photometry and periods for 261 nearby pulsating M giants",Monthly Notices of the Royal Astronomical Society 400 (4):1945– 61,arXiv :0908.3228 Bibcode :2009MNRAS.400.1945T ,doi :10.1111/j.1365-2966.2009.15588.x S2CID 15358380 . ^ 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 ,S2CID 119257644 . ^a b c d McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars",Monthly Notices of the Royal Astronomical Society ,427 (1):343– 57,arXiv :1208.2037 Bibcode :2012MNRAS.427..343M ,doi :10.1111/j.1365-2966.2012.21873.x S2CID 118665352 . ^ "* phi02 Hya" .SIMBAD Centre de données astronomiques de Strasbourg . Retrieved2017-03-17 .{{cite web }}: CS1 maint: postscript (link )^ Wagman, M. (August 1987), "Flamsteed's Missing Stars",Journal for the History of Astronomy ,18 (3): 216,Bibcode :1987JHA....18..209W ,doi :10.1177/002182868701800305 ,S2CID 118445625 . ^a b Eggen, Olin J. (July 1992), "Asymptotic giant branch stars near the sun",Astronomical Journal ,104 (1):275– 313,Bibcode :1992AJ....104..275E ,doi :10.1086/116239 . ^ Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog",The Astronomical Journal ,122 (6):3466– 3471,Bibcode :2001AJ....122.3466M ,doi :10.1086/323920
