Beta Hydri

β Hydri
Location of β Hydri (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hydrus
Right ascension 00h 25m 45.07036s[1]
Declination –77° 15′ 15.2860″[1]
Apparent magnitude (V) 2.80[2]
Characteristics
Spectral type G2 IV[3]
U−B color index +0.11[2]
B−V color index +0.62[2]
Astrometry
Radial velocity (Rv)+22.4[4] km/s
Proper motion (μ) RA: +2,219.54[1] mas/yr
Dec.: +324.09[1] mas/yr
Parallax (π)134.07 ± 0.11 mas[1]
Distance24.33 ± 0.02 ly
(7.459 ± 0.006 pc)
Absolute magnitude (MV)3.45 ± 0.01[5]
Details
Mass1.08 ± 0.03[3] M☉
Radius1.809 ± 0.015[3] R☉
Luminosity3.494 ± 0.087[3] L☉
Surface gravity (log g)4.02 ± 0.04[5] cgs
Temperature5,872 ± 44[3] K
Metallicity [Fe/H]−0.10 ± 0.07[3] dex
Rotational velocity (v sin i)6.0[6] km/s
Age6.40 ± 0.56[3] Gyr
Other designations
CD−77° 15, Gl 19, HD 2151, HIP 2021, HR 98, LHS 6, LTT 226, GCTP 69, SAO 255670, CPD–77° 16, FK5 11, LPM 22, LFT 43.
Database references
SIMBADdata

Beta Hydri (β Hyi, β Hydri) is a star in the southern circumpolar constellation of Hydrus. (Note that Hydrus is not the same as Hydra.) With an apparent visual magnitude of 2.8,[2] this is the brightest star in the constellation. Based upon parallax measurements the distance to this star is about 24.33 light-years (7.46 parsecs).[1]

This star has about 104% of the mass of the Sun and 181% of the Sun's radius, with more than three times the Sun's luminosity.[3] The spectrum of this star matches a stellar classification of G2 IV, with the luminosity class of 'IV' indicating this is a subgiant star. As such, it is a slightly more evolved star than the Sun, with the supply of hydrogen at its core becoming exhausted. It is one of the oldest stars in the solar neighborhood. This star bears some resemblance to what the Sun might look like in the far distant future, making it an object of interest to astronomers.[3]

At a distance of 13°, it is the closest easily visible star to the south celestial pole, and around 150 BC it was within two degrees of it, which made it the southern pole star.[7]

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  2. ^ a b c d Cite error: The named reference clpl4_99 was invoked but never defined (see the help page).
  3. ^ a b c d e f g h i Cite error: The named reference aaa527_A37 was invoked but never defined (see the help page).
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  5. ^ a b Cite error: The named reference aaa458_2_609 was invoked but never defined (see the help page).
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  7. ^ "Beta Hydri".