| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Hydrus |
| Right ascension | 00h 25m 45.07s [1] |
| Declination | –77° 15′ 15.3″ [1] |
| Apparent magnitude (V) | 2.80 |
| Characteristics | |
| Spectral type | G2 IV |
| U-B color index | 0.11 |
| B-V color index | 0.61 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | 22.9 km/s |
| Proper motion (μ) | RA: 2,219.54 ± 0.11 [1] mas/yr Dec.: 324.09 ± 0.11 [1] mas/yr |
| Parallax (π) | 134.07 ± 0.11[1] mas |
| Distance | 24.33 ± 0.02 ly (7.459 ± 0.006 pc) |
| Absolute magnitude (MV) | 3.43 |
| Details | |
| Mass | 1.1 M☉ |
| Radius | 1.9 R☉ |
| Luminosity | 3.53 L☉ |
| Temperature | 5,750 K |
| Metallicity | 49-100% |
| Rotation | 3.3 km/s. (~29 days) |
| Age | 6.7 × 109 years |
| Other designations | |
Beta Hydri (β Hyi / β Hydri) is a star in the constellation Hydrus (Note that Hydrus is not the same as Hydra).
It is about 24.4 light years away from Earth. Beta Hydri is often studied because it might give insights on what might happen to our Sun in the next 2.5 billion years.[citation needed] It is larger and slightly more massive than the Sun.
At around 150 BC, this star was two degrees away from the southern celestial pole. It is currently the nearest relatively bright star to the southern pole.
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A planetary system?
In 2002 Endl et al. inferred the possible presence of an unseen companion orbiting Beta Hydri as hinted by radial velocity linear trend with a periodicity exceeding 20 years. A substellar object with minimum mass of 4 Jupiter masses and orbital separation of roughly 8 Astronomical Units could explain the observed trend[2]. If confirmed, it would be a true Jupiter-analogue, though 4 times more massive. So far no planetary/substellar object has been certainly detected.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity |
|---|---|---|---|---|
| b (unconfirmed) | ≥4 MJ | 7.6 | >20 | 0 |
See also
References
- ^ a b c d e van Leeuwen, F. (2007). "HIP 2021". Hipparcos, the New Reduction. http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/311/hip2&recno=2016. Retrieved 2009-12-07.
- ^ a b Endl et al. (2002). "The planet search program at the ESO Coudé Echelle spectrometer. III. The complete Long Camera survey results". Astronomy and Astrophysics 392: 671-690. Bibcode: 2002A&A...392..671E. http://fr.arxiv.org/abs/astro-ph/0306551.
External links
- "Beta Hydri". SolStation. http://www.solstation.com/stars/bethydri.htm. Retrieved November 3 2005.
- "Beta Hydri". Dr. Jim Kaler. http://www.astro.uiuc.edu/~kaler/sow/betahyi.html. Retrieved March 15 2005.
- Stellar Activity - Beta Hydri
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