Alphard
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- Alphard is also the name of a programming language.
 Alphard is the α star in the constellation of Hydra. |
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation (pronunciation) |
Hydra |
| Right ascension | 09h 27m 35.2s |
| Declination | -08° 39′ 31″ |
| Apparent magnitude (V) | +1.98 |
| Characteristics | |
| Spectral type | K3 II-III |
| U-B color index | 1.72 |
| B-V color index | 1.44 |
| Variable type | ? |
| Astrometry | |
| Radial velocity (Rv) | -4 km/s |
| Proper motion (μ) | RA: -14.49 mas/yr Dec.: 33.25 mas/yr |
| Parallax (π) | 18.4 ± 0.78 mas |
| Distance | 177 ± 8 ly (54 ± 2 pc) |
| Absolute magnitude (MV) | −1.70 |
| Details | |
| Mass | ? M☉ |
| Radius | 34.5 R☉ |
| Luminosity | 400 L☉ |
| Temperature | 4,400 K |
| Metallicity | ? |
| Rotation | <17 km/s. |
| Age | ? years |
| Other designations | |
Alphard (α Hya / α Hydrae / Alpha Hydrae) is the brightest star in the constellation Hydra, marking the heart of the snake.
Alphard is an orange giant star. The name Alphard is from the Arabic فرد|الفرد (Al Fard), "the solitary one."
Precise radial velocity measurements [1] have shown variations in the stellar radial velocities and spectral line profiles. The oscillations are multi-periodic with periods from several hours up to several days. The short-term oscillations were assumed to be a result of stellar pulsations, similar to the solar ones. A correlation between the variations in the asymmetry of the spectral line profile and the radial velocity has also been found. The multi-periodic oscillations make HD 81797 (Alphard) an object of interest for asteroseismologic investigations.
[edit] References
- ^ Setiawan, J., Roth, M., Weise, P., Dölinger, M. P. (2006) Multi-periodic oscillations of HD 32887 and HD 81797. Memorie della Societa Astronomica Italiana, 77, p.510
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