vendredi 19 septembre 2008

Hydra 6


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 فردالفرد (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.


Gamma Hydrae (γ Hya / γ Hydrae) is a Class G8, third-magnitude star in the constellation Hydra. It is sometimes called Cauda Hydrae or Dhanab al Shuja, meaning "Hydra's Tail" or "the Snake's Tail".


Zeta Hydrae (ζ Hya / ζ Hydrae) is a Class G9, third-magnitude star in the constellation Hydra. As the brightest star of the Hydra's head, it is occasionally called by the proper name Hydrobius, meaning "Water-dweller", in Greek.


Nu Hydrae (ν Hya / ν Hydrae) is a Class K2, third-magnitude star in the constellation Hydra. It is sometimes called by the proper names Sherasiph and Pleura, each name referring to the "ribs" or "side" (of Hydra) in Arabic and Greek, respectively.


Pi Hydrae (π Hya / π Hydrae) is a Class K2, third-magnitude star in the constellation Hydra. It is sometimes called by the Sanskrit proper name Sataghni. Some sources also name it Markeb.


Epsilon Hydrae (ε Hya / ε Hydrae) is a Class G5, third-magnitude star in the constellation Hydra. The Vedic Sanskrit name Ashlesha (Azleṣa) [1], meaning "The Embracing One", is sometimes applied to this star.
Epsilon Hydrae is a binary star with components of magnitudes 3.3 and 6.8, separated by 2.7 arcseconds. This stellar system is located about 135 light-years from Earth.
Delta Hydrae (δ Hya / δ Hydrae) is a Class A1, fourth-magnitude star in the constellation Hydra. It is sometimes called Mautinah, meaning "Circlet of Pearls" in Arabic, which refers to an asterism imagined by ancient Arabs among the semicircle of stars in the Hydra's head.
Delta Hydrae is a binary double star, located about 180 light-years from Earth.
Sigma Hydrae (σ Hya / σ Hydrae) is a star in the constellation Hydra. It also has the traditional name Minchir (or Michar or al Minchar al Shuja (Arabic for "Nose of the Hydra").
The Bayer designation Tau Hydrae (τ Hya / τ Hydrae) is shared by two star systems, τ¹ Hydrae and τ² Hydrae, in the constellation Hydra. The two stars are separated by 1.74° on the sky. Tau Hydrae also has the traditional name Ukdah, from the Arabic عقدة uqdah meaning the Knot.

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