Draconis alpha

Thuban is the name of the star α of the Constellation of the Dragon. It is far from being the most brilliant star of the constellation (it is acted in fact of 8th) but it is probably most known. It indicated the celestial pole northern there is 4  700 years.

Physical characteristics

Of Magnitude connect 3,67, Thuban is a hot giant star (9  200 K), 250 times more luminous than the Sun and distant of 309 light-years.

It is slightly variable, of the class of α2 Canum Venaticorum: its magnitude varies very slightly from 1% throughout its rotation; its fort Magnetic field causes an irregular distribution of the Silicium, Strontium, chromium and Rare earths on its surface, which involves a modification its magnitude when it turns.

Stellar environment

α Draconis is probably the most known star of the constellation of the Dragon, so much so that l'α was indicated to him by Johann Bayer. Because of the phenomenon of Precession of the equinoxes, Thuban indicated there is 4  700 years exactly the celestial north pole, places which fell nowadays to the pole star; consequently, Thuban was the pole star at the time of the apogee of Egyptian civilization ancient and it would seem that certain Egyptian temples were built in reference to Thuban. It is from now on with more 25° pole.

It is also a star doubles, his/her companion - invisible since the Ground - turns around it in 51 days. It would be probably of a Naine red or a white Naine.

Name

The name of Thuban comes from an Arab expression meaning “the head of the snake”. Taking into account its median position in the constellation, it is possible that it is about the name of another star whose Thuban - more known - would have inherited thereafter, which is rather frequent.

It is sometimes indicated by Adib, of Arabic Al Dhi' bah which means “the hyenas”, generic expression several stars of this part of the sky. Lastly, it was sometimes called the tail of the Dragon.

Designations

External bond

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