The
fifth star in the Nautical Almanac is Achernar (Alpha Eridanus), the
brightest star in the constellation Eridanus ("The River"). In the
Northern Hemisphere Achernar rises only as high as the latitude of
Dallas, Texas, but can be visualized easily from the Southern
Hemisphere. Until 1600 CE, it could not be seen north of the Equator at
all, but due to precession, changes in Earth's rotation, eventually
Achernar will rise as high as Vienna.
Achernar is a binary system, with a small star circling its much larger hot blue primary at a distance of over 1,000,000,000 miles.
The name Achernar is contracted Arabic for "The End of the River," referring to Achernar's place in the constellation. The Chinese name, Shu Wei, means "Crooked Running Water".
Achernar is a Main Sequence star, meaning that it is in the prime of its stellar life. It rotates very quickly, at over 150 miles per second, and this has flattened it at the poles and bulged it at the Equator. The star is young at just over 35 million years. It has more than 3,000 times the luminosity of our Sun and is seven times as massive. Its hottest temperature (at the poles, due to its shape) is about 36,000 surface degrees. Since it rotates so quickly, it throws off a great deal of plasma and is surrounded by an envelope of stellar matter and energy that reaches almost as far as its companion star, which may be pulling the substance of Achernar into itself.
No comments:
Post a Comment