Beta
Centauri is the second-brightest star in the Southern Hemisphere's
constellation of Centaurus The Centaur, an asterism that sprawls across
the sky. Beta Centauri can barely be seen in the Northern Hemisphere. It
is visible only for a few days in May in latitudes south of Key West,
Honolulu and Brownsville, Texas. It was known to the ancients however,
by reputation at least, and was called Agena, a Greco-Roman word meaning
"Knee" (which describes its position in the constellation). The Arabs
called it Hadar, which means "earth" or "ground" or "village," probably
because it barely rises above the horizon in the North. In 2016, "Hadar"
was approved as it's official name, but Agena and Beta Centauri are
actually more common. Beta Centauri is a First Magnitude star.
Beta Centauri is not a single star. It is rather a tri-star system. It lies 410 light years from Earth. It is comprised of Beta Centauri Alpha Alpha, Beta Centauri Alpha Beta, and Beta Centauri Beta (these should not be confused with the nearby tri-star system of Alpha Centauri). In ocular telescopes the three stars appear to be one.
Beta Centauri Alpha Beta orbits Beta Centauri Alpha Alpha, and Beta Centauri Beta orbits both Beta Centauri Alpha Alpha and Alpha Centauri Alpha Beta. All three stars are blue giants. The system is about 15 million years old. It is expected not to live very long (only a few million more years) because of the prodigious energy output of the three Beta Centauri stars. When it dies, the twins will go supernova.
Aa and Ab are both eleven times the mass of our Sun and burn at 45,000 degrees F. They are both each a terrifying 55,000 times as bright as the Sun. Beta Centauri Beta has 4.6 times the mass of the sun and is only (only!) 1500 times as bright as the Sun (its relative dimness makes it hard to observe). Aa and Ab are about eleven times the radius of the Sun. B is about seven times the radius. The temperature of B is undetermined, but, as a blue star it is assumed to be among the hotter stars.
An imaginary line can be drawn directly from the Beta Centauri system to the star Gacrux, from which can be found Acrux; and although Earth lacks a southern pole star, a line drawn directly downward from Acrux gives the celestial navigator the position of True South. Thus, this thirty-fifth star in the Nautical Almanac is crucial to proper celestial navigation.
Beta Centauri is not a single star. It is rather a tri-star system. It lies 410 light years from Earth. It is comprised of Beta Centauri Alpha Alpha, Beta Centauri Alpha Beta, and Beta Centauri Beta (these should not be confused with the nearby tri-star system of Alpha Centauri). In ocular telescopes the three stars appear to be one.
Beta Centauri Alpha Beta orbits Beta Centauri Alpha Alpha, and Beta Centauri Beta orbits both Beta Centauri Alpha Alpha and Alpha Centauri Alpha Beta. All three stars are blue giants. The system is about 15 million years old. It is expected not to live very long (only a few million more years) because of the prodigious energy output of the three Beta Centauri stars. When it dies, the twins will go supernova.
Aa and Ab are both eleven times the mass of our Sun and burn at 45,000 degrees F. They are both each a terrifying 55,000 times as bright as the Sun. Beta Centauri Beta has 4.6 times the mass of the sun and is only (only!) 1500 times as bright as the Sun (its relative dimness makes it hard to observe). Aa and Ab are about eleven times the radius of the Sun. B is about seven times the radius. The temperature of B is undetermined, but, as a blue star it is assumed to be among the hotter stars.
An imaginary line can be drawn directly from the Beta Centauri system to the star Gacrux, from which can be found Acrux; and although Earth lacks a southern pole star, a line drawn directly downward from Acrux gives the celestial navigator the position of True South. Thus, this thirty-fifth star in the Nautical Almanac is crucial to proper celestial navigation.
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