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| Zubenenelgenubi |
Zubenelgenubi
(Alpha Librae) is, despite it's name, only the second-brightest star in
the Zodiacal constellation of Libra The Scales, and it is not very
bright at that, ringing in at the third magnitude. Its tongue-twister of
a name comes from Arabic, and it means "The Southern Claw of The
Scorpion" because in remote days Libra was not a separate constellation
from Scorpius The Scorpion (better-known by its astrological name,
Scorpio).
Zubenelgenubi is the 39th numbered star in the Nautical Almanac ( Polaris, as you may recall, is Zero). It lies along the Ecliptic, and is sometimes occulted by the Moon, and far more rarely, other planets.
As can be seen by anyone with sharp eyes, Zubenelgenubi is a multistar system. Again counterintutively, the dimmer of the pair is called Alpha Librae 1 by scientists, and the brighter Alpha Librae 2. Alpha Librae 2 is actually a binary itself, and its two stars orbit each other at the distance of the Sun and Mercury, while they both are in synchronous orbit with Alpha Librae 1 at a distance of 560 billion miles (about twice as far as the Oort Cloud is from the Sun). This widely-spaced system is about 77 light years from Earth, and it may contain other stars that are not obvious from the Earth at present.
Zubenelgenubi is a white star (system), with A2 at a temperature of about 14,000 F. and A1 at 11,500 F. A2's mass is about twice that of the Sun, while A1 is about one-and-a-half times as massive. Due to the close proximity of A2's twin stars, the radii of A2 are thus far impossible to measure from Earth. A1's radius is 1.5 times the radius of our Sun. The Zubenelgenubi system is about a billion years old, and as a whole, is three times as luminous as our own Sun.
To the casual stargazer, Zubenelgenubi is less interesting than the visually nearby "Northern Claw of The Scorpion," Zubeneschamali, also known as Beta Librae, which is, despite its name, the brightest star in Libra, a relatively dim Second Magnitude star (though in ancient days it appeared brighter).
Zubeneschamali is not one of the 58 navigational stars, though it is of particular interest because it is the only star in our skies that is visible to the naked eye that appears to be green (or properly, aqua, making it greenish-blue). It is a single star about 185 light years from the Sun. It has a mass about three and a half times that of the Sun, and a radius five times that of the Sun. It is about 130 times as bright as the Sun, and is a young star, only 80 million years old. It burns at about 22,000 degrees F. In high-powered telescopes it is a bluish star, though images taken of it give it a greenish cast. No one knows why Zubeneschamali appears to be green to the naked eye, though this oddity would seem to make it a better choice for a navigational star than the dimmer white Zubenelgenubi.
Zubenelgenubi is the 39th numbered star in the Nautical Almanac ( Polaris, as you may recall, is Zero). It lies along the Ecliptic, and is sometimes occulted by the Moon, and far more rarely, other planets.
As can be seen by anyone with sharp eyes, Zubenelgenubi is a multistar system. Again counterintutively, the dimmer of the pair is called Alpha Librae 1 by scientists, and the brighter Alpha Librae 2. Alpha Librae 2 is actually a binary itself, and its two stars orbit each other at the distance of the Sun and Mercury, while they both are in synchronous orbit with Alpha Librae 1 at a distance of 560 billion miles (about twice as far as the Oort Cloud is from the Sun). This widely-spaced system is about 77 light years from Earth, and it may contain other stars that are not obvious from the Earth at present.
Zubenelgenubi is a white star (system), with A2 at a temperature of about 14,000 F. and A1 at 11,500 F. A2's mass is about twice that of the Sun, while A1 is about one-and-a-half times as massive. Due to the close proximity of A2's twin stars, the radii of A2 are thus far impossible to measure from Earth. A1's radius is 1.5 times the radius of our Sun. The Zubenelgenubi system is about a billion years old, and as a whole, is three times as luminous as our own Sun.
To the casual stargazer, Zubenelgenubi is less interesting than the visually nearby "Northern Claw of The Scorpion," Zubeneschamali, also known as Beta Librae, which is, despite its name, the brightest star in Libra, a relatively dim Second Magnitude star (though in ancient days it appeared brighter).
Zubeneschamali is not one of the 58 navigational stars, though it is of particular interest because it is the only star in our skies that is visible to the naked eye that appears to be green (or properly, aqua, making it greenish-blue). It is a single star about 185 light years from the Sun. It has a mass about three and a half times that of the Sun, and a radius five times that of the Sun. It is about 130 times as bright as the Sun, and is a young star, only 80 million years old. It burns at about 22,000 degrees F. In high-powered telescopes it is a bluish star, though images taken of it give it a greenish cast. No one knows why Zubeneschamali appears to be green to the naked eye, though this oddity would seem to make it a better choice for a navigational star than the dimmer white Zubenelgenubi.
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| Zubeneschamali |
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