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Upsilon Librae

39 Librae, Zuben Hakrabi*

A fourth-magnitude star in the southern reaches of Libra, Upsilon Librae falls close to the borders of that constellation with neighbouring Scorpius and Lupus, southwestwards of the formation known as the Crown of the Scorpion. Its current apparent magnitude is a moderate +3.59, but its radial velocity shows that this star and the Sun are approaching one other as they travel through the Galaxy, and over the next two million years Upsilon Librae will become very considerably brighter in the skies of Earth.

Imagery provided by Aladin sky atlas

Upsilon Librae is a giant star with a deep orange hue. As a giant, the outer shell of the star has expanded from its core, reaching a diameter of some thirty times that of the Sun, with a luminosity some three hundred times greater than the Sun's. It presently lies some 210 light years from the Solar System.


* Several sources list this star with the proper name of Zuben Hakrabi, but this name seems to stem from an error, rather than representing a true traditional name for the star. In addition to Upsilon Librae, variations on the same name are assigned to various stars within Libra, including Gamma, Eta, Nu and Sigma Librae. The variant Zubenelhakrabi is formally recognised as the name of Gamma Librae, also called Zuben Elakrab, which lies northward of Upsilon Librae in the sky. All these different variants derive from Arabic, and mean 'claws of the Scorpion', a tradition dating from a time when this part of the sky was seen as belonging to Scorpius, rather than forming the distinct constellation of Libra.

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