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Lesuth, Upsilon Scorpii, 34 Scorpii

Proper NamesLesath, Lesuth
Bayer DesignationUpsilon Scorpii
Flamsteed Number34 Scorpii
HR (BSC)6508
Right Ascension17h 30m 46s
Declination-37° 17' 45"
Distance576 light years
177 parsecs
MagnitudeApparent: +2.7
Absolute: -3.6
Spectral ClassB2IV blue subgiant
Optimum VisibilityJune / July

The western of a pair of blue stars that together form the stinger at the end of Scorpius' tail. The other star of the pair - somewhat brighter than Lesath - is named Shaula, and together these two stars are sometimes known named the Cat's Eyes. In ancient times the name Shaula (referring to the Scorpion's tail) was given to both the stars, but Lesath acquired its own name via a circuitous route. It originated with Arabic al latkha, describing the misted appearance of nearby Ptolemy's Cluster, M7. Through a serious of historical mistranslations and misapplications, the name mutated to Lesath (or sometimes Lesuth) and came to be applied to the star Upsilon Scorpii. To confuse matters further, the name Lesath is also occasionally given to Nu Scorpii, a star more usually known as Jabbah.

Lesath and Shaula are not so close that they form a double star, but they lie less than a degree from one another in the sky, and also seem to be relatively close together in space. According to their parallax data, the stars are perhaps no more than five light years apart, though some sources suggest that they may be considerably more distant from one another than this.

The stars of the Cat's Eyes appear to share a common origin, both belonging to the extensive Scorpius-Centaurus Association of stars. The two stars appear to share a similar age, and are very close in spectral type, each being a blue subgiant considerably larger, hotter and more luminous than the Sun (Lesath in some 2,000 times brighter than the Sun in the visible spectrum). It is a star of the 'Be' type, characterised by ejected material forming a cloud that extends out into space from the star itself.


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