Scorpius is a zodiac constellation located in the Southern celestial hemisphere, where it sits near the center of the Milky Way, between Libra to the west and Sagittarius to the east. Scorpius is an ancient constellation that pre-dates the Greeks; it is one of the 48 constellations identified by the Greek astronomer Ptolemy in the second century. Its old astronomical symbol is (♏︎). Notable features Stars Scorpius contains many bright stars, including Antares (α Sco), "rival of Mars," so named because of its distinct reddish hue; β1 Sco (Graffias or Acrab), a triple star; δ Sco (Dschubba, "the forehead"); θ Sco (Sargas, of unknown origin); ν Sco (Jabbah); ξ Sco; π Sco (Fang); σ Sco (Alniyat); and τ Sco (Paikauhale). Marking the tip of the scorpion's curved tail are λ Sco (Shaula) and υ Sco (Lesath), whose names both mean "sting." Given their proximity to one another, λ Sco and υ Sco are sometimes referred to as the Cat's Eyes. The constellation's bright stars form a pattern like a longshoreman's hook. Most of them are massive members of the nearest OB association: Scorpius–Centaurus. The star δ Sco, after having been a stable 2.3 magnitude star, flared in July 2000 to 1.9 in a matter of weeks. It has since become a variable star fluctuating between 2.0 and 1.6. This means that at its brightest it is the second brightest star in Scorpius. U Scorpii is the fastest known nova, with a period of about 10 years. The close pair of stars ω1 Scorpii and ω² Scorpii are an optical double, which can be resolved by the unaided eye. One is a yellow giant, while the other is a blue B-type star in the Scorpius-Centaurus Association. The star once designated γ Sco (despite being well within the boundaries of Libra) is today known as σ Lib. Moreover, the entire constellation of Libra was considered to be claws of Scorpius (Chelae Scorpionis) in Ancient Greek times, with a set of scales held aloft by Astraea (represented by adjacent Virgo) being formed from these westernmost stars during later Greek times. The division into Libra was formalised during Roman times. Deep-sky objects Due to its location straddling the Milky Way, this constellation contains many deep-sky objects such as the open clusters Messier 6 (the Butterfly Cluster) and Messier 7 (the Ptolemy Cluster), NGC 6231 (by ζ² Sco), and the globular clusters Messier 4 and