A prominent constellation formed by a sinuous line of stars running into the band of the Milky Way. The stars of Scorpius form a shape remarkably reminiscent of a scorpion's body and raised sting. This distinct form explains why the constellation has been known as the 'Scorpion' by various cultures since ancient times, with the associations going back some 5,000 years or more. In its more ancient form, the Scorpion had a pair of claws pointing westward in the sky, but in Roman times these claws were divided off into a separate constellation, which is still known today as Libra.
According to the Greeks Scorpius represented the great mythical scorpion known as Scorpio, whose slaying of Orion the Hunter earned it a place mong the stars. Given the ancient history of the constellation, this tale is more likely an attempt to explain the long-recognised Scorpion shape in the sky rather than the origin of the constellation's name.
Scorpius in the Sky
Scorpius lies on the Ecliptic, the line representing the apparent path of the Sun through the sky, at the point where that line crosses into the band of the Milky Way. It is thus a zodiacal constellation, one of those through which the Sun passes on its annual journey around the sky. Of all such constellations, Scorpius contains the shortest stretch of the line of the Ecliptic. The Sun's short passage across Scorpius covers a period of just six days as it passes through a narrow stripe of sky between neighboring Libra and Ophiuchus in late November each year.
Scorpius is dominated by the first magnitude red star known as Antares, which lies near the head of the Scorpion's curving body in the sky. This is a vast and highly luminous star: though it lies more than 500 light years from the Solar System, it still ranks among the brightest of the stars in Earth's sky.
To the northwest of Antares is a blue binary star, Dschubba or Delta Scorpii. Dschubba is notable for a sudden flare in brightness that took place in the year 2000, and since then its brightness has varied, at times approaching that of Antares itself. Dschubba marks the axis of the constellation: from this point, branches of stars representing the remnants of the Scorpion's two claws extend northward and southward, while the Scorpion's body runs southward and eastward.
The body of the Scorpion is composed of a string of bright stars, most notably orange Epsilon Scorpii and bright yellow Sargas, before it terminates with two stars nearby one another in the sky - Shaula and Lesath - representing the tip of Scorpio's sting, and lying in the general direction of the Galaxy's core. The curving lower parts of this formation create hook-like pattern in the sky, and are sometimes collectively known as the Fishhook, with Shaula and Lesath marking the point of the hook as well as the Scorpion's sting.
Deep Sky Objects
Scorpius describes an area of the sky close to the Galactic nucleus, and is busy with deep sky objects, especially star clusters. Near the end of the Scorpion's tail, and thus in the direction of the Galaxy's centre, lie two prominent open clusters: M6 the Butterfly Cluster and M7, known as Ptolemy's Cluster. Across the constellation to the west, near the Scorpion's head, are two more distant globular clusters, M4 near Antares in the sky, and M80.
In the middle of the Fishhook formation lies NGC 6302, known as the Bug Nebula, a planetary nebula some 3,400 light years from the Sun in which material is erupting to form two great ragged lobes. Nearby in the sky, but actually rather closer to the Solar System, lies the Cat's Paw Nebula, NGC 6334, a star-forming region filled with newly born stars creating a cluster of their own.