Scorpius, the Scorpion, is one of the most distinctive constellations in the night sky. On July evenings, it sits just above the southern horizon at mid-northern latitudes. Antares, the brightest star in Scorpius, is a reddish star marking the scorpion’s heart. From Antares, several stars marking the scorpion’s claws extend northwest, and the scorpion’s body curves down to the southeast.
Scorpius lies near the densest section of the Milky Way, so it is rich in star clusters and nebulas. The nebulas in Scorpius are faint and challenging to observe, but several of the constellation’s star clusters are bright and easy to observe. Scorpius also holds several striking double stars.
Xi Scorpii is perhaps the best multiple star in Scorpius. More than just a basic double star, this pair is reminiscent of the famous Double Double in Lyra. Moderate magnification shows two double stars separated by about 5 arcminutes. The brightest star in the northwestern pair also has a companion separated by about 1 arcsecond, but this third star is quite difficult to split from the primary star. To find Xi Sco, draw an imaginary line from the scorpion’s southern claw, Pi Scorpii, to the northern claw, Acrab. Continue the line the same distance beyond Acrab, then go northwest a couple degrees to find Xi Scorpii.
M4 is a bright globular star cluster located just over 1° west of Antares. This cluster is visible with binoculars as a fuzzy spot of light, but a mid-sized telescope and moderate magnification will give a much better view, resolving many of the cluster’s stars. M4 is less dense than most globulars, although it still contains tens of thousands of stars. This cluster is also one of the nearest globular clusters to Earth.
Several of the open star clusters in Scorpius are good binocular targets. One of these, NGC 6231, is located just north of Grafias, the star where the tail of Scorpius begins to curve. This cluster is bright enough to be visible with the unaided eye, and binoculars resolve its individual stars. NGC 6231 is also a good target for telescopes at low magnification.
M6 and M7 are two more nice binocular clusters. The two clusters are several degrees apart, and lie about 5° northeast of Shaula, the star at the tip of the scorpion’s tail. Both clusters are easily visible with the unaided eye as fuzzy spots in the Milky Way. Binoculars show both clusters in the same field of view, and resolve some of the stars in each one. Telescopes at low magnification also provide good views of the clusters, especially M6.
M7 is the larger and brighter of the two clusters, and lies to the southeast of M6. M7 consists of a loose arrangement of bright stars spanning more than 1° of the sky. M6, also known as the Butterfly Cluster, is much more compact. Its stars are arranged in a rectangular shape that does indeed bear a slight resemblance to a butterfly.