Scorpius is the 33rd largest of the 88 recognized constellations and the 9th largest of the zodiac constellations, covering 497 square degrees of the southern sky. Its brightest star is Antares (Alpha Scorpii), a red supergiant located about 550 light-years away. With an apparent magnitude of around +1.0, Antares is one of the brightest stars in the night sky.
Scorpius is visible from latitudes between about +40° and -90° and is best placed for evening viewing from the Northern Hemisphere during the summer months. Because it is the southernmost zodiac constellation, however, it remains relatively low in the sky for observers at mid-northern latitudes and is only partly visible from far northern locations.
Against the rich star fields of the Milky Way, Scorpius contains an impressive collection of open clusters, globular clusters and nebulae. Four of its best-known deep-sky objects are included in the Messier catalog, while several large star-forming regions add even more interest to this part of the sky.
Messier 4 (M4, NGC 6121)
Located about 7,200 light-years away, Messier 4 is one of the nearest globular clusters to Earth. It spans roughly 75 light-years and was also the first globular cluster in which individual stars were resolved.
With an apparent magnitude of about 5.6, M4 can even approach naked-eye visibility under exceptionally dark skies, although binoculars or a small telescope make it much easier to see. It is also particularly easy to locate, lying only about 1.3 degrees west of bright Antares.
Butterfly Cluster (M6, NGC 6405)
The Butterfly Cluster is a bright open cluster whose stars form a pattern that can resemble the outstretched wings of a butterfly. Most of its prominent members are hot, blue B-type stars, although its brightest member, BM Scorpii, is an orange giant.
M6 lies roughly 1,600 light-years away and has an apparent magnitude of about 4.2. Under dark skies it can be spotted with the naked eye, while binoculars readily reveal its distinctive shape. The cluster spans roughly the same apparent width as the full Moon, making it particularly well suited to low-magnification viewing.
Ptolemy Cluster (M7, NGC 6475)
The Ptolemy Cluster is one of the most conspicuous open clusters in the night sky and was recorded by the astronomer Ptolemy in antiquity. Under dark skies it is easily visible to the naked eye as a concentrated patch of stars near the Scorpion’s tail.
M7 lies roughly 1,000 light-years away and contains dozens of readily visible stars spread across a large area of sky. With an apparent magnitude of about 3.3, it is an excellent binocular target and is even more striking against the dense Milky Way star fields surrounding it.
Messier 80 (NGC 6093)
Messier 80 is a remarkably dense globular cluster containing hundreds of thousands of stars packed into a relatively small region. It lies about 32,600 light-years away and can be found roughly halfway between Antares and Acrab in Scorpius.
M80 is particularly interesting because of its large population of blue stragglers. These stars appear younger and more massive than the surrounding cluster population and are thought to form through interactions such as stellar collisions or mergers.
The cluster was also the site of a rare nova observed in 1860. Known as T Scorpii, the event was a classical nova rather than a supernova: a white dwarf in a binary system underwent a thermonuclear eruption after accumulating material from its companion.
Cat’s Paw Nebula (NGC 6334)
The Cat’s Paw Nebula is a vast star-forming region located about 5,500 light-years away. Stretching roughly 50 light-years across, it contains large numbers of young stars, including massive hot stars whose intense ultraviolet radiation causes the surrounding hydrogen gas to glow.
Much of the ongoing star formation is concealed by thick clouds of dust, which makes infrared observations particularly valuable for studying the region. In visible-light images, glowing hydrogen produces much of the nebula’s characteristic red appearance.
Butterfly Nebula (NGC 6302, Caldwell 69)
Located about 3,800 light-years away, the Butterfly Nebula is one of the most structurally complex planetary nebulae known. Its spectacular bipolar form was produced as an aging star expelled its outer layers near the end of its life.
A dense band of dust crosses the nebula’s center and helps channel the expanding material into two enormous lobes. The gas in these wings is moving through space at hundreds of thousands of miles per hour, while ultraviolet radiation from the extremely hot central stellar remnant causes the expelled material to glow.
War and Peace Nebula (NGC 6357)
NGC 6357 is a vast emission nebula and active star-forming region in Scorpius. Embedded within it is the young open cluster Pismis 24, whose massive hot stars pour ultraviolet radiation into the surrounding gas and help sculpt the nebula’s dramatic structure.
One of its most remarkable members is Pismis 24-1. It was once thought to be a single extraordinarily massive star, but observations with the Hubble Space Telescope resolved it into multiple components. This discovery helped explain how the apparently enormous object could fit within the expected upper mass range for individual stars.
NGC 6357 lies about 8,000 light-years away, making this one of several major stellar nurseries visible toward the rich Milky Way fields of Scorpius.
