How to Spot the Scorpius Constellation

scorpius.jpg
The constellation Scorpius, set against the backdrop of the Milky Way, with two of its many deep-sky objects and its brightest star, Antares, labeled. Carolyn Collins Petersen

The Scorpius constellation glitters against the backdrop of the Milky Way. It has a curvy S-shaped body ending in a set of claws at the head and a pair of "stinger" stars at the tail. Both northern and southern hemisphere stargazers can see it, although it will look "upside down" when observed from below the equator.

Finding Scorpius Constellation

Northern hemisphere summer constellations.
Northern hemisphere summer skies, looking south. Carolyn Collins Petersen

In the northern hemisphere, Scorpius is most visible by looking to the south during July and August around 10:00 PM. The constellation remains visible until mid-September. In the southern hemisphere, Scorpio appears very high in the northern part of the sky until close to the end of September.

Scorpius has a distinctive shape and thus is fairly easy to spot. Simply look for an S-shaped pattern of stars between the constellations Libra (the scales) and Sagittarius, and below another constellation called Ophiuchus. 

History of Scorpius

Scorpius has long been recognized as a constellation. Its roots in mythology stretch back to the ancient Babylonians and Chinese, as well as Hindu astrologers and Polynesian navigators. The Greeks associated it with the constellation Orion, and today we often hear the tale of how both constellations are never seen together in the sky. That's because, in the ancient legends, the scorpion stung Orion, killing him. Keen observers will notice that Orion sets in the east as the scorpion rises, and the two will never meet.  

The Stars of the Scorpius Constellation

The IAU star chart showing Scorpius.
The official IAU constellation of Scorpius shows the boundaries of the entire region that contains the S-shaped pattern of the scorpion. IAU/Sky Publishing

At least 18 bright stars make up the curving body of the starry scorpion. The larger "region" of Scorpius is defined by the I boundaries set by the International Astronomical Union. These were made by international agreement and allow astronomers to use common references for stars and other objects in all areas of the sky. Within that region, Scorpius has dozens of stars that can be seen with the naked eye, and part of it lies against the backdrop of the Milky Way with its countless stars and clusters. 

Each star in Scorpius has a Greek letter next to it in the official star chart. The alpha (α) denotes the brightest star, beta (β) the second-brightest star, and so on. The brightest star in Scorpius is α Scorpii, with the common name of Antares (meaning "the rival of Ares (Mars)." It's a red supergiant star and is one of the largest stars we can see in the sky. It lies about 550 light-years away from us. If Antares were part of our solar system, it would encompass the inner solar system out beyond the orbit of Mars. Antares is traditionally thought of as the heart of the scorpion and is easy to spot with the naked eye. 

Scorpius and Sagittarius star patterns.
Scorpius (upper right) along with Sagittarius (lower left). Notice how the Milky Way makes a backdrop for the two star patterns. The object marked Sag A* is the location of the black hole at the heart of our galaxy. Carolyn Collins Petersen

The second-brightest star in Scorpius is actually a triple-star system. The brightest member is called Graffias (alternatively it's also called Acrab) and its official designation is β1 Scorpii. Its two companions are much fainter but can be seen in telescopes. Down at the tail end of Scorpius lies a pair of stars colloquially known as "the stingers". The brighter of the two is called gamma Scorpii, or Shaula. The other stinger is called Lesath. 

Deep Sky Objects in Constellation Scorpius

Deep-sky objects in Scorpius and nearby Sagittarius.
A selection of deep-sky objects awaits stargazers who search the skies in Scorpius and Sagittarius. It's a great area of the sky to study with binoculars or small telescopes. Carolyn Collins Petersen 

Scorpius is on the plane of the Milky Way. Its stinger stars point roughly toward the center of our galaxy, which means that observers can spot many star clusters and nebulae in the region. Some are visible to the naked eye, while others are best observed with binoculars or telescopes.

Due to its location near the heart of the galaxy, Scorpius has a fine collection of globular clusters, marked here by yellow circles with "+" symbols inside them. The easiest cluster to spot is called M4. There are also many "open" clusters in Scorpius, such as NGC 6281, that can be seen with binoculars or small telescopes.

Closeup of M4

Globular clusters are satellites of the Milky Way galaxy. They often contain hundreds, thousands, or sometimes millions of stars, all tightly bound together by gravity. M4 orbits the core of the Milky Way and lies about 7,200 light-years away from the Sun. It has around 100,000 ancient stars more than 12 billion years old. This means they were born when the universe was quite young and existed before the Milky Galaxy was formed. Astronomers study these clusters, and in particular, the metal "content" of their stars to understand more about them. 

How to find the globular cluster M4.
The globular cluster Messier 4 (M4) lies not too far from the bright star Antares in Scorpius. Carolyn Collins Petersen 

For amateur observers, M4 is easy to spot, not far from Antares. From a good dark-sky sight, it's just bright enough to be picked out with the naked eye. However, it's much easier to observe through binoculars. A good backyard-type telescope will show a very nice view of the cluster.