The Scorpius Constellation
The Scorpius constellation lies in the southern sky but can be also be viewed from the northern hemisphere.
Scorpius has a distinctive shape and thus is fairly easy to spot. Simply look for a J-shaped pattern of stars between the constellations Libra (the scales) and Sagittarius, and below another constellation called Ophiuchus.
- Abbreviation: Sco
- Symbolism: The Scorpion
- Right ascension: 16.8875h
- Declination: −30.7367°
- Quadrant: SQ3
- Size: 497 sq. deg. (33rd largest)
- Brightest Star: Antares
- Messier Objects: 4
- Meteor Showers: Alpha Scorpiids; Omega Scorpiids
The Scorpius Constellation as seen from my backyard in Canada.
Scorpius is one of the zodiac constellations, first cataloged by the Greek astronomer Ptolemy in the 2nd century. Scorpius pre-dates the Greeks and is one of the oldest constellations known.
Because this constellation is nestled so close to the core of the Milky Way, Scorpius contains many deep-sky objects. These include open clusters Messier 6, and Messier 7, and the globular clusters Messier 4 and Messier 80.
The name is Latin for scorpion, or literally translated as the “creature with the burning sting.” There are at least 18 bright stars that make up the curving body of the starry scorpion. Scorpius is the southernmost constellation of the Zodiac.
The Sumerians called it GIR-TAB, or “the scorpion”. However, we commonly associate this constellation with the Greek origins, associated with the story of Orion in Greek mythology.
Scorpius constellation star chart. IAU, Sky & Telescope.
The Scorpius Constellation
Scorpius is the 33rd constellation in size, occupying an area of 497 square degrees. It lies in the third quadrant of the southern hemisphere (SQ3) and can be seen at latitudes between +40° and -90°.
The neighboring constellations are Ara, Corona Australis, Libra, Lupus, Norma, Ophiuchus, and Sagittarius. Very little of the constellation Scorpius goes north of the ecliptic or sun’s path across our sky.
The constellation Scorpius is most visible by looking to the south during July and August around 10:00 PM (northern hemisphere).
Scorpius and the Milky Way. Mars and Saturn visible (June 2016).
Scorpius remains visible in the northern hemisphere night sky until mid-September. In the southern hemisphere, Scorpius will appear very high in the northern area of the sky until the month of September.
The brightest stars in Scorpius form a J-shape in the night sky. The bright red star, Antares, is conveniently placed in the sky where the Scorpion’s Heart should be.
Some astronomers also associate this ruby-red star as a “Rival of Mars” in the summer.
Two stars make up the fishhook-shaped stinger of the scorpion, Shaula and Lesath. These two stars sit within the Milky Way’s stream of dense stars, which means many interesting star clusters are nearby.
There are two meteor showers associated with the constellation: the Alpha Scorpiids and the Omega Scorpiids.
Summer constellations (northern hemisphere) in June. Scorpius and Ophiuchus.
Scorpius is not a scorpion to all civilizations and cultures. The Javanese people of Indonesia call this constellation Banyakangrem, meaning “the brooded swan” or Kalapa Doyong, meaning “leaning coconut tree.”
In Hawaii, it is known as the demigod Maui’s Fishhook. In Chinese mythology, the constellation was part of the Azure Dragon.
The Greeks associated the constellation Scorpius with the constellation Orion. In ancient legends, the scorpion stung Orion the hunter, and killed him. Both constellations are never seen together in the sky.
The Orion constellation sets in the east as Scorpius rises, and the two will never meet.
The Main Stars in Scorpius
Dschubba (Delta Scorpii)
Delta Scorpii has the stellar classification B0.3 IV and is approximately 490 light-years distant. It has a visual magnitude of 2.307. The star has a class B companion orbiting it every 20 days, and another star in a very eccentric orbit that orbits the primary star every 10 years.
Delta Scorpii’s traditional name, Dschubba (or Dzuba) comes from the Arabic jabhat, which means “the forehead,” referring to the scorpion’s forehead. Sometimes the star is also known as Iclarcrau or Iclarkrav.
The entire Scorpius constellation. Photo by Joyce Tanihara.
Antares (Alpha Scorpii)
This star is Scorpius’ most famous and brightest star. Antares is a red supergiant star with a visual magnitude of 0.96, approximately 550 light-years distant from the Sun.
It is the brightest star in the Scorpius constellation and the 16th brightest star in the night sky.
Antares next to the M4 globular cluster in Scorpius.
It can be occulted by the Moon and very infrequently by Venus. (The last recorded occultation by Venus occurred on September 17, 525 BC.)
Antares is the most massive, brightest, and most evolved member of the Scorpius-Centaurus association, the nearest OB stellar association to the solar system. The star belongs to the spectral class M1.5lab-b and has a radius of about 883 times solar.
It is approximately 10,000 times more luminous than the Sun, and has between 15 and 18 solar masses. The star’s estimated age is about 12 million years.
Antares is classified as a type LC slow irregular variable star. The star’s magnitude slowly varies from 0.88 to 1.16. It has a companion star, Antares B, about 529 astronomical units (AU) away.
Antares B has the stellar classification B2.5 and an apparent magnitude of 5.5. It is 170 more luminous than the Sun and has an orbital period estimated at 878 years.
Antares marks the heart of the scorpion, which is also its alternative name. The name Antares comes from the ancient Greek Άντάρης, which has been translated as “anti-Ares,” “rival of Mars,” or “like Mars,” referring to the similarity of the star’s red hue to that of the planet Mars.
The comparison possibly dates way back to Mesopotamian astronomers. Another theory suggests that the name Antares may have come from the name Antar or Antarah ibn Shaddad, which was the name of an Arabic warrior-hero celebrated in the Golden Mu’allaqat, one of the seven long Arabic pre-Islamic poems.
Shaula (Lambda Scorpii)
Shaula is the second brightest star in Scorpius and the 25th brightest star in the sky. It is approximately 700 light-years distant from the solar system.
Lambda Scorpii is a multiple star system with three visible components, Lambda Scorpii A, Lambda Scorpii B, and Lambda Scorpii C. Lambda Scorpii A is a triple star system composed of two class B stars and a pre-main sequence star.
Lambda Scorpii B lies 42 arc seconds away from the first component, and Lambda Scorpii C is a 12th magnitude star 95 arc seconds away from component A.
The primary star in the Lambda Scorpii A system is a Beta Cephei type variable. The estimated age of the star system is about 10-13 million years.
Lambda Scorpii’s traditional name, Shaula, comes from the Arabic al-šawlā´, which means “the raised (tail).”
Deep-Sky Objects in Scorpius
Messier 4 (M4, NGC 6121)
Messier 4 is a globular cluster in Scorpius. It has an apparent magnitude of 5.9 and is approximately 7,200 light-years distant from the solar system.
It was the first globular cluster discovered in which individual stars could be resolved. The brightest stars in M4 have an apparent magnitude of 10.8.
Messier 4 globular cluster. Photo by Trevor Jones.
The estimated age of the cluster is around 12.2 billion years and less densely packed than its’ companion Messier 80.
M4 is about 75 light-years across. It was discovered by the Swiss astronomer Philippe Loys de Chéseaux in 1746 and included in Messier’s catalog in 1764.
M4 is easy to find in the sky, as it lies 1.3 degrees west of Antares. Along with NGC 6397 in the constellation Ara, which is also 7,200 light-years away, Messier 4 is the closest globular cluster to our solar system.
Butterfly Cluster – Messier 6 (M6, NGC 6405)
Messier 6 is an open cluster also known as the Butterly Cluster because its stars form a shape similar to that of a butterfly. is an open cluster of 80 stars that form the shape of a butterfly. The cluster was first discovered by the Italian astronomer Giovanni Batista Hodierna in 1654 and Charles Messier included it in his catalog in 1764.
The bright stars in M4 are mostly hot, blue, class B stars, but the brightest one is a class K orange giant, BM Scorpii.
The Butterfly Cluster has an apparent magnitude of 4.2 and is approximately 1,600 light-years distant from the Sun.
Ptolemy Cluster – Messier 7 (M7, NGC 6475)
Messier 7 is another open star cluster in Scorpius, located near the scorpion’s stinger. It has an apparent magnitude of 3.3 and can easily be seen with the naked eye. M7, also known as the Ptolemy cluster, is an open cluster of about 80 stars.
It is also known as the Ptolemy Cluster because it was the Greek astronomer Ptolemy who first recorded it in 130 AD. Ptolemy believed the cluster to be a nebula. The Ptolemy Cluster contains about 80 stars, the brightest of which has a visual magnitude of 5.6.
M7 is approximately 980 light-years distant from the solar system. It is roughly 25 light-years in diameter. The age of the cluster is estimated to be around 200 million years.
Messier 80 (NGC 6093)
Messier 80 is a globular cluster discovered by Charles Messier in 1781. It has an apparent magnitude of 7.87 and is approximately 32,600 light-years distant from the Sun.
M80 is one of the most densely populated clusters in our galaxy. M80 is about 95 light-years in diameter and contains hundreds of thousands of stars.
The cluster lies halfway between the stars Antares and Acrab. It is visible in moderate-sized amateur telescopes.
It is home to a significant number of blue stragglers, blue main sequence stars that appear to be much younger because they are bluer and more luminous than stars at the main sequence turn-off point for the cluster.
A nova, Nova 1860 AD, was observed in the cluster on April 21, 1860 by the German astronomer Arthur Auwers. The progenitor star was T Scorpii.
Other notable but dim deep sky objects include the Cat’s Paw Nebula, the Butterfly Nebula, the War and Peace Nebula.
Cat’s Paw Nebula (Bear Claw Nebula) – NGC 6334 (Gum 64)
The Cat’s Paw Nebula is an emission nebula in Scorpius.
It is a vast star-forming region and one of the most active stellar nurseries containing some of the most massive stars known in the Milky Way. It is believed to contain tens of thousands of stars.
The nebula was discovered by the English astronomer John Herschel in 1837.
The Cat’s Paw Nebula. NASA’s Spitzer Space Telescope.
Butterfly Nebula (Bug Nebula) – NGC 6302 (Caldwell 69)
The Butterfly Nebula is a bipolar planetary nebula in Scorpius. It has an apparent magnitude of 7.1. It is one of the most structurally complex nebulae known.
The central star, a white dwarf, has a surface temperature in excess of 200,000 K, which makes it one of the hottest stars in the galaxy. It has about 0.64 solar masses and is enveloped in a very dense equatorial disc of dust and gas.
War and Peace Nebula – NGC 6357
NGC 6357 is a diffuse nebula in Scorpius. It contains many proto-stars and young stars. It got the name War and Peace Nebula because, when observed in infrared, the nebula’s western part resembles a dove, while the eastern part resembles a skull.