The constellation of Ophiuchus contains 11 named stars and seven stars with known planets. The names, as approved by the International Astronomical Union (IAU), are Barnard’s Star, Cebalrai, Guniibuu, Mahsati, Marfik, Rasalhague, Rosalíadecastro, Sabik, Timir, Yed Posterior, and Yed Prior. The brightest star in the Ophiuchus constellation is Rasalhague, with an apparent magnitude of 2.08.
It is also home to famous deep sky objects, including the the Little Ghost Nebula, the dark nebulae Barnard 68 and the Pipe Nebula. Ophiuchus contains seven Messier objects — Messier 9, Messier 10, Messier 12, Messier 14, Messier 19, Messier 62 and Messier 107. It also has four meteor showers associated with the constellation: the Ophiuchids, the Northern May Ophiuchids, the Southern May Ophiuchids and the Theta Ophiuchids.
History and Mythology Of The Ophiuchus Constellation
In Greek mythology, Ophiuchus constellation is associated with the figure of Asclepius, the famous healer. Asclepius was said to be able to bring people back from the dead, after seeing one snake bringing healing herbs to another.
The constellation was also said to represent the god Apollo struggling with a huge snake that guarded the Oracle of Delphi. Other myths identified Ophiuchus with Laocoön, the Trojan priest of Poseidon, who warned his fellow Trojans about the Trojan Horse and was later slain by a pair of sea serpents sent by the gods to punish him.
In Babylonian astronomy, a “Sitting Gods” constellation seems to have been located in the general area of Ophiuchus. However, some propose that Ophiuchus may be descended from an ancient Babylonian constellation that represented the serpent-god Nirah who was sometimes depicted with his upper half human but with serpents for legs.
Location Of The Ophiuchus Constellation
Ophiuchus is the 11th largest constellation in the sky and occupies an area of 948 square degrees. It is located in the third quadrant of the southern hemisphere (SQ3) and can be seen at latitudes between +80° and -80°.
Its right ascension is 17h and its declination is −8°. It is best seen at 9pm during the month of July in the northern hemisphere, making it the opposite of Orion. In contrast to Orion, from November to January, Ophiuchus is in the daytime sky and thus not visible at most latitudes.
The constellation of Ophiuchus is one of the constellations that cross the ecliptic, but it does not belong to the Zodiac family. It belongs to the Hercules family of constellations, along with Aquila, Ara, Centaurus, Corona Australis, Corvus, Crater, Crux, Cygnus, Hercules, Hydra, Lupus, Lyra, Sagitta, Scutum, Sextans, Serpens, Triangulum Australe and Vulpecula. Its neighboring constellations are Aquila, Hercules, Libra, Sagittarius, Scorpius and Serpens.
Notable Stars
Rasalhague
Rasalhague, also known as Alpha Ophiuchi, is the brightest star in Ophiuchus and has an apparent magnitude of 2.07. It is a binary star that is around 48.6 light years away from Earth and marks Asclepius’ head. Its name is derived from the Arabic raʾs al-ḥawwἄ, which means “the head of the serpent collector”.
It is composed of a white giant star with the stellar classification of A5 III and an orange main sequence dwarf with the stellar classification K5-7 V that have an orbital period of 8.62 years. The main component has a mass 2.4 times that of the Sun and is about 25 times more luminous than the Sun. It is also a very fast spinner, with a projected rotational velocity of 240 km/s. The companion has 85 percent of the Sun’s mass.
Sabik
Sabik, also known as Eta Ophiuchi, is the second brightest star in Ophiuchus and has a combined visual magnitude of 2.43. It is a binary star that is composed of two white main sequence dwarfs belonging to the spectral classes A1 V and A3 V. They have an orbital period of 87.58 years and apparent magnitudes of 3.05 and 3.27, respectively. Sabik is located around 88 light years away from the Sun and is not easy to resolve in smaller telescopes.
Zeta Ophiuchi
Zeta Ophiuchi is the third brightest star in Ophiuchus and has an apparent magnitude of 2.569. It is located around 366 light years away from the Solar System and is thought to be around 3 million years old.
It is an extremely large blue main sequence star with the stellar classification of O9.5 V that is also a Beta Cephei variable, which is a star that exhibits variations in brightness as a result of pulsation of its surface. Zeta Ophiuchi has a mass that is 19 times that of the Sun and a radius that is 8 times that of the Sun. It is also a fast rotating star, with an estimated rotational velocity of 400 km/s.
Yed Prior
Yed Prior, also known as Delta Ophiuchi, is the fourth brightest star in the constellation and has an apparent magnitude of 2.75. It is a suspected variable star with possible variations in magnitude by 0.03.
Yed Prior is a red giant with the stellar classification of M0.5 III and is located around 171 light years away from the Sun. It has a mass 1.5 times that of the Sun and a radius that is 59 times that of the Sun.
The name “Yed” comes from Arabic and means “the hand” and the forms an optical double with the star Epsilon Ophiuchi, also known as Yed Posterior.
Celbalrai
Celbalrai, also known as Beta Ophiuchi, is the fifth brightest star in Ophiuchus and is an orange giant star belonging to the spectral class K2 III. It has a visual magnitude that ranges from 2.75 to 2.77 and is 63.4 times more luminous than the Sun. It also has a radius that is 12.42 times that of the Sun and a mass that is 113 percent of the Sun’s mass.
Celbalrai is located 81.8 light years away from us and has an unconfirmed planetary companion in its orbit. Its name comes from the Arabic kalb al-rā‘ī, which means “the shepherd dog”.
Yed Posterior
Yed Posterior, also known as Epsilon Ophiuchi, is a yellow giant star with the spectral classification of G9.5 IIIb and a visual magnitude of 3.220. It is 54 times more luminous than the Sun, 1.85 times more massive and has a radius that is 10.39 times that of the Sun.
Yed Posterior is located around 106.4 light years away from the Solar System and has an estimated age of about a billion years.
Sinistra
Sinistra, also known as Nu Ophiuchi, is an orange giant with the stellar classification of K0 IIIa CN-1 and an apparent magnitude of 3.332. It is located around 151 light years away from the Sun and is 23 times more luminous than the Sun. It also has a radius that is 14 times that of the Sun and is three times as massive. The name Sinistra means “the left side” in Latin.
In 2004, a brown dwarf was discovered orbiting Sinistra with a period of 536 days. It has a mass at least 21.9 times that of Jupiter. In 2010, another brown dwarf was found orbiting the star with a period of 3,169 days. Its mass is at least 24.5 times that of Jupiter.
Marfik
Marfik, also known as Lambda Ophiuchi, is a triple star system with a combined apparent magnitude of 3.90. It is a suspected variable with the stellar classification of A0V+A, meaning it matches the spectrum of a white main sequence dwarf.
Marfik is about 170 light years away from the Solar System and its name means “the elbow” in Arabic.
Gamma Ophiuchi
Gamma Ophiuchi is a white main sequence dwarf with the stellar classification of A0 V and a visual magnitude of 3.75. It is 29 times more luminous than the Sun and is located approximately 95 light years away from Earth. This dwarf star has a mass that is 2.9 times that of the Sun and a radius that is 1.8 times that of the Sun.
It is thought to be around 184 million years old and is radiating an excess emission of infrared, which indicates there is a circumstellar disk of dust in its orbit.
Kappa Ophiuchi
Kappa Ophiuchi is an orange giant with the stellar classification of K2 III and a mean apparent magnitude of 3.20. It is a suspected variable star, 46 times more luminous than the Sun, that is located 91.5 light years away from the Solar System. It has a radius 11 times that of the Sun and a mass that is 119 times that of the Sun.
Theta Ophiuchi
Theta Ophiuchi is a multiple star system with an apparent magnitude of 3.26. It is located around 436 light years away from the Solar System and marks Ophiuchus’ right foot.
Theta Ophiuchi is also a Beta Cephei variable that is 5,000 times more luminous than the Sun. The main component is a spectroscopic binary with the stellar classification of B2 IV, making it a blue-white subgiant star.
Chi Ophiuchi
Chi Ophiuchi is a Gamma Cassiopeiae type variable with the stellar classification of B2Vne. Its apparent magnitude ranges from 4.18 to 5.0 and it has a mass that is 10.1 times that of the Sun. It is also 200,000 times more luminous than the Sun and has a radius that is 4.5 times that of the Sun.
Chi Ophiuchi is also a Be star, which is a star that radiates emissions from hydrogen which are indicative of a circumstellar ring of gas.
12 Ophiuchi
12 Ophiuchi is an orange main sequence dwarf with the stellar classification of K2V and an apparent magnitude of 5.77. It is also classified as a BY Draconis type variable and has 39 percent of the Sun’s luminosity. It also has 91 percent of the Sun’s mass and 84 percent of the Sun’s radius.
12 Ophiuchi is located 31.8 light years away from the Sun.
36 Ophiuchi
36 Ophiuchi is a triple star system composed of three orange dwarfs with the stellar classifications of K0 V, K1 V, and K5 V. Their apparent magnitudes are 5.29, 5.33 and 6.34 respectively, and the system is located around 19.5 light years from Earth.
The primary and secondary components are separated by 4.6 arc seconds. The third star is classified as an RS Canum Venaticorum variable and is separated from the main pair by 700 arc seconds.
51 Ophiuchi
51 Ophiuchi is a blue-white giant star with the stellar classification of B9.5IIIe and a visual magnitude of 4.81. It is located approximately 410 light years away from the Solar System and it has a disk of dust that seems to be a young debris disk.
67 Ophiuchi
67 Ophiuchi is a blue-white supergiant with the stellar classification of B5Ib and an apparent magnitude of 3.93. Its absolute magnitude is -4.26. It is located around 1,400 light years away from Earth and is a member of the open cluster Collinder 359.
70 Ophiuchi
70 Ophiuchi is a binary star system that is located around 16.58 light years away from the Sun and is composed of an orange dwarf with the stellar classification of K0V as the primary, and an orange dwarf with the spectral class K4V as the companion.
The primary star has an apparent magnitude of 4.03 and is classified as a BY Draconis type variable. The companion is has an apparent magnitude of 6.00. The two stars have an orbital period of 88.3 years.
Barnard’s Star
Barnard’s Star is the fourth closest known individual star to the Sun and is located 5.980 light years away from Earth. Around the year 9,800, the star will make its closest approach to the Sun and come within 3.75 light years.
It is a red dwarf with the stellar classification of M4Ve and has a visual magnitude of 9.54, but it is too faint to be seen without a telescope. It is also classified as a BY Draconis variable.
Barnard’s Star is around 7 to 12 billion years and, despite its age, has been seen exhibiting an intense stellar flare. It was named after the American astronomer E. E. Barnard, who was the first to measure the star’s proper motion in 1916, which is 10.3 arc seconds per year.
GJ 1214
GJ 1214 is a red dwarf with the stellar classification of M4.5 and a visual magnitude of 14.71. It has a mass that is only 15.7 percent of the Sun’s mass and a radius that is only 20 percent. It is located around 47.5 light years away from Earth.
GJ 1214 was found to have a transiting extrasolar planet orbiting it in December 2009. It completes an orbit around the star every 1.58 days.
Wolf 1061
Wolf 1061 is a red dwarf that belongs to the spectral class M3 V. It has an apparent magnitude of 10.10 and is 13.82 light years away from us.
RS Ophiuchi
RS Ophiuchi is a recurrent nova in Ophiuchus that consists of a white dwarf and a red giant star in a close orbit. It has an apparent magnitude ranging from 9.6 to 13.5 in the quiet phase, but reaches magnitude 5 during eruptions. Eruptions were observed in 1898, 1933, 1958, 1967, 1985 and 2006.
COROT-6
COROT-6 is a yellow-white main sequence dwarf with the stellar classification of F5V and a visual magnitude of 13.9. It has roughly the same mass and radius as the Sun, and also has a confirmed planet in its orbit. The planet is called COROT-6b and has a mass 2.96 times that of Jupiter. It completes an orbit every 8.887 days.
Kepler’s Supernova
Kepler’s Supernova, also known as Supernova 1604, is a supernova remnant that was first observed in October 1604 by German mathematician and astronomer Johannes Kepler. It was the most most recent supernova in the Milky Way that could be seen by the naked eye.
The supernova happened at a distance of approximately 20,000 light years from Earth and reached a peak magnitude of -2.25 to -2.5. This meant that it was brighter than all the stars and planets in the sky. It could be seen during the day for several weeks.
Deep Sky Objects
Messier 9
Messier 9, also known as M9 or NGC 6333, is a globular cluster that was discovered by Charles Messier in 1764. It has an apparent magnitude 8.42 and is located around 25,800 light years away from Earth. The brightest stars have a visual magnitude of 13.5 and can, therefore, be observed in moderately sized telescopes. It is one of the nearest globular clusters to the centre of our Galaxy, located around 5,500 light years away.
Messier 10
Messier 10, also known as M10 or NGC 6254, is a globular cluster that was discovered by Charles Messier on May 29, 1764. It has an apparent magnitude of 6.4 and is located around 14,300 light years away from the Sun. It is also located around 16,000 light years from the Galactic Centre and completes an orbit around the Milky Way every 140 years.
NGC 6254’s spatial diameter spans about 83 light years and the core spans around 35 light years.
Messier 12
Messier 12, also known as M12 or NGC 6218, is a globular cluster that was discovered by Charles Messier in May 1764. It has an apparent magnitude of 7.68 and is located around 15,700 light years away from the Solar System, around 3 degrees from Messier 10. The brightest stars in the cluster are of 12th magnitude and the cluster itself spans around 75 light years in diameter.
Messier 14
Messier 14, also known as M14 or NGC 6402, is a globular cluster that was discovered by Charles Messier in 1764. It has a visual magnitude of 8.32 and is located around 30,300 light years away from Earth. Many of the stars are of 14th magnitude and can be seen without binoculars. The cluster itself spans around 100 light years.
Messier 19
Messier 19, also known as M19 or NGC 6273, is a globular cluster that was discovered by Charles Messier in June 1764. It has an apparent magnitude of 7.47 and is located around 28,700 light years away from the Solar System, around 4.5 degrees to the west-southwest of the star Theta Ophiuchi and 6,500 light years from the Galactic Centre. It can be seen with binoculars.
Messier 62
Messier 62, also known as M62 or NGC 6266, is a globular cluster that was discovered by Charles Messier in 1771. It has an apparent magnitude of 7.39 and is located about 22,200 light years across. It is around 100 light years across.
Messier 107
Messier 107, also known as M107 or NGC 6171, is a globular cluster that was discovered by the French astronomer Pierre Méchain in April 1782, and then independently discovered by the German-born British astronomer William Herschel in 1793. It is the last globular cluster entered in Messier’s catalogue and was added by the Canadian astronomer Helen Sawyer Hogg in 1947. The NGC 6171 cluster has an apparent magnitude of 8.85 and is located around 20,900 light years away from us.
NGC 6240
NGC 6240 is an ultraluminous infrared galaxy (ULIRG) with an apparent magnitude of 12.8. It is a remnant of a collision of two smaller galaxies, which has resulted in formation of a single larger galaxy. The galaxy, however, does have two nuclei, which are both active galactic nuclei (AGN), and a highly irregular structure. TheNGC 6240 galaxy is about 400 million light years away from the Solar System.
NGC 6304
NGC 6304 is a globular cluster that was discovered by William Herschel in 1786. It has an apparent magnitude of 9.03 and is located approximately 19,200 light years away from the Solar System, near the Milky Way’s central bulge.
NGC 6572
NGC 6572 is a planetary nebula that was discovered by the German astronomer Friedrich Georg Wilhelm von Struve in 1825. It has an apparent magnitude of 8.1 and can be seen with amateur telescopes.
NGC 6633
NGC 6633 is an open cluster that was discovered by Philippe Loys de Chéseaux in 1745-1746. It has a visual magnitude of 4.6 and contains about 30 stars. The cluster is almost the size of the Moon and is about 660 million years old. It is around 1,040 light years away from the Sun.
Barnard 68
Barnard 68 is a molecular cloud, dark absorption nebula or Bok globule that consists of a high concentration of molecular gas and dust. It also absorbs the visible light of the stars in the background. It is located around 500 light years from the Sun and has a mass twice that of the Sun. Barnard 68 also has a radius that is 0.25 light years in radius.
IC 4665
IC 4665 is an open cluster with an apparent magnitude of 4.2 that was discovered by the Swiss astronomer Philippe Loys de Chéseaux in 1745. It is located around 1,400 light years away from the Solar System and is less than 40 million years old. It can be seen with binoculars and small telescopes.
IC 4603—4604
IC 4603—04 is a reflection nebula. The IC 4603 is located near the bright star Antares in Scorpius constellation and IC 4604 contains several bright stars. The stars that illuminate the two nebulae are around 400-440 light years away from Earth.
Palomar 6
Palomar 6 is a globular cluster that is one of only four globular clusters known to contain a planetary nebula. It is a relatively loose cluster and belongs to the halo of the Milky Way Galaxy. It is located around 18,900 light years away from Earth and was discovered by Robert G. Harrington and Fritz Zwicky.
Little Ghost Nebula
The Little Ghost Nebula is a planetary nebula that was discovered by William Herschel. It has an apparent magnitude of 12.9 and is located about 2,000 light years away from Earth. The nebula is illuminated by the central white dwarf and its main ring structure spans about a light year across
Dark Horse Nebula
The Dark Horse Nebula, also sometimes known as the Great Dark Horse, is a large dark nebula that is located near the border with the zodiac constellations Sagittarius and Scorpius. It is one of the largest dark nebulae in the sky and obscures a part of the upper central bulge of the Milky Way Galaxy. When there is no light pollution, the nebula can be seen without binoculars.
It was named the Dark Horse Nebula because its shape resembles that of a side silhouette of a horse.
Snake Nebula
The Snake Nebula, also known as Barnard 72, is a dark nebula located around 650 light years from Earth, left of the molecular cloud Barnard 68. It can be found in the north-western part of the bowl of the Pipe Nebula and is part of the larger Dark Horse Nebula.
The Snake Nebula is small but has a distinctive S-shape of a snake, which is how it got its name.
Pipe Nebula
The Pipe Nebula, also known as Barnard 59, is a dark nebula which is part of the larger Dark Horse Nebula and forms the hind quarters of the Dark Horse. It is located around 600-700 light years away from the Solar System. It appears as a pipe shaped dust lane that obscures the Milky Way in the background and can be seen without visual aids.
Twin Jet Nebula (Minkowski’s Butterfly)
The Twin Jet Nebula, also known as Minkowski’s Butterfly or Planetary Nebula M2-9, is a planetary nebula with an apparent magnitude of 14.7 that was discovered by the German-American astronomer Rudolph Minkowski is 1947. It is located around 2,100 light years away from the Solar System.
The Twin Jet Nebula was is a bipolar nebula formed in the shape of twin lobes of material ejected from the central star. The central star is actually a binary star, with the primary component the hot core of a star that ejected its outer layers and contracted into a white dwarf. The secondary component is a smaller star in a close orbit with the primary.
Rho Ophiuchi Cloud Complex
The Rho Ophiuchi Cloud Complex is a dark nebula that is around 460 light years away from Earth, around a degree to the south of the star Rho Ophiuchi. The nebula is one of the nearest star-forming regions to the Sun and covers an area of 4.5°x6.5°. It consists of two major regions of dust and gas where new stars are being formed.
Extra Facts
- In the northern hemisphere’s spring and summer months, when Ophiuchus is normally visible in the night sky, the constellation is actually not visible, because the midnight sun obscures the stars at those times and places in the Arctic.
- In countries close to the equator, Ophiuchus appears overhead in June around midnight and in the October evening sky.
- The earliest mention of the constellation is in Aratus, informed by the lost catalogue of Eudoxus of Cnidus (4th century BCE).
- Ophiuchus is one of thirteen constellations that cross the ecliptic and has therefore been called the “13th sign of the zodiac”.
- Ophiuchus was formerly referred to as Serpentarius.
Images:
- Some Images created with the NightVision app – https://www.nvastro.com/nvj.html
- Some Images created with the Stelvision Sky Map https://www.stelvision.com/en/sky-map/
- Ophiuchus 1 – https://starregistration.net/constellations/ophiuchus-constellation.html
- Rasalhague -https://www.star-facts.com/rasalhague/
- Sabik – https://www.star-facts.com/sabik/
- Cebalrai – https://theskylive.com/sky/stars/cebalrai-beta-ophiuchi-star
- Kepler’s Supernova -https://www.space.com/20670-johannes-kepler-supernova-white-dwarf.html
- Little Ghost Nebula – https://en.wikipedia.org/wiki/Little_Ghost_Nebula
- Dark Horse Nebula – https://earthsky.org/todays-image/saturn-riding-the-dark-horse-nebula-photo