Visible at latitudes between +60° and −75°. Best visible at 21:00 (9 p.m.) during the month ofJuly.
Ophiuchus (/ˌɒfiˈjuːkəs/) is a largeconstellation straddling thecelestial equator. Its name comes from theAncient Greekὀφιοῦχος (ophioûkhos), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constellationSerpens. Ophiuchus was one of the 48 constellations listed by the 2nd-century astronomerPtolemy, and it remains one of the88 modern constellations. An old alternative name for the constellation wasSerpentarius.[1]
Rho Ophiuchi, shown with a surrounding bluish cloud slightly above a pentagon of stars in Scorpius, with the main band of the Milky Way much further to the left
Ophiuchus lies betweenAquila,Serpens,Scorpius,Sagittarius, andHercules, northwest of the center of theMilky Way. The southern part lies betweenScorpius to the west andSagittarius to the east.[2] In theNorthern Hemisphere, it is best visible in summer.[3] It is opposite ofOrion. Ophiuchus is depicted as a man grasping aserpent; the interposition of his body divides the snake constellation Serpens into two parts,Serpens Caput andSerpens Cauda. Ophiuchus straddles the equator with the majority of itsarea lying in the Southern Hemisphere.Rasalhague, its brightest star, lies near the northern edge of Ophiuchus at about +12° 30′ declination.[4] The constellation extends southward to −30° declination. Segments of the ecliptic within Ophiuchus are south of −20° declination (see chart at right).
In contrast to Orion, from November to January (summer in the Southern Hemisphere, winter in the Northern Hemisphere), Ophiuchus is in the daytime sky and thus not visible at most latitudes. However, for much of the polar region north of theArctic Circle in the Northern Hemisphere's winter months, the Sun is below the horizon even at midday. Stars (and thus parts of Ophiuchus, especially Rasalhague) are then visible at twilight for a few hours around local noon, low in the south. 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 themidnight 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.[citation needed]
The brightest stars in Ophiuchus includeα Ophiuchi, called Rasalhague ("head of the serpent charmer"), at magnitude 2.07, andη Ophiuchi, known as Sabik ("the preceding one"), at magnitude 2.43.[5][6] Alpha Ophiuchi is composed of an A-type (bluish-white) giant star[7] and aK-type main sequence star.[8] The primary is a rapid rotator[9] with an inclined axis of rotation.[10] Eta Ophiuchi is a binary system.[11] Other bright stars in the constellation includeβ Ophiuchi, Cebalrai ("dog of the shepherd")[12] andλ Ophiuchi, or Marfik ("the elbow").[13] Beta Ophiuchi is an evolvedred giant star that is slightly more massive than the Sun.[14][15] Lambda Ophiuchi is a binary star system with the primary being more massive and luminous than the Sun.[16][17]
RS Ophiuchi is part of a class called recurrentnovae, whose brightness increase at irregular intervals by hundreds of times in a period of just a few days. It is thought to be at the brink of becoming a Type Iasupernova.[18] It erupts around every 15 years and usually has a magnitude of around 5.0 during eruptions, most recently in 2021.[19][20]
Barnard's Star, one of thenearest stars to theSolar System (the only stars closer are theAlpha Centauribinary star system andProxima Centauri), lies in Ophiuchus. It is located to the left of β and just north of the V-shaped group of stars in an area that was once occupied by the now-obsolete constellation ofTaurus Poniatovii (Poniatowski's Bull). It is thought that an exoplanet orbits around the star,[21]but later studies have refuted this claim.[22] In 1998, an intense flare was observed.[23][24] The star has also been a target of plans for interstellar travel such asProject Daedalus.[25][26] In 2005, astronomers using data from theGreen Bank Telescope discovered asuperbubble so large that it extends beyond the plane of the galaxy.[27] It is called theOphiuchus Superbubble.
In April 2007,astronomers announced that theSwedish-builtOdin satellite had made the first detection of clouds ofmolecularoxygen in space, following observations in the constellation Ophiuchus.[28] Thesupernova of 1604 was first observed on 9 October 1604, near θ Ophiuchi.Johannes Kepler saw it first on 16 October and studied it so extensively that thesupernova was subsequently calledKepler's Supernova. He published his findings in a book titledDe stella nova in pede Serpentarii (On the New Star in Ophiuchus's Foot).Galileo used its brief appearance to counter theAristoteliandogma that the heavens are changeless. It was a Type Ia supernova[29] and the most recent Milky Way supernova visible to the unaided eye.[30] In 2009 it was announced thatGJ 1214, a star in Ophiuchus, undergoes repeated, cyclical dimming with a period of about 1.5 days consistent with the transit of a small orbiting planet.[31] The planet's low density (about 40% that of Earth) suggests that the planet might have a substantial component of low-density gas—possiblyhydrogen orsteam.[32] The proximity of this star to Earth (42 light years) makes it a feasible target for further observations. The host star emits X-rays which could have removed mass from the exoplanet.[33] In April 2010, the naked-eye starζ Ophiuchi was occulted by the asteroid824 Anastasia.[34][35][36]
The constellation Ophiuchus as it can be seen by naked eye.[37]
M9 is a globular cluster which may have an extra-galactic origin.[38]M10 is a fairly closeglobular cluster, only 20,000 light-years from Earth. It has a magnitude of 6.6 and is a Shapley class VII cluster. This means that it has "intermediate" concentration; it is only somewhat concentrated towards its center.[39] M12 is a globular cluster which is around 5 kiloparsecs from the Solar System.[40]M14 is another globular cluster which is somewhat farther away.[41] Globular cluster M19 isoblate-shaped[42] with multiple different types of variable stars.[43] M62 is a globular cluster rich invariable stars such asRR Lyrae variables[44] and has two generations of stars with different element abundances.[45] M107 is also rich in variable stars.[46]
In 2006, a new nearbystar cluster was discovered associated with the 4th magnitude starMu Ophiuchi.[49] TheMamajek 2 cluster appears to be a poor cluster remnant analogous to theUrsa Major Moving Group, but 7 times more distant (approximately 170 parsecs away). Mamajek 2 appears to have formed in the same star-forming complex as theNGC 2516 cluster roughly 135 million years ago.[50]
Barnard 68 is a largedark nebula, located 410 light-years from Earth. Despite its diameter of 0.4 light-years, Barnard 68 only has twice the mass of the Sun, making it both very diffuse and very cold, with a temperature of about 16 kelvins. Though it is currently stable, Barnard 68 will eventually collapse, inciting the process ofstar formation. One unusual feature of Barnard 68 is its vibrations, which have a period of 250,000 years. Astronomers speculate that this phenomenon is caused by theshock wave from asupernova.[47] Barnard 68 has blocked thousands of stars visible at other wavelengths[51] and the distribution of dust in Barnard 68 has been mapped.[52][53]
The space probeVoyager 1, the furthest man-made object from earth, is traveling in the direction of Ophiuchus. It is located betweenα Herculis,α Ophiuchi andκ Ophiuchi at right ascension 17h 13m and declination +12° 25’ (July 2020).[54]
There is no evidence of the constellation preceding theclassical era, and inBabylonian astronomy, a "Sitting Gods" constellation seems to have been located in the general area of Ophiuchus. However, Gavin White proposes that Ophiuchus may in fact be remotely descended from this Babylonian constellation, representingNirah, a serpent-god who was sometimes depicted with his upper half human but with serpents for legs.[56]
The earliest mention of the constellation is inAratus, informed by the lost catalogue ofEudoxus of Cnidus (4th century BC):[57]
To thePhantom's back theCrown is near, but by his head mark near at hand the head of Ophiuchus, and then from it you can trace the starlit Ophiuchus himself: so brightly set beneath his head appear his gleaming shoulders. They would be clear to mark even at the midmonth moon, but his hands are not at all so bright; for faint runs the gleam of stars along on this side and on that. Yet they too can be seen, for they are not feeble. Both firmly clutch theSerpent, which encircles the waist of Ophiuchus, but he, steadfast with both his feet well set, tramples a huge monster, even theScorpion, standing upright on his eye and breast. Now the Serpent is wreathed about his two hands – a little above his right hand, but in many folds high above his left.[58]
Later myths identified Ophiuchus withLaocoön, theTrojan priest ofPoseidon, who warned his fellow Trojans about theTrojan Horse and was later slain by a pair of sea serpents sent by the gods to punish him.[59] According toRoman era mythography,[60] the figure represents the healerAsclepius, who learned the secrets of keeping death at bay after observing one serpent bringing another healing herbs. To prevent the entire human race from becomingimmortal under Asclepius' care,Jupiter killed him with a bolt oflightning, but later placed his image in the heavens to honor his good works. In medievalIslamic astronomy (Azophi'sUranometry, 10th century), the constellation was known asAl-Ḥawwa', "the snake-charmer".[61]
Aratus describes Ophiuchus as trampling onScorpius with his feet. This is depicted in Renaissance to Early Modernstar charts, beginning withAlbrecht Dürer in 1515; in some depictions (such as that ofJohannes Kepler inDe Stella Nova, 1606), Scorpius also seems to threaten to sting Serpentarius in the foot. This is consistent withAzophi, who already includedψ Oph andω Oph as the snake-charmer's "left foot", andθ Oph andο Oph as his "right foot", making Ophiuchus azodiacal constellation at least as regards his feet.[62] This arrangement has been taken as symbolic in later literature and placed in relation to the words spoken by God to the serpent in theGarden of Eden (Genesis 3:15).[63]
Ophiuchus in a manuscript copy ofAzophi'sUranometry, 18th century copy of a manuscript prepared forUlugh Beg in 1417 (note that as in all pre-modernstar charts, the constellation is mirrored, withSerpens Caput on the left andSerpens Cauda on the right).
Ophiuchus holding the serpent, Serpens, as depicted inUrania's Mirror, a set of constellation cards published in London c. 1825. Above the tail of the serpent is the now-obsolete constellationTaurus Poniatovii while below it isScutum.
Ophiuchus is one of the 13 constellations that cross theecliptic.[64] It has sometimes been suggested as the "13th sign of thezodiac". However, this confuseszodiac or astrological signs withconstellations.[65] The signs of the zodiac are a 12-fold division of the ecliptic, so that each sign spans 30° of celestial longitude, approximately the distance the Sun travels in a month, and (in the Western tradition) are aligned with the seasons so that theMarch equinox always falls on the boundary between Pisces and Aries.[66][67] Constellations, on the other hand, are unequal in size and are based on the positions of the stars. Theconstellations of the zodiac have only a loose association with the signs of the zodiac, and do not in general coincide with them.[68] In Western astrology the constellation of Aquarius, for example, largely corresponds to the sign of Pisces. Similarly, the constellation of Ophiuchus occupies most (29 November – 18 December[69]) of the sign of Sagittarius (23 November – 21 December). The differences are due to the fact that the time of year that the Sun passes through a particular zodiac constellation's position has slowly changed (because of theprecession of the Earth's rotational axis) over the millennia from when theBabylonians originally developed the zodiac.[70][71]
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![The constellation Ophiuchus as it can be seen by naked eye.[37]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aOphiuchusCC.jpg)
