Ophiuchus

Ophiuchus

Constellation
List of stars in Ophiuchus
Abbreviation	Oph
Genitive	Ophiuchi
Pronunciation	/ɒfiˈjuːkəs/ Ophiúchus, genitive /ɒfiˈjuːkaɪ/
Symbolism	the serpent-bearer
Right ascension	17
Declination	−8
Quadrant	SQ3
Area	948 sq. deg. (11th)
Main stars	10
Bayer/Flamsteed stars	62
Stars with planets	15
Stars brighter than 3.00m	5
Stars within 10.00 pc (32.62 ly)	11
Brightest star	α Oph (Ras Alhague) (2.08m)
Nearest star	Barnard's Star (5.98 ly, 1.83 pc)
Messier objects	7
Meteor showers	Ophiuchids Northern May Ophiuchids Southern May Ophiuchids Theta Ophiuchids
Bordering constellations	Hercules Serpens Libra Scorpius Sagittarius Aquila
Visible at latitudes between +80° and −80°. Best visible at 21:00 (9 p.m.) during the month of July.

Ophiuchus /ɒfiˈjuːkəs/ is a large constellation located around the celestial equator. Its name is from the Greek Ὀφιοῦχος "serpent-bearer", and it is commonly represented as a man grasping the snake that is represented by the constellation Serpens. Ophiuchus was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. It was formerly referred to as Serpentarius /sɜrpənˈtɛəriəs/ and Anguitenens.

Location

Ophiuchus is located between Aquila, Serpens and Hercules, northwest of the center of the Milky Way. The southern part lies between Scorpius to the west and Sagittarius to the east. In the northern hemisphere, it is best visible in summer. It is located opposite Orion in the sky. Ophiuchus is depicted as a man grasping a serpent; the interposition of his body divides the snake constellation Serpens into two parts, Serpens Caput and Serpens Cauda, which are nonetheless counted as one constellation.

Ophiuchus straddles the equator but lies predominately to its north. Rasalhague, a fairly conspicuous star in its north, is circumpolar north of 78° north latitude and invisible south of 78° south latitude. The constellation extends southward to −30° declination, so the constellation can never be seen in full even in such places as Anchorage, Reykjavík, and Helsinki north of 60° north latitude. Segments of the ecliptic that lie within Ophiuchus lie south of −20° declination and are thus invisible north of 70° north latitude.

In contrast to Orion, it is in the period November–January (summer in the Southern Hemisphere, winter in the Northern Hemisphere) when Ophiuchus is in the daytime sky and thus not visible at most latitudes. However for much of the Arctic 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 summer months, when Ophiuchus is normally visible in the night sky, the constellation is actually not visible in the Arctic Circle because the sun does not set at that time of year north of the Arctic Circle. In countries close to the equator Ophiuchus appears overhead in June around midnight and in the October evening sky.

Notable features

Stars

The brightest stars in Ophiuchus include α Ophiuchi, called Ras Alhague ("head of the serpent charmer"), at magnitude 2.07, and η Ophiuchi, known as Sabik ("the preceding one"), at magnitude 2.43.^[2] Other bright stars in the constellation include β Ophiuchi, Cebalrai ("heart of the shepherd") and λ Ophiuchi, or Marfik ("the elbow").^[3]

RS Ophiuchi is part of a class called recurrent novae, 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-1a supernova.^[4]

Barnard's Star, one of the nearest stars to the Solar System (the only stars closer are the Alpha Centauri binary star system and Proxima 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 of Taurus Poniatovii (Poniatowski's Bull).

In 2005, astronomers using data from the Green Bank Telescope discovered a superbubble so large that it extends beyond the plane of the galaxy.^[5] It is called the Ophiuchus Superbubble.

In April 2007, astronomers announced that the Swedish-built Odin satellite had made the first detection of clouds of molecular oxygen in space, following observations in the constellation Ophiuchus.^[6]

The supernova 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 the supernova was subsequently called Kepler's Supernova. He published his findings in a book titled De stella nova in pede Serpentarii (On the New Star in Ophiuchus' Foot). Galileo used its brief appearance to counter the Aristotelian dogma that the heavens are changeless.

In 2009 it was announced that GJ 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.^[7] The planet's low density (about 40% that of Earth) suggests that the planet may have a substantial component of low-density gas—possibly hydrogen or steam.^[8] The proximity of this star to Earth (42 light years) makes it a tempting target for further observations.

In April 2010, the naked-eye star ζ Ophiuchi was occulted by 824 Anastasia.

Deep-sky objects

Ophiuchus contains several star clusters, such as IC 4665, NGC 6633, M9, M10, M12, M14, M19, M62, and M107, as well as the nebula IC 4603-4604.

M10 is a fairly close globular 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.^[9]

The unusual galaxy merger remnant and starburst galaxy NGC 6240 is also in Ophiuchus. At a distance of 400 million light-years, this "butterfly-shaped" galaxy has two supermassive black holes 3,000 light-years apart. Confirmation of the fact that both nuclei contain black holes was obtained by spectra from the Chandra X-ray Observatory. Astronomers estimate that the black holes will merge in another billion years. NGC 6240 also has an unusually high rate of star formation, classifying it as a starburst galaxy. This is likely due to the heat generated by the orbiting black holes and the aftermath of the collision.^[10]

In 2006, a new nearby star cluster was discovered associated with the 4th magnitude star Mu Ophiuchi.^[11] The Mamajek 2 cluster appears to be a poor cluster remnant analogous to the Ursa 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 the NGC 2516 cluster roughly 135 million years ago.^[12]

Barnard 68 is a large dark 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 - about 16 degrees Kelvin. Though it is currently stable, Barnard 68 will eventually collapse, inciting the process of star 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 the shock wave from a supernova.^[10]

History and Mythology

There is no evidence of the constellation preceding the classical era, and in Babylonian 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, representing Nirah, a serpent-god who was sometimes depicted with his upper half human but with serpents for legs.^[13]

The earliest mention of the constellation is in Aratus, informed by the lost catalogue of Eudoxus of Cnidus (4th century BC):^[14]

To the Phantom's back the Crown 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 the Serpent, which encircles the waist of Ophiuchus, but he, steadfast with both his feet well set, tramples a huge monster, even the Scorpion, 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.^[15]

To the ancient Greeks, the constellation represented the god Apollo struggling with a huge snake that guarded the Oracle of Delphi.^[16] Later 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.^[16]

According to Roman era mythography,^[17] the figure represents the healer Asclepius, who learned the secrets of keeping death at bay after observing one serpent bringing another healing herbs. To prevent the entire human race from becoming immortal under Asclepius' care, Zeus killed him with a bolt of lightning, but later placed his image in the heavens to honor his good works.

In medieval Islamic astronomy (Azophi's Uranometry, 10th century), the constellation was known as Al-Ḥawwaʾ "the snake-charmer".

Aratus describes Ophiuchus as trampling on Scorpio with his feet. This is depicted in Renaissance to Early Modern star charts, beginning with Albrecht Dürer in 1515; in some depictions (such as that of Johannes Kepler, 1604), Scorpio also seems to threaten to sting Serpentarius in the foot. This is consistent with Azophi, who already included ψ Oph and ω Oph as the snake-charmer's "left foot", and θ Oph and ο Oph as his "right foot", making Ophiuchus a zodiacal constellation at least as regards his feet.^[18] This arrangement has been taken as symbolic in later literature, and placed in relation to the words spoken by God to the serpent in the Garden of Eden (Genesis 3:15).^[19]

Literary References

John Milton used Opiuchus as the vehicle for an epic simile in Book 2 of Paradise Lost, comparing Satan to a comet burning across the length of Opiuchus (lines 706-10): 'on th' other side / Incensed with indignation Satan stood / Unterrified, and like a comet burned / That fires the length of Opiuchus huge / In th' arctic sky'.

Ophiuchus and the zodiac

Ophiuchus is one of thirteen constellations that cross the ecliptic.^[20] It has therefore been called the '13th sign of the zodiac'. However, this confuses sign with constellation.

The signs of the zodiac are a twelve-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 the March equinox falls on the boundary between Pisces and Aries.

Constellations, on the other hand, are unequal in size and are based on the positions of the stars. The constellations of the zodiac have only a loose association with the signs of the zodiac, and do not in general coincide with them. In Western astrology the constellation of Aquarius, for example, largely corresponds to the sign of Pisces. Similarly, the constellation of Ophiuchus occupies most of the sign of Sagittarius. 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 over the centuries from when the Greeks and Babylonians originally developed the Zodiac.^[21][22] This phenomenon is due to the Earth's axial precession.

Citations

References

• Levy, David H. (2005). Deep Sky Objects. Prometheus Books. ISBN 1-59102-361-0. 
• Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0-00-725120-9. Princeton University Press, Princeton. ISBN 978-0-691-13556-4.
• Klaudio Zic (2011). True Zodiac : True Ascendant, NOOK Book ISBN 1257550268.

External links

Wikisource has the text of the 1911 Encyclopædia Britannica article Serpentarius.

Media related to Ophiuchus at Wikimedia Commons

• The Deep Photographic Guide to the Constellations: Ophiuchus
• Star Tales – Ophiuchus
• Ophiuchus Constellation at Constellation Guide

v t e Stars of Ophiuchus Bayer α (Rasalhague) β (Cebalrai) γ δ (Yed Prior) ε (Yed Posterior) ζ (Han) η (Sabik) θ ι κ λ (Marfik) μ ν ξ ο ρ σ τ υ φ χ ψ ω Flamsteed 12 14 15 16 18 19 20 21 23 24 26 28 29 30 31 36 37 38 41 43 44 45 47 50 51 52 53 54 58 61 66 67 68 70 71 72 73 74 24 Sco Variable U V X Y RS RV RZ ST SW TT TW UU WZ XX BF IX KK V380 V426 V438 V442 V445 V451 V453 V502 V508 V566 V567 V716 V839 V841 V849 V986 V1010 V1054 V2051 V2052 V2076 V2105 V2112 V2113 V2114 V2118 V2126 V2129 V2213 V2214 V2247 V2291 V2292 V2301 V2307 V2324 V2368 V2388 V2393 V2400 V2487 V2502 V2540 V2542 HR 5989 5990 6041 6067 6096 6124 6136 6137 6140 6144 6179 6189 6190 6193 6201 6202 6235 6248 6269 6284 6294 6296 6302 6308 6329 6340 6350 6353 6354 6358 6359 6361 6365 6367 6372 6375 6387 6390 6404 6413 6428 6433 6435 6439 6441 6465 6472 6473 6474 6476 6489 6490 6494 6497 6504 6507 6512 6516 6520 6521 6524 6532 6534 6575 6577 6578 6590 6593 6601 6633 6639 6650 6659 6667 6670 6686 6689 6690 6696 6706 6719 6784 6797 6800 6851 6857 6883 6925 6976 6985 6987 7010 HD 147888 147889 148390 148427 148531 149143 149382 149414 150052 150381 150433 150493 152581 154088 156992 157172 160042 160346 164509 167162 170469 171028 Gliese Gliese 673 GJ 1207 Other AS 239 Barnard's Star BD -9 4395 COROT-6 DoAr 21 Elias 29 GRO J1719-24 GRS 1739-278 GSS 30 GX 1+4 GX 9+9 H 1705-250 Hen 3-1341 IRAS 16293-2422 KS 1731-260 LS IV -1 2 2MASS J16452211-1319516 MXB 1659-29 Nova Ophiuchi 1993 Oph 162225-240515 Oph S1 PG 1627-017 PSR B1642-03 PSR B1702-19 PSR B1706-16 PSR B1737+13 PSR B1929+10 PSR J1713+0447 PSR J1744-1134 RNO 91 SDSS 1624+0029 SLX 1735-269 SR 21 Swift J1753.5-0127 Van Biesbroeck 8 VLA 1623 VVV BD001 WISE 1800+0134 WL 16 Wolf 635 Wolf 1061 XTE J1739-285 YLW 15 YLW 16A List

v t e The 88 modern constellations Andromeda Antlia Apus Aquarius Aquila Ara Aries Auriga Boötes Caelum Camelopardalis Cancer Canes Venatici Canis Major Canis Minor Capricornus Carina Cassiopeia Centaurus Cepheus Cetus Chamaeleon Circinus Columba Coma Berenices Corona Australis Corona Borealis Corvus Crater Crux Cygnus Delphinus Dorado Draco Equuleus Eridanus Fornax Gemini Grus Hercules Horologium Hydra Hydrus Indus Lacerta Leo Leo Minor Lepus Libra Lupus Lynx Lyra Mensa Microscopium Monoceros Musca Norma Octans Ophiuchus Orion Pavo Pegasus Perseus Phoenix Pictor Pisces Piscis Austrinus Puppis Pyxis Reticulum Sagitta Sagittarius Scorpius Sculptor Scutum Serpens Sextans Taurus Telescopium Triangulum Triangulum Australe Tucana Ursa Major Ursa Minor Vela Virgo Volans Vulpecula List of constellations

v t e Constellation history v t e The 48 constellations listed by Ptolemy after 150 AD Andromeda Aquarius Aquila Ara Argo Navis Aries Auriga Boötes Cancer Canis Major Canis Minor Capricornus Cassiopeia Centaurus Cepheus Cetus Corona Australis Corona Borealis Corvus Crater Cygnus Delphinus Draco Equuleus Eridanus Gemini Hercules Hydra Leo Lepus Libra Lupus Lyra Ophiuchus Orion Pegasus Perseus Pisces Piscis Austrinus Sagitta Sagittarius Scorpius Serpens Taurus Triangulum Ursa Major Ursa Minor Virgo v t e The 41 additional constellations added in the 16th and 17th centuries Vespucci or Corsalius early 16c: Crux Triangulum Australe Vopel 1536: Coma Berenices Keyser & de Houtman 1596: Apus Chamaeleon Dorado Grus Hydrus Indus Musca Pavo Phoenix Tucana Volans Plancius 1613: Camelopardalis Columba Monoceros Habrecht 1621: Reticulum Hevelius 1683: Canes Venatici Lacerta Leo Minor Lynx Scutum Sextans Vulpecula de Lacaille 1763: Antlia Caelum Carina Circinus Fornax Horologium Mensa Microscopium Norma Octans Pictor Puppis Pyxis Sculptor Telescopium Vela v t e Obsolete constellations (including Ptolemy's Argo Navis) Anser Antinous Argo Navis Asterion Cancer Minor Cerberus Chara Custos Messium Felis Frederici Honores/Gloria Frederici Gallus Globus Aerostaticus Jordanus Lochium Funis Machina Electrica Malus Mons Maenalus Musca Borealis Noctua Officina Typographica Polophylax Psalterium Georgianum/Harpa Georgii Quadrans Muralis Ramus Pomifer Robur Carolinum Sceptrum Brandenburgicum Sceptrum et Manus Iustitiae Solarium Rangifer/Tarandus Taurus Poniatovii Telescopium Herschelii Testudo Tigris Triangulum Minus Turdus Solitarius Vespa Vultur cadens Vultur volans obsolete constellation names Apis Phoenicopterus Serpentarius Xiphias

v t e The Zodiac Astrological signs Aries Taurus Gemini Cancer Leo Virgo Libra Scorpio Sagittarius Capricorn Aquarius Pisces Ophiuchus Western astrology House Triplicity Mode Cardinal Fixed Mutable Binary Positive Negative Related Ecliptic coordinate system Axial precession Walter Berg Zodiacal light Astronomy Constellations of the Ecliptic Planets in astrology

Coordinates: 17^h 00^m 00^s, +00° 00′ 00″