Constellations: Scorpius 'the Scorpion' Content from the guide to life, the universe and everything

Constellations: Scorpius 'the Scorpion'

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A small scorpion, embedded in green plastic to make a paperweight.
Then Day and Night weigh'd in Libra's scales,
Equal awhile, at last the Night prevails,
And longer grown the heavier scale inclines
And draws bright Scorpius from the Winter signs.

– Manilius: Now Constellations

Name:Scorpius (Latin: 'scorpion')
Genitive:Scorpii
Short form:Sco
Area:497 sq deg
Co-ordinates1:17h, −37°
Zodiac:Yes
Origin:Ancient

The constellation  Scorpius is one of the oldest-recognised shapes of stars, that of a scorpion's body and tail. Scorpions are the most primitive of arachnids, barely changed since the Silurian Period (438-408 million years ago).

However, not everyone knows it as the outline of a scorpion; the Chinese view it as a dragon. Scorpius is prominent in southern skies during the autumn/winter months. It is bordered by (clockwise, from top) Ophiuchus, Libra, Lupus, Norma, Ara, Corona Australis and Sagittarius. Scorpius boasts four Messier objects, numerous clusters and nebulae, a black hole binary system, and five stars with confirmed extrasolar planets.

The Sun appears to pass through Scorpius from our vantage point, making it (as 'Scorpio') a member of the zodiac (see 'The Zodiac' section below).

Mythology

According to Ancient Greek legend, Orion (the Hunter) boasted that he could kill any of the animals of the Earth because he was so skilled at tracking and a fearsome warrior to boot. This so alarmed the goddess of the Earth, Gaia, that she sent a giant scorpion to do battle with Orion. During this fight, the scorpion managed to sting Orion on his leg, inflicting a deadly wound. Asclepius2, the demigod of healing, used his knowledge and skill to revive the fallen Orion. The gods could not allow this, so Asclepius was killed by Zeus. The rest of the Greek gods were so entertained by the events that they decided all of the players should be honoured with their own constellations. Asclepius was placed between Serpens, and he became known as Ophiuchus, the serpent bearer, because Asclepius had learned his healing skills from watching snake behaviour. Orion and Scorpius were placed on opposing sides of the celestial sphere so there could never be a repeat of the titanic battle. The bright star Rigel (beta Orionis) marks the place where the scorpion inflicted its venomous sting upon Orion.

Stars

The scientific star names are simple to understand (if you know your Greek alphabet). For example: the 'alpha' star means that it is the brightest star in that constellation. Combined with the genitive name, this is known as the 'Bayer designation'. Some stars have proper names as well; for example, alpha Scorpii is Antares. Others are known by their catalogue number.

Antares (alpha Scorpii) is a red supergiant of the first magnitude. In comparison to our Sun, Antares is 400 times larger and ten thousand times brighter. The Romans knew this star as Cor Scorpionis  'the heart of the scorpion'. Antares literally means 'rival of Mars' and indeed, they appear very similar to us. Due to its position on the ecliptic (the apparent path of the sun across the sky) Antares can be occulted (covered) by the moon and (very rarely) the planets of our solar system. During one such occultation by our moon on 13 April, 1819, a companion star Antares B was discovered. Antares is one of the four 'Royal Stars' in Mesopotamian culture, the others being Aldebaran (alpha Tauri), Regulus (alpha Leonis) and Fomalhaut (alpha Piscis Austrini).

The star designated gamma Scorpii was reclassified as sigma Librae in the 19th Century.

Lambda Scorpii Shaula (literally meaning 'the raised tail') is a multiple star system comprising three components: lambda Scorpii A, B and C; however with more powerful optical aides it is possible to see that lambda Scorpii A is a triple system itself. Shaula shines +1.6, the 25th-brightest star overall.

Nu Scorpii is a multiple star system which lights the very fine dust of Reflection nebula IC 4592, causing it to shine bright blue.

Due to its similarity to our own Sun, the unnamed 18 Scorpii features highly on the list of stars called the Catalogue of Nearby Habitable Stellar Systems (HabCat) which are being analysed by a team of researchers at the University of Arizona as part of the ongoing search for habitable extrasolar planets.

GRO J1655-40 is a binary star system with a difference! There's a main sequence star approximately double the mass of our Sun, then there's its rather aggressive companion, a black hole! The Astronomy Picture of the Day website published an artist's impression of the unusual partnership for our better understanding of the mechanics of the system.

Star Table

StarDesignationName or
catalogue number
Brightness (m)Distance
(light years3)
Spectral classification
and/or comments
α Scoalpha ScorpiiAntares+0.9 var600Binary star system
λ Scolambda ScorpiiShaula+1.6 var700Multiple star system
θ Scotheta ScorpiiSargas+1.8 var270Yellow-white giant
δ Scodelta ScorpiiDschubba+2.3 var400Multiple star system
ε Scoepsilon ScorpiiWei+2.3 var66Orange giant
κ Scokappa ScorpiiGirtab+2.4 var464Binary star system
β Scobeta ScorpiiGraffias+2.6 var530Binary star system
υ Scoupsilon ScorpiiLesath+2.7 var518Blue-white subgiant
τ Scotau Scorpii23 Scorpii+2.8 var430Blue-white dwarf
σ Scosigma ScorpiiAlniyat+2.9 var734Multiple star system
π Scopi Scorpii6 Scorpii+2.9 var404Multiple star system
ι Scoiota ScorpiiHD 161471+3.0 var1,790Yellow-white supergiant
μ ScoMu ScorpiiHD 151890+3.1 var820Binary star system
η Scoeta ScorpiiHD 155203+3.3 var70Yellow-white giant
ρ Scorho Scorpii5 Scorpii+3.8 var350Binary star system
ω Scoomega ScorpiiJabhat al Akrab+3.9 var360Yellow giant/blue dwarf
binary star system
ν Sconu ScorpiiJabbah+4 var400Multiple star system;
lights IC 4592
ξ Scoxi ScorpiiHD 144069+4.1 var86Multiple star system
ο Scoomicron Scorpii19 Scorpii+4.551,170White giant
ψ Scopsi Scorpii15 Scorpii+4.9 var150White subgiant
χ Scochi Scorpii17 Scorpii+5.2 var400Orange giant
18 Sco18 ScorpiiHD 146233+5.5 var45Yellow main sequence
GRO J1655-40N/A11,000Binary star/Black hole

Clusters and Nebulae

IC 4628 is an emission nebula approximately 250 light years across. More commonly known as the Prawn Nebula, it lies over 6,000 light years away.

Reflection nebulae  IC 4592 and IC 4601 are both in close proximity to nu Scorpii, the star which forms the 'eye' of the horse-head shape of IC 4592.

NGC 6121 (M4) is a tightly packed ball of 100,000 stars. It was formed when the Universe was just a billion years of age.

NGC 6475 (M7) is a 200 million year old open cluster which spans 25 light years. It contains over 100 stars and is quite prominent. This open cluster was known to Ptolemy in 130 AD and has been named Ptolemy's Cluster in his honour.

NGC 6334 is a red emission nebula better known as the Cat's Paw Nebula. If you look closely, you'll see why!

NGC 6302 is a planetary nebula called the Butterfly Nebula. It has also been called 'Barnard', but it's the insect moniker that stuck. Its central dying star is thought to have a surface temperature of a quarter of a million degrees centigrade. The rate of gas ejection is 400km per second!

NGC 6388 is a globular cluster which was discovered in 1826 by Scottish astronomer James Dunlop (1793 - 1848) when he was working in Parramatta, New South Wales, Australia.

NGC Table

CatalogueNameTypeBrightness (m)Distance
(light years)
Remarks
NGC 6121M4Globular cluster+5.67,20013 billion years old
NGC 6405M6Open cluster+4.21,600The Butterfly Cluster
NGC 6475M7Open cluster+3.3800Ptolemy's Cluster
NGC 6093M80Globular cluster+7.332,60095 light years across
NGC 6231Caldwell 76Open cluster+2.66,000100+ stars
NGC 6388Dun 457Globular cluster+6.732,600Discovered in 1826 by James Dunlop
NGC 6453GC 4336Globular cluster+9.931,300Discovered in 1837 by John Herschel
NGC 6334Cat's Paw NebulaEmission nebula+155,500Diffuse
NGC 6302Bug (Barnard) NebulaPlanetary nebula+134,000Ejection rate 400km/sec

Meteor Showers

The space debris which creates a meteor shower comes from the tail of a comet, as the Earth crosses where the comet passed previously on its own orbit. Imagine a trail of breadcrumbs, or sawdust like that used in hashing.

There are three meteor showers associated with this constellation, none of them are very prominent.

  • Alpha Scorpiids: 20 April to 19 May with the peak around 3 May.
  • Chi Scorpiids: 6 May to 2 July, maxim between 28 May and 5 June.
  • Omega Scorpiids: 19 May to 11 July, peaking between 3-6 June.

Extrasolar Planets in Scorpius

There have been many extrasolar planetary systems found in the constellation Scorpius. Figures given in the table below are the length of the planet's orbital period around its parent star, which we know of as a year. The mass of the extrasolar planet is compared to that of Jupiter, our Solar System's largest planet, known by astronomers as the 'Jovian scale'.

HD 147513 is a yellow main sequence star which lies 42 light years distant. In 2002 a planet in orbit around it was discovered by the radial velocity method. HD 147513 b is a gas giant with an orbit so eccentric the surface temperature ranges must be extreme.

NGC 6121 contains a pulsar, PSR B1620-26 which has a white dwarf companion star, B1620-26B. A third object was discovered in 1993, but with its mass being so low it was obviously a planet, not another star. B1620-26 b is its official designation, but this has flown in the face of the previous nomenclature, with some researchers believing it should be described as B1620-26AB b due to the fact that the planet orbits both stars. Because it is the oldest-known extrasolar planet discovered so far, the whole system is over 12 billion years of age, it has been affectionately nicknamed 'Methuselah' after the Biblical character. At 12,400 light years distant, it's also the furthest away. An interesting graphical explanation of the planet's remarkable history has been drawn up by Space.com.

OGLE-2005-BLG-390L b (or OGLE-05-390L b) is a rocky/ice world approximately five Earth mass. It's too far out from its star (a red dwarf, smaller and cooler than our Sun) to support life.

WASP-17 b was discovered in 2009 and a remarkable feature is its orbit, which is the opposite direction to the spin of its star. The planet is a gas giant, half the mass of Jupiter but twice its size.

Red dwarf GJ 667 C, also known as Gliese 667 C, is a member of a triple star system just 22 light years from our Sun. It has at least six planets, all of which are terrestrial worlds. Three of the confirmed discoveries lie within that system's habitable zone.

Extrasolar Planets Table

Star name or
catalogue number
Planet
catalogue number
Planet mass
(Jovian scale)
Orbital period
(Earth days or AU)
Year of discoveryComments
PSR B1620-26B1620-26 b2.536,5251994Orbits two stars
HD 147513HD 147513 b1.05402003Eccentric orbit
HD 159868HD 159868 b1.79862007Gas giant
HD 153950HD 153950 b2.73499.42008Superjovian
HD 145377HD 145377 b5.76103.952008Superjovian
OGLE-2005-BLG-071LOGLE-2005-BLG-071L b0.92,9002005Gas giant
OGLE-2005-BLG-390LOGLE-2005-BLG-390L b0.0173,5002005Orbiting red dwarf
OGLE-2007-BLG-368LOGLE-2007-BLG-368L b0.0693.3AU2008cold Neptune
MOA-2008-BLG-310LMOA-2008-BLG-310L b0.231.25AU2009Gas giant
HD 162020HD 162020 b13.78.42002Possible brown dwarf
WASP-17WASP-17 b0.53.72009Hot gas giant; orbits backwards
GJ 667CGJ 667C b6-12 Earth mass7.22009Hot terrestrial
GJ 667CGJ 667C c4-8 Earth mass28.12011Hot terrestrial
GJ 667CGJ 667C d5-10 Earth mass92.12013Super-Earth
GJ 667CGJ 667C e2.7-5.4 Earth mass62.22013Super-Earth
GJ 667CGJ 667C f2-4 Earth mass39.12013Super-Earth
GJ 667CGJ 667C g4.4-8.8 Earth mass2512013Super-Earth
HIP 79431HIP 79431 b2.1111.72010Superjovian
HIP 78530HIP 78530 b23710AU2011Brown dwarf

The Zodiac

The constellation Scorpius is a member of the zodiac; one of the 13 which the Sun appears to pass through over the course of a year. Yes, 13. When the IAU redrew the constellation borders it was found there were 13 constellations that the Sun was passing though. Precession (the wobble of the Earth upon its axis) has shifted the timings somewhat, moving the points at which the equinoxes occur to a different place, and point to other north/south pole stars. Rather than upset astrologers by asking them to change their dates for their horoscopes to bring them into line, astrological predictions have carried on as before, with no discernible difference.

They probably wouldn't want to recognise 13 zodiacal constellations anyway, as some people deem that an unlucky number. Western astrologers like to profess that the Sun passes through the sign of the scorpion between 24 October and 22 November, and assign certain traits to the people born between these dates. Astronomers could tell you that the Sun passes through Scorpius so quickly you'd barely notice, as it's just a week: 23 November to 30 November give or take a day depending upon whether the year is 'leap' or not.

As the zodiac has already been mentioned, it's reasonable to include some famous people who consider themselves born under the star sign Scorpio:

What About Elvis, you say?

In addition to Western astrology, there's also Vedic astrology, which calculates possibilities from the position of the heavenly bodies at birth and the length of time of each dasha (the Sun = 6 years; Venus = 20 years, etc) can calculate life-changing events. Take Elvis Presley, for instance, his dashas and bhuktis (sub-dashas) clearly mark all the important events of his life including his fabulous voice and magnetic personality. With the Vedic Scorpio Ascendant for Elvis falling within the house of sex appeal, he was always going to charm the birds off the trees even if he'd ended up a roadsweeper.

Scorpius in Modern Culture

  • The Scorpions are a German rock band, famed for their ballad 'Wind of Change'.

  • Scorpio is the depraved serial killer who went ahead and made Clint Eastwood's day in the movie Dirty Harry, and also the name of Simpsons character Hank Scorpio.

  • A recurring cast member in Farscape was a half-Sebacean, half-Scarran alien 'Peacekeeper' called Scorpius. The product of an experiment, Scorpius alternated from being the villain trying to bump off the hero John Crichton, to converting to the good-guys side. Scorpius (and his alter-ego 'Harvey' who lived only in Crichton's consciousness) was played by Wayne Pygram for all four seasons.

1Current IAU guidelines use a plus sign (+) for northern constellations and a minus sign (−) for southern ones.2Various other spellings include Aesculapius and Asklepios.3A light year is the distance light travels in one year, roughly 5.88 trillion miles or 9.46 trillion km.4Diana and Camilla.

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