Constellations: Capricornus 'the Sea Goat' Content from the guide to life, the universe and everything

Constellations: Capricornus 'the Sea Goat'

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The shield of the Science, Mathematics and Engineering faculty of the h2g2 University.Constellations: Overview | Andromeda | Antlia | Apus | Aquarius | Aquila | Ara | Aries | Auriga | Boötes | Caelum
Camelopardalis | Cancer | Canes Venatici | Canis Major | Canis Minor | Capricornus | Carina | Cassiopeia | Centaurus
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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
Capricornus 'the Sea Goat'.
As it was in the days of Noah,
When men ignored the signs
It's that way again my friend;
Don't pay it any mind!
O Capricornus, thou with curly tail-
Can you see behind the veil?

  - an h2g2 Researcher

Name:Capricornus (Latin: 'sea goat')
Genitive:Capricorni
Short Form:Cap
Area:414 sq deg
Co-ordinates1: Right Ascension 21h, Declination −20°
Zodiac:Yes
Origin:Ancient

In the autumn sky, to the upper right of Piscis Austrinus, between the constellations  Aquarius and Sagittarius, stands Capricornus the Sea Goat - a male deity that was turned into a hybrid creature. Star names suggest that this goat was associated with one used as a sacrificial offering at the start of winter. Two thousand years ago, the sun was in this constellation during the winter solstice, so the southernmost point at which the sun can be directly overhead at noon is known as the Tropic of Capricorn2.

Neptune and Neptune Returns

In the mid-1800s, men like Jean-Baptiste Joseph Delambre (1749 - 1822) speculated about the position of an unknown planet causing slight deviations in the orbit of Uranus. Mathematicians John Couch Adams (1819 - 1892), and Urbain Jean Joseph Le Verrier (1811 - 1877) calculated where it should be. Le Verrier gave his calculations to a German astronomer, Johann Galle (1812 - 1910), and in September of 1846, Galle found the planet a short distance from Mu Capricorni, just to the left of where Le Verrier had predicted. One hundred and sixty-two years later, the 'new' planet, Neptune, is once again in the tail of Capricornus, not far from where it was first seen.

Mythology

While Capricornus literally means 'male goat' or 'mountain goat', the constellation is usually depicted as a 'sea goat', with the upper body of a horned goat and the lower body of a fish. There are various explanations for this image and its connection with the asterism. Capricornus is associated with an area of the sky called the 'Sea', in which many of the more aquatic constellations, such as Aquarius and Pisces, can be found.

Pan

Greek myth suggests that Pan, a minor god, was on the banks of the Nile when the monster Typhon suddenly appeared. When Pan jumped into the water to hide, his lower half became a fish. The part of his body above the waterline became a horned goat - though his usual figure was that of a man above the waist and a goat below. This so amused Zeus, the king of the gods, that he created the constellation Capricornus to remember the event.

Another version states that Pan helped Zeus in his battle against the Titans by finding the Conchas, large shells that were the 'horns of the sea', whose trumpet-like noise caused the Titans to run away in fear. Zeus honoured him by placing Capricornus in the heavens, an image meant to represent both horns and water.

Aegipan

Aegipan or Goat-Pan is another Greek god who may or may not be identical with Pan in his fish-tailed goat form - or might be his father. Together with Hermes, the messenger of the gods, he helped Zeus fight Typhon by retrieving Zeus' stolen sinews through use of a plan involving a broken lyre, a prince, and a flock of sheep. Zeus recognised his efforts by placing an image of Aegipan in the heavens.

Other Legends

The constellation Capricornus also represented the Augaean Stables, accumulating all the sin and uncleanliness accumulated during the year which were to be 'washed out' at the solstice - perhaps by Aquarius pouring out his river, reflecting one of the Twelve Labours of Hercules.

To the ancient Sumerians and Babylonians, Capricornus was associated with the god Enki or Ea, who brought civilisation from the sea and was symbolised by a goat and a fish, later combined to make the 'sea goat'.

Stars

About 400 years ago, Johann Bayer (1572 – 1625) first started putting Greek letters to the brighter stars. Below, you will find Bayer designations, the lowercase Greek letters associated with the stars. Following Bayer's system, the brightest star would be designated as alpha, but here, delta is brightest - this may be due to inaccurate measurements, or to variations in the stars' light intensity.

   Star  Bayer
Designation
NameCatalogue NoBrightness (m)Distance
(light years)
Spectral
Classification
δ Cap deltaDeneb AlgiediHR 8322+2.8739Mainly A53
β Cap betaDahibHR 7776+3.08328A5
α2 Cap alpha2Secunda GeidiHR 7754+3.57109G3
α1 Capalpha1Prima GeidiHR 7747+4.24663G8
γ CapgammaNashiraHR 8278+3.68139F2
θ CapthetaDorsumHR 8075+4.19156F0
ε CapepsilonCastraHR 8260+4.68663B5
ν CapnuAl ShatHR 7773+4.76272F0
ρ CaprhoBosHR 7822+4.7899F1
μ Capmumu CapHR 8351+5.0890F1
π CappiOculusHR 7814+5.25665B8

Deep Sky

Charles Messier (1730 – 1817) wrote the Messier Tables, a first attempt at cataloguing astronomical objects, which contained a total of 110 entries. The New General Catalogue, compiled by John Louis Emil Dreyer (1852 - 1926), was first published by the Royal Astronomical Society in the late 19th Century. It was expanded to include two Index Catalogues. This list of star clusters, nebulae and galaxies was revised again in 1973, and is continually updated by the NGC/IC Project. Below is a list of the deep space objects within Capricornus with their Messier (M), New General Catalogue (NGC) and Index Catalogue (IC) designations.

Catalogue NoType Brightness (m)Distance
M30
(NGC7099)
Globular
cluster
+7.226,100 ly4
NGC6907 Galaxy+11.344 Mly5
NGC6908 Galaxy+14.643 Mly
NGC7103 Galaxy+14.3412 Mly
NGC7104 Galaxy+13.8395 Mly
IC1408 Galaxy+15.0220 Mly
MS2137.3-2353Galactic
Cluster
+18.53.5 Gly6

Long Ago and Far Away

Since light does not reach us instantly, just travels very fast, scientists using tools like the Chandra telescope look far back into the past of the universe. One galactic cluster labelled MS2173.3-2353 is being observed with light that has travelled 3.5×109 years to reach us. Using such information, workers on the Einstein Medium Sensitivity Survey are making new estimates of the total mass and energy (including dark energy) of the cosmos, and their effect on the expansion of the Universe.

Extrasolar Planets

The first planetary system to have been found in this constellation, 151 light years from Earth, orbits the star HD 202206. The innermost planet, HD 202206 b, circles at a distance of 0.83 AU7 and has a mass 17.4 times that of Jupiter which leads to the suspicion that it is not a planet at all but rather a brown dwarf8 star. The outermost, HD 202206 c, circles at a distance of 2.4 AU and has a mass of 2.44 times that of Jupiter. Neither planet is remotely Earth-like, so the chance of extraterrestrial life there is considered slim. Another star with an attendant is yellow dwarf HD 204313; its planet HD 204313 b, a gas giant, takes over five years to orbit the star, and it was detected in August 2009. In 2010 a gas giant planet was discovered in orbit around Gliese 785, with a second being detected in 2011.

Meteor Showers

Meteor showers are caused by very small objects (often just specks of dust) which burn up from friction with the air in the upper reaches of the Earth's atmosphere. They usually result from the trails of comets that have crossed the Earth's orbit, leaving debris behind them. Several of them cross Earth's orbit in the constellation Capricornus, and are thus associated with the constellation.

Name Dates Peak
Alpha Capricornids 3 July - 15 August 1 August
Chi Capricornids 29 January - 28 February 13 February
Sigma Capricornids 18 June - 30 July (23 June) 10 July
Tau Capricornids 2 June - 29 July 12 July
October Capricornids 20 September - 14 October 3 October
Capricornids-Sagittariids 13 January - 28 February 2 February
1Current IAU guidelines use a plus sign (+) for northern constellations and a minus sign (−) for southern ones.2The Tropic of Capricorn, at 23° 26' 22" S, is of the five major circles of latitude, the others being, from north to south: the Arctic Circle (66° 33' 38" N), the Tropic of Cancer (23° 26' 22" N), the Equator (0° latitude), and the Antarctic Circle (66° 33' 38" S).3This system is composed of four stars gravitationally bound. The main star is type A5.4A light year is just under ten trillion kilometres, defined as the distance light travels in a vacuum in one Julian year of 365.25 days.5One megalight-year is equal to one million light years.6 The gigalight-year is equal to one billion (short scale) or 109 light years. It is the largest unit for measuring distance commonly used.7An Astronomical Unit is about 150 million kilometres, defined as the distance from the Earth to the Sun.8A sub-stellar object that isn't massive enough for hydrogen-burning nuclear fusion, but shares other properties with stars.

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