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Constellations: Aries 'the Ram'

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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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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
Name:Aries
Genitive:Arietis
Short form:Ari
Area:441 sq deg
Co-ordinates1:Right Ascension 03h, Declination +20°
Zodiac:Yes
Origin:Ancient

The constellation of Aries the Ram is located in the northern hemisphere and is on the ecliptic2 making it one of the zodiacal signs. For observers in the northern hemisphere it is at its most prominent in the winter months. Aries is an ancient constellation passed down by Ptolemy as one of the 48 recorded in his Almagest. It is bounded by the zodiacal constellations of Taurus 'the Bull' on the one side and Pisces 'the Fish' on the other.

The stars that form the constellation are not particularly bright, but it is easy enough to identify by the prominent constellations that surround it. The Pleiades star cluster in Taurus, probably one of the most noticeable features in the northern sky, lies almost on the border with Aries. To Aries's north is the prominent triangle of stars that make up the main feature of Triangulum.

Mythology and History

Aries has figured large in ancient lore, containing as it did the First Point of Aries. Its significance was that the Spring Equinox3 occurred in Aries for some two thousand years BC. Due to precession, the wobble in the Earth's axis, the equinox has now moved along the ecliptic into the neighbouring constellation of Pisces.

Today, our appreciation of Aries is from Greek legend and the saga of Jason and the Argonauts. Aries represents the flying ram on which the children of the King of Thebes, Phryxus and his sister Helle, fled from their wicked stepmother Ino, who was plotting to have them killed. During their flight Helle died when she lost her grip and fell into the sea. The place where she fell, now part of Turkey, was named Hellespont4 after her. However, Phryxus hung on, completed the journey, and sacrificed the ram when he reached safety. Whether this seemingly ungrateful act upon the unfortunate beast was in thanks for his deliverance, or was retribution for dropping his sister, is not recorded.

Phryxus placed the ram's fleece in the branches of an oak tree in the sacred grove of Ares5 where it turned to gold. It was this Golden Fleece that inspired Jason to undertake his quest to retrieve it.

Stars

The scientific star names are simple to understand (if you know your Greek alphabet). For example, 'alpha Arietis' means it is the brightest star in the constellation Aries. The next brightest is designated 'beta' etc. This is known as the 'Bayer designation'. Some stars have proper names as well, for example, alpha Arietis is Hamal. Other stars are known by their catalogue number.

Principal Stars of Aries

The three principal stars alpha, beta and gamma Arietis represent the head of the Ram, and all three have Arabic names. Early Babylonian lore had the principal star, alpha Arietis, as the head of the sheep and the Arabic name 'al Ras al Hamal', means that literally, but is now shortened in common usage to Hamal.

Beta Arietis is Sharatan, 'the Sign'. This refers to beta being the closest star to the position of the Vernal Equinox on the ecliptic at about the time the stars were named, and its appearance with gamma heralds spring, the beginning of the seasons.

Gamma Arietis is Mesarthim, also called 'the First Star in Aries' - somewhat later becoming the closest star to the equinoctial point. Delta Arietis carries the name Botein, meaning 'the belly', although this possibly refers to a previous configuration of the asterism as it now denotes the tail of the Ram.

Hamal is the brightest star in the constellation at magnitude +2.0 while Sharatan is over half a magnitude dimmer. Their companion Mesarthim is a double star and easily separated with a small telescope. They are almost a matched pair of white stars with magnitudes of +4.64 and +4.70. Combined, to the naked eye they appear to be brighter at +3.9. They were first separated by the 17th Century astronomer Robert Hooke in 1664.

Star Table

StarDesignationNameMagnitudeDistance
(light years)
Remarks
α Arialpha ArietisHamal+2.0075Single K class
β Aribeta ArietisSharatan+2.6052Single A class
γ Arigamma ArietisMesarthim+3.9075Double +4.64 and +4.60
δ Aridelta ArietisBotein+4.35168Single K class

Star Clusters and Nebulae

A small grouping of fourth and fifth magnitude stars at the northern side of the constellation show as a dim cluster. They include 33, 35 and 39 Arietis while 41 Arietis is the brightest of the group. This cluster has been known under various incarnations, variously Vespa 'the Wasp', Apis 'the Bee', the Fleur de Lis and latterly as Musca Borealis, 'the Northern Fly'. Ptolemy included it in the Ram, but all those descriptions have now passed into history.

A number of galaxies can be seen within the confines of Aries but they all are faint and require the use of larger telescopes to observe. Only one, the spiral galaxy NGC 772, at an apparent magnitude of +9.8, is possibly within range of amateur equipment when viewing conditions are good.

Meteor Shower

A heavy meteor shower takes its name from Aries, occurring between 22 May and 2 July, with the peak rate of up to 60 per hour on 8 June. Although the Arietids is a major shower, most of the fireballs will pass unseen because Aries rises only an hour or so before the Sun, meaning many will whizz through during daylight hours. Some of these so-called 'Earthgrazers' may be seen just before dawn shooting upwards from the horizon, and can be of several seconds duration.

Meteor showers are the result of the Earth passing through the debris from the trail of a comet which burns up in the Earth's atmosphere. The origin of this particular path of debris is uncertain, but is thought to have been laid by the one kilometre wide asteroid  Icarus, whose orbit crosses that of the Earth and swings in closer to the Sun than the planet Mercury.

Extrasolar Planets in Aries

Some stars within Aries have been found to possibly have planets in orbit around them. HD 20367 shows one observed planet, HD 20367 b, with a mass just a little larger than that of our own Solar System's Jupiter, and orbiting its star in a period of 500 Earth days.

HD 12661 has two planets. HD 12661 b, the largest and closest to its star, is some 2.35 times the mass of Jupiter. The other, HD 12661 c, is nearly twice Jupiter's mass but orbits much further out at almost three times the distance.

HIP 14810 is a dwarf star with three planets. HIP 14810 b, the innermost, is a 'Hot Jupiter'. It is almost four times Jupiter's mass and orbits very close to its star, closer in fact than our own Mercury is to our Sun. The second planet HIP 14810 c is a little smaller than Jupiter, but is much further out. The third planet, HIP 14810 d is a gas giant half Jupiter's mass, orbiting approximately 1.9AU (about twice as far as the Earth's orbit around our Sun).

30 Ari B b is a superjovian world orbiting a yellow dwarf star at an average 1AU.

Alf Ari b (Hamal) is a superjovian world orbiting a K-class giant star in 380 days.

HD 14067 b is a superjovian world orbiting a yellow dwarf star at 3.4AU.

WASP-11b/HAT-P-10b is a hot gas giant orbiting an orange dwarf star in just under four days.

HAT-P-25 b is a hot gas giant orbiting a sun-like star in just under four days.

HAT-P-52 b is a hot gas giant orbiting a sun-like star in less than three days.

Astrology

As already mentioned, Aries is a zodiacal sign (in fact it's the first). Astrology is an ancient science which was quite a lucrative way to earn a living for astronomers with a vivid imagination and a talent for flattering a gullible wealthy patron. Nowadays the 12 astrological signs (omitting Ophiuchus because 13 is considered unlucky by some) are written about in popular magazines and tabloid newspapers to entertain people who are amused by what 'astrologers' type up about 'their sign', which may or may not be the sign they were actually born under. Interest in astrology is quite a popular pastime, and a lot of people exchange 'star signs' as an ice-breaker or as a chat-up line on the pretext of finding out if they are romantically compatible.

Aries popularly covers the dates 21 March to 20 April. However, since these dates were set, the Sun and the Earth have very inconveniently (for astrologers) shifted somewhat6, but the forecasts carry on as before with no loss of accuracy in the predictions.

Aries People

Aries people (as well as fellow Leos and Sagittarians) are considered 'Fire' element types, and they are 'Cardinal' along with their Cancerian, Libran and Capricornian counterparts, but only an Aries person is Fire/Cardinal. They are considered leaders rather than sheep, and can have a fiery temper when roused. If slighted, they would likely harbour thoughts of revenge rather than turn the other cheek.

Just a few famous Aries people with their own Edited Guide Entries you might like to read about include: Brian Clough OBE (21 March); Ayrton Senna (21 March), Josef Locke (23 March), Donald Campbell (23 March), Sir Elton John (25 March), Diana Ross (26 March), Quentin Tarantino (27 March), Mariah Carey (27 March), Eric Clapton (30 March) and Marvin Gaye (2 April).

1Current IAU guidelines use a plus sign (+) for northern constellations and a minus sign (−) for southern ones.2The apparent path of the Sun through the sky.3The point on the ecliptic at which the Sun appears to cross over from south to north.4Now called the Dardanelles Straights.5Ares was the Greek god of war. The Roman name for him was Mars.6Today the Sun passes through the sign of Aries between 19 April and 13 May.

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