Aquarius

Aquarius

Constellation
List of stars in Aquarius
Abbreviation	Aqr
Genitive	Aquarii
Pronunciation	/əˈkwɛəriəs/, genitive /əˈkwɛəriaɪ/
Symbolism	the Water-Bearer[1]
Right ascension	23 h
Declination	−15°
Quadrant	SQ4
Area	980[2][1] sq. deg. (10thUNIQ1a3980e168741601-nowiki-0000000A-QINU2UNIQ1a3980e168741601-nowiki-0000000B-QINU)
Main stars	10, 22
Bayer/Flamsteed stars	97
Stars with planets	11
Stars brighter than 3.00m	2[2]
Stars within 10.00 pc (32.62 ly)	7
Brightest star	β Aqr (Sadalsuud) (2.91[2]m)
Nearest star	EZ Aqr (11.27 ly, 3.45 pc)
Messier objects	3
Meteor showers	March Aquariids Eta Aquariids[3] Delta Aquariids[3] Iota Aquariids[3]
Bordering constellations	Pisces Pegasus Equuleus Delphinus Aquila Capricornus Piscis Austrinus Sculptor Cetus[2]
Visible at latitudes between +65° and −90°. Best visible at 21:00 (9 p.m.) during the month of October.

Aquarius ( /əˈkwɛəriəs/) is a constellation of the zodiac, situated between Capricornus and Pisces. Its name is Latin for "water-bearer" or "cup-bearer", and its symbol is (Unicode ♒), a representation of water.

Aquarius is one of the oldest of the recognized constellations along the zodiac (the sun's apparent path).^[4] It was one of the 48 constellations listed by the 2nd century AD astronomer Ptolemy, and it remains one of the 88 modern constellations. It is found in a region often called the Sea due to its profusion of constellations with watery associations such as Cetus the whale, Pisces the fish and Eridanus the river.^[2]

History and mythology

Aquarius is identified as GU.LA "The Great One" in the Babylonian star catalogues and represents the god Ea himself, who is commonly depicted holding an overflowing vase. The Babylonian star-figure appears on entitlement stones and cylinder seals from the second millennium. It contained the winter solstice in the Early Bronze Age.^[5] In Old Babylonian astronomy, Ea was the ruler of the southernmost quarter of the Sun's path, the "Way of Ea", corresponding to the period of 45 days on either side of winter solstice. Aquarius was also associated with the destructive floods that the Babylonians regularly experienced, and thus was negatively connoted.^[2] In the Greek tradition, the constellation became represented as simply a single vase from which a stream poured down to Piscis Austrinus. The name in the Hindu zodiac is likewise kumbha "water-pitcher", showing that the zodiac reached India via Greek intermediaries.^[4]

In Greek mythology, Aquarius is sometimes associated with Deucalion, the figure who built a ship with his wife Pyrrha to survive an imminent flood. They sailed for nine days before washing ashore on Mount Parnassus.^[2] Aquarius is also sometimes identified with Ganymede, a youth in Greek mythology who was taken to Mount Olympus by Zeus to act as cup-bearer to the gods.^[1][3]

Notable features

The constellation Aquarius as it can be seen by the naked eye. AlltheSky.com

Aquarius (left) and Capricornus (right). The brightest star of the picture is Jupiter.

Stars and planetary systems

Despite both its prominent position on the zodiac and its large size, Aquarius has no particularly bright stars, with its 4 brightest stars less than magnitude 2.^[1] However, recent research has shown that there are several stars lying within its borders that possess planetary systems.

• α Aquarii, also known as Sadalmelik, is a G2 spectral class star^[6] (yellow supergiant) named in Arabic for the phrase "the lucky stars of the king".^[3] It is the second brightest star in Aquarius with a magnitude of 2.96^[6] (though it has an absolute magnitude of -4.5)^[1] and is 523 light-years from Earth.^[7] It has a luminosity of 5250 L_☉.^[1]
• β Aquarii, sometimes called Sadalsuud, is a G0 spectral class star^[6] (yellow supergiant) named for the Arabic phrase meaning "luckiest of the lucky stars".^[3] It is the brightest star in Aquarius with an apparent magnitude of 2.91^[6] and an absolute magnitude of -4.5. Sadalsuud is 537 light-years from Earth^[8] and has a luminosity of 5250 L_☉, the same as α Aquarii.^[1]
• γ Aquarii, also called Sadachbia, is a blue-white^[3] A0 spectral class star of magnitude 3.84 and a luminosity of 50 L_☉^[1] that is 163 light years away.^[9] It has a luminosity of 50 L_☉.^[1]
• δ Aquarii, also known as Scheat^[1] or Skat,^[3] is a blue-white A2 spectral class star of magnitude 3.27 and luminosity of 105 L_☉.^[1]
• ε Aquarii, also known as Albali, is a blue-white A1 spectral class star with an apparent magnitude of 3.77, an absolute magnitude of 1.2, and a luminosity of 28 L_☉.^[3][1]
• ζ Aquarii is an F2 spectral class double star; both stars are white.^[3] Overall, it appears to be of magnitude 3.6 and luminosity of 50 L_☉. The primary has a magnitude of 4.53 and the secondary a magnitude of 4.31, but both have an absolute magnitude of 0.6.^[1] Its orbital period is 760 years; the two components are currently moving farther apart.^[3]
• θ Aquarii, sometimes called Ancha, is a G8 spectral class star with an apparent magnitude of 4.16 and an absolute magnitude of 1.4.^[1]
• λ Aquarii is an M2 spectral class star of magnitude 3.74 and luminosity of 120 L_☉.^[1]
• ξ Aquarii, also called Bunda, is an A7 spectral class star with an apparent magnitude of 4.69 and an absolute magnitude of 2.4.^[1]
• π Aquarii, also called Seat, is a B0 spectral class star with an apparent magnitude of 4.66 and an absolute magnitude of -4.1.^[1]
• Gliese 876, one of the nearest stars to Earth at a distance of 15 light-years,^[10] was the first red dwarf star to be found to possess a planetary system. It is orbited by four planets, including one terrestrial planet 6.6 times the mass of Earth. The planets vary in orbital period from 2 days to 124 days.^[11]
• 91 Aquarii is an orange giant star orbited by one planet, 91 Aquarii b. The planet's mass is 2.9 times the mass of Jupiter, and its orbital period is 182 days.^[12]
• Gliese 849 is a red dwarf star orbited by the first known long-period Jupiter-like planet, Gliese 849 b. The planet's mass is 0.99 times that of Jupiter and its orbital period is 1,852 days.^[13]

Deep sky objects

Because of its position away from the galactic plane, the majority of deep-sky objects in Aquarius are galaxies, globular clusters, and planetary nebulae.^[2] Aquarius contains three deep sky objects that are in the Messier catalog: the globular clusters Messier 2, Messier 72, and the open cluster Messier 73. Two well-known planetary nebulae are also located in Aquarius: the Saturn Nebula (NGC 7009), to the eastwest of μ Aquarii; and the famous Helix Nebula (NGC 7293), southwest of δ Aquarii.

• M2, also catalogued as NGC 7089, is an incredibly rich globular cluster located approximately 37,000 light-years from Earth. At magnitude 6.5, it is viewable in small-aperture instruments, but a 100 mm aperture telescope is needed to resolve any stars.^[3]

• M72, also catalogued as NGC 6981, is a small 9^th magnitude globular cluster located approximately 56,000 light-years from Earth.^[3]

• M73, also catalogued as NGC 6994, is an open cluster with highly disputed status.

• NGC 7009, also known as the Saturn Nebula, is an 8^th magnitude planetary nebula located 3,000 light-years from Earth. It was given its moniker by the 19^th century astronomer Lord Rosse for its resemblance to the planet Saturn in a telescope; it has faint protrusions on either side that resemble Saturn's rings. It appears blue-green in a telescope and has a central star of magnitude 11.3.^[3]

• NGC 7293, also known as the Helix Nebula, is the closest planetary nebula to Earth at a distance of 300 light-years. It covers 0.25 square degrees, making it also the largest planetary nebula as seen from Earth. However, because it is so large, it is only viewable as a very faint object.^[3]

Meteor showers

There are three major meteor showers with radiants in Aquarius: the Eta Aquariids, the Delta Aquariids, and the Iota Aquariids.

• The Eta Aquariids is the strongest meteor shower radiating from Aquarius. It peaks between May 5 and May 6 with a rate of approximately 35 meteors per hour.^[3]
• The Delta Aquariids is a double radiant meteor shower that peaks first on July 29 and second on August 6. The first radiant is located in the south of the constellation, while the second radiant is located in the northern circlet of Pisces asterism. The southern radiant's peak rate is about 20 meteors per hour, while the northern radiant's peak rate is about 10 meteors per hour.^[3]
• The Iota Aquariids is a fairly weak meteor shower that peaks on August 6 with a rate of approximately 8 meteors per hour.^[3]

Illustrations

Aquarius pours water from a jar into the mouth of the southern fish, as depicted in Urania's Mirror, a set of constellation cards published in London c.1825

In illustrations, the brightest stars of Aquarius are represented as the figure of a man, while the fainter naked eye stars are represented as a vessel from which is pouring a stream of water. The water flows southwards into the mouth of the southern fish, Piscis Austrinus.

Equivalents

In Chinese astronomy, the stars of the constellation Aquarius are part of the The Black Tortoise of the North (北方玄武, Běi Fāng Xuán Wǔ).^{[citation needed]}

Namesakes

USS Aquarius (AKA-16), was a United States Navy ship named after the constellation.

Astrology

As of 2002^[update], the Sun appears in the constellation Aquarius from February 16 to March 11. In tropical astrology, the Sun is considered to be in the sign Aquarius from January 20 to February 19, and in sidereal astrology, from February 15 to March 14.

Aquarius is also associated with the Age of Aquarius, a concept popular in 1960s counterculture. Despite this prominence, the Age of Aquarius will not dawn until the year 2597, as an astrological age does not begin until the Sun is in a particular constellation on the vernal equinox.^[2][3]

Notes

References

• 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.
• H. A. Rey, The Stars—A New Way To See Them. Enlarged World-Wide Edition. Houghton Mifflin, Boston, 1997. ISBN 0-395-24830-2.

Attribution

•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Aquarius". Encyclopædia Britannica (11th ed.). Cambridge University Press. http://www.1911encyclopedia.com/Aquarius. 

External links

Wikimedia Commons has media related to: Aquarius (constellation) (category)

• The Deep Photographic Guide to the Constellations: Aquarius
• NightSkyInfo.com: Constellation Aquarius
• WIKISKY.ORG: Aquarius constellation
• Star Tales – Aquarius

v t e The Zodiac
Astrology | Signs of the Zodiac
Aries													Taurus													Gemini													Cancer													Leo													Virgo													Libra													Scorpio													Sagittarius													Capricorn													Aquarius													Pisces
Astronomy | Constellations of the Ecliptic
Aries												Taurus												Gemini												Cancer												Leo												Virgo												Libra												Scorpius												Ophiuchus												Sagittarius												Capricornus												Aquarius												Pisces
See also: Ecliptic coordinates Precession of the equinoxes 13-sign zodiac Zodiacal light

Coordinates: 23^h 00^m 00^s, −15° 00′ 00″