Aquarius constellation is located in the southern hemisphere. It is one of the 12 zodiac constellations. The constellation’s name means ‘the water-bearer’ (or ‘cup-bearer’) in Latin and its symbol, ♒, represents water. Aquarius lies in the region of the sky which is sometimes referred to as the Sea, because it contains a number of other constellations with names associated with water; Pisces (the fish), Eridanus (the river), and Cetus (the whale), among others. Aquarius is the 10th largest constellation in the sky, occupying an area of 980 square degrees. It is located in the fourth quadrant of the southern hemisphere (SQ4) and can be seen at latitudes between +65° and -90°. Constellations bordering Aquarius are Aquila, Capricornus, Cetus, Delphinus, Equuleus, Pegasus, Pisces, Piscis Austrinus, and Sculptor.
[http://www.constellation-guide.com/constellation-list/aquarius-constellation/]
Aquarius is a summer constellation, situated between Capricornus and Pisces in the zodiac. Under the Tropical Zodiac, the sun is in Aquarius typically between January 20 and February 18, while under the Sidereal Zodiac, the sun is in Aquarius from approximately February 15 to March 14, depending on leap year.
[https://en.wikipedia.org/wiki/Aquarius_(astrology)]
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.
Johannes Hevelius’ Aquarius from Uranographia (1690)
[http://chandra.harvard.edu/photo/constellations/aquarius.html]
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. 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.
In Ancient Egypt, Aquarius was associated with the annual flood of the Nile; the banks were said to flood when Aquarius put his jar into the river, beginning spring.
In Greek mythology, Aquarius is often identified with beautiful Ganymede, a youth in Greek mythology and the son of Trojan king Tros, who was taken to Mount Olympus by Zeus to act as cup-carrier to the gods. Neighboring Aquila represents the eagle, under Zeus’ command, that snatched the young boy; some versions of the myth indicate that the eagle was in fact Zeus transformed. An alternative version of the tale recounts Ganymede’s kidnapping by the goddess of the dawn, Eos, motivated by her affection for young men; Zeus then stole him from Eos and employed him as cup-bearer.
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.
In Chinese astronomy, the stream of water flowing from the Water Jar was depicted as the ‘Army of Yu-Lin’ (Yu-lin-kiun or Yulinjun). The name ‘Yu-lin’ means ‘feathers and forests,’ referring to the numerous light-footed soldiers from the northern reaches of the empire represented by these faint stars. The constellation’s stars were the most numerous of any Chinese constellation, numbering 45, the majority of which were located in modern Aquarius.
In the first century CE, Ptolemy’s Almagest established the common Western depiction of Aquarius. His water jar, an asterism itself, consists of Gamma, Pi, Eta, and Zeta Aquarii; it pours water in a stream of more than 20 stars terminating with Fomalhaut, now assigned solely to Piscis Austrinus. The water bearer’s head is represented by 5th magnitude 25 Aquarii while his left shoulder is Beta Aquarii; his right shoulder and forearm are represented by Alpha and Gamma Aquarii respectively.
Zodiac constellations Aquarius, Pisces, Aries and Taurus
[http://www.constellation-guide.com/constellation-map/zodiac-constellations/]
[http://astropixels.com/constellations/charts/Aqr.html]
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.
Beta Aquarii is a double star and has the traditional name Sadalsuud, from an Arabic expression ‘al-su‘ūd,’ the ‘luck of lucks.’ Other spellings that are sometimes encountered are Sad es Saud, Sadalsund, and Saad el Sund. In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Nir Saad al Saaoud, which was translated into Latin as Lucida Fortunæ Fortunarum, meaning the brightest of luck of lucks.
Sadalsuud is the brightest star in Aquarius with an apparent magnitude of 2.87 and a stellar classification of G0 Ib. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is located at a distance of about 540 light-years (160 parsecs) from the Earth. The mass of this star is about 6.0 to 6.5 times the mass of the Sun, but it is emitting roughly 2,300 times the Sun’s luminosity implying a radius that is 50 times that of the Sun. It has an estimated age of 60 million years; old enough for a star of this mass to evolve into a supergiant. The estimated effective temperature of the star’s outer envelope is about 5,700 K, giving it the characteristic yellow hue of G-type stars.
X-ray emissions from the corona of this star have been detected using the Chandra X-ray Observatory; among the first such detections of X-rays for a G-type supergiant. A secondary X-ray source discovered near Beta Aquarii probably has an extragalactic origin. This star belongs to a group of three intermediate mass stars with a space velocity that is carrying them perpendicular to the plane of the galaxy. The other members of this grouping are Alpha Aquarii and Eta Pegasi.
[https://en.wikipedia.org/wiki/Beta_Aquarii]
Alpha Aquarii is a single star with the traditional name Sadalmelik, which is derived from the Arabic ‘sa‘d al-malik,’ meaning ‘luck of the king.’ The apparent visual magnitude of 2.94 makes this the second-brightest star in Aquarius. It is located at a distance of roughly 520 light-years (160 parsecs) from Earth.
With an age of 53 million years, this star has evolved into a supergiant with a stellar classification of G2 Ib. It has 6.5 times as much mass as the Sun and has expanded to around 77 times the Sun’s radius. It is radiating 3,000 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 5,210 K. At this heat, the star glows with the yellow hue of a G-type star. Examination of this star with the Chandra X-ray Observatory shows it to be significantly X-ray deficient compared to G-type main sequence stars. This deficit is a common feature of early G-type giant stars.
Sadalmelik has a visual companion, designated CCDM J22058-0019B, with an apparent visual magnitude of approximately 12.2. It is at an angular separation of 110.4 arcseconds from Sadalmelik along a position angle of 40°.
[https://en.wikipedia.org/wiki/Alpha_Aquarii]
Delta Aquarii is the third-brightest star in the constellation Aquarius. It has the traditional name Skat, which has also been used for Beta Pegasi. The apparent visual magnitude is 3.3, which can be seen with the naked eye. The distance to this star is estimated as 160 light-years (49 parsecs) based upon parallax measurements.
The spectrum of Skat matches a stellar classification of A3 V, indicating this is an A-type main sequence star that is generating energy through the nuclear fusion of hydrogen at its core. This star has double the Sun’s mass and a radius 2.4 times as large. It is radiating 26 times the luminosity of the Sun from its outer atmosphere at an effective temperature of around 9,000 K. This heat gives it the characteristic white-hued glow of an A-type star. It has a relatively high rate of rotation, with a projected rotational velocity of 81 km s−1.
Delta Aquarii has been closely examined for a companion, but none has been discovered. Nor does it display a strong signal of excess infrared emission that might indicate the presence of circumstellar matter. Delta Aquarii is a probable stream star member of the Ursa Major Moving Group, which has an estimated age of 500 million years.
The traditional name has generally been thought to derive from the Arabic ‘as-saq,’ which means ‘leg’ or ‘shin;’ however, the medieval forms Scheat, Seat, Sheat suggest it may be instead from the Arabic ‘ši'at,’ ‘wish.’
[https://en.wikipedia.org/wiki/Delta_Aquarii]
Zeta Aquarii has the traditional name Sadaltager (or Altager), from the Arabic ‘sa‘d al-tājir,’ ‘luck of the merchant.’ In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated ‘Achr al Achbiya,’ which was translated into Latin as Postrema Tabernaculorum, meaning the end of luck of the homes (tents). This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and η Aqr (Hydria), were ‘al Aḣbiyah,’ the Tent.
Zeta Aquarii is a binary or possibly a triple star system; it is the central star of the ‘water jar’ asterism in the equatorial constellation of Aquarius. The brighter component, ζ Aquarii A (also called ζ2 Aquarii), is a yellow-white-hued F-type main sequence star with an apparent magnitude of +4.42. Its companion, ζ Aquarii B (also called ζ1 Aquarii), is a yellow-white-hued F-type subgiant with an apparent magnitude of +4.51. The fact that their brightness is so similar makes the pair easy to measure and resolve. The combined apparent visual magnitude of this system is 3.65, which is readily visible to the naked eye. Its distance is around 92 light-years (28 parsecs) from Earth.
ζ Aquarii B is a suspected astrometric binary system with a 25.8 year orbital period and a semimajor axis of 10.8 astronomical units. If this is confirmed, then the smaller companion may be a red dwarf with a classification of M0 V and 40% of the Sun’s mass.
[https://en.wikipedia.org/wiki/Zeta_Aquarii]
R Aquarii
R Aquarii (R Aqr) is a variable star in the constellation Aquarius. It is a symbiotic star believed to contain a white dwarf and a Mira-type variable in a binary system. The orbital period is approximately 44 years. The main Mira-type star is a red giant, and varies in brightness by a factor of several hundred and with a period of slightly more than a year; this variability was discovered by Karl Ludwig Harding in 1810. It has a distance of about 200 parsec, and is one of the nearest symbiotic stars and a well known jet source.
By its gravitational pull, the white dwarf draws in material from the red giant and occasionally ejects some of the surplus in weird loops to form the nebula seen in the previous image. The whole system appears reddened because it is situated in a very dusty region of space, and its blue light is absorbed before reaching us.
The nebula around R Aquarii is also known as Cederblad 211. It is possible that this nebula is the remnant of a nova-like outburst, which may have been observed by Japanese astronomers, in the year 930 AD.
[https://en.wikipedia.org/wiki/R_Aquarii]
Gliese 876
Artist’s impression of Gliese 876 and its two Jupiter-class planets as viewed from a rocky moon
Previously well known as Ross 780, this dim star lies around 15.2 light-years from Sol. It is located in the southeastern part of Constellation Aquarius- north of Skat (Delta Aquarii), east of Tau Aquarii, and south of Hydor (Lambda Aquarii). Like other red dwarf stars, however, it is not visible to the naked eye. The high proper motion of Gliese 876 may have been noticed first by Frank Elmore Ross (1874-1960), who reported on this star in February 1928. However, many astronomers now refer to this star by its designation in the famous Gliese Catalogue of Nearby Stars of Wilhelm Gliese (1915-93).
Gliese 876 is a very cool and dim, main sequence red dwarf (M3.5 V). Compared with our Sun, Sol, this star may have about a third of Sol’s mass, possibly 36 to 39 percent of its diameter, and a bit more than a thousandth of its visual luminosity. However, if all wavelengths such as the much more abundant infrared radiation generated by red dwarf stars are included, the absolute bolometric luminosity of Gliese 876 is estimated to be much greater- 0.012 to to 0.014 Solar. The star is probably around 2.5 times as enriched as Sol in elements heavier than hydrogen and helium based on the abundance of iron relative to hydrogen. It has a rotational period of at least 40 days.
The star is neither young nor elderly. It lacks a detectable, circumstellar dust disk and is chromospherically inactive, which suggests that it is more than one billion years old. However, its space motion is slow, which suggests that Gliese 876 is less than 10 billion years old. Gliese 876 is a variable star with the designation ‘IL Aquarii.’ Some other useful star catalogue designations include: IL Aqr, Gl 876, and Ross 780.
Since this red dwarf star is so cool and dim, an Earth-type rocky planet would have to be located very close to Gliese 876 to be warmed sufficiently to have liquid water at the surface. According to one type of model calculations performed for the NASA Star and Exoplanet Database, the inner edge of Gliese 876’s habitable zone should be located around 0.117 AU from the star, while the outer edge edge lies around 0.228 AUs; however, calculations from another source estimate a slightly more close-orbiting habitable zone between one to two tenths- 0.112 to 0.221 AU - of the Earth-Sun distance, given a bolometric luminosity around 0.0124. Hence, planets ‘b’ and ‘e’ would orbit outside of the the star’s habitable zone, while planets ‘c’ and ‘d’ orbit near the inner and outer edges of the habitable zone, respectively. Although planets c and d are presumed gas giants that would lack a rocky surface, they could have moons with sufficient mass and atmospheres to maintain liquid water on their surfaces.
As of June 22, 2010, astronomers have found four planets in orbit around Gliese 876. Planet ‘b’ was discovered in 1998. It has an estimated mass of around 2.3 Jupiter-masses. It is probably located at an ‘average’ distance (semi-major axis of orbit) of about one-fifth of Earth’s orbital distance (0.21 AU)- about half of Mercury’s orbital distance- in the Solar System, with an orbital period of around 61. Despite its close orbital distance, Gliese 876 is so dim that the presumed gaseous surface of the planet has a temperature around -75° C (-103° F)- far below the freezing point of water. However, water could exist as liquid droplets in warmer layers not far below the surface of the planet.
Planet ‘c,’ discovered in 2001, is a Jupiter-class planet orbiting even closer to Gliese 876- semi-major axis of 0.13 AU- than Gliese 876 b. With over half the mass of Jupiter, this second planet orbits its host star in only about 30 days, about half that of the other planet. Thus, the orbits of the two planets are ‘locked’ into a near 2:1 resonance, shepherding each other to maintain a stable synchrony of elongated orbits. The orbit of Gliese 876 c is also more elliptical, even more than that of the planet Pluto in the Solar System.
Planet ‘d’ was discovered in 2005. This is a probably rocky, innermost planet, although a large gaseous atmosphere cannot be excluded. Designated Gliese 876 d and classified by some astronomers as an ‘super-Earth,’ the object has a minimum mass of 5.9 Earth-masses but a larger, probable mass around 7 Earth-masses and a diameter less than twicethat of Earth’s. Located only 0.021 AUs from Gliese 876, the planet completes its orbit around the star in less than two days. Due to its close orbit, the planet is presumed to be tidally locked with one surface eternally facing its host star, and so may have a bright-side temperature around 157-377° C but be extremely cold on the dark side. The object may be the first rocky planet found around a main sequence star.
Planet ‘e,’ discovered in 2010, is a Uranus-mass planet in a 124-day, outer orbit around two larger Jupiter- and Saturn-class planets ‘b’ and ‘c’ and innermost super-Earth planet ‘d’ around Gliese 876. The three giant planets (b, c, and e) have 4:2:1 resonance orbits, where the innermost giant planet completes four orbits for every orbit by the outermost giant, and completes two orbits for every two orbits by the middle giant. Hence, the three giant planets should nearly line up every 124 days and come close to a triple ‘planetary conjunction.’
[http://www.solstation.com/stars/gl876.htm]
Three Worlds for TRAPPIST-1
Three new found worlds orbit the ultracool dwarf star TRAPPIST-1, a mere 40 light-years away. Their transits were first detected by the Belgian robotic TRAnsiting Planets and Planetesimals Small Telescope, TRAPPIST, at ESO’s La Silla Observatory in Chile. The newly discovered exoplanets are all similar in size to Earth. Because they orbit very close to their faint, tiny star they could also have regions where surface temperatures allow for the presence of liquid water, a key ingredient for life. Their tantalizing proximity to Earth makes them prime candidates for future telescopic explorations of the atmospheres of these potentially habitable planets. All three worlds appear in this artist’s vision, an imagined scene near the horizon of the system’s outermost planet. Of course, the inner planet is transiting the dim, red, nearly Jupiter-sized parent star.
[http://apod.nasa.gov/apod/ap160507.html]
HD 215152 is another system, which consists of the planets HD 215152 b and HD 215152 c orbiting their K0-type, magnitude 8.13 sun. Both discovered in 2011 by the radial velocity method, the two tiny planets orbit very close to their host star. HD 215152 c is the larger at 0.0097 Jupiter masses (still significantly larger than the Earth, which weighs in at 0.00315 Jupiter masses); its smaller sibling is barely smaller at 0.0087 Jupiter masses. The error in the mass measurements (0.0032 and 0.0049 MJ respectively) is large enough to make this discrepancy statistically insignificant. HD 215152 c also orbits further from the star than HD 215152 b, 0.0852 AU compared to 0.0652.
Because of its position away from the galactic plane, the majority of deep-sky objects in Aquarius are galaxies, globular clusters, and planetary nebulae. Aquarius contains three deep sky objects that are in the Messier catalog: the globular clusters M2, M72, and the open cluster M73. 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. M72, also catalogued as NGC 6981, is a small 9th magnitude globular cluster located approximately 56,000 light-years from Earth. M73, also catalogued as NGC 6994, is an open cluster with highly disputed status.
Two well-known planetary nebulae are also located in Aquarius: the Saturn Nebula (NGC 7009), to the southeast of μ Aquarii; and the famous Helix Nebula (NGC 7293), southwest of δ Aquarii:
Helix Nebula- Unraveling at the Seams
A dying star is throwing a cosmic tantrum in this combined image from NASA’s Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX). In death, the star’s dusty outer layers are unraveling into space, glowing from the intense ultraviolet radiation being pumped out by the hot stellar core.
This object, called the Helix nebula, lies 650 light-years away, in the constellation of Aquarius. Also known by the catalog number NGC 7293, it is a typical example of a class of objects called planetary nebulae. Discovered in the 18th century, these cosmic works of art were erroneously named for their resemblance to gas-giant planets.
Planetary nebulae are actually the remains of stars that once looked a lot like our sun. These stars spend most of their lives turning hydrogen into helium in massive runaway nuclear fusion reactions in their cores. In fact, this process of fusion provides all the light and heat that we get from our sun. Our sun will blossom into a planetary nebula when it dies in about five billion years.
When the hydrogen fuel for the fusion reaction runs out, the star turns to helium for a fuel source, burning it into an even heavier mix of carbon, nitrogen and oxygen. Eventually, the helium will also be exhausted, and the star dies, puffing off its outer gaseous layers and leaving behind the tiny, hot, dense core, called a white dwarf. The white dwarf is about the size of Earth, but has a mass very close to that of the original star; in fact, a teaspoon of a white dwarf would weigh as much as a few elephants!
The glow from planetary nebulae is particularly intriguing as it appears surprisingly similar across a broad swath of the spectrum, from ultraviolet to infrared. The Helix remains recognizable at any of these wavelengths, but the combination shown here highlights some subtle differences.
The intense ultraviolet radiation from the white dwarf heats up the expelled layers of gas, which shine brightly in the infrared. GALEX has picked out the ultraviolet light pouring out of this system, shown throughout the nebula in blue, while Spitzer has snagged the detailed infrared signature of the dust and gas in yellow. A portion of the extended field beyond the nebula, which was not observed by Spitzer, is from NASA’s all-sky Wide-field Infrared Survey Explorer (WISE). The white dwarf star itself is a tiny white pinprick right at the center of the nebula.
The brighter purple circle in the very center is the combined ultraviolet and infrared glow of a dusty disk circling the white dwarf (the disk itself is too small to be resolved). This dust was most likely kicked up by comets that survived the death of their star.
Before the star died, its comets, and possibly planets, would have orbited the star in an orderly fashion. When the star ran out of hydrogen to burn, and blew off its outer layers, the icy bodies and outer planets would have been tossed about and into each other, kicking up an ongoing cosmic dust storm. Any inner planets in the system would have burned up or been swallowed as their dying star expanded.
Infrared data from Spitzer for the central nebula is rendered in green (wavelengths of 3.6 to 4.5 microns) and red (8 to 24 microns), with WISE data covering the outer areas in green (3.4 to 4.5 microns) and red (12 to 22 microns). Ultraviolet data from GALEX appears as blue (0.15 to 2.3 microns).
[http://www.nasa.gov/multimedia/imagegallery/image_feature_2368.html]
NGC 7293 or the Helix Nebula is the closest planetary nebula to Earth. 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, though it has a fairly high integrated magnitude of 6.0.
Hubble’s Planetary Nebula Gallery: A View of NGC 7009
NGC 7009 has a bright central star at the centre of a dark cavity bounded by a football-shaped rim of dense, blue and red gas. The cavity and its rim are trapped inside smoothly-distributed greenish material in the shape of a barrel and comprised of the star’s former outer layers. At larger distances, and lying along the long axis of the nebula, a pair of red ‘ansae,’ or ‘handles’ appears. Each ansa is joined to the tips of the cavity by a long greenish jet of material. The handles are clouds of low-density gas. NGC 7009 is 1,400 light-years away in the constellation Aquarius. The Hubble telescope observation was taken April 28, 1996 by the Wide Field and Planetary Camera 2.
[http://stardustobservatory.org/images.php?page=details&id=357]
NGC 7009, also known as the Saturn Nebula, was given its moniker by the 19th 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, it is an 8th magnitude planetary nebula, and has a central star of magnitude 11.3. Compared to the Helix Nebula, another planetary nebula in Aquarius, it is quite small.
One of the visible galaxies in Aquarius is NGC 7727, of particular interest for amateur astronomers who wish to discover or observe supernovae:
NGC 7727 is two separate (likely spiral) galaxies that are nearing the final process of merging into one larger galaxy after a billions year clash. You can even trace the path the galactic nuclei took starting from lower left and circling each other five to six countable times in this image. The image also shows two bright points of light near the center. The bringer one is certainly the center of the larger original galaxy. The fainter may well be the second nuclei or merely a foreground star. At the center of each these two nuclei is a super massive black hole containing millions of stellar masses each compressed into an infinitesimally small point. These black holes will circle each other for many millions of years before combining masses. The final appearance of the galaxy is still not well predicted but it is likely to be an elliptical galaxy mostly devoid of spiral arms or dust lanes necessary for new star formation.
[http://www.kentbiggs.com/images/galaxies/N7727.htm]
This object is located at a distance of 23.3 megaparsecs (76 million light years) of the Milky Way and is notable for its peculiar aspect, with several plumes and streams of irregular shape that explains its inclusion on Halton C. Arp’s Atlas of Peculiar Galaxies. In all likelihood, this system is the product of the merger of two previous spiral galaxies that took place 1 billion years ago, with the aforementioned stellar plumes and streams being the remmants of the disks of the two galaxies that collided to form this object.
Two starlike objects can be seen in NGC 7727’s center, at least one of them likely being the former core of one of those two spiral galaxies. In addition to this, 23 objects candidates to be young globular clusters formed in the collision can be found in this system.
NGC 7727’s most likely fate is to become an elliptical galaxy in the future, with very little interstellar dust and star formation.
[https://en.wikipedia.org/wiki/NGC_7727]
NGC 7727 is very similar to NGC 7252, another galaxy product of the collision and merging of two former spiral galaxies, in the same constellation:
Atoms-for-Peace Galaxy Collision
Is this what will become of our Milky Way Galaxy? Perhaps if we collide with the Andromeda Galaxy in a few billion years, it might. Pictured above is NGC 7252, a jumble of stars created by a huge collision between two large galaxies. The collision will take hundreds of millions of years and so is effectively caught frozen in time in the above image. The resulting pandemonium has been dubbed the Atoms-for-Peace galaxy because of its similarity to a cartoon of a large atom. The above image was taken recently by the MPG/ESO 2.2 meter telescope in Chile. NGC 7252 spans about 600,000 light years and lies about 220 million light years away toward the constellation of the Water Bearer (Aquarius). Since the sideways velocity of the Andromeda Galaxy (M31) is presently unknown, no one really knows for sure if the Milky Way will ever collide with M31.
[http://apod.nasa.gov/apod/ap101116.html]
The Aquarius Dwarf galaxy is a dwarf galaxy and an irregular galaxy, first catalogued in 1959 by the DDO survey. It is located within the boundaries of the constellation of Aquarius. It is a member of the Local Group of galaxies, albeit an extremely isolated one; it is one of only a few known Local Group members for which a past close approach to the Milky Way or Andromeda galaxy can be ruled out, based on its current location and velocity:
The Aquarius Dwarf
Our Milky Way Galaxy is not alone. It is part of a gathering of about 50 galaxies known as the Local Group. Members include the Great Andromeda Galaxy (M31), M32, M33, the Large Magellanic Cloud, the Small Magellanic Cloud, Dwingeloo 1, several small irregular galaxies, and many dwarf elliptical and dwarf spheroidal galaxies. Pictured above is the Aquarius Dwarf, a faint dwarf irregular galaxy over 3 million light years away. An earlier APOD erroneously identified the above image as the Sagittarius Dwarf.
[http://apod.nasa.gov/apod/ap030727.html]
Local Group membership of the Aquarius Dwarf galaxy was firmly established only in 1999, with the derivation of a distance (3.2 ±0.2 Mly (980 ±40 kpc)) based on the tip of the red-giant branch method. This distance from the Milky Way means that the Aquarius Dwarf is quite isolated in space. It is one of the least luminous Local Group galaxies to contain significant amounts of neutral hydrogen and support to ongoing star formation, although it does so only at an extremely low level. Because of its large distance, the Hubble Space Telescope is required in order to study its stellar populations in detail. RR Lyrae stars have been discovered in Aquarius, indicating the existence of stars more than 10 billion years old, but the majority of its stars are much younger (median age 6.8 billion years). Among Local Group galaxies, only Leo A has a younger mean age, leading to the suggestion that delayed star formation could be correlated with galaxy isolation.
[https://en.wikipedia.org/wiki/Aquarius_Dwarf]
Comet 96P Machholz, the possible parent of the Delta Aquarid meteor shower, was discoverd on May 12, 1986, by Donald Machholz.
[http://earthsky.org/?p=159138]
There are three major meteor showers with radiants in Aquarius: the Eta Aquariids, the Delta Aquariids, and the Iota Aquariids. The Eta Aquariids are the strongest meteor shower radiating from Aquarius. It peaks between 5 and 6 May with a rate of approximately 35 meteors per hour. Originally discovered by Chinese astronomers in 401 CE, Eta Aquariids can be seen coming from the Water Jar beginning on April 21 and as late as May 12. The parent body of the shower is Halley’s Comet, a periodic comet. Fireballs are common shortly after the peak, approximately between May 9 and May 11. The normal meteors appear to have yellow trails. The Delta Aquariids is a double radiant meteor shower that peaks first on 29 July and second on 6 August. 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. The Iota Aquariids is a fairly weak meteor shower that peaks on 6 August, with a rate of approximately 8 meteors per hour.
[https://en.wikipedia.org/wiki/Aquarius_%28constellation%29]
[https://en.wikipedia.org/wiki/Aquarius_%28astrology%29]
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