A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived outline or pattern, typically representing an animal, mythological person or creature, or an inanimate object. The origins of the earliest constellations likely go back to prehistory. People used them to relate stories of their beliefs, experiences, creation, or mythology. Different cultures and countries adopted their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized. The recognition of constellations has changed significantly over time. Many have changed in size or shape. Some became popular, only to drop into obscurity.
Introduction
Constellation
Constellation | Introduction
Sorry. I cannot find the answer based on the context. Orion, Leo or Scorpius. There are 88 modern constellations which usually share the names of their Graeco-Roman predecessors, such as Orion, Leo or Scorpius. Orion, Leo or Scorpius
what is hydrus?
user
Small constellation in the deep southern sky.
assistant
what are its characteristics?
user
Irregular in shape and its tail has been shortened to make space for this last constellation he had drawn up.
assistant
name a few stars in the constellation?
user
Beta Hydri, Alpha Hydri, etc.
assistant
where did the second star get its name from?
user
Chinese system
assistant
who decribed the constellation for the first time?
user
Goes back to prehistory.
assistant
what does deep sky objects mean in the context of the constellation?
user
Sorry. I cannot find the answer based on the context.
assistant
name a few mordern constellations?
user
The constellation also contains a spiral galaxy, NGC 1511, which lies edge on to observers on Earth and is readily viewed in amateur telescopes. Located mostly in Dorado, the Large Magellanic Cloud extends into Hydrus. The globular cluster NGC 1466 is an outlying component of the galaxy, and contains many RR Lyrae-type variable stars. It has a magnitude of 11.59 and is thought to be over 12 billion years old. Two stars, HD 24188 of magnitude 6.3 and HD 24115 of magnitude 9.0, lie nearby in its foreground. NGC 602 is composed of an emission nebula and a young, bright open cluster of stars that is an outlying component on the eastern edge of the Small Magellanic Cloud, a satellite galaxy to the Milky Way.
Hydrus | Deep-sky objects
It is a large nebula, 55 by 18 arcminutes, that possesses several stars around magnitude 13. These stars have been dimmed by up to 8 magnitudes by its dust clouds.
Corona Australis | Deep sky objects
Its extremely low metallicity indicates it is very old—one of the oldest clusters in the Milky Way. Extending south from it is the Dark Doodad Nebula, resembling a dark L-shaped river through a bright field of stars. Another dark nebula in the constellation is BHR 71.
Musca | Deep-sky objects
Most of the cloud is located in the neighbouring constellation Tucana.
Hydrus | Deep-sky objects
The galaxies in the constellation are faint. IC 4633 is a very faint spiral galaxy surrounded by a vast amount of Milky Way line-of-sight integrated flux nebulae—large faint clouds thought to be lit by large numbers of stars.
Apus | Deep-sky objects
M37's Trumpler class is given as both I 2 r and II 1 r. The stars visible in a telescope range in magnitude from 9.0 to 13.0; there are two 9th magnitude stars in the center of the cluster and an east to west chain of 10th and 11th magnitude stars.
Auriga (constellation) | Deep-sky objects
The cluster, 6200 light-years from Earth and 20 light-years in diameter, contains approximately 3000 stars, making it a particularly rich cluster. It is 220 million years old.
Scutum (constellation) | Deep sky objects
Because Dorado contains part of the Large Magellanic Cloud, it is rich in deep sky objects. The Large Magellanic Cloud, 25,000 light-years in diameter, is a satellite galaxy of the Milky Way Galaxy, located at a distance of 179,000 light-years. It has been deformed by its gravitational interactions with the larger Milky Way. In 1987, it became host to SN 1987A, the first supernova of 1987 and the closest since 1604. This 25,000-light-year-wide galaxy contains over 10,000 million stars. All coordinates given are for Epoch J2000.0.
Dorado | Deep-sky objects
Due to its location on the Milky Way, this constellation contains many deep-sky objects such as star clusters, including eight open clusters visible through binoculars. NGC 6087 is the brightest of the open clusters in Norma with a magnitude of 5.4. It lies in the southeastern corner of the constellation between Alpha Centauri and Zeta Arae. Thought to be around 100 million years old, it is about 3300 light-years away and is around 14 light-years in diameter. Its brightest member is the Cepheid variable S Normae. A rich background star field makes it less distinct, though around 36 member stars are visible though a 10 cm telescope at 150x magnification.
Norma (constellation) | Deep-sky objects
A barred spiral galaxy, its distorted shape is probably due to a past collision, possibly with the nearby NGC 4027A. NGC 4782 and NGC 4783 are a pair of merging elliptical galaxies in the northeastern part of the constellation, around 200 million light-years distant.
Corvus (constellation) | Deep-sky objects
The smaller galaxy in the collision is now incorporated into the core, after moving from a distance of 250,000 light-years. The shock waves from the collision sparked extensive star formation in the outer ring.
Sculptor (constellation) | Deep sky objects
It is also very large, with an apparent diameter of over 0.25 degrees, half the size of the full moon; its physical diameter is more than 100 light-years. Individual stars in M13 are resolvable in a small amateur telescope.
Hercules (constellation) | Deep-sky objects
Due to its location straddling the Milky Way, this constellation contains many deep-sky objects such as the open clusters Messier 6 (the Butterfly Cluster) and Messier 7 (the Ptolemy Cluster), NGC 6231 (by ζ² Sco), and the globular clusters Messier 4 and Messier 80. Messier 80 (NGC 6093) is a globular cluster of magnitude 7.3, 33,000 light-years from Earth. It is a compact Shapley class II cluster; the classification indicates that it is highly concentrated and dense at its nucleus. M80 was discovered in 1781 by Charles Messier. It was the site of a rare discovery in 1860 when Arthur von Auwers discovered the nova T Scorpii.
Scorpius | Deep-sky objects
The tail of stars drawn off the Tadpole Galaxy appears blue because the gravitational interaction disturbed clouds of gas and sparked star formation.
Draco (constellation) | Deep-sky objects
3100 light-years from Earth, more than 30 stars are visible in a diameter of 8 arcseconds. The prominent star in the north of the cluster has a golden color, whereas the stars in the south of the cluster appear orange. Collinder 421 appears to be embedded in nebulosity, which extends past the cluster's borders to its west. Berkeley 90 is a smaller open cluster, with a diameter of 5 arcminutes. More than 16 members appear in an amateur telescope.
Cygnus (constellation) | Deep-sky objects
The Horologium-Reticulum Supercluster is a galaxy supercluster, second in size only to the Shapley Supercluster in the local universe (anything within 200 mpc of Earth). It contains over 20 Abell galaxy clusters and covers more than 100 deg of the sky, centered roughly at equatorial coordinates α = , δ = .
Horologium (constellation) | Deep-sky objects
NGC 1535 is a small blue-gray planetary nebula visible in small amateur telescopes, with a disk visible in large amateur instruments. 2000 light-years away, it is of the 9th magnitude. IC 2118 is a faint reflection nebula believed to be an ancient supernova remnant or gas cloud illuminated by nearby supergiant star Rigel in Orion. Eridanus contains the galaxies NGC 1232, NGC 1234, NGC 1291 and NGC 1300, a grand design barred spiral galaxy.
Eridanus (constellation) | Deep-sky objects
However, the remnant itself was not discovered until 1731, when John Bevis found it.
Taurus (constellation) | Deep-sky objects
Approximately 200 million light-years from Earth with a redshift of 0.016 is Abell 3627; also called the Norma Cluster, it is one of the most massive galaxy clusters known to exist, at ten times the average cluster mass. Abell 3627 is thus theorized to be the Great Attractor, a massive object that is pulling the Local Group, the Virgo Supercluster, and the Hydra-Centaurus Supercluster towards its location at 600–1000 kilometres per second.
Norma (constellation) | Deep-sky objects
Libra is home to one bright globular cluster, NGC 5897. It is a loose cluster, 50,000 light-years from Earth; it is fairly large and has an integrated magnitude of 9. IC 1059 is a galaxy in the constellation Libra.
Libra (constellation) | Deep-sky objects
Carina also contains the naked-eye globular cluster NGC 2808. Epsilon Carinae and Upsilon Carinae are double stars visible in small telescopes.
Carina (constellation) | Deep-sky objects
The Milky Way covers much of the constellation's area. Of the deep-sky objects in Apus, there are two prominent globular clusters—NGC 6101 and IC 4499—and a large faint nebula that covers several degrees east of Beta and Gamma Apodis. NGC 6101 is a globular cluster of apparent magnitude 9.2 located around 50,000 light-years distant from Earth, which is around 160 light-years across. Around 13 billion years old, it contains a high concentration of massive bright stars known as blue stragglers, thought to be the result of two stars merging. IC 4499 is a loose globular cluster in the medium-far galactic halo; its apparent magnitude is 10.6.
Apus | Deep-sky objects
The constellation of Andromeda lies well away from the galactic plane, so it does not contain any of the open clusters or bright nebulae of the Milky Way. Because of its distance in the sky from the band of obscuring dust, gas, and abundant stars of our home galaxy, Andromeda's borders contain many visible distant galaxies. The most famous deep-sky object in Andromeda is the spiral galaxy cataloged as Messier 31 (M31) or NGC 224 but known colloquially as the Andromeda Galaxy for the constellation. M31 is one of the most distant objects visible to the naked eye, 2.2 million light-years from Earth (estimates range up to 2.5 million light-years).
Andromeda (constellation) | Deep-sky objects
NGC 1851 a globular cluster in Columba appears at 7th magnitude in a far part of our galaxy as is 39,000 light-years away - it is resolvable south of at greatest latitude +40°N in medium-sized amateur telescopes (under good conditions).
Columba (constellation) | Deep-sky objects
Monoceros contains many clusters and nebulae, most notable among them:
Monoceros | Deep-sky objects
Its rich Milky Way star field means many modestly deep-sky objects. NGC 6891 is a planetary nebula of magnitude 10.5; another is NGC 6905 or the Blue Flash nebula. NGC 6934 is a globular cluster of magnitude 9.75. At a distance of about 185,000 light-years, the globular cluster NGC 7006 is at the outer reaches of the galaxy. It is also fairly dim at magnitude 11.5.
Delphinus | Deep-sky objects
The ancient Chinese interpreted the object as a ghost or demon riding in a carriage, calling it a "cloud of pollen blown from under willow catkins." The smaller, denser open cluster Messier 67 can also be found in Cancer, 2600 light-years from Earth. It has an area of approximately 0.5 square degrees, the size of the full Moon. It contains approximately 200 stars, the brightest of which are of the tenth magnitude. QSO J0842+1835 is a quasar used to measure the speed of gravity in VLBI experiment conducted by Edward Fomalont and Sergei Kopeikin in September 2002.
Cancer (constellation) | Deep-sky objects
Appearing ring-shaped, it is thought that it actually is cylindrical and oriented directly at Earth. Around 8700 years old, it lies about five degrees west-northwest of Gamma Normae. Its integrated magnitude is 13.6 and its mean surface brightness is 13.9. The central star is a white dwarf of magnitude 14.03. Mz 1 is a bipolar planetary nebula, thought to be an hourglass shape tilted at an angle to observers on Earth, some 3500 light-years distant. Mz 3—known as the Ant Nebula as it resembles an ant—has a complex appearance, with at least four outflow jets and two large lobes visible.
Norma (constellation) | Deep-sky objects
TY Coronae Australis ranges irregularly between magnitudes 8.7 and 12.4, and the brightness of the nebula varies with it. Blue-white, it is of spectral type B8e. The largest young stars in the region, R, S, T, TY and VV Coronae Australis, are all ejecting jets of material which cause surrounding dust and gas to coalesce and form Herbig–Haro objects, many of which have been identified nearby. Lying adjacent to the nebulosity is the globular cluster known as NGC 6723, which is actually in the neighbouring constellation of Sagittarius and is much much further away. Near Epsilon and Gamma Coronae Australis is Bernes 157, a dark nebula and star forming region.
Corona Australis | Deep sky objects
Its shape has been described as "triangular"; this 80-star cluster is unusually large, more than half a degree in diameter, larger than the diameter of the full Moon.
Hydra (constellation) | Deep-sky objects
A deep-sky object (DSO) is any astronomical object that is not an individual star or Solar System object (such as Sun, Moon, planet, comet, etc.). The classification is used for the most part by amateur astronomers to denote visually observed faint naked eye and telescopic objects such as star clusters, nebulae and galaxies. This distinction is practical and technical, implying a variety of instruments and techniques appropriate to observation, and does not distinguish the nature of the object itself.
Deep-sky object | Introduction
Hanging from Orion's belt is his sword, consisting of the multiple stars θ1 and θ2 Orionis, called the Trapezium and the Orion Nebula (M42). This is a spectacular object that can be clearly identified with the naked eye as something other than a star. Using binoculars, its clouds of nascent stars, luminous gas, and dust can be observed. The Trapezium cluster has many newborn stars, including several brown dwarfs, all of which are at an approximate distance of 1,500 light-years. Named for the four bright stars that form a trapezoid, it is largely illuminated by the brightest stars, which are only a few hundred thousand years old.
Orion (constellation) | Deep-sky objects
Though it probably formed as a disk shape, tidal forces from the Milky Way have distorted it. Along with the Large Magellanic Cloud, it lies within the Magellanic Stream, a cloud of gas that connects the two galaxies. NGC 346 is a star-forming region located in the Small Magellanic Cloud. It has an apparent magnitude of 10.3. Within it lies the triple star system HD 5980, each of its members among the most luminous stars known.
Tucana | Deep-sky objects
It is very similar in size and shape to the Milky Way and is located 25 million light-years from Earth. In its core, NGC 2903 has many "hotspots", which have been found to be near regions of star formation. The star formation in this region is thought to be due to the presence of the dusty bar, which sends shock waves through its rotation to an area with a diameter of 2,000 light-years. The outskirts of the galaxy have many young open clusters.
Leo (constellation) | Deep-sky objects
Both lie more than 7,000 light-years from Earth and are several hundred light-years apart. Both clusters are of approximately magnitude 4 and 0.5 degrees in diameter. The two are Trumpler class I 3 r clusters, though NGC 869 is a Shapley class f and NGC 884 is a Shapley class e cluster. These classifications indicate that they are both quite rich (dense); NGC 869 is the richer of the pair. The clusters are both distinct from the surrounding star field and are clearly concentrated at their centers. The constituent stars, numbering over 100 in each cluster, range widely in brightness.
Perseus (constellation) | Deep-sky objects
The planetary nebula NGC 2438 is superimposed; it is approximately 2900 light-years from Earth. M46 is classified as a Shapley class f and a Trumpler class III 2 m cluster. This means that it is a rich cluster that appears distinct from the star field. However, it is not at its center. The cluster's stars, numbering between 50 and 100, have a moderate range in brightness.
Puppis | Deep-sky objects
In the north of the constellation is the Corona Australis Molecular Cloud, a dark molecular cloud with many embedded reflection nebulae, including NGC 6729, NGC 6726–7, and IC 4812. A star-forming region of around , it contains Herbig–Haro objects (protostars) and some very young stars. About 430 light years (130 parsecs) away, it is one of the closest star-forming regions to the Solar System. The related NGC 6726 and 6727, along with unrelated NGC 6729, were first recorded by Johann Friedrich Julius Schmidt in 1865. The Coronet cluster, about 554 light years (170 parsecs) away at the edge of the Gould Belt, is also used in studying star and protoplanetary disk formation.
Corona Australis | Deep sky objects
Larger still is El Gordo, or officially ACT-CL J0102-4915, whose discovery was announced in 2012. Located around 7.2 billion light years away, it is composed of two subclusters in the process of colliding, resulting in the spewing out of hot gas, seen in X-rays and infrared images.
Phoenix (constellation) | Deep-sky objects
Hydrus contains only faint deep-sky objects. IC 1717 was a deep-sky object discovered by the Danish astronomer John Louis Emil Dreyer in the late 19th century. The object at the coordinate Dreyer observed is no longer there, and is now a mystery. It was very likely to have been a faint comet. PGC 6240, known as the White Rose Galaxy, is a giant spiral galaxy surrounded by shells resembling rose petals, located around 345 million light years from the Solar System. Unusually, it has cohorts of globular clusters of three distinct ages suggesting bouts of post-starburst formation following a merger with another galaxy.
Hydrus | Deep-sky objects
There is an abundance of deep-sky objects, with many open clusters, nebulae of various types and supernova remnants found in Cygnus due to its position on the Milky Way. Some open clusters can be difficult to make out from a rich background of stars. M39 (NGC 7092) is an open cluster 950 light-years from Earth that is visible to the unaided eye under dark skies. It is loose, with about 30 stars arranged over a wide area; their conformation appears triangular. The brightest stars of M39 are of the 7th magnitude. Another open cluster in Cygnus is NGC 6910, also called the Rocking Horse Cluster, possessing 16 stars with a diameter of 5 arcminutes visible in a small amateur instrument; it is of magnitude 7.4.
Cygnus (constellation) | Deep-sky objects
M34 is an open cluster that appears at magnitude 5.5, and is approximately 1,500 light-years from Earth. It contains about 100 stars scattered over a field of view larger than that of the full moon. M34 can be resolved with good eyesight but is best viewed using a telescope at low magnifications. IC 348 is a somewhat young open cluster that is still contained within the nebula from which its stars formed. It is located about 1,027 light-years from Earth, is about 2 million years old, and contains many stars with circumstellar disks. Many brown dwarfs have been discovered in this cluster due to its age; since brown dwarfs cool as they age, it is easier to find them in younger clusters.
Perseus (constellation) | Deep-sky objects
As the Milky Way runs through Puppis, there are many open clusters in the constellation. M46 and M47 are two open clusters in the same binocular field. M47 can be seen with the naked eye under dark skies, and its brightest stars are 6th magnitude. Messier 93 (M93) is another open cluster somewhat to the south. NGC 2451 is a very bright open cluster containing the star c Puppis, and the near NGC 2477 is a good target for small telescopes. The star Pi Puppis is the main component of a bright group of stars known as Collinder 135. M46 is a circular open cluster with an overall magnitude of 6.1 at a distance of approximately 5400 light-years from Earth.
Puppis | Deep-sky objects
It was discovered in 2000 by Joselino Vasquez, and confirmed by a team of astronomers under the leadership of R. J. Hurt at 2MASS.
Sagittarius (constellation) | Other deep sky objects
The name originates from the huge tidal tails that come off the ends of the two galaxies, formed because of the spiral galaxies' original rotation. Both original galaxies were spiral galaxies and are now experiencing extensive star formation due to the interaction of gas clouds. The galaxies are 45 million light-years from Earth and each has multiple ultraluminous X-ray sources, the source of which is unknown. Astronomers theorize that they may be a rare type of x-ray emitting binary stars or intermediate-mass black holes. The Antennae Galaxies appear in a telescope at the 10th magnitude. SN 2004gt was a type Ic supernova that erupted on December 12, 2004.
Corvus (constellation) | Deep-sky objects
Although Ara lies close to the heart of the Milky Way, two spiral galaxies (NGC 6215 and NGC 6221) are visible near star Eta Arae.
Ara (constellation) | Deep-sky objects
Its outer arms have a high number of Cepheid variables, which are used as standard candles to determine astronomical distances. Because of this, astronomers used several Cepheid variables in NGC 4639 to calibrate type 1a supernovae as standard candles for more distant galaxies.
Virgo (constellation) | Deep-sky objects
It is seen under a dark, transparent sky as a hazy patch in the north of the constellation. M31 is the largest neighboring galaxy to the Milky Way and the largest member of the Local Group of galaxies. In absolute terms, M31 is approximately 200,000 light-years in diameter, twice the size of the Milky Way. It is an enormous – 192.4 by 62.2 arcminutes in apparent size – barred spiral galaxy similar in form to the Milky Way and at an approximate magnitude of 3.5, is one of the brightest deep-sky objects in the northern sky. Despite being visible to the naked eye, the "little cloud" near Andromeda's figure was not recorded until AD 964, when the Arab astronomer al-Sufi wrote his "Book of Fixed Stars".
Andromeda (constellation) | Deep-sky objects
In 1999, a nearby open cluster was discovered centered on the star η Chamaeleontis. The cluster, known as either the Eta Chamaeleontis cluster or Mamajek 1, is 8 million years old, and lies 316 light years from Earth. The constellation contains a number of molecular clouds (the Chamaeleon dark clouds) that are forming low-mass T Tauri stars. The cloud complex lies some 400 to 600 light years from Earth, and contains tens of thousands of solar masses of gas and dust. The most prominent cluster of T Tauri stars and young B-type stars are in the Chamaeleon I cloud, and are associated with the reflection nebula IC 2631.
Chamaeleon | Deep-sky objects
Cancer is best known among stargazers as the home of Praesepe (Messier 44), an open cluster also called the "Beehive Cluster", located right in the centre of the constellation. Located about 590 light-years from Earth, it is one of the nearest open clusters to our Solar System. M 44 contains about 50 stars, the brightest of which are of the sixth magnitude. Epsilon Cancri is the brightest member at magnitude 6.3. Praesepe is also one of the larger open clusters visible; it has an area of 1.5 square degrees, or three times the size of the full Moon. It is most easily observed when Cancer is high in the sky.
Cancer (constellation) | Deep-sky objects
The Milky Way is at its densest near Sagittarius, as this is where the galactic center lies. As a result, Sagittarius contains many star clusters and nebulae.
Sagittarius (constellation) | Deep-sky objects
It is the third nearest to the Local Group after the Virgo Cluster and the Fornax Cluster. The cluster's distance from earth is to Located in the southeastern corner of the constellation, it boasts the giant elliptical galaxies NGC 3268 and NGC 3258 as the main members of a southern and northern subgroup respectively, and contains around 234 galaxies in total.
Antlia | Deep-sky objects
The 13th magnitude planetary nebula PN G243-37.1 is also in the eastern regions of the constellation. It is one of only a few planetary nebulae found in the galactic halo, being light-years below the Milky Way's 1000 light-year-thick disk.
Caelum | Deep-sky objects
M35 (NGC 2168) is a large, elongated open cluster of magnitude 5, discovered in the year 1745 by Swiss astronomer Philippe Loys de Chéseaux. It has an area of approximately 0.2 square degrees, the same size as the full moon. Its high magnitude means that M35 is visible to the unaided eye under dark skies; under brighter skies it is discernible in binoculars. The 200 stars of M35 are arranged in chains that curve throughout the cluster; it is 2800 light-years from Earth. Another open cluster in Gemini is NGC 2158. Visible in large amateur telescopes and very rich, it is more than 12,000 light-years from Earth.
Gemini (constellation) | Deep-sky objects
Although not a large constellation, Scutum contains several open clusters, as well as a globular cluster and a planetary nebula. The two best known deep sky objects in Scutum are M11 (the Wild Duck Cluster) and the open cluster M26 (NGC 6694). The globular cluster NGC 6712 and the planetary nebula IC 1295 can be found in the eastern part of the constellation, only 24 arcminutes apart. The most prominent open cluster in Scutum is the Wild Duck Cluster, M11. It was named by William Henry Smyth in 1844 for its resemblance in the eyepiece to a flock of ducks in flight.
Scutum (constellation) | Deep sky objects
The brightest of these are two gold-hued stars, which represent the bottom of the toy it is named for. A larger amateur instrument reveals 8 more stars, nebulosity to the east and west of the cluster, and a diameter of 9 arcminutes. The nebulosity in this region is part of the Gamma Cygni Nebula. The other stars, approximately 3700 light-years from Earth, are mostly blue-white and very hot. Other open clusters in Cygnus include Dolidze 9, Collinder 421, Dolidze 11, and Berkeley 90. Dolidze 9, 2800 light-years from Earth and relatively young at 20 million light-years old, is a faint open cluster with up to 22 stars visible in small and medium-sized amateur telescopes.
Cygnus (constellation) | Deep-sky objects
Horologium is home to many deep-sky objects, including several globular clusters. NGC 1261 is a globular cluster of magnitude 8, located 53,000 light-years from Earth. It lies 4.7 degrees north-northeast of Mu Horologii. The globular cluster Arp-Madore 1 is the most remote known globular cluster in the Milky Way at a distance of from Earth. NGC 1512 is a barred spiral galaxy 2.1 degrees west-southwest of Alpha Horologii with an apparent magnitude of 10.2. About five arcmin (13.8 kpc) away is the dwarf lenticular galaxy NGC 1510. The two are in the process of a merger which has been going on for 400 million years.
Horologium (constellation) | Deep-sky objects
AT2018cow, a large astronomical explosion detected on 16 June 2018. As of 22 June 2018, this astronomical event has generated a very large amount of interest among astronomers throughout the world and may be, as of 22 June 2018, considered a supernova tentatively named Supernova 2018cow. Hercules contains two bright globular clusters: M13, the brightest globular cluster in the northern hemisphere, and M92. It also contains the nearly spherical planetary nebula Abell 39. M13 lies between the stars η Her and ζ Her; it is dim, but may be detected by the unaided eye on a very clear night. M13, visible to both the naked eye and binoculars, is a globular cluster of the 6th magnitude that contains more than 300,000 stars and is 25,200 light-years from Earth.
Hercules (constellation) | Deep-sky objects
ω Centauri (NGC 5139), despite being listed as the constellation's "omega" star, is in fact a naked-eye globular cluster, 17,000 light-years away with a diameter of 150 light-years. It is the largest and brightest globular cluster in the Milky Way; at ten times the size of the next-largest cluster, it has a magnitude of 3.7. It is also the most luminous globular cluster in the Milky Way, at over one million solar luminosities. Omega Centauri is classified as a Shapley class VIII cluster, which means that its center is loosely concentrated. It is also the only globular cluster to be designated with a Bayer letter; the globular cluster 47 Tucanae is the only one designated with a Flamsteed number.
Centaurus | Deep-sky objects
Nebulosity is visible to the north and east of the cluster, which is 7 arcminutes in diameter. The brightest star appears in the eastern part of the cluster and is of the 7th magnitude; another bright star has a yellow hue. Dolidze 11 is an open cluster 400 million years old, farthest away of the three at 3700 light-years. More than 10 stars are visible in an amateur instrument in this cluster, of similar size to Dolidze 9 at 7 arcminutes in diameter, whose brightest star is of magnitude 7.5. It, too, has nebulosity in the east. Collinder 421 is a particularly old open cluster at an age of approximately 1 billion years; it is of magnitude 10.1.
Cygnus (constellation) | Deep-sky objects
NGC 7172, NGC 7174 and NGC 7314 are three galaxies of magnitudes 11.9, 12.5 and 10.9, respectively. NGC 7259 is another spiral galaxy, which hosted a supernova—SN 2009ip—in 2009. At redshift z = 0.116, the BL Lacertae object PKS 2155-304 is one of the brightest blazars in the sky.
Piscis Austrinus | Deep sky objects
Observations by the Chandra X-ray Observatory show both the extreme temperatures of the main stars—up to 60,000 kelvins—and the star forming regions still extant in the surrounding nebula. M78 (NGC 2068) is a nebula in Orion. With an overall magnitude of 8.0, it is significantly dimmer than the Great Orion Nebula that lies to its south; however, it is at approximately the same distance, at 1600 light-years from Earth. It can easily be mistaken for a comet in the eyepiece of a telescope. M78 is associated with the variable star V351 Orionis, whose magnitude changes are visible in very short periods of time.
Orion (constellation) | 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. 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 southeast of μ Aquarii; and the famous Helix Nebula (NGC 7293), southwest of δ Aquarii. M2, also catalogued as NGC 7089, is a 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.
Aquarius (constellation) | Deep sky objects
Hydra contains three Messier objects. M83, also known as the Southern Pinwheel Galaxy, is located on the border of Hydra and Centaurus, M68 is a globular cluster near M83, and M48 is an open star cluster in the western end of the serpent. NGC 3242 is a planetary nebula of magnitude 7.5, 1400 light-years from Earth. Discovered in 1785 by William Herschel, it has earned the nickname "Ghost of Jupiter" because of its striking resemblance to the giant planet. Its blue-green disk is visible in small telescopes and its halo is visible in larger instruments. M48 (NGC 2548) is an open cluster that is visible to the naked eye under dark skies.
Hydra (constellation) | Deep-sky objects
Towards the north of the constellation are globular clusters NGC 5824 and NGC 5986, and close by the dark nebula B 228. To the south are two open clusters, NGC 5822 and NGC 5749, as well as globular cluster NGC 5927 on the eastern border with Norma. On the western border are two spiral galaxies and the Wolf–Rayet planetary nebula IC 4406, containing some of the hottest stars in existence. IC 4406, also called the Retina Nebula, is a cylindrical nebula at a distance of 5,000 light-years. It has dust lanes throughout its center. Another planetary nebula, NGC 5882, is towards the center of the constellation.
Lupus (constellation) | Deep-sky objects
There is one Messier object in Lepus, M79. It is a globular cluster of magnitude 8.0, 42,000 light-years from Earth. One of the few globular clusters visible in the Northern Celestial Hemisphere's winter, it is a Shapley class V cluster, which means that it has an intermediate concentration towards its center. It is often described as having a "starfish" shape. M79 was discovered in 1780 by Pierre Méchain.
Lepus (constellation) | Deep-sky objects
The Dumbbell Nebula (M27), is a large, bright planetary nebula which was discovered by the French astronomer Charles Messier in 1764 as the very first object of its kind. It can be seen with good binoculars in a dark sky location, appearing as a dimly glowing disk approximately 6 arcminutes in diameter. A telescope reveals its double-lobed shape, similar to that of an hourglass. Brocchi's Cluster (Collinder 399) is an asterism formerly thought to be an open cluster. It is also called "the Coathanger" because of its distinctive star pattern when viewed with binoculars or a low power telescope. NGC 7052 is an elliptical galaxy in Vulpecula at a distance of 214 million light-years from Earth.
Vulpecula | Deep-sky objects
Leo contains many bright galaxies; Messier 65, Messier 66, Messier 95, Messier 96, Messier 105, and NGC 3628 are the most famous, the first two being part of the Leo Triplet. The Leo Ring, a cloud of hydrogen, helium gas, is found in orbit of two galaxies found within this constellation.M66 is a spiral galaxy that is part of the Leo Triplet, whose other two members are M65 and NGC 3628. It is at a distance of 37 million light-years and has a somewhat distorted shape due to gravitational interactions with the other members of the Triplet, which are pulling stars away from M66.
Leo (constellation) | Deep-sky objects
The component Abell clusters 3695 and 3696 are likely to be gravitationally bound, while the relations of Abell clusters 3693 and 3705 in the same field are unclear.
Microscopium | Deep sky objects
The second-brightest globular cluster in the sky after Omega Centauri, 47 Tucanae (NGC 104) lies just west of the Small Magellanic Cloud. Only 14,700 light-years distant from Earth, it is thought to be around 12 billion years old. Mostly composed of old, yellow stars, it does possess a contingent of blue stragglers, hot stars that are hypothesized to form from binary star mergers. 47 Tucanae has an apparent magnitude of 3.9, meaning that it is visible to the naked eye; it is a Shapley class III cluster, which means that it has a clearly defined nucleus. Near to 47 Tucana on the sky, and often seen in wide-field photographs showing it, are two much more distant globular clusters associated with the SMC: NGC 121, 10 arcminutes away from the bigger cluster's edge, and Lindsay 8.
Tucana | Deep-sky objects
It contains Theta Carinae, along with several other stars visible to the unaided eye. In total, the cluster possesses approximately 60 stars. The Southern Pleiades is particularly large for an open cluster, with a diameter of approximately one degree. Like IC 2602, NGC 3532 is visible to the unaided eye and is of comparable size. It possesses approximately 150 stars that are arranged in an unusual shape, approximating an ellipse with a dark central area. Several prominent orange giants are among the cluster's bright stars, of the 7th magnitude. Superimposed on the cluster is Chi Carinae, a yellow-white hued star of magnitude 3.9, far more distant than NGC 3532.
Carina (constellation) | Deep-sky objects
It is also more distant, at 8200 light-years from Earth. Its most prominent member is actually a closer, superimposed double star; it consists of a 7th-magnitude primary and 10th-magnitude secondary.
Cassiopeia (constellation) | Deep-sky objects
Corona Borealis contains few galaxies observable with amateur telescopes. NGC 6085 and 6086 are a faint spiral and elliptical galaxy respectively close enough to each other to be seen in the same visual field through a telescope. Abell 2142 is a huge (six million light-year diameter), X-ray luminous galaxy cluster that is the result of an ongoing merger between two galaxy clusters. It has a redshift of 0.0909 (meaning it is moving away from us at 27,250 km/s) and a visual magnitude of 16.0. It is about 1.2 billion light-years away. Another galaxy cluster in the constellation, RX J1532.9+3021, is approximately 3.9 billion light-years from Earth.
Corona Borealis | Deep-sky objects
It is also related to IC 4677, a nebula that appears as a bar 1.8 arcminutes to the west of the Cat's Eye nebula. In long-term exposures, IC 4677 appears as a portion of a ring surrounding the planetary nebula. There are several faint galaxies in Draco, one of which is the lenticular galaxy NGC 5866 (sometimes considered to be Messier Object 102) that bears its name to a small group that also includes the spiral galaxies NGC 5879 and NGC 5907. Another is the Draco Dwarf Galaxy, one of the least luminous galaxies with an absolute magnitude of −8.6 and a diameter of only about 3,500 light years, discovered by Albert G.
Draco (constellation) | Deep-sky objects
GOODS-S 29323 is located in the constellation Fornax, at RA: 03h 32m 28s and Dec: –27° 48′ 30″
Great Observatories Origins Deep Survey | Instruments
At the cluster's center is a large elliptical galaxy containing one of the most massive and most powerful supermassive black holes yet discovered. Abell 2065 is a highly concentrated galaxy cluster containing more than 400 members, the brightest of which are 16th magnitude; the cluster is more than one billion light-years from Earth. On a larger scale still, Abell 2065, along with Abell 2061, Abell 2067, Abell 2079, Abell 2089, and Abell 2092, make up the Corona Borealis Supercluster. Another galaxy cluster, Abell 2162, is a member of the Hercules Superclusters.
Corona Borealis | Deep-sky objects
Mensa contains several described open clusters, most of which can be only be clearly observed from large telescopes. PKS 0637-752 is a distant quasar with a calculated redshift of z = 0.651. It was chosen as the first target of the then newly-operational Chandra X-Ray Observatory in 1999. The resulting images revealed a gas jet approximately 330,000 light-years long. It is visible at radio, optical and x-ray wavelengths.
Mensa (constellation) | Deep-sky objects
The northwest corner of Ara is crossed by the galactic plane of the Milky Way and contains several open clusters (notably NGC 6200) and diffuse nebulae (including the bright cluster/nebula pair NGC 6188 and NGC 6193). The brightest of the globular clusters, sixth magnitude NGC 6397, lies at a distance of just , making it one of the closest globular clusters to the Solar System. Ara also contains Westerlund 1, a super star cluster containing itself the red supergiant Westerlund 1-237 and the red hypergiant Westerlund 1-26. The latter is possibly the largest star known with an estimate varying between and .
Ara (constellation) | Deep-sky objects
The constellation does not lie on the galactic plane of the Milky Way, and there are no prominent star clusters. NGC 625 is a dwarf irregular galaxy of apparent magnitude 11.0 and lying some 12.7 million light years distant. Only 24000 light years in diameter, it is an outlying member of the Sculptor Group. NGC 625 is thought to have been involved in a collision and is experiencing a burst of active star formation. NGC 37 is a lenticular galaxy of apparent magnitude 14.66. It is approximately 42 kiloparsecs (137,000 light-years) in diameter and about 12.9 billion years old. Robert's Quartet (composed of the irregular galaxy NGC 87, and three spiral galaxies NGC 88, NGC 89 and NGC 92) is a group of four galaxies located around 160 million light-years away which are in the process of colliding and merging.
Phoenix (constellation) | Deep-sky objects
NGC 3395 and NGC 3396 are a spiral and irregular barred spiral galaxy, respectively, that are interacting, located 1.33 degrees southwest of 46 Leonis Minoris. The unique deep-sky object known as Hanny's Voorwerp was discovered in Leo Minor in 2007 by Dutch school teacher Hanny van Arkel while participating as a volunteer in the Galaxy Zoo project. Lying near the 650-million-light-year-distant spiral galaxy IC 2497, it is around the same size as the Milky Way. It contains a 16,000-light-year-wide hole. The voorwerp is thought to be the visual light echo of a quasar now gone inactive, possibly as recently as 200,000 years ago.
Leo Minor | Deep-sky objects
Due to its small size and its distance from the plane of the Milky Way, Equuleus contains no notable deep sky objects. Some very faint galaxies between magnitudes 13 and 15 include NGC 7015, NGC 7040, NGC 7045 and NGC 7046.
Equuleus | Deep-sky objects
The Sagittarius Dwarf Elliptical Galaxy is located just outside the Milky Way. Baade's Window is an area with very little obscuring dust that shows objects closer to the Milky Way's center than would normally be visible. NGC 6522, magnitude 8.6, and NGC 6528, magnitude 9.5, are both globular clusters visible through Baade's Window. 20,000 and 24,000 light-years from Earth, with Shapley classes of VI and V respectively, both are moderately concentrated at their cores. NGC 6528 is closer to the galactic core at an approximate distance of 2,000 light-years. 2MASS-GC02, also known as Hurt 2, is a globular cluster at a distance of about 16 thousand light-years from Earth.
Sagittarius (constellation) | Other deep sky objects
One of deep-sky objects in Draco is the Cat's Eye Nebula (NGC 6543), a planetary nebula approximately 3,000 light-years away that was discovered by English astronomer William Herschel in 1786. It is 9th magnitude and was named for its appearance in the Hubble Space Telescope, though it appears as a fuzzy blue-green disk in an amateur telescope. NGC 6543 has a very complex shape due to gravitational interactions between the components of the multiple star at its center, the progenitor of the nebula approximately 1,000 years ago. It is located 9.6 arcminutes away from the north ecliptic pole to the west-northwest.
Draco (constellation) | Deep-sky objects
Eventually, the outermost stars may form a dwarf galaxy orbiting M66. Both M65 and M66 are visible in large binoculars or small telescopes, but their concentrated nuclei and elongation are only visible in large amateur instruments. M95 and M96 are both spiral galaxies 20 million light-years from Earth. Though they are visible as fuzzy objects in small telescopes, their structure is only visible in larger instruments. M95 is a barred spiral galaxy. M105 is about a degree away from the M95/M96 pair; it is an elliptical galaxy of the 9th magnitude, also about 20 million light-years from Earth. NGC 2903 is a barred spiral galaxy discovered by William Herschel in 1784.
Leo (constellation) | Deep-sky objects
Two ultraluminous X-ray sources and one supernova have been observed in NGC 7424. SN 2001ig was discovered in 2001 and classified as a Type IIb supernova, one that initially showed a weak hydrogen line in its spectrum, but this emission later became undetectable and was replaced by lines of oxygen, magnesium and calcium, as well as other features that resembled the spectrum of a Type Ib supernova. A massive star of spectral type F, A or B is thought to be the surviving binary companion to SN 2001ig, which was believed to have been a Wolf–Rayet star.
Grus (constellation) | Deep-sky objects
Several bright galaxies are found in Ursa Major, including the pair Messier 81 (one of the brightest galaxies in the sky) and Messier 82 above the bear's head, and Pinwheel Galaxy (M101), a spiral northeast of η Ursae Majoris. The spiral galaxies Messier 108 and Messier 109 are also found in this constellation. The bright planetary nebula Owl Nebula (M97) can be found along the bottom of the bowl of the Big Dipper. M81 is a nearly face-on spiral galaxy 11.8 million light-years from Earth. Like most spiral galaxies, it has a core made up of old stars, with arms filled with young stars and nebulae.
Ursa Major | Deep-sky objects
Copeland, written for the majority of its run by Walter Scott Houston, and currently penned by Sue French. Houston's columns, and later book compilations of those columns, helped popularize the term, each month giving the reader a guided tour of a small part of the sky highlighting well known and lesser known objects for binoculars and small telescopes.
Deep-sky object | Origins and classification
The deep-sky objects in Pavo include NGC 6752, the third-brightest globular cluster in the sky, after 47 Tucanae and Omega Centauri. An estimated 100 light years across, it is thought to contain 100,000 stars. Barely visible behind the cluster is a dwarf spheroidal galaxy known as Bedin I. Lying three degrees to the south is NGC 6744, a spiral galaxy around 30 million light years away from Earth that resembles the Milky Way, but is twice its diameter. A type 1c supernova was discovered in the galaxy in 2005; known as SN2005at, it peaked at magnitude 16.8. The dwarf galaxy IC 4662 lies 10 arcminutes northeast of Eta Pavonis, and is of magnitude 11.62.
Pavo (constellation) | Deep-sky objects
Three interesting planetary nebulae lie in Aquila: More deep-sky objects: Aquila also holds some extragalactic objects. One of them is what may be the largest single mass concentration of galaxies in the Universe known, the Hercules–Corona Borealis Great Wall. It was discovered in November 2013, and has the size of 10 billion light years. It is the biggest and the most massive structure in the Universe known.
Aquila (constellation) | Deep-sky objects
NGC 7243 is an open cluster 2500 light-years from Earth, visible in small amateur telescopes. It has a few dozen "scattered" stars, the brightest of which are of the 8th magnitude. BL Lacertae is the prototype of the BL Lacertae objects, which appear to be dim variable stars but are actually the variable nuclei of elliptical galaxies; they are similar to quasars. It lent its name to a whole type of celestial objects, the BL Lacertae objects (a subtype of blazar). The object varies irregularly between magnitudes 14 and 17 over a few days.
Lacerta | Deep-sky objects
NGC 2573 (also known as Polarissima Australis) is a faint barred spiral galaxy that happens to be the closest NGC object to the South Celestial Pole. NGC 7095 and NGC 7098 are two barred spiral galaxies that are 115 million and 95 million light-years distant from Earth respectively. The sparse open cluster Collinder 411 is also located in the constellation.
Octans | Deep sky objects
M36 features a 10-arcminute-wide knot of bright stars in its center, anchored by Struve 737, a double star with components separated by 10.7 arcseconds. Most of the stars in M36 are B type stars with rapid rates of rotation. M36's Trumpler class is given as both I 3 r and II 3 m. Besides the central knot, most of the cluster's other stars appear in smaller knots and groups. M37 (NGC 2099) is an open cluster, larger than M36 and at a distance of 4,200 light-years. It has 150 stars, making it the richest cluster in Auriga; the most prominent member is an orange star that appears at the center.
Auriga (constellation) | Deep-sky objects
The Large Magellanic Cloud lies partially within Mensa's boundaries, although most of it lies in neighbouring Dorado. It is a satellite galaxy of the Milky Way, located at a distance of 163,000 light-years. Among its stars within Mensa are W Mensae, an unusual yellow-white supergiant that belongs to a rare class of star known as a R Coronae Borealis variable, HD 268835, a blue hypergiant that is girded by a vast circumstellar disk of dust, and R71, a luminous blue variable star that brightened in 2012 to over a million times as luminous as the Sun. Also within the galaxy is NGC 1987, a globular cluster estimated to be around 600 million years old that has a significant number of red ageing stars, and NGC 1848, a 27 million year old open cluster.
Mensa (constellation) | Deep-sky objects
NGC 2516 is an open cluster that is both quite large (approximately half a degree square) and bright, visible to the unaided eye. It is located 1100 light-years from Earth and has approximately 80 stars, the brightest of which is a red giant star of magnitude 5.2. NGC 3114 is another open cluster approximately of the same size, though it is more distant at 3000 light-years from Earth. It is more loose and dim than NGC 2516, as its brightest stars are only 6th magnitude. The most prominent open cluster in Carina is IC 2602, also called the "Southern Pleiades".
Carina (constellation) | Deep-sky objects
It is one of the largest constellations, with an area of 722 square degrees. This is over 1,400 times the size of the full moon, 55% of the size of the largest constellation, Hydra, and over 10 times the size of the smallest constellation, Crux. Its brightest star, Alpha Andromedae, is a binary star that has also been counted as a part of Pegasus, while Gamma Andromedae is a colorful binary and a popular target for amateur astronomers. Only marginally dimmer than Alpha, Beta Andromedae is a red giant, its color visible to the naked eye. The constellation's most obvious deep-sky object is the naked-eye Andromeda Galaxy (M31, also called the Great Galaxy of Andromeda), the closest spiral galaxy to the Milky Way and one of the brightest Messier objects.
Andromeda (constellation) | Introduction
The band of the Milky Way goes through Canis Major, with only patchy obscurement by interstellar dust clouds. It is bright in the northeastern corner of the constellation, as well as in a triangular area between Adhara, Wezen and Aludra, with many stars visible in binoculars. Canis Major boasts several open clusters. The only Messier object is M41 (NGC 2287), an open cluster with a combined visual magnitude of 4.5, around 2300 light-years from Earth. Located 4 degrees south of Sirius, it contains contrasting blue, yellow and orange stars and covers an area the apparent size of the full moon—in reality around 25 light-years in diameter.
Canis Major | Deep-sky objects
The smaller star remained in orbit inside the larger, whose rotation speed increased greatly, resulting in it flinging its outer layers off into space, forming a ring with knots of bright gas formed from clumps of stellar material. Both nebulae are around from Earth.
Sagitta | Deep-sky objects
Camelopardalis is in the part of the celestial sphere facing away from the galactic plane. Accordingly, many distant galaxies are visible within its borders.
Camelopardalis | Deep-sky objects
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. Aquarius is also home to several planetary nebulae. NGC 7009, also known as the Saturn Nebula, is an 8th magnitude planetary nebula located 3,000 light-years from Earth. It 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 and has a central star of magnitude 11.3.
Aquarius (constellation) | Deep sky objects
Several galaxies and star clusters are contained within Capricornus. Messier 30 is a globular cluster located 1 degree south of the galaxy group that contains NGC 7103. The constellation also harbors the wide spiral galaxy NGC 6907. M30 (NGC 7099) is a centrally-condensed globular cluster of magnitude 7.5 . At a distance of 30,000 light-years, it has chains of stars extending to the north that are resolvable in small amateur telescopes. One galaxy group located in Capricornus is HCG 87, a group of at least three galaxies located 400 million light-years from Earth (redshift 0.0296). It contains a large elliptical galaxy, a face-on spiral galaxy, and an edge-on spiral galaxy.
Capricornus | Deep-sky objects
It is located 5 degrees south of Epsilon Trianguli Australis. ESO 69-6 is a pair of merging galaxies located about 600 million light-years (185 megaparsecs) away. Their contents have been dragged out in long tails by the interaction.
Triangulum Australe | Deep-sky objects