Emission nebula | |
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![]() NGC 2467 and surrounding area, from European Southern Observatory | |
Observation data: J2000 epoch | |
Right ascension | 07h 52m 24.22s [1] |
Declination | −26° 24′ 58.40″ [1] |
Distance | 4420 ly (1355 [1] pc) |
Constellation | Puppis |
Physical characteristics | |
Radius | 200 ly |
Designations | Cr 164, Gum 9, Sh 2-311, ESO 493-25 [2] |
NGC 2467, nicknamed the "Skull and Crossbones Nebula", [3] is a star-forming region whose appearance has occasionally also been likened to that of a colorful mandrill. It includes areas where large clouds of hydrogen gas incubate new stars. [4] This region was one of the areas featured in the book Hubble's Universe: Greatest Discoveries and Latest Images by Terence Dickinson. [5] [nb 1]
NGC 2467 had long been considered to be the nucleus of the Puppis I association. However, NGC 2467 does not represent a distinct open cluster; [6] rather, it represents a superimposition of several stellar groups along the same approximate line of sight that have distinctly different distances and distinctly different radial velocities. [7] One of these is a young and very distant group beyond Puppis OB2, while another, nearer group with later-type stars lies at a similar distance as Puppis OB1. [8]
The region is dominated by a massive young star, HD 64315 (annotated in Commons, below and left of center), of spectral type O6. Two stellar clusters also exist in the area, Haffner 19 (H19, annotated) and Haffner 18 (H18, annotated). H19 is a compact cluster containing a Strömgren sphere which is ionized by a hot B0 V-type star. H18 contains a very young star, FM3060a (annotated), that has just come into existence and still surrounded by its birth cocoon of gas. The age of H19 is estimated to be 2 Myr, while the age H18 is somewhat controversial, some considering it to be as young as only 1 Myr. [9] The field contains other early-type stars such as HD 64568 (annotated, upper right) whose relationship with the clusters is unclear. [10]
The H II region of NGC 2467 has been the target of various investigations to elucidate the process of star formation. Unresolved questions include understanding the degree to which the stars already formed in such regions, especially the massive O or B stars, can affect the future formation of stars in the region: Do these pre-existing stars trigger the formation of others? [9] One such investigation was conducted using the Spitzer Space Telescope, which discovered 45 young stellar objects (YSOs), or protostars, in the region during its "cold" mission, i.e. before its supply of liquid helium ran out. [9] The YSOs are mostly along the edge of the HII region. [9] The concentrated distribution of these objects spatially correlated with the ionization fronts provides evidence for triggered star formation. The newly forming ptotostars are concentrated in areas where the shock front driven in advance of the ionization front compresses the molecular gas. [9]
It has been estimated that H19, H18, and the S311 nebula (in which lies HD 64315) are about 6.4 kiloparsecs (21,000 light-years), 5.9 kpc (19,000 ly), and 6.3 kpc (21,000 ly) away, placing them in the Perseus Arm of the Milky Way. [10] A significant discrepancy has existed between the distances to these features estimated kinematically versus distances estimated photometrically. [11] Regardless of these discrepancies, H19 and H18 may be considered to be a binary cluster. [10]
The Orion Nebula is a diffuse nebula situated in the Milky Way, being south of Orion's Belt in the constellation of Orion, and is known as the middle "star" in the "sword" of Orion. It is one of the brightest nebulae and is visible to the naked eye in the night sky with apparent magnitude 4.0. It is 1,344 ± 20 light-years (412.1 ± 6.1 pc) away and is the closest region of massive star formation to Earth. The M42 nebula is estimated to be 24 light-years across. It has a mass of about 2,000 times that of the Sun. Older texts frequently refer to the Orion Nebula as the Great Nebula in Orion or the Great Orion Nebula.
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds of light years, and density from a few to about a million particles per cubic centimetre. The Orion Nebula, now known to be an H II region, was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered.
The Rosette Nebula is an H II region located near one end of a giant molecular cloud in the Monoceros region of the Milky Way Galaxy. The open cluster NGC 2244 is closely associated with the nebulosity, the stars of the cluster having been formed from the nebula's matter.
The Trifid Nebula is an H II region in the north-west of Sagittarius in a star-forming region in the Milky Way's Scutum-Centaurus Arm. It was discovered by Charles Messier on June 5, 1764. Its name means 'three-lobe'. The object is an unusual combination of an open cluster of stars, an emission nebula, a reflection nebula, and a dark nebula. Viewed through a small telescope, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers.
NGC 185 is a dwarf spheroidal galaxy located 2.08 million light-years from Earth, appearing in the constellation Cassiopeia. It is a member of the Local Group, and is a satellite of the Andromeda Galaxy (M31). NGC 185 was discovered by William Herschel on November 30, 1787, and he cataloged it "H II.707". John Herschel observed the object again in 1833 when he cataloged it as "h 35", and then in 1864 when he cataloged it as "GC 90" within his General Catalogue of Nebulae and Clusters. NGC 185 was first photographed between 1898 and 1900 by James Edward Keeler with the Crossley Reflector of Lick Observatory. Unlike most dwarf elliptical galaxies, NGC 185 contains young stellar clusters, and star formation proceeded at a low rate until the recent past. NGC 185 has an active galactic nucleus (AGN) and is usually classified as a type 2 Seyfert galaxy, though its status as a Seyfert is questioned. It is possibly the closest Seyfert galaxy to Earth, and is the only known Seyfert in the Local Group.
NGC 2362, also known as Caldwell 64, is an open cluster of stars in the southern constellation of Canis Major. It was discovered by the Italian court astronomer Giovanni Batista Hodierna, who published his finding in 1654. William Herschel called it a "beautiful cluster", while William Henry Smyth said it "has a beautiful appearance, the bright white star being surrounded by a rich gathering of minute companions, in a slightly elongated form, and nearly vertical position". In the past it has also been listed as a nebula, but in 1930 Robert J. Trumpler found no evidence of nebulosity. The brightest member star system is Tau Canis Majoris, and therefore it is sometimes called the Tau Canis Majoris Cluster.
NGC 3603 is a nebula situated in the Carina–Sagittarius Arm of the Milky Way around 20,000 light-years away from the Solar System. It is a massive H II region containing a very compact open cluster HD 97950.
NGC 1850 is a double cluster and a super star cluster in the Dorado constellation, located in the northwest part of the bar of the Large Magellanic Cloud, at a distance of 168 kly (51.5 kpc) from the Sun. It was discovered by Scottish astronomer James Dunlop in 1826.
The Flame Nebula, designated as NGC 2024 and Sh2-277, is an emission nebula in the constellation Orion. It is about 900 to 1,500 light-years away.
A super star cluster (SSC) is a very massive young open cluster that is thought to be the precursor of a globular cluster. These clusters called "super" because they are relatively more luminous and contain more mass than other young star clusters. The SSC, however, does not have to physically be larger than other clusters of lower mass and luminosity. They typically contain a very large number of young, massive stars that ionize a surrounding HII region or a so-called "Ultra dense HII region (UDHII)" in the Milky Way Galaxy or in other galaxies. An SSC's HII region is in turn surrounded by a cocoon of dust. In many cases, the stars and the HII regions will be invisible to observations in certain wavelengths of light, such as the visible spectrum, due to high levels of extinction. As a result, the youngest SSCs are best observed and photographed in radio and infrared. SSCs, such as Westerlund 1 (Wd1), have been found in the Milky Way Galaxy. However, most have been observed in farther regions of the universe. In the galaxy M82 alone, 197 young SSCs have been observed and identified using the Hubble Space Telescope.
NGC 6357 is a diffuse nebula near NGC 6334 in the constellation Scorpius. The nebula contains many proto-stars shielded by dark discs of gas, and young stars wrapped in expanding "cocoons" or expanding gases surrounding these small stars. It is also known as the Lobster Nebula. This nebula was given the name War and Peace Nebula by the Midcourse Space Experiment scientists because of its appearance, which, in infrared images the bright, western part resembles a dove, while the eastern part looks like a skull. A petition by anime fans to rename it as the Madokami nebula, due to resemblance with a character, did not prosper.
NGC 2366 is a Magellanic barred irregular dwarf galaxy located in the constellation Camelopardalis.
WR 7 is a Wolf–Rayet star in the constellation of Canis Major. It lies at the centre of a complex bubble of gas which is shocked and partially ionised by the star's radiation and winds.
IRC −10414 is a red supergiant and runaway star in the constellation Scutum, a rare case of a red supergiant with a bow shock.
Vela Molecular Ridge is a molecular cloud complex in the constellations Vela and Puppis. Radio 12CO observations of the region showed the ridge to be composed of several clouds, each with masses 100,000–1,000,000 M☉. This cloud complex lies on the sky in the direction of the Gum Nebula (foreground) and the Carina–Sagittarius Spiral Arm (background). The most important clouds in the region are identified by the letters A, B, C and D, and in fact belong to two different complexes: the clouds A, C and D are located at an average distance of about 700-1000 parsecs and are related to the OB association Vela R2, while cloud B is located at a greater distance, up to 2000 parsecs away, and is physically connected to the extended Vela OB1 association.
NGC 654 is an open cluster in the constellation Cassiopeia. It was discovered by William Herschel in 1787. With apparent magnitude 6.5, it can be observed by binoculars. It is located 2,5° northeast of the star Delta Cassiopeiae. In the same low power field can also be seen the open clusters NGC 663 and NGC 659. It surrounds a 7th magnitude yellowish star, an F5Ia supergiant, which is a possible member of the group.
NGC 2539 is an open cluster in the constellation Puppis, located at the north edge of the constellation. It was discovered by William Herschel on January 31, 1785. It is a moderately rich cluster and with little central concentration, with Trumpler class II1m.
N11 is the brightest emission nebula in the north-west part of the Large Magellanic Cloud in the Dorado constellation. The N11 complex is the second largest H II region of that galaxy, the largest being the Tarantula Nebula. It covers an area approximately 6 arc minutes across. It has an elliptical shape and consists of a large bubble, generally clear interstellar area, surrounded by nine large nebulae. It was named by Karl Henize in 1956.
NGC 3256 is a peculiar galaxy formed from the collision of two separate galaxies in the constellation of Vela. NGC 3256 is located about 100 million light-years away and belongs to the Hydra–Centaurus Supercluster complex. NGC 3256 provides a nearby template for studying the properties of young star clusters in tidal tails. The system hides a double nucleus and a tangle of dust lanes in the central region. The telltale signs of the collision are two extended luminous tails swirling out from the galaxy. The tails are studded with a particularly high density of star clusters. NGC 3256 is the most luminous galaxy in the infrared spectrum located within z 0.01 from Earth.
NGC 1142 is a distorted spiral galaxy in the constellation of Cetus. It is located about 370 million light years away from Earth, which means, given its apparent dimensions, that NGC 1142 is approximately 170,000 light years across. It is a type 2 Seyfert galaxy. It interacts with the elliptical galaxy NGC 1141.
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