Orion Nebula

The entire Orion Nebula in visible light. Credit: NASA/ESA Image File history File links Download high-resolution version (18000x18000, 18853 KB)Do not load this image in your browser; it is too large and may cause your browser to hang. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States Government, responsible for that nations public space program. ... This article is about the European Space Agency. ...
Observation data: J2000 epoch
Type:	Reflection and Emission
Right ascension:	05h 35m 17.3s[1]
Declination:	-05° 23′ 28″[1]
Distance:	1,500 ly (450 pc)[2]
Apparent magnitude (V):	+3.0[3]
Apparent dimensions (V):	65 × 60 arcmins[4]
Constellation:	Orion
Physical characteristics
Radius:	15 ly[a]
Absolute magnitude (V):	—
Notable features:	Trapezium cluster
Other designations:	NGC 1976, M42, LBN 974
See also: Diffuse nebula, Lists of nebulae

The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a diffuse nebula situated south^[b] of Orion's Belt. It is one of the brightest nebulae, and is visible to the naked eye in the night sky. M42 is located at a distance of about 1,500 light years away, and is the closest region of star formation to Earth. The M42 nebula is estimated to be 30 light years across. Older texts frequently referred to the Orion Nebula as the Great Nebula. The J2000. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... In astronomy, diffuse nebulae is the common term for both reflection nebulae and emission nebulae. ... Equatorial Coordinates Right ascension (abbrev. ... In astronomy, declination (abbrev. ... To help compare different orders of magnitude, this page lists distances between 1019 m (1,100 light years) and 1020 m (11,000 light years). ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one Julian year. ... Stellar parallax motion The parsec (symbol pc) is a unit of length used in astronomy. ... // Headline text HEY!! HOW ARE YOU ALL?? Its nice of you to come read this page. ... This article or section does not cite its references or sources. ... This article or section does not cite its references or sources. ... Orion (IPA: ), a constellation often referred to as The Hunter, is a prominent constellation, perhaps the best-known and most conspicuous in the sky. ... Remote Authentication Dial In User Service (RADIUS) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one Julian year. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ... This article is about the open cluster. ... In astronomy, diffuse nebulae is the common term for both reflection nebulae and emission nebulae. ... In astronomy, diffuse nebulae is the common term for both reflection nebulae and emission nebulae. ... Orion (IPA: ), a constellation often referred to as The Hunter, is a prominent constellation, perhaps the best-known and most conspicuous in the sky. ... The Triangulum Emission Nebula NGC 604 lies in a spiral arm of Galaxy M33, 2. ... The naked eye is a figure of speech referring to human visual perception that is unaided by enhancing equipment, such as a telescope or binoculars. ... To help compare different orders of magnitude, this page lists distances between 1019 m (1,100 light years) and 1020 m (11,000 light years). ... Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... To help compare different distances this page lists lengths between 1017 m (11 light years) and 1018 m (110 light years). ...

The Orion Nebula is considered to be one of the most scrutinized and photographed objects in the night sky, and is among the most intensely-studied celestial features.^[5] The nebula has revealed much about the process of how stars and planetary systems are formed from collapsing clouds of gas and dust. Astronomers have directly observed protoplanetary disks, brown dwarfs, intense and turbulent motions of the gas, and the photo-ionizing effects of massive nearby stars in the nebula. This article is about the astronomical object. ... The eight planets and three dwarf planets of the Solar System. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. ... Photoionisation is a physical process in which a photon strikes an atom, ion or molecule, resulting in the ejection of an electron. ...

General information

The Orion Nebula is in fact part of a much larger nebula that is known as the Orion Molecular Cloud Complex. The Orion Molecular Cloud Complex extends throughout the constellation of Orion and includes Barnard's Loop, the Horsehead Nebula, and M78. M43 is also part of M42, as well as several nearby reflection nebulae noted in the New General Catalogue. Stars are forming throughout the Orion Nebula, and due to this heat-intensive process the region is particularly prominent in the infrared. A picture of Barnards Loop, which is a primary component of the nebula complex. ... This article or section does not cite its references or sources. ... Barnards Loop nebula can be seen on the photo as a diffuse red semi-circle Above photo of Barnards Loop nebula in inverted black and white of the red channel; the loop can be seen now better Barnards Loop (catalogue designation Sh 2-276) is an emission... The Horsehead Nebula (also known as Barnard 33 or IC 434) is a dark nebula in the Orion constellation. ... The Diffuse Nebula M78 (also known as Messier Object 78, Messier 78, M78, or NGC 2068) is a diffuse nebula in the Orion constellation. ... De Mairans Nebula (also known as M43 and NGC 1982) is an H II region in the Orion constellation. ... The New General Catalogue (NGC) is the most well-known catalogue of deep sky objects in amateur astronomy. ... Image of two girls in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ...

The nebula is visible with the naked eye even from areas affected by some light pollution. It is seen as the middle "star" in the sword of Orion, which are the three stars located south of Orion's Belt. The star appears fuzzy to sharp-eyed observers, and the nebulosity is obvious through binoculars or a small telescope. This time exposure photo of New York City shows sky glow, one form of light pollution. ... Porro-prism binoculars with central focusing Binocular telescopes, or binoculars, (also known as field glasses) are two identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes (Binocular vision) when viewing distant objects. ... A telescope (from the Greek tele = far and skopein = to look or see; teleskopos = far-seeing) is an instrument designed for the observation of remote objects. ...

The Orion Nebula contains a very young open cluster, known as the Trapezium due to the asterism of its primary four stars. Two of these can be resolved into their component binary systems on nights with good seeing, giving a total of six stars. The stars of the Trapezium, along with many other stars, are still in their early years. The Trapezium may be a component of the much-larger Orion Nebula Cluster, an association of about 2,000 stars within a diameter of 20 light years. Two million years ago this cluster may have been the home of the runaway stars AE Aurigae, 53 Arietis, and Mu Columbae, which are currently moving away from the nebula at velocities greater than 100 km/s.^[6] The Pleiades is one of the most famous open clusters. ... This article is about the open cluster. ... In astronomy, an asterism is a recognized pattern of stars seen in Earths sky which is neither an official constellation nor a true star cluster. ... Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a turbulent layer in the atmosphere. ... Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ... A runaway star is one which is moving through space with an abnormally high velocity compared to other stars around it. ... AE Aurigae is a runaway star in the constellation Auriga. ... 54 Arietis is a star in the constellation Aries. ... Mu Columbae (μ Col / μ Columbae) is a star in the constellation of Columba. ...

Observers have long noted a distinctive greenish tint to the nebula, in addition to regions of red and areas of blue-violet. The red hue is well-understood to be caused by H^α recombination line radiation at a wavelength of 656.3 nm. The blue-violet coloration is the reflected radiation from the massive O-class stars at the core of the nebula. In physics and astronomy, H-alpha, also written Hα, is a particular emission line created by hydrogen. ... Radiation in physics is the process of emitting energy in the form of waves or particles. ... The wavelength is the distance between repeating units of a wave pattern. ... A nanometre (American spelling: nanometer) is 1. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ...

The green hue was a puzzle for astronomers in the early part of the 20th century because none of the known spectral lines at that time could explain it. There was some speculation that the lines were caused by a new element, and the name "nebulum" was coined for this mysterious material. With better understanding of atomic physics, however, it was later determined that the green spectra was caused by a low-probability electron transition in doubly-ionized oxygen, a so-called "forbidden transition". This radiation was all but impossible to reproduce in the laboratory because it depended on the quiescent and nearly collision-free environment found in deep space.^[7] A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ... e- redirects here. ... “Multivalent” redirects here. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... A forbidden line is a spectral line emitted by atoms undergoing energy transitions not normally allowed by the selection rules of quantum mechanics. ...

History

Messier's drawing of the Orion Nebula in his 1771 memoir

The Maya of Central America had a folk tale which dealt with the Orion constellation's part of the sky. Their traditional hearths included in their middle a smudge of glowing fire that corresponded with the Orion nebula. This is clear pre-telescope evidence that the Maya detected a diffuse area of the sky contrary to the pin points of stars.^[8] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... 74. ... Map of Central America Central America is the central geographic region of the Americas. ... In common historic and modern usage, a hearth (Her-earth) is a brick- or stone-lined fireplace or oven used for cooking and/or heating. ...

This nebula is currently visible to the unaided eye, yet oddly there is no mention of the nebulosity in the written astronomical records prior to the 17th century. In particular, neither Ptolemy in the Almagest nor Al Sufi in his Book of Fixed Stars noted this nebula, even though they both listed patches of nebulosity elsewhere in the night sky. Curiously this nebula was also not mentioned by Galileo, even though he made telescope observations of this part of the Orion constellation in 1610 and 1617.^[9] This has led to some speculation that a flare-up of the illuminating stars may have increased the brightness of the nebula.^[10] A medieval artists rendition of Claudius Ptolemaeus Claudius Ptolemaeus (Greek: ; c. ... Almagest is the Latin form of the Arabic name (al-kitabu-l-mijisti, i. ... Al Sufi The constellation Centaurus from The Depiction of Celestial Constellations. ... Abd Al-Rahman Al Sufi published his famous Book of Fixed Stars around 964, in Arabic, although the author himself was probably Persian. ... KDFSAJFKASJDKFJASDKLJFDKLASJFLKJASKLFJLAKSJFLKSJALFKJSKLJFto the Sun-centered solar system which Galileo supported. ...

The Orion Nebula is generally credited as being first discovered in 1610 by Nicolas-Claude Fabri de Peiresc as noted in Peiresc's own records. Johann Baptist Cysat, a Jesuit astronomer, was the first to publish note of it (albeit somewhat ambiguously) in a book about a bright comet in 1618. It was independently discovered by several prominent astronomers in the following years, including Christiaan Huygens in 1656 (whose sketch was the first published in 1659). Charles Messier first noted the nebula on March 4, 1769, and he also noted three of the stars in Trapezium. (The first detection of these three stars is now credited to Galileo in 1617, but he did not notice the surrounding nebula—possible due to the narrow field of vision of his early telescope.) Charles Messier published the first edition of his catalog of deep sky objects in 1774 (completed in 1771).^[11] As the Orion Nebula was the 42nd object in his list, it became identified as M42. // Events January 7 - Galileo Galilei discovers the Galilean moons of Jupiter. ... Nicolas-Claude Fabri de Peiresc (December 1, 1580 – June 24, 1637) was a French astronomer and savant who maintained a wide correspondence with scientists and was a successful organizer of scientific inquiry, whose own researches were not confined to the matter of determining the difference in longitude of various locations... Johann Baptist Cysat, holding a Jacobs staff Johann Baptist Cysat (Latinized as Cysatus; in French, Jean-Baptiste Cysat) (ca. ... Comet Hale-Bopp Comet McNaught as seen from Swifts Creek, Victoria, Australia on 23 January 2007 A comet is a small body in the solar system that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail â€” both primarily from the effects of... Events March 8 - Johannes Kepler discovers the third law of planetary motion (he soon rejects the idea after some initial calculations were made but on May 15 confirms the discovery). ... Christiaan Huygens Christiaan Huygens (pronounced in English (IPA): ; in Dutch: )(April 14, 1629–July 8, 1695), was a Dutch mathematician, astronomer and physicist; born in The Hague as the son of Constantijn Huygens. ... // Events Mehmed Köprülü becomes Grand Vizier of the Ottoman Empire. ... // Events May 25 - Richard Cromwell resigns as Lord Protector of England following the restoration of the Long Parliament, beginning a second brief period of the republican government called the Commonwealth. ... Charles Messier Charles Messier (June 26, 1730 – April 12, 1817) was a French astronomer who in 1774 published a catalogue of 45 deep sky objects such as nebulae and star clusters. ... March 4 is the 63rd day of the year in the Gregorian Calendar (64th in leap years). ... 1769 was a common year starting on Sunday (see link for calendar). ... Events Change of emperor of the Ottoman Empire from Ahmed I (1603-1617) to Mustafa I (1617-1623). ... A telescope (from the Greek tele = far and skopein = to look or see; teleskopos = far-seeing) is an instrument designed for the observation of remote objects. ... Chesma Column in Tsarskoe Selo, commemorating the end of the Russo-Turkish War. ... 1771 was a common year starting on Tuesday (see link for calendar). ...

Spectroscopy done by William Huggins showed the gaseous nature of the nebula in 1865. Henry Draper took the first astrophoto of the Orion Nebula on September 30, 1880, which is credited with being the first instance of deep-sky astrophotography in history. Extremely high resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of matter and its properties by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation. ... William Huggins Sir William Huggins, OM , FRS (February 7, 1824 – May 12, 1910) was a British astronomer. ... 1865 (MDCCCLXV) is a common year starting on Sunday. ... Henry Draper (March 7, 1837 – November 20, 1882) was an American doctor and astronomer. ... Astrophotography is a specialised type of photography that entails making photographs of astronomical objects in the night sky such as planets, stars, and deep sky objects such as star clusters and galaxies. ... September 30 is the 273rd day of the year (274th in leap years) in the Gregorian calendar. ... Year 1880 (MDCCCLXXX) was a leap year starting on Thursday (link will display the full calendar). ...

In 1902, Vogel and Eberhard discovered differing velocities within the nebula and by 1914 astronomers at Marseilles had used the interferometer to detect rotation and irregular motions. Campbell and Moore confirmed these results using the spectrograph, demonstrating turbulence within the nebula.^[12] 1902 (MCMII) was a common year starting on Wednesday (see link for calendar). ... Hermann Carl Vogel (April 3, 1841 – August 13, 1907) was a German astronomer. ... 1914 (MCMXIV) was a common year starting on Thursday (see link for calendar). ... Marseilles redirects here. ...

In 1931, Robert J. Trumpler noted that the fainter stars near the Trapezium formed a cluster, and he was the first to name them the Trapezium cluster. Based on their magnitudes and spectral types, he derived a distance estimate of 1,800 light years. This was three times further than the commonly-accepted distance estimate of the period but was much closer to the modern value. ^[13] 1931 (MCMXXXI) was a common year starting on Thursday (link is to a full 1931 calendar). ... Robert Julius Trumpler (October 2, 1886 – September 10, 1956) was a Swiss-American astronomer. ... This article is about the open cluster. ...

In 1993, the Hubble Space Telescope first observed the Orion Nebula. Since then, the nebula has been a frequent target for HST studies. The images have been used to build a detailed model of the nebula in three dimensions. Protoplanetary disks have been observed around most of the newly-formed stars in the nebula, and the destructive effects of high level of ultraviolet energy from the most massive stars has been studied.^[14] el 18 de mayo nacio claudia // 1993 (MCMXCIII) was a common year starting on Friday of the Gregorian calendar and marked the Beginning of the International Decade to Combat Racism and Racial Discrimination (1993-2003). ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... UV redirects here. ...

In 2005, the Advanced Camera for Surveys instrument of the Hubble Space Telescope finished capturing the most detailed image of the nebula yet taken. The image was taken through 104 orbits of the telescope, capturing over 3,000 stars down to the 23rd magnitude, including infant brown dwarfs and possible brown dwarf binary stars.^[15] A year later, scientists working with the HST announced the first ever masses of a pair of eclipsing binary brown dwarfs, 2MASS J05352184–0546085. The pair are located in the Orion Nebula and have approximate masses of 0.054 M_☉ and 0.034 M_☉ respectively, with an orbital period of 9.8 days. Surprisingly, the more massive of the two also turned out to be the less luminous.^[16] 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. ... This article is about the astronomical phenomenon. ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ...

Structure

Optical images reveal clouds of gas and dust in the Orion Nebula; an infrared image (right) reveals the new stars shining within. Credit: C. R. O'Dell-Vanderbilt University, NASA, and ESA.

The entirety of the Orion Nebula extends across a 10° region of the sky, and includes neutral clouds of gas and dust, associations of stars, ionized volumes of gas and reflection nebulae. Two views of the Trapezium cluster in the Orion Nebula, from the Hubble Space Telescope. ... Two views of the Trapezium cluster in the Orion Nebula, from the Hubble Space Telescope. ... Interstellar cloud is the generic name given to an accumulation of gas, plasma and dust in our and other galaxies. ... This article or section does not cite its references or sources. ... NGC 604, a giant H II region in the Triangulum Galaxy. ... The Witch Head reflection nebula (IC2118), about 1000 light years from earth, is associated with the bright star Rigel in the constellation Orion. ...

The nebula forms a roughly spherical cloud that peaks in density near the core.^[17] The cloud has a temperature ranging up to 10,000 K, but this temperature falls dramatically near the edge of the nebula.^[18] Unlike the density distribution, the cloud displays a range of velocities and turbulence, particularly around the core region. Relative movements are up to 10 km/s (22,000 mi/h), with local variations of up to 50 km/s and possibly higher.

The current astronomical model for the nebula consists of an ionized region roughly centered on θ¹ C Orionis, the star responsible for most of the ultraviolet ionizing radiation. (It emits 3-4 times as much photoionizing light as the next brightest star, θ² A Orionis.^[19]) This is surrounded by an irregular, concave bay of more neutral, high-density cloud, with clumps of neutral gas lying outside the bay area. This in turn lies on the perimeter of the Orion Molecular Cloud. Theta1 C Orionis is a member of the Trapezium open cluster that lies within the Orion Nebula. ... UV redirects here. ...

Observers have given names to various features in the Orion Nebula. The dark lane that extends from the north toward the bright region is called the "Fish's Mouth". The illuminated regions to both sides are called the "Wings". Other features include "The Sword", "The Thrust" and "The Sail".^[20]

Stellar formation

View of several proplyds within the Orion Nebula taken by the Hubble Space Telescope. Credit:NASA/ESA.

The Orion Nebula is an example of a stellar nursery where new stars are being born. Observations of the nebula have revealed approximately 700 stars in various stages of formation within the nebula. Image File history File links M42proplyds. ... Image File history File links M42proplyds. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... A stellar nursery is a massive cosmic dust cloud in which microscopic particles may slowly aggregate due to gravitational attraction and eventually give rise to protostars and subsequently planetary systems, with one or more stars and planets. ...

Recent observations with the Hubble Space Telescope have yielded the major discovery of protoplanetary disks within the Orion Nebula, which have been dubbed proplyds.^[21] HST has revealed more than 150 of these within the nebula, and they are considered to be systems in the earliest stages of solar system formation. The sheer numbers of them have been used as evidence that the formation of solar systems is fairly common in our universe. The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... The theories concerning the formation and evolution of the Solar System are complex and varied, interweaving various scientific disciplines, from astronomy and physics to geology and planetary science. ... Universe is a word derived from the Old French univers, which in turn comes from the Latin roots unus (one) and versus (a form of vertere, to turn). Based on observations of the observable universe, physicists attempt to describe the whole of space-time, including all matter and energy and...

Stars form when clumps of hydrogen and other gases in an H II region contract under their own gravity. As the gas collapses, the central clump grows stronger and the gas heats to extreme temperatures by converting gravitational potential energy to thermal energy. If the temperature gets high enough, nuclear fusion will ignite and form a protostar. The protostar is 'born' when it begins to emit enough radiative energy to balance out its gravity and halt gravitational collapse. In astronomy, stellar evolution is the sequence of radical changes that a star undergoes during its lifetime (the time in which it emits light and heat). ... This article is about the chemistry of hydrogen. ... NGC 604, a giant H II region in the Triangulum Galaxy. ... Potential energy (U, or Ep), a kind of scalar potential, is energy by virtue of matter being able to move to a lower-energy state, releasing energy in some form. ... 1. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... A Protostar is an object that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium. ... This article or section does not cite its references or sources. ...

Typically, a cloud of material remains a substantial distance from the star before the fusion reaction ignites. This remnant cloud is the protostar's protoplanetary disk, where planets may form. Recent infrared observations show that dust grains in these protoplanetary disks are growing, beginning on the path towards forming planetesimals.^[22] Image of two girls in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... ÈàÌàìòòIn cosmogony, planetesimals are objects thought to exist within solar nebulae. ...

Once the protostar enters into its main sequence phase, it is classified as a star. Even though most planetary disks can form planets, observations show that intense stellar radiation should have destroyed any proplyds that formed near the Trapezium group, if the group is as old as the low mass stars in the cluster.^[14] Since proplyds are found very close to the Trapezium group, it can be argued that those stars are much younger than the rest of the cluster members.^[c] Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ...

Stellar wind and effects

Once formed, the stars within the nebula emit a stream of charged particles known as a stellar wind. Massive stars and young stars have much stronger stellar winds than the Sun.^[23] The wind forms shock waves when it encounters the gas in the nebula, which then shapes the gas clouds. The shock waves from stellar wind also play a large part in stellar formation by compacting the gas clouds, creating density inhomogeneities that lead to gravitational collapse of the cloud. A solar wind is a stream of particles (mostly high-energy protons ~ 500 keV) which are ejected from the upper atmosphere of a star (in the case of a star other than the Earths Sun, it may be called a stellar wind instead). ... OB stars are hot, massive stars stars which form in loosely organized groups called OB associations. ... Drawing of a T-Tauri star with a circumstellar accretion disk T Tauri stars are a class of variable stars named after their prototype - T Tauri. ... The Sun is the star at the center of the Solar System. ...

Herbig-Haro 47 seen with a bow shock and a series of jet-driven shocks [1].

There are three different kinds of shocks in the Orion Nebula. Many are featured in Herbig-Haro objects:^[24] Image File history File links Download high resolution version (888x496, 2174 KB) Animation of Hubble Space Telescope images of Herbig-Haro object HH47. ... Image File history File links Download high resolution version (888x496, 2174 KB) Animation of Hubble Space Telescope images of Herbig-Haro object HH47. ... Herbig-Haro object HH47, imaged by the Hubble Space Telescope. ... In a planetary magnetosphere, the bow shock is the boundary at which the solar wind abruptly drops as a result of its approach to the magnetopause. ... Herbig-Haro object HH47, imaged by the Hubble Space Telescope. ...

• Bow shocks are stationary and are formed when two particle streams collide with each other. They are present near the hottest stars in the nebula where the stellar wind speed is estimated to be thousands of kilometers per second and in the outer parts of the nebula where the speeds are tens of kilometers per second. Bow shocks can also form at the front end of stellar jets when the jet hits interstellar particles.

• Jet-driven shocks are formed from jets of material sprouting off newborn T Tauri stars. These narrow streams are traveling at hundreds of kilometers per second, and become shocks when they encounter relatively stationary gasses.

• Warped shocks appear bow-like to an observer. They are produced when a jet-driven shock encounters gas moving in a cross-current.

The dynamic gas motions in M42 are complex, but are trending out through the opening in the bay and toward the Earth.^[25] The large neutral area behind the ionized region is currently contracting under its own gravity. In a planetary magnetosphere, the bow shock is the boundary at which the solar wind abruptly drops as a result of its approach to the magnetopause. ... The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. ... T Tauri stars are a class of variable stars named after their prototype T Tauri. ...

Evolution

Panoramic image of the center of the nebula, taken by the Hubble Telescope. This view is about 2.5 light years across. The Trapezium is at center left. Credit:NASA/ESA.

Interstellar clouds like the Orion Nebula are found throughout galaxies such as the Milky Way. They begin as gravitationally-bound blobs of cold, neutral hydrogen, intermixed with traces of other elements. The cloud can contain hundreds of thousands of solar masses and extend for hundreds of light years. The tiny force of gravity that could compel the cloud to collapse is counter-balanced by the very faint pressure of the gas in the cloud. Image File history File links Download high resolution version (743x800, 77 KB)The Orion nebula in true colour. ... Image File history File links Download high resolution version (743x800, 77 KB)The Orion nebula in true colour. ... Interstellar cloud is the generic name given to an accumulation of gas, plasma and dust in our and other galaxies. ... NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 17,000 parsecs in diameter and approximately 20 million parsecs distant. ... It has been suggested that Andromeda-Milky Way collision be merged into this article or section. ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ...

Whether due to collisions with a spiral arm, or through the shock wave emitted from supernovae, the atoms are precipitated into heavier molecules and the result is a molecular cloud. This presages the formation of stars within the cloud, usually thought to be within a period of 10-30 million years, as regions pass the Jeans mass and the destabilized volumes collapse into disks. The disk concentrates at the core to form a star, which may be surrounded by a protoplanetary disk. This is the current stage of evolution of the nebula, with additional stars still forming from the collapsing molecular cloud. The youngest and brightest stars we now see in the Orion Nebula are thought to be less than 300,000 years old^[26], and the brightest may be only 10,000 years in age. Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... The British physicist Sir James Jeans considered the process of gravitional collapse within a gaseous cloud. ...

Some of these collapsing stars can be particularly massive, and can emit large quantities of ionizing ultraviolet radiation. An example of this is seen with the Trapezium cluster. Over time the ultraviolet light from the massive stars at the center of the nebula will push away the surrounding gas and dust in a process called photo evaporation. This process is responsible for creating the interior cavity of the nebula, allowing the stars at the core to be viewed from Earth.^[5] The largest of these stars have short life spans and will evolve to become supernovae. UV redirects here. ... Photo evaporation is the effect when a young stellar object (YSO) disperses its disk by radiation. ...

Within about 100,000 years, most of the gas and dust will be ejected. The remains will form a young open cluster, a cluster of bright, young stars surrounded by wispy filaments from the former cloud. The Pleiades is a famous example of such a cluster. The Pleiades are an open cluster dominated by hot blue stars surrounded by reflection nebulosity A shorter exposure shows less nebulosity. ...

See also

• List of Messier objects
• New General Catalogue
• List of diffuse nebulae

Table of images of all 110 Messier objects. ... The New General Catalogue (NGC) is the most well-known catalogue of deep sky objects in amateur astronomy. ... Barnards Loop Boomerang Nebula Bubble Nebula Bubble Nebula in Barnards Galaxy California Nebula Corona Australis Nebula Cone Nebula Crescent Nebula Double Helix Nebula Eagle Nebula Elephants Trunk Nebula Eta Carinae Nebula Flame Nebula Gum Nebula Lagoon Nebula North America Nebula Omega Nebula Orion Nebula Pistol Nebula Rosette...

Notes

References

For the Manfred Mann album, see 2006 (album). ... October 20 is the 293rd day of the year (294th in leap years) in the Gregorian Calendar, with 72 days remaining. ... For the Manfred Mann album, see 2006 (album). ... October 14 is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... For the Manfred Mann album, see 2006 (album). ... October 19 is the 292nd day of the year (293rd in leap years) in the Gregorian calendar. ... For the Manfred Mann album, see 2006 (album). ... October 27 is the 300th day of the year (301st in leap years) in the Gregorian Calendar, with 65 days remaining. ... For the Manfred Mann album, see 2006 (album). ... October 27 is the 300th day of the year (301st in leap years) in the Gregorian Calendar, with 65 days remaining. ... Charles Messier Charles Messier (June 26, 1730 – April 12, 1817) was a French astronomer who in 1774 published a catalogue of 45 deep sky objects such as nebulae and star clusters. ... Chesma Column in Tsarskoe Selo, commemorating the end of the Russo-Turkish War. ... 1974 (MCMLXXIV) was a common year starting on Tuesday. ... 2000 (MM) was a leap year starting on Saturday of the Gregorian calendar. ...

External links

• Orion Nebula at ESA/Hubble
• Messier 42, SEDS Messier pages and specifically NGC 1976.
• January 2006 Hubble Space Telescope image of the Orion Nebula
• January 2006 Hubble Space Telescope image of the Trapezium cluster
• Orion Nebula M42, Hubble Images
• Remarkable new views captured of Orion Nebula, SpaceFlight Now, 2001.
• NightSkyInfo.com - The Great Orion Nebula
• Computer visualization of Orion Nebula. Data gathered from the Hubble Space Telescope and ground-based sensors were combined to form a 3D volume visualization of the nebula. Narration of the planetarium-like flythrough describes notable features and views from angles not possible from Earth. Link contains downloadable MPEG and Quicktime movies of flythrough.