Crab Nebula

M1, the Crab Nebula. Courtesy of NASA/ESA Image File history File linksMetadata Download high resolution version (2224x2212, 3149 KB) Summary Image: A Giant Hubble Mosaic of the Crab Nebula Source: http://hubblesite. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States federal government, responsible for the nations public space program. ... This article is about the European Space Agency. ...
Observation data: J2000.0 epoch
Type:	Supernova Remnant
Right ascension:	05h 34m 31.97s[1]
Declination:	+22° 00′ 52.1″[1]
Distance:	6,300 ly
Apparent magnitude (V):	+8.4
Apparent dimensions (V):	6 × 4 arcmin
Constellation:	Taurus
Physical characteristics
Radius:	3 ly
Absolute magnitude (V):	−3
Notable features:	Optical pulsar
Other designations:	M 1,[1] NGC 1952[1]
See also: Diffuse nebula, Lists of nebulae

The Crab Nebula (catalogue designations M 1, NGC 1952, Taurus A) is a supernova remnant in the constellation of Taurus. The nebula was first observed in 1731 by John Bevis. It is the remnant of a supernova that was recorded, as a star visible in daylight, by Chinese and Arab astronomers in 1054. Located at a distance of about 6,300 light years (2 kpc) from Earth, the nebula has a diameter of 11 ly (3.4 pc) and is expanding at a rate of about 1,500 kilometres per second. It has been suggested that this article or section be merged into Julian epoch. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... The Crab Nebula is an expanding cloud of gas created by the 1054 supernova. ... Equatorial Coordinates Right ascension (abbrev. ... In astronomy, declination (abbrev. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... This article or section does not cite its references or sources. ... This article or section does not adequately cite its references or sources. ... |10 Tau]] | stardistance = 44. ... Circle illustration In classical geometry, a radius (plural: radii) of a circle or sphere is any line segment from its center to its boundary. ... 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. ... It has been suggested that Radio pulsar be merged into this article or section. ... In astronomy, diffuse nebulae is the common term for both reflection nebulae and emission nebulae. ... The Messier objects are a set of astronomical objects catalogued by Charles Messier in his catalogue of Nebulae and Star Clusters first published in 1774. ... The New General Catalogue (NGC) is the most well-known catalogue of deep sky objects in amateur astronomy. ... The Crab Nebula is an expanding cloud of gas created by the 1054 supernova. ... This article or section does not adequately cite its references or sources. ... |10 Tau]] | stardistance = 44. ... It has been suggested that Types of Nebulae be merged into this article or section. ... John Bevis (October 31, 1693 – November 6, 1771) was an English doctor and astronomer. ... This is a sub-article of Islamic science and astronomy. ... SN 1054 was a supernova that was widely seen on Earth in the year 1054. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... Stellar parallax motion The parsec (symbol pc) is a unit of length used in astronomy. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... It has been suggested that Types of Nebulae be merged into this article or section. ... km redirects here. ... Look up second in Wiktionary, the free dictionary. ...

The nebula contains a pulsar in its centre which rotates thirty times per second, emitting pulses of radiation, from gamma rays to radio waves. The nebula was the first astronomical object identified with a historical supernova explosion. It has been suggested that Radio pulsar be merged into this article or section. ... Radiation as used in physics, is energy in the form of waves or particles. ... This article is about electromagnetic radiation. ... Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ...

The nebula acts as a source of radiation for studying celestial bodies that occult it. In the 1950s and 1960s, the Sun's corona was mapped from observations of the Crab's radio waves passing through it, and more recently, the thickness of the atmosphere of Saturn's moon Titan was measured as it blocked out X-rays from the nebula. In this July, 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation. ... 1950 (MCML) was a common year starting on Sunday. ... 1960 (MCMLX) was a leap year starting on Friday (the link is to a full 1960 calendar). ... The Sun is the star at the center of the Solar System. ... A corona is a type of plasma atmosphere of the Sun or other celestial body, extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. ... Adjectives: Saturnian Atmosphere Surface pressure: 140 kPa Composition: >93% hydrogen >5% helium 0. ... Titan (, from Ancient Greek Τῑτάν) or Saturn VI is the largest moon of Saturn and the second largest moon in the solar system,[4] after Jupiters moon Ganymede. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz...

Origins

Main article: SN 1054

First observed in 1731 by John Bevis, the nebula was independently rediscovered in 1758 by Charles Messier as he was observing a bright comet. Messier catalogued it as the first entry in his catalogue of comet-like objects. The Earl of Rosse observed the nebula at Birr Castle in the 1840s, and referred to the object as the Crab Nebula because a drawing he made of it looked like a crab.^[2] SN 1054 was a supernova that was widely seen on Earth in the year 1054. ... John Bevis (October 31, 1693 – November 6, 1771) was an English doctor and astronomer. ... 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. ... Comet Hale-Bopp Comet McNaught as seen from Swifts Creek, Victoria, Australia on 23 January 2007 For other uses, see Comet (disambiguation). ... Table of all 110 Messier objects. ... Lord Rosse William Parsons, 3rd Earl of Rosse (June 17, 1800 – October 31, 1867) was an Irish astronomer. ... The castle. ... // Events and Trends Technology First use of general anesthesia in an operation, by Crawford Long The first electrical telegraph sent by Samuel Morse on May 24, 1844 from Baltimore to Washington, D.C.. War, peace and politics First signing of the Treaty of Waitangi (Te Tiriti o Waitangi) on February... Superfamilies Dromiacea Homolodromioidea Dromioidea Homoloidea Eubrachyura Raninoidea Cyclodorippoidea Dorippoidea Calappoidea Leucosioidea Majoidea Hymenosomatoidea Parthenopoidea Retroplumoidea Cancroidea Portunoidea Bythograeoidea Xanthoidea Bellioidea Potamoidea Pseudothelphusoidea Gecarcinucoidea Cryptochiroidea Pinnotheroidea * Ocypodoidea * Grapsoidea * An asterisk (*) marks the crabs included in the clade Thoracotremata. ...

In the early 20th century, the analysis of early photographs of the nebula taken several years apart revealed that it was expanding. Tracing the expansion back revealed that the nebula must have formed about 900 years ago. Historical records revealed that a new star bright enough to be seen in the daytime had been recorded in the same part of the sky by Chinese and Arab astronomers in 1054^[3][4] Given its great distance, the daytime "guest star" observed by the Chinese and Arabs could only have been a supernova—a massive, exploding star, having exhausted its supply of energy from nuclear fusion and collapsed in on itself. 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. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ...

Recent analyses of historical records have found that the supernova that created the Crab Nebula probably occurred in April or early May, rising to its maximum brightness of between apparent magnitude −7 and −4.5 (brighter than everything in the night sky except the Moon) by July. The supernova was visible to the naked eye for about two years after its first observation.^[5] Thanks to the recorded observations of Far Eastern and Middle Eastern astronomers of 1054, Crab Nebula became the first astronomical object recognized as being connected to a supernova explosion.^[4] The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... Apparent magnitude: up to -12. ... 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. ...

Physical conditions

The Crab Pulsar. This image combines optical data from Hubble (in red) and X-ray images from Chandra X-ray Observatory (in blue).

In visible light, the Crab Nebula consists of a broadly oval-shaped mass of filaments, about 6 arcminutes long and 4 arcminutes wide, surrounding a diffuse blue central region (by comparison, the full moon is 30 arcminutes across). The filaments are the remnants of the progenitor star's atmosphere, and consist largely of ionised helium and hydrogen, along with carbon, oxygen, nitrogen, iron, neon and sulphur. The filaments' temperatures are typically between 11,000 and 18,000 K, and their densities are about 1,300 particles per cm³.^[6] Image File history File links Download high-resolution version (2400x2400, 314 KB) A composite image of the Crab Nebula showing the X-ray (blue), and optical (red) images superimposed. ... Image File history File links Download high-resolution version (2400x2400, 314 KB) A composite image of the Crab Nebula showing the X-ray (blue), and optical (red) images superimposed. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... ROSAT image of X-ray fluorescence of, and occultation of the X-ray background by, the Moon. ... For other uses, see Chandra (disambiguation). ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... An oval or ovoid was originally an egg shape (from Latin OVVM); it is now usually used to refer to ellipses, but can also mean any similar shape, such as egg shapes or race-course shapes (a semicircle on either side of a quadrilateral). ... A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60) of one degree. ... Composite image of the Moon as taken by the Galileo spacecraft on 7 December 1992. ... Ionisation can be: the process of creating an ion, see ionization a piece of music by Edgar Varèse; see Ionisation (Varèse) This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Standard atomic weight 4. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Standard atomic weight 12. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... General Name, Symbol, Number neon, Ne, 10 Chemical series noble gases Group, Period, Block 18, 2, p Appearance colorless Standard atomic weight 20. ... For the chemical element see: sulfur. ... The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ... On cubic metre of concrete (figuring the world annual production per inhabitant) The cubic metre (symbol m3) is the SI derived unit of volume. ...

In 1953 Iosif Shklovsky proposed that the diffuse blue region is predominantly produced by synchrotron radiation, which is radiation given off by the curving of electrons moving at speeds up to half the speed of light.^[7] Three years later the theory was confirmed by observations. In the 1960s it was found that the source of the electron curved paths was the strong magnetic field produced by a neutron star at the centre of the nebula.^[8] Iosif Samuilovich Shklovsky (Ио́сиф Самуи́лович Шкло́вский) (July 1, 1916 – March 3, 1985) was a Russian astronomer and astrophysicist. ... Synchrotron radiation is electromagnetic radiation, similar to cyclotron radiation, but generated by the acceleration of ultrarelativistic (i. ... e- redirects here. ... A line showing the speed of light on a scale model of Earth and the Moon The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness. It is the speed of all electromagnetic radiation... In physics, a magnetic field is a force field that surrounds electric current circuits. ...

The Crab Nebula is currently expanding outwards at about 1,500 km/s.^[9] Images taken several years apart reveal the slow expansion of the nebula, and by comparing this angular expansion with its spectroscopically-determined expansion velocity, the nebula's distance can be estimated. Modern observations give a distance to the nebula of about 6,300 ly,^[10] meaning that it is about 11 ly in length. Redshift of spectral lines in the optical spectrum of a supercluster of distant galaxies (right), as compared with that of the Sun (left). ...

Tracing back its expansion consistently yields a date for the creation of the nebula several decades after 1054, implying that its outward velocity has accelerated since the supernova explosion.^[11] This acceleration is believed to be caused by energy from the pulsar that feeds into the nebula's magnetic field, which expands and forces the nebula's filaments outwards.^[12]

Estimates of the total mass of the nebula are important for estimating the mass of the supernova's progenitor star. Estimates of the amount of matter contained in the filaments of the Crab Nebula range from about 1–5 solar masses^[13]; although other estimates based on the investigation of the Crab Pulsar yield different numbers^{[citation needed]}. In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... Categories: Astronomy stubs | Pulsars ...

Central star

Main article: Crab Pulsar

This sequence of Hubble Space Telescope images shows features in the inner Crab Nebula changing over a period of four months. Credit: NASA/ESA.

At the centre of the Crab Nebula are two faint stars, one of which is the star responsible for existence of the nebula. It was identified as such in 1942, when Rudolf Minkowski found that its optical spectrum was extremely unusual.^[14] The region around the star was found to be a strong source of radio waves in 1949^[15] and X-rays in 1963,^[16] and was identified as one of the brightest objects in the sky in gamma rays in 1967.^[17] Then, in 1968, the star was found to be emitting its radiation in rapid pulses, becoming one of the first pulsars to be discovered. Categories: Astronomy stubs | Pulsars ... Image File history File links Download high resolution version (851x550, 57 KB)Hubble Space Telescope observations of features very close to the Crab Pulsar, changing over time. ... Image File history File links Download high resolution version (851x550, 57 KB)Hubble Space Telescope observations of features very close to the Crab Pulsar, changing over time. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States federal government, responsible for the nations public space program. ... This article is about the European Space Agency. ... 1942 (MCMXLII) was a common year starting on January 18 1815 (the link is to a full 1942 calendar). ... Rudolph Minkowski (born Rudolf Leo Bernhard Minkowski) (May 28, 1895 – January 4, 1976) was a German-American astronomer. ... This article is about electromagnetic radiation. ... 1967 (MCMLXVII) was a common year starting on Sunday of the Gregorian calendar (the link is to a full 1967 calendar). ... It has been suggested that Radio pulsar be merged into this article or section. ...

Pulsars are sources of powerful electromagnetic radiation, emitted in short and extremely regular pulses many times a second. They were a great mystery when discovered in 1967, and the team which identified the first one considered the possibility that it could be a signal from an advanced civilization.^[18] However, the discovery of a pulsating radio source in the centre of the Crab Nebula was strong evidence that pulsars were formed by supernova explosions. They are now understood to be rapidly rotating neutron stars, whose powerful magnetic field concentrates their radiation emissions into narrow beams. It has been suggested that this article or section be merged with light. ... A neutron star is one of the few possible endpoints of stellar evolution. ... In physics, a magnetic field is a force field that surrounds electric current circuits. ...

The Crab Pulsar is believed to be about 28-30 km in diameter^[19]; it emits pulses of radiation every 33 milliseconds.^[20] Pulses are emitted at wavelengths across the electromagnetic spectrum, from radio waves to X-rays. Like all isolated pulsars, its period is slowing very gradually. Occasionally, its rotational period shows sharp changes, known as 'glitches', which are believed to be caused by a sudden realignment inside the neutron star. The energy released as the pulsar slows down is enormous, and it powers the emission of the synchrotron radiation of the Crab Nebula, which has a total luminosity about 75,000 times greater than that of the Sun.^[21] One millisecond is one-thousandth of a second. ... The wavelength is the distance between repeating units of a wave pattern. ... Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... Luminosity has different meanings in several different fields of science. ...

The pulsar's extreme energy output creates a unusually dynamic region at the centre of the Crab Nebula. While most astronomical objects evolve so slowly that changes are visible only over timescales of many years, the inner parts of the Crab show changes over timescales of only a few days.^[22] The most dynamic feature in the inner part of the nebula is the point where the pulsar's equatorial wind slams into the bulk of the nebula, forming a shock front. The shape and position of this feature shifts rapidly, with the equatorial wind appearing as a series of wisp-like features that steepen, brighten, then fade as they move away from the pulsar to well out into the main body of the nebula. Introduction The shock wave is one of several different ways in which a gas in a supersonic flow can be compressed. ...

Progenitor star

The Crab Nebula seen in infrared by the Spitzer Space Telescope.

The star that exploded as a supernova is referred to as the supernova's progenitor star. Two types of star explode as supernovae: white dwarfs and massive stars. In the so-called Type Ia supernovae, gases falling onto a white dwarf raise its mass until it nears a critical level, the Chandrasekhar limit, resulting in an explosion; in Type Ib/c and Type II supernovae, the progenitor star is a massive star which runs out of fuel to power its nuclear fusion reactions and collapses in on itself, reaching such phenomenal temperatures that it explodes. The presence of a pulsar in the Crab means it must have formed in a core-collapse supernova; Type Ia supernovae do not produce pulsars. Image File history File links Crab_3. ... Image File history File links Crab_3. ... 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 Spitzer Space Telescope (formerly the Space Infrared Telescope Facility [SIRTF]) is an infrared space observatory, the fourth and final of NASAs Great Observatories. ... This article or section does not adequately cite its references or sources. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... The Chandrasekhar limit, is the maximum mass possible for a white dwarf (one of the end stages of stars when they cool down) and is approximately 3 × 1030 kg, around 1. ... Type Ib and Ic supernovae are categories of stellar explosions. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... Fig. ...

Theoretical models of supernova explosions suggest that the star that exploded to produce the Crab Nebula must have had a mass of between 8 and 12 solar masses. Stars with masses lower than 8 solar masses are thought to be too small to produce supernova explosions, and end their lives by producing a planetary nebula instead, while a star heavier than 12 solar masses would have produced a nebula with a different chemical composition to that observed in the Crab.^[23] Unsolved problems in physics: What causes anything to have mass? The U.S. National Prototype Kilogram, which currently serves as the primary standard for measuring mass in the U.S. Mass is the property of a physical object that quantifies the amount of matter and energy it is equivalent to. ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... NGC 6543, the Cats Eye Nebula A planetary nebula is an astronomical object consisting of a glowing shell of gas and plasma formed by certain types of stars at the end of their lives. ...

A significant problem in studies of the Crab Nebula is that the combined mass of the nebula and the pulsar add up to considerably less than the predicted mass of the progenitor star, and the question of where the 'missing mass' is remains unresolved.^[24] Estimates of the mass of the nebula are made by measuring the total amount of light emitted, and calculating the mass required, given the measured temperature and density of the nebula. Estimates range from about 1–5 solar masses, with 2–3 solar masses being the generally accepted value.^[23] The neutron star mass is estimated to be between 1.4 and 2 solar masses.

The predominant theory to account for the missing mass of the Crab is that a substantial proportion of the mass of the progenitor was carried away before the supernova explosion in a fast stellar wind. However, this would have created a shell around the nebula. Although attempts have been made at several different wavelengths to observe a shell, none has yet been found.^[25] 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). ...

Transits by solar system bodies

Hubble Space Telescope image of a small region of the Crab Nebula, showing its intricate filamentary structure. Credit: NASA/ESA.

The Crab Nebula lies roughly 1½ ° away from the ecliptic—the plane of Earth's orbit around the Sun. This means that the Moon — and occasionally, planets — can transit or occult the nebula. Although the Sun does not transit the nebula, its corona passes in front of it. These transits and occultations can be used to analyse both the nebula and the object passing in front of it, by observing how radiation from the nebula is altered by the transiting body. Image File history File links Download high resolution version (712x800, 87 KB)Hubble Space Telescope image of filaments in the Crab Nebula. ... Image File history File links Download high resolution version (712x800, 87 KB)Hubble Space Telescope image of filaments in the Crab Nebula. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States federal government, responsible for the nations public space program. ... This article is about the European Space Agency. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... Apparent magnitude: up to -12. ... The eight planets and three dwarf planets of the Solar System. ... 2003 Transit of Mercury The term transit or astronomical transit has two meanings in astronomy: A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, as seen by an observer at some particular vantage point. ... In this July, 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation. ... A corona is a type of plasma atmosphere of the Sun or other celestial body, extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. ...

Lunar transits have been used to map X-ray emissions from the nebula. Before the launch of X-ray-observing satellites, such as the Chandra X-ray Observatory, X-ray observations generally had quite low angular resolution, but when the Moon passes in front of the nebula, its position is very accurately known, and so the variations in the nebula's brightness can be used to create maps of X-ray emission.^[26] When X-rays were first observed from the Crab, a lunar occultation was used to determine the exact location of their source.^[16] For other uses, see Chandra (disambiguation). ... Angular resolution describes the resolving power of any optical device such as a telescope, a microscope, a camera, or an eye. ...

The Sun's corona passes in front of the Crab every June. Variations in the radio waves received from the Crab at this time can be used to infer details about the corona's density and structure. Early observations established that the corona extended out to much greater distances than had previously been thought; later observations found that the corona contained substantial density variations.^[27]

Very rarely, Saturn transits the Crab Nebula. Its transit in 2003 was the first since 1296; another will not occur until 2267. Observers used the Chandra X-ray Observatory to observe Saturn's moon Titan as it crossed the nebula, and found that Titan's X-ray 'shadow' was larger than its solid surface, due to absorption of X-rays in its atmosphere. These observations showed that the thickness of Titan's atmosphere is 880 km.^[28] The transit of Saturn itself could not be observed, because Chandra was passing through the Van Allen belts at the time. Adjectives: Saturnian Atmosphere Surface pressure: 140 kPa Composition: >93% hydrogen >5% helium 0. ... Events March 30 - Edward I stormed Berwick-upon-Tweed, sacking the then Scottish border town with much bloodshed. ... The 23rd century (Gregorian Calendar) comprises the years 2201-2300. ... Titan (, from Ancient Greek Τῑτάν) or Saturn VI is the largest moon of Saturn and the second largest moon in the solar system,[4] after Jupiters moon Ganymede. ... Van Allen belts The Van Allen radiation belt is a torus of energetic charged particles around Earth, trapped by Earths magnetic field. ...

In fiction

See Crab Nebula in fiction.

Crab Nebula // Nebulae, being often visually interesting astronomical objects, frequently find themselves used as settings or backdrops for works of science fiction. ...

References

For the Manfred Mann album, see 2006 (album). ... December 25 is the 359th day of the year (360th in leap years) in the Gregorian calendar, with 6 days remaining in the year. ...

External links

Wikimedia Commons has media related to:

Crab Nebula

• Crab Nebula at ESA/Hubble
• Messier 1, SEDS Messier pages
• Images of the Crab from the Chandra X-ray Observatory
• Chandra page about the nebula
• Images of the Crab from the Hubble Space Telescope
• Lord Rosse's drawings of M1, the Crab Nebula from SEDS
• NightSkyInfo.com - M1, the Crab Nebula

Image File history File links Commons-logo. ... The Wikimedia Commons (also called Wikicommons) is a repository of free content images, sound and other multimedia files. ... Students for the Exploration and Development of Space (SEDS) is an international student organization whose purpose is to promote space exploration and development through educational and engineering projects. ... For other uses, see Chandra (disambiguation). ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... Students for the Exploration and Development of Space (SEDS) is an international student organization whose purpose is to promote space exploration and development through educational and engineering projects. ...