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The "Pillars of Creation" from the Eagle Nebula
The Triangulum Emission Garren Nebula NGC 604
The Crab Nebula NASA.ogv
The Crab Nebula video by NASA

A nebula (from Latin: "cloud";[1] pl. nebulae or nebulæ, with ligature or nebulas) is an interstellar cloud of dust, hydrogen gas, helium gas and plasma. Originally nebula was a general name for any extended astronomical object, including galaxies beyond the Milky Way (some examples of the older usage survive; for example, the Andromeda Galaxy was referred to as the Andromeda Nebula before galaxies were discovered by Edwin Hubble). Nebulae often form star-forming regions, such as in the Eagle Nebula. This nebula is depicted in one of NASA's most famous images, the "Pillars of Creation". In these regions the formations of gas, dust and other materials "clump" together to form larger masses, which attract further matter, and eventually will become big enough to form stars. The remaining materials are then believed to form planets, and other planetary system objects.



Evidence exists to support that the Maya may have known about nebulae before the invention of a telescope. The information that supports this theory comes from a folk tale that deals with the Orion constellation's area of the sky. It mentions that there is a smudge around the glowing fire.[1]

At about A.D. 150, Claudius Ptolemaeus (Ptolemy) recorded, in books vii-viii of his Almagest, five stars that appeared nebulous. He also noted a region of nebulosity between the constellations Ursa Major and Leo that was not associated with any star.[2] The first true nebula, as distinct from a star cluster, was mentioned by the Persian astronomer, Abd al-Rahman al-Sufi, in his Book of Fixed Stars (964).[3] He noted the presence of "a little cloud" where the Andromeda Galaxy is located.[4] He also cataloged the Omicron Velorum star cluster as a "nebulous star" as well as other nebulous objects such as Brocchi's Cluster.[3] The supernova that created the Crab Nebula, the SN 1054, was observed by Arabic and Chinese astronomers in 1054.[5][6]

For reasons unknown, Al-Sufi failed to note the Orion Nebula, which is at least as prominent as the Andromeda galaxy in the night sky. On November 26, 1610, Nicolas-Claude Fabri de Peiresc discovered the Orion Nebula using a telescope. This nebula was also observed by Johann Baptist Cysat in 1618. However, the first detailed study of the Orion Nebula wouldn't be performed until 1659 by Christian Huygens, who likewise believed himself to be the first person to discover this nebulosity.[4]

In 1715, Edmund Halley published a list of six nebulae.[7] This number steadily increased during the century, with Jean-Philippe de Cheseaux compiling a list of 20 (including eight not previously known) in 1746. From 1751–53, Nicolas Louis de Lacaille cataloged a total of 42 nebulae from the Cape of Good Hope, with most of them being previously unknown. Charles Messier then compiled a catalog of 103 nebulae by 1781, although his primary goal in doing so was to avoid the false detection of comets.[8]

The number of nebulae was then greatly expanded by the efforts of William Herschel and his sister Caroline Herschel. Their Catalogue of One Thousand New Nebulae and Clusters of Stars was published in 1786. A second catalog of a thousand was published in 1789 and the third and final catalog of 510 appeared in 1802. During much of their work, William Herschel believed that these nebulae were merely unresolved clusters of stars. In 1790, however, he discovered a star surrounded by nebulosity and concluded that this was a true nebulosity, rather than a more distant cluster.[8]

Beginning in 1864, William Huggins examined the spectra of about 70 nebulae. He found that roughly a third of them had the absorption spectra of a gas. The remainder showed a continuous spectrum and thus were thought to consist of a mass of stars.[9][10] A third category was added in 1912 when Vesto Slipher showed that the spectrum of the nebula that surrounded the star Merope matched the spectra of the Pleiades open cluster. Thus the nebula radiates by reflected star light.[11]

Slipher and Edwin Hubble continued to collect the spectra from a number of diffuse nebulae, finding 29 that showed emission spectra and 33 had the continuous spectra of star light.[10] In 1922, Hubble announced that nearly all nebulae are associated with stars, and their illumination comes from star light. He also discovered that the emission spectrum nebulae are nearly always associated with stars having spectral classifications of B1 or hotter (including all O-type main sequence stars), while nebulae with continuous spectra appear with cooler stars.[12] Both Hubble and Henry Norris Russell concluded that the nebulae surrounding the hotter stars are transformed in some manner.[10]


NGC 2024, The Flame Nebula

Many nebulae form from the gravitational collapse of gas in the interstellar medium or ISM. As the material collapses under its own weight, massive stars may form in the center, and their ultraviolet radiation ionises the surrounding gas, which creates plasma, making it visible at optical wavelengths. Examples of these types of nebulae are the Rosette Nebula and the Pelican Nebula. The size of these nebulae, known as HII regions, varies depending on the size of the original cloud of gas. These are sites where star formation occurs. The formed stars are sometimes known as a young, loose cluster.

Some nebulae are formed as the result of supernova explosions, the death throes of massive, short-lived stars. The materials thrown off from the supernova explosion are ionized by the energy and the compact object that it can produce. One of the best examples of this is the Crab Nebula, in Taurus. The supernova event was recorded in the year 1054 and is designated as SN 1054. The compact object that was created after the explosion lies in the center of the Crab Nebula and is a neutron star.

Other nebulae may form as planetary nebulae. This is the final stage of a low-mass star's life, like Earth's Sun. Stars with a mass up to 8-10 solar masses evolve into red giants and slowly lose their outer layers during pulsations in their atmospheres. When a star has lost a sufficient amount of material, its temperature increases and the ultraviolet radiation it emits is capable of ionizing the surrounding nebula that it has thrown off. The nebula is 97% Hydrogen and 3% Helium with trace materials. The main goal in this stage is to achieve equilibrium.

Types of nebulae


Classical types

Nebulae are classified in four major groups. In the past galaxies and globular clusters were thought to be other types of nebulae. Spiral nebula were used to explain the spiral structures of galaxies.

  • H II regions, which encompass diffuse nebulae, bright nebulae, and reflection nebulae.
  • Planetary nebulae
  • Supernova remnant
  • Dark nebula

This classification does not encompass all known cloud-like structures. An example is a Herbig–Haro object.

Diffuse nebulae

The Omega Nebula, an example of an emission nebula.

The diffuse nebulae near the stars are examples of reflection nebula.

Most nebulae can be described as diffuse nebulae, which means that they are extended and contain no well-defined boundaries.[13] In visible light these nebulae may be divided into emission nebulae and reflection nebulae, a categorization that depends on how the light we see is created. Emission nebulae contain ionized gas (mostly ionized hydrogen) that produces spectral line emission.[14] These emission nebulae are often called HII regions; the term "HII" is used in professional astronomy to refer to ionized hydrogen. In contrast to emission nebulae, reflection nebulae do not produce significant amounts of visible light by themselves but instead reflect light from nearby stars.[14]

The Horsehead Nebula, an example of a dark nebula.

Dark nebulae are similar to diffuse nebulae, but they are not seen by their emitted or reflected light. Instead, they are seen as dark clouds in front of more distant stars or in front of emission nebulae.[14]

Although these nebulae appear different at optical wavelengths, they all appear to be bright sources of emission at infrared wavelengths. This emission comes primarily from the dust within the nebulae.[14]

Planetary nebulae

The Cat's Eye Nebula, an example of a planetary nebula.

Planetary nebulae are nebulae that form from the gaseous shells that are ejected from low-mass asymptotic giant branch stars when they transform into white dwarfs.[14] These nebulae are emission nebulae with spectral emission that is similar to the emission nebulae found in star formation regions.[14] Technically, they are a type of HII region because the majority of hydrogen will be ionized. However, planetary nebulae are denser and more compact than the emission nebulae in star formation regions.[14] Planetary nebulae are so called because the first astronomers who observed these objects thought that the nebulae resembled the disks of planets, although they are not at all related to planets.[15]

Protoplanetary nebula

A protoplanetary nebula (PPN) is an astronomical object which is at the short-lived episode during a star's rapid stellar evolution between the late asymptotic giant branch (LAGB) phase and the subsequent planetary nebula (PN) phase.[16] A PPN emits strong infrared radiation, and is a kind of reflection nebula. The exact point when a PPN becomes a planetary nebula (PN) is defined by the temperature of the central star.

Supernova remnants

The Crab Nebula, an example of a supernova remnant.

A supernova occurs when a high-mass star reaches the end of its life. When nuclear fusion ceases in the core of the star, the star collapses inward on itself. The gas falling inward either rebounds or gets so strongly heated that it expands outwards from the core, thus causing the star to explode.[14] The expanding shell of gas forms a supernova remnant, a special type of diffuse nebula.[14] Although much of the optical and X-ray emission from supernova remnants originates from ionized gas, a substantial amount of the radio emission is a form of non-thermal emission called synchrotron emission.[14] This emission originates from high-velocity electrons oscillating within magnetic fields.

Notable named nebulae

Nebula catalogs

See also


  1. ^ Krupp, Edward C. (1999), Igniting the Hearth, Sky & Telescope (February): 94
  2. ^ Kunitzsch, P. (1987), "A Medieval Reference to the Andromeda Nebula", Messenger 49: 42–43, Bibcode1987Msngr..49...42K,, retrieved 2009-10-31 
  3. ^ a b Kenneth Glyn Jones (1991), Messier's nebulae and star clusters, Cambridge University Press, p. 1, ISBN 0521370795 
  4. ^ a b Harrison, T. G. (March 1984). "The Orion Nebula - where in History is it". Royal Astronomical Society Quarterly Journal 25 (1): 70–73. Bibcode1984QJRAS..25...65H. 
  5. ^ Lundmark K. (1921), Suspected New Stars Recorded in Old Chronicles and Among Recent Meridian Observations'', Publications of the Astronomical Society of the Pacific, v. 33, p.225
  6. ^ Mayall N.U. (1939), The Crab Nebula, a Probable Supernova, Astronomical Society of the Pacific Leaflets, v. 3, p.145
  7. ^ Halley (1714–16). "An account of several nebulae or lucid spots like clouds, lately discovered among the fixt stars by help of the telescope". Philosophical Transactions XXXIX: 390–2. 
  8. ^ a b Hoskin, Michael (2005). "Unfinished Business: William Herschel’s Sweeps for Nebulae". History of Science 43: 305–320. Bibcode2005HisSc..43..305H. 
  9. ^ Watts, William Marshall; Huggins, Sir William; Lady Huggins (1904). An introduction to the study of spectrum analysis. Longmans, Green, and co.. pp. 84–85. Retrieved 2009-10-31. 
  10. ^ a b c Struve, Otto (1937). "Recent Progress in the Study of Reflection Nebulae". Popular Astronomy 45: 9–22. Bibcode1937PA.....45....9S. 
  11. ^ Slipher, V. M. (1912). "On the spectrum of the nebula in the Pleiades". Lowell Observatory Bulletin 1: 26–27. Bibcode1912LowOB...2...26S. 
  12. ^ Hubble, E. P. (December 1922). "The source of luminosity in galactic nebulae.". Astrophysical Journal 56: 400–438. doi:10.1086/142713. Bibcode1922ApJ....56..400H. 
  13. ^ "The Messier Catalog: Diffuse Nebulae". University of Illinois SEDS. Retrieved 2007-06-12. 
  14. ^ a b c d e f g h i j F. H. Shu (1982). The Physical Universe. Mill Valley, California: University Science Books. ISBN 0-935702-05-9. 
  15. ^ E. Chaisson, S. McMillan (1995). Astronomy: a beginner's guide to the universe (2nd ed.). Upper Saddle River, New Jersey: Prentice-Hall. ISBN 0-13-733916-X. 
  16. ^ R. Sahai, C. Sánchez Contreras, M. Morris (2005). "A Starfish Preplanetary Nebula: IRAS 19024+0044". Astrophysical Journal 620: 948–960. doi:10.1086/426469. 

External links

1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

NEBULA (Lat. for " cloud," connected with the Gr. vecEXri, mist or cloud), in astronomy, the name given to certain luminous cloudy patches in the heavens. They resemble the stars in that they retain the same relative positions, and thus may be distinguished from the comets which appear to wander across the stars. When examined with sufficient telescopic power, a great many of these luminous patches are perceived to be composed of clusters of little stars, which in a smaller telescope are invisible separately, but whose rays of light blend together so as to produce a confused luminous appearance. Others, however, cannot be resolved into individual stars even with the bes t telescopes, and in many cases the spectroscope gives direct evidence that the nebula has a constitution altogether different from that of a star-cluster. We thus distinguish between the nebulae proper and the star-clusters; but owing to the difficulty of deciding the nature in any particular case, and especially owing to the fact that some of the earlier observers.believed it probable that all nebulae would with sufficient telescopic power become resolvable into stars, the term nebula is often used to cover both star-clusters and the true nebulae.

An enumeration of nebulae was made by Charles Messier in Paris in 1771, who recorded 103; Sir William Herschel increased the number known to over 250o; whilst Sir John Herschel between 1825 and 1847 catalogued and described 3926 nebulae (including 1700 observed at the Cape of Good Hope). About 1848 the earl of Rosse with his famous six-foot reflector at Parsonstown began his examination of the nebulae, which added greatly to our knowledge of their forms and structure. In more modern times the development of photography has enabled the features of the nebulae to be ascertained and recorded with a certainty, which, unfortunately, the older visual observations and drawings cannot claim to possess. In this connexion the photographic work of Isaac Roberts, A. A. Common, E. E. Barnard and J. E. Keeler in particular must be mentioned. The total number of known nebulae has, too, been enormously increased; Perrine estimates that the number within the power of the Crossley reflector at Lick is not less than half a million.

Nebulae may be conveniently classified according to their telescopic appearance; we enumerate below some of the principal forms that have been recognized, but it must be observed that this classification is rather superficial, and that the differentiation is often one of appearance only and not of real structure. The types are: (r) Irregular nebulae, examples: the great nebula of Orion (M. 42), 1 the " key-hole " nebula near n Argus, 1 i.e. No. 42 in Messier's catalogue. Nebulae not contained in that catalogue are generally known by their number in Dreyer's New General Catalogue (N.G.C.). the " Omega " nebula (M. 17); (2) Annular nebulae, example: M. 37 in Lyra; (3) Double nebulae, example: the dumb-bell nebula (M. 27) in Vulpecula; (4) Planetary nebulae, examples: the " owl " nebula (M. 97) in Ursa Major, M. i in Taurus; (5) Elliptical nebulae, example: the great nebula of Andromeda (M. 31); (6) Spiral nebulae, example: M. 51 in Canes Venatici; (7) Nebulous stars; (8) Diffused nebulosities. Most of these names require little explanation. The first class have ill-defined irregular boundaries; their forms often suggest the appearance of curdled liquid or wreaths of smoke. The annular nebulae have a ringed appearance, the centre being much darker than the outer parts, though it is filled with faintly luminous matter. Double nebulae have two principal centres of condensation. The planetary nebulae are nearly uniformly illuminated compact patches of light generally circular or elliptical in shape; they were so called because they appeared to possess disks like planets. Elliptical nebulae are usually nebulae of some flat type (such as annular or spiral) seen rather edgeways, so that the structure is not readily recognizable. The typical spiral nebulae are in the form of a double spiral, the two branches of which proceed from diametrically opposite points of a bright nucleus and wind round it in the same sense; the whole is generally studded with points of condensation. The great majority of the nebulae, including the abundant small nebulae which shine with a white light (in contrast with the blue-green light of the planetary and irregular nebulae - see below Spectra of nebulae), are generally classed as spiral nebulae. The spiral structure has been shown to exist in a few of them, but for the remainder it is only inferred. Nebulous stars are true stars surrounded by an atmosphere or aureole of nebulous light. Diffused nebulosities are very faint nebulae of enormous extent, sometimes forming the background of a whole constellation. We proceed to describe some of the more famous nebulae.

One of the most remarkable nebulae is that which is situated in the sword-handle of Orion and about the multiple star 0 Orionis; it is faintly visible to the naked eye. It seems to have been first noticed by Huygens in 1656, who described and figured it in his System Saturnium. It has now been found that nebulous streamers connected with the bright nucleus wind through the whole constellation of Orion. It is well known that all the brighter stars of the constellation except Betelgeuse appear to be related to one another by their similarity both of spectra and of proper motion; it seems probable that they are actually situated in the nebula and in some way connected with it.

The only other nebula which can be seen with the naked eye is the elliptical nebula in Andromeda. Modern photographs show very clearly that its structure is spiral. The nucleus is large and appears circular, but the spirals proceeding from it lie in a plane inclined at a rather sharp angle to the line of sight, and this gives to the nebula its elliptical appearance. Two small dense nebulae accompany it, and appear to belong to the system.

The finest example of a ring nebula is M. 57 between f3 and y Lyrae. The ring is slightly elliptical, its dimensions being 87" by 64". At the ends of the major axis the ring becomes very faint, so that the form of the bright part may justly be compared to a pair of marks of parenthesis (). The centre is marked by a star which appears to be intimately associated with the ring, for the whole space within the ring is filled with a very faint nebulosity. According to Schaeberle, there is evidence of a spiral structure in this nebula also. It must, however, clearly be of an essentially different character from the structure of an ordinary spiral nebula, and the spectroscope reveals a fundamental difference between the annular and spiral nebulae.

The " dumb-bell " nebula in Vulpecula consists of two almost separated fan-shaped patches of light. It exhibits a close resemblance to the annular nebula; for we have only to assume a continuation of the thinning out along the longest diameter and a slight filling in of the centre of the Lyra nebula to obtain the dumb-bell form. .


By permission of Yerkes Observatory


By permission of Yerkes Observatory.

Scale: Minutes of arc

01, 2

I 3

Scale: Minutes of arc


3357 8 4 Io

I 20 30 40 50 Scale: Minutes of arc 10 20 30 0 Scale: Minutes of arc 40 50 (I) [[Annular Nebula, Lyra, 1899, July 14. (2) Spiral Nebula, Canes Venatici, 1899, May]] To.

By permission of Lick Observatory. By permission of Lick Observatory.

Of planetary nebulae one of the best known is the "owl nebula " in the Great Bear about midway between " the pointers." As seen with Lord Rosse's reflector, it presented a startling appearance, resembling the face of a goblin; two faint stars shone in the centres of the two dark circles which represented the saucereyes of the creature. Some change has certainly taken place since then, for the two stars no longer could be supposed to represent the pupils of the eyes; the cause may, however, be merely the proper motion of the stars or of the nebula.

The discovery of great regions having a faint nebulous background is one of the most remarkable results of modern work. Particularly interesting is the fact that, whilst the large telescopes are unable to render them perceptible to the eye or to photograph them, they are revealed by what at first sight seems an absurdly simple apparatus. For the study of the ordinary nebulae large reflecting telescopes (preferably of short focal length) are used, the great light-gathering power being all important; but for photographing these diffused nebulosities portrait lenses of very small aperture and focal length are most successful. Thus the great extension of the Orion nebula was photographed by W. H. Pickering in 1890 with a lens 2.6 in. in aperture and of 8.6 in. focal length; the exposure was rather more than six hours. Other extensive nebulous regions of a similar character have been found by Barnard in the constellations Ophiuchus, Scorpio and Taurus.

Spectra of Nebulae

Owing to the feebleness of their light the study of the spectra of nebulae is one of particular difficulty. Two varieties of spectra are recognized; the one consists of a few narrow bright lines with sometimes a faint continuous spectrum for a background; the other consists of a continuous spectrum crossed by dark lines and is indistinguishable from that of ordinary stars. The former variety unmistakably shows that the light proceeds from diffuse incandescent vapour; nebulae showing this spectrum are accordingly called " gaseous." Irregular, annular and planetary nebulae are of this nature. The visual spectrum is marked by three bright lines in the blue and green of wave-lengths 5007, 4959 and 4861. Of these the last is the line H /3 of the hydrogen series; the other two are of unknown origin, and as they are always found together and have always the same relative intensity, they have both been attributed to the same unknown element, which has been named " nebulium." Usually there are no other conspicuous lines in the visual spectrum, but in the ultra-violet region numerous lines can be photographed, including most of the hydrogen series. The yellow line (D 3) of helium can be detected in many nebulae. The great majority of the nebulae, however, show the second variety of spectrum, and are thus indistinguishable spectroscopically from irresolvable star-clusters. The great nebula of Andromeda and the spiral nebulae are of this kind. It is not necessary to conclude that they, therefore, are star-clusters whose components are, owing to their remoteness from us, too faint and close together to be separately distinguishable. A gaseous mass only gives a bright line spectrum when it is so rarefied as to be transparent through and through. If the density and thickness are such that a ray of light cannot pass through it the spectrum will, in general, be continuous like that of a solid body.

The inquiry into the physical state and constitution of the nebulae raises problems of great difficulty. In the case of " gaseous " nebulae it is very hard to understand how such extremely tenuous masses are maintained in a state of incandescence. Only one theory has been put forward which at all accounts for this fact, and unfortunately, it is not altogether satisfactory in other respects. This is Sir Norman Lockyer's " Meteoritic Hypothesis," which attributes the light to collisions between numbers of small discrete solid particles, these being vaporized and made luminous owing to the heat developed by their impacts. Formidable difficulties, however, prevent the entire acceptance of this suggestion.

The spiral nebulae are not distributed at random over the sky, nor are they condensed along the galactic plane like the clusters which they spectroscopically resemble. There is a well-marked centre of aggregation of the northern nebulae near the north galactic pole. In the southern hemisphere they are more evenly distributed, but the avoidance of the galactic plane is marked. The remarkable Nubeculae or Magellanic Clouds in the southern hemisphere, which Iook like detached portions of the Milky Way, are found on telescopic examination to consist, not of stars alone, like the Milky Way, but of stars and nebulae clustering together. In the greater cloud Sir John Herschel counted 286 nebulae; in the lesser cloud they are rather less numerous.


The characters of nebulae receive treatment in all text-books on descriptive astronomy; mention may be made of Miss A. M. Clerke, The System of the Stars (2nd ed., 1905), which contains a full account of these objects, illustrated by many photographs; the same work is replete with references to original papers. Of recent catalogues of nebula, we notice J. L. E. Dreyer, " A new general catalogue of nebulae and clusters of stars," Memoirs R.A.S. (1888), published separately in 1890; and " Index Catalogue of Nebulae (1888-1894), "Mem. R.A.S. (1895). Excellent photographs of the more famous nebulae are given in Sir R. Ball's Popula r Guide to the Heavens (1905); a more comprehensive collection is given in Isaac Roberts, Photographs of Stars, Star Clusters and Nebulae (2 vols., 1873-1899). (A. S. E.)

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Definition from Wiktionary, a free dictionary

Wikipedia has an article on:






  • enPR: neb'jə-lə, IPA: /ˈnebjələ/, SAMPA: /"nebj@l@/


From Latin nebula (little cloud", "mist). Akin to Greek νεφέλη, "cloud", German Nebel, "mist", "nebula", Old Norse nifl.



nebulae or nebulas

nebula (plural nebulae or nebulas)

  1. (astronomy) A cloud in outer space consisting of gas or dust (e.g. a cloud formed after a star explodes).


Derived terms

Related terms

See also






nebula (plural nebulas)

  1. fog, mist, haze
  2. (pathology) nebula



nebula f. (plural nebule)

  1. (archaic) fog, mist; cloud
  2. nebula

Related terms



From Proto-Indo-European *nébʰos (cloud). Cognate with Ancient Greek νέφος (nephos), Sanskrit नभस् (nábhas).


nebula (genitive nebulae); f, first declension

  1. fog
  2. cloud
  3. vapor
  4. vocative singular of nebula

nebulā f.

  1. ablative singular of nebula


First declension (1).

Number Singular Plural
nominative nebula nebulae
genitive nebulae nebulārum
dative nebulae nebulīs
accusative nebulam nebulās
ablative nebulā nebulīs
vocative nebula nebulae



Up to date as of January 23, 2010

From Wikispecies


Main Page
Cladus: Eukaryota
Supergroup: Unikonta
Cladus: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Ecdysozoa
Phylum: Arthropoda
Subphylum: Hexapoda
Classis: Insecta
Cladus: Dicondylia
Cladus: Pterygota
Cladus: Metapterygota
Cladus: Neoptera
Cladus: Eumetabola
Cladus: Endopterygota
Superordo: Panorpida
Cladus: Amphiesmenoptera
Ordo: Lepidoptera
Subordo: Glossata
Infraordo: Heteroneura
Divisio: Ditrysia
Sectio: Cossina
Subsection: Bombycina
Superfamilia: Geometroidea
Familia: Geometridae
Subfamilia: Larentiinae
Tribus: Cidariini
Genus: Nebula
Species: N. mantelorum

Simple English

is an example of a nebula]]

A nebula, which comes from the Latin word for mist or cloud,[1] is an interstellar cloud of dust, hydrogen, helium, and other gases. An interstellar cloud is a bunch of dust, plasma, or gas in a galaxy. The Persian astronomer, Abd al-Rahman al-Sufi, mentioned a true nebula for the first time in his book, Book of Fixed Stars (964).[2] He said that there was a "little cloud" near the Andromeda Galaxy.[3]


A nebula is usually made up of hydrogen gas and plasma. It is the first stage of a star's cycle. There are four different types of nebula. These are; Emission, Reflection, Dark, and Planetary. Opinions on the number of Nebulae do vary, however, and some of these other types include Planetary and Bright nebula. In the past Galaxies and Star Clusters were also thought to be certain types of nebulae.


  1. "Online Etymology Dictionary". Retrieved 24 September 2010. 
  2. Kenneth Glyn Jones (1991). Messier's nebulae and star clusters. Cambridge University Press. p. 1. ISBN 0521370795
  3. Harrison, T. G. (March 1984). [Expression error: Unexpected < operator "The Orion Nebula — where in History is it"]. Royal Astronomical Society Quarterly Journal 25 (1): 70–73. Bibcode: 1984QJRAS..25...65H. 

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