In astronomy , reflection nebulae are clouds of interstellar dust which might reflect the light of a nearby star or stars. The energy from the nearby stars is insufficient to ionize the gas of the nebula to create an emission nebula , but is enough to give sufficient scattering to make the dust visible. Thus, the frequency spectrum shown by reflection nebulae is similar to that of the illuminating stars. Among the microscopic particles responsible for the scattering are carbon compounds (e. g. diamond dust) and compounds of other elements such as iron and nickel. The latter two are often aligned with the galactic magnetic field and cause the scattered light to be slightly polarized .
17-516: The New General Catalogue of Nebulae and Clusters of Stars (abbreviated NGC ) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies , star clusters and emission nebulae . Dreyer published two supplements to the NGC in 1895 and 1908, known as the Index Catalogues (abbreviated IC ), describing
34-557: A further 5,386 astronomical objects. Thousands of these objects are best known by their NGC or IC numbers, which remain in widespread use. The NGC expanded and consolidated the cataloguing work of William and Caroline Herschel , and John Herschel 's General Catalogue of Nebulae and Clusters of Stars . Objects south of the celestial equator are catalogued somewhat less thoroughly, but many were included based on observation by John Herschel or James Dunlop . The NGC contained multiple errors, but attempts to eliminate them were made by
51-503: A number of objects catalogued as star clusters which in subsequent studies were regarded as coincidental groupings. A 1993 monograph considered the 229 star clusters called non-existent in the RNGC. They had been "misidentified or have not been located since their discovery in the 18th and 19th centuries". It found that one of the 229—NGC 1498—was not actually in the sky. Five others were duplicates of other entries, 99 existed "in some form", and
68-762: A supplement to Herschel's General Catalogue of Nebulae and Clusters (GC), containing about 1,000 new objects. In 1886, he suggested building a second supplement to the General Catalogue , but the Royal Astronomical Society asked Dreyer to compile a new version instead. This led to the publication of the New General Catalogue in the Memoirs of the Royal Astronomical Society in 1888. Assembling
85-614: Is a 1988 compilation of the NGC and IC made by Roger W. Sinnott, using the J2000.0 coordinates. It incorporates several corrections and errata made by astronomers over the years. The NGC/IC Project was a collaboration among professional and amateur astronomers formed by Steve Gottlieb in 1990, although Steve Gottlieb already started to observe and record NGC objects as early as 1979. Other primary team members were Harold G. Corwin Jr., Malcolm Thomson, Robert E. Erdmann and Jeffrey Corder. The project
102-490: Is a compilation made by Wolfgang Steinicke in 2009. It is a comprehensive and authoritative treatment of the NGC and IC catalogues. The number of objects with status of "not found" in this catalogue is 301 objects (2.3%). The brightest star in this catalogue is NGC 771 with magnitude of 4.0. NGC 2000.0 (also known as the Complete New General Catalog and Index Catalog of Nebulae and Star Clusters )
119-450: Is true for asteroids , comets and other solar system bodies . Astronomical catalogs such as those for asteroids may be compiled from multiple sources, but most modern catalogs are the result of a particular astronomical survey of some kind. Since the late 20th century catalogs are increasingly often compiled by computers from an automated survey, and published as computer files rather than on paper. Reflection nebula Analyzing
136-479: Is very red ( spectral class M1), is surrounded by a large, yellow reflection nebula. Reflection nebulae may also be the site of star formation . In 1922, Edwin Hubble published the result of his investigations on bright nebulae . One part of this work is the Hubble luminosity law for reflection nebulae, which makes a relationship between the angular size ( R ) of the nebula and the apparent magnitude ( m ) of
153-681: The Revised New General Catalogue (RNGC) by Jack W. Sulentic and William G. Tifft in 1973, NGC2000.0 by Roger W. Sinnott in 1988, and the NGC/IC Project in 1993. A Revised New General Catalogue and Index Catalogue (abbreviated as RNGC/IC) was compiled in 2009 by Wolfgang Steinicke and updated in 2019 with 13,957 objects. The original New General Catalogue was compiled during the 1880s by John Louis Emil Dreyer using observations from William Herschel and his son John , among others. Dreyer had already published
170-519: The IC objects. It summarizes the discoveries of galaxies, clusters and nebulae between 1888 and 1907, most of them made possible by photography . A list of corrections to the IC was published in 1912. The Revised New Catalogue of Nonstellar Astronomical Objects (abbreviated as RNGC ) was compiled by Sulentic and Tifft in the early 1970s, and was published in 1973, as an update to the NGC. The work did not incorporate several previously published corrections to
187-477: The NGC data (including corrections published by Dreyer himself), and introduced some new errors. For example, the well-known compact galaxy group Copeland Septet in the Leo constellation appears as non-existent in the RNGC. Nearly 800 objects are listed as "non-existent" in the RNGC. The designation is applied to objects which are duplicate catalogue entries, those which were not detected in subsequent observations, and
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#1732781015053204-428: The NGC was a challenge, as Dreyer had to deal with many contradictory and unclear reports made with a variety of telescopes with apertures ranging from 2 to 72 inches. While he did check some himself, the sheer number of objects meant Dreyer had to accept them as published by others for the purpose of his compilation. The catalogue contained several errors, mostly relating to position and descriptions, but Dreyer referenced
221-528: The catalogue, which allowed later astronomers to review the original references and publish corrections to the original NGC. The first major update to the NGC is the Index Catalogue of Nebulae and Clusters of Stars (abbreviated as IC ), published in two parts by Dreyer in 1895 (IC I, containing 1,520 objects) and 1908 (IC II, containing 3,866 objects). It serves as a supplement to the NGC, and contains an additional 5,386 objects, collectively known as
238-601: The other 124 required additional research to resolve. As another example, reflection nebula NGC 2163 in Orion was classified "non-existent" due to a transcription error by Dreyer. Dreyer corrected his own mistake in the Index Catalogues, but the RNGC preserved the original error, and additionally reversed the sign of the declination, resulting in NGC 2163 being classified as non-existent. The Revised New General Catalogue and Index Catalogue (abbreviated as RNGC/IC )
255-496: The scattering is more efficient for blue light than red (this is the same scattering process that gives us blue skies and red sunsets). Reflection nebulae and emission nebulae are often seen together and are sometimes both referred to as diffuse nebulae . Some 500 reflection nebulae are known. A blue reflection nebula can also be seen in the same area of the sky as the Trifid Nebula . The supergiant star Antares , which
272-528: The spectrum of the nebula associated with the star Merope in the Pleiades , Vesto Slipher concluded in 1912 that the source of its light is most likely the star itself, and that the nebula reflects light from the star (and that of the star Alcyone ). Calculations by Ejnar Hertzsprung in 1913 lend credence to that hypothesis. Edwin Hubble further distinguished between the emission and reflection nebulae in 1922. Reflection nebula are usually blue because
289-911: Was completed by 2017. This project identified all NGC and IC objects, corrected mistakes, collected images and basic astronomical data and checked all historical data related to the objects. Astronomical catalog An astronomical catalog or catalogue is a list or tabulation of astronomical objects , typically grouped together because they share a common type, morphology , origin, means of detection, or method of discovery. The oldest and largest are star catalogues . Hundreds have been published, including general ones and special ones for such objects as infrared stars , variable stars , giant stars , multiple star systems , star clusters , and so forth. General catalogs for deep space objects or for objects other than stars are also large. Again, there are specialized ones for nebulas , galaxies , X-ray sources , radio sources , quasars and other classes. The same
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