The Omega Nebula, also known as the Swan Nebula, Checkmark Nebula, Lobster Nebula, and the Horseshoe Nebula (catalogued as Messier 17 or M17 or NGC 6618) is an

H II region An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Sagittarius. It was discovered by

Philippe Loys de Chéseaux Jean-Philippe Loys de Cheseaux (; 4 May 1718 – 30 November 1751) was a Swiss astronomer. Biography Loys de Cheseaux was born on 4 May 1718 in Lausanne, Vaud, to Paul-Etienne Loys de Cheseaux, a banneret, and Estienne-Judith de Crousaz. His ...

in 1745.

Charles Messier Charles Messier (; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the ''Messier objects''. Messier's purpose f ...

catalogued it in 1764. It is by some of the richest starfields of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

, figuring in the northern two-thirds of Sagittarius.

Characteristics

The Omega Nebula is between 5,000 and 6,000

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

and it spans some 15 light-years in diameter. The cloud of

interstellar matter In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar s ...

of which this

nebula A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...

is a part is roughly 40 light-years in diameter and has a mass of 30,000 solar masses. The total

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...

of the Omega Nebula is an estimated 800

solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es. It is considered one of the brightest and most massive star-forming regions of our galaxy. Its local geometry is similar to the

Orion Nebula The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a diffuse nebula situated in the Milky Way, being south of Orion's Belt in the constellation of Orion. It is one of the brightest nebulae and is visible to the naked eye in the nig ...

except that it is viewed edge-on rather than face-on.. The

open cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

NGC 6618 lies embedded in the nebulosity and causes the

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

es of the nebula to shine due to

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...

from these hot,

young star Various methods and tools are involved in stellar age estimation, an attempt to identify within reasonable degrees of confidence what the age of a star is. These methods include stellar evolutionary models, membership in a given star cluster or s ...

s; however, the actual number of stars in the nebula is much higher – up to 800, 100 of

spectral type In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

earlier than B9, and 9 of spectral type O, plus over a thousand stars in formation on its outer regions. It is also one of the youngest clusters known, with an age of just 1 million years. The

luminous blue variable Luminous blue variables (LBVs) are massive evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Larg ...

HD 168607 HD 168607 (V4029 Sagittarii) is a blue hypergiant and luminous blue variable (LBV) star located in the constellation of Sagittarius, easy to see with amateur telescopes. It forms a pair with HD 168625, also a blue hypergiant and poss ...

, in the south-east part of the nebula, is generally assumed to be associated with it; its close neighbor, the blue

hypergiant A hypergiant (luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term ''hypergiant'' is defined as luminosity class 0 (zero) in the MK ...

HD 168625 HD 168625 (V4030 Sagittarii) is a blue hypergiant star and candidate luminous blue variable located in the constellation of Sagittarius easy to see with amateur telescopes. It forms a visual pair with the also blue hypergiant (and lum ...

, may be too. The Swan portion of M17, the Omega Nebula in the Sagittarius

nebulosity A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...

is said to resemble a

barber's pole A barber's pole is a type of sign used by barbers to signify the place or shop where they perform their craft. The trade sign is, by a tradition dating back to the Middle Ages, a staff or pole with a helix of colored stripes (often red and whi ...

Early research

The first attempt to accurately draw the nebula (as part of a series of sketches of nebulae) was made by

John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint and did botanical wor ...

in 1833, and published in 1836. He described the nebula as such: A second, more detailed sketch was made during his visit to South Africa in 1837. The nebula was also studied by

Johann von Lamont Johann von Lamont, FRSE (13 December 1805 – 6 August 1879), born John Lamont, was a Scottish-German astronomer and physicist. Biography Lamont was born at Corriemulzie near Inverey in Aberdeenshire, Scotland. The son of Robert Lamont ( ...

and separately by an undergraduate at

Yale College Yale College is the undergraduate college of Yale University. Founded in 1701, it is the original school of the university. Although other Yale schools were founded as early as 1810, all of Yale was officially known as Yale College until 1887, ...

, Mr Mason, starting from around 1836. When Herschel published his 1837 sketch in 1847, he wrote: Sketches were also made by

William Lassell William Lassell (18 June 1799 – 5 October 1880) was an English merchant and astronomer.telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

Malta Malta ( , , ), officially the Republic of Malta ( mt, Repubblika ta' Malta ), is an island country in the Mediterranean Sea. It consists of an archipelago, between Italy and Libya, and is often considered a part of Southern Europe. It lies ...

, and by M. Trouvelot from

Cambridge, Massachusetts Cambridge ( ) is a city in Middlesex County, Massachusetts, United States. As part of the Boston metropolitan area, the cities population of the 2020 U.S. census was 118,403, making it the fourth most populous city in the state, behind Boston, ...

and

Edward Singleton Holden Edward Singleton Holden (November 5, 1846 – March 16, 1914) was an American astronomer and the fifth president of the University of California. Early years He was born in St. Louis, Missouri, in 1846 to Edward and Sarah Frances (Singleton) ...

in 1875 using the twenty-six inch Clark refractor at the

United States Naval Observatory United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the Depo ...

Gallery

File:The VST captures three spectacular nebulae in one image.jpg, Omega Nebula (left), Eagle Nebula (center), and Sharpless 2-54 (right). File:The star formation region Messier 17.jpg, Gas and dust clouds measure about 15 light-years across. File:Omega Nebula.jpg, Section of the nebula. File:ESO-The Omega Nebula-phot-25a-09-fullres.jpg, Composite images obtained with the 3.58-metre NTT at La Silla Observatory. File:TPSMV8P284 Fig 1.jpg, A drawing of the nebula by

in 1833. File:TPSMV8P285 Fig 2.jpg, Herschel's second drawing in 1837. File:TPSMV8P294 Fig 7.jpg, A sketch by Trouvelot in 1875. File:A close looks at the star formation region Messier 17.webm, This video gives us a close-up view of the rose-coloured star forming region Messier 17.

References

External links

*
Messier 17, SEDS Messier pages

Omega Nebula at ESA/Hubble
*
Omega Nebula (Messier 17) at Constellation Guide
{{Sky, 18, 20, 26, -, 16, 10, 36, 6000 Carina–Sagittarius Arm H II regions Messier objects NGC objects Sagittarius (constellation) Sharpless objects ? Articles containing video clips Star-forming regions

Characteristics

Early research

Gallery

See also

References

External links