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 Sagittarius. It was discovered by Philippe Loys de Chéseaux 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 ...

catalogued it in 1764. It is by some of the richest starfields of the Milky Way, figuring in the northern two-thirds of Sagittarius.

Characteristics

The Omega Nebula is between 5,000 and 6,000 light-years 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 ...

of which this nebula 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 eleme ...

of the Omega Nebula is an estimated 800 solar masses. 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 except that it is viewed edge-on rather than face-on.. The open cluster 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 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 spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

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 HD 168607, 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 MKK ...

HD 168625, may be too. The Swan portion of M17, the Omega Nebula in the Sagittarius nebulosity 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 wh ...

Early research

The first attempt to accurately draw the nebula (as part of a series of sketches of nebulae) was made by John Herschel 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 and separately by an undergraduate at Yale College, 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 observ ...

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 in 1875 using the twenty-six inch Clark refractor at the United States Naval Observatory.

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 John Herschel 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