The Omega Nebula is an

H II region An H II 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 of light year ...

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 first constellati ...

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'', referred to with th ...

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

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

, figuring in the northern two-thirds of Sagittarius. This feature is also known as the Swan Nebula, Checkmark Nebula, Lobster Nebula, and the Horseshoe Nebula, and catalogued as Messier 17 or M17 or NGC 6618.

Characteristics

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

light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...

s from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

and it spans some 15 light-years in diameter. The cloud of interstellar matter of which this

nebula A nebula (; 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 regions, such as in the Pillars of Creation in ...

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 and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

of the Omega Nebula is an estimated 800

solar mass The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxie ...

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 in the Milky Way situated south of Orion's Belt in the Orion (constellation), constellation of Orion, and is known as the middle "star" in the "sword" of Orion. It ...

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 tens 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 a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...

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 a material medium. This includes: * ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...

from these hot,

young star A pre-main-sequence star (also known as a PMS star and PMS object) is a star in the stage when it has not yet reached the main sequence. Earlier in its life, the object is a protostar that grows by acquiring mass from its surrounding envelope o ...

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 Luminous blue variables (LBVs) are rare, 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 th ...

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, 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 Signage, 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 :wikt:pole, pole with a helix of colored Strip ...

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 and experimental photographer who invented the blueprint and did botanical work. ...

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 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 (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

Malta Malta, officially the Republic of Malta, is an island country in Southern Europe located in the Mediterranean Sea, between Sicily and North Africa. It consists of an archipelago south of Italy, east of Tunisia, and north of Libya. The two ...

, and by M. Trouvelot from

Cambridge, Massachusetts Cambridge ( ) is a city in Middlesex County, Massachusetts, United States. It is a suburb in the Greater Boston metropolitan area, located directly across the Charles River from Boston. The city's population as of the 2020 United States census, ...

, and Edward Singleton Holden in 1875 using the twenty-six inch Clark refractor at the

United States Naval Observatory The 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 ...

Observations by SOFIA

In January 2020, the Stratospheric Observatory for Infrared Astronomy (

SOFIA Sofia is the Capital city, capital and List of cities and towns in Bulgaria, largest city of Bulgaria. It is situated in the Sofia Valley at the foot of the Vitosha mountain, in the western part of the country. The city is built west of the Is ...

) provided new insights into the Omega Nebula. SOFIA's composite image revealed that blue areas (20 microns) near the center indicate gas heated by massive stars, while green areas (37 microns) trace dust warmed by massive stars and newborn stars. Nine previously unseen protostars were discovered primarily in the southern regions. Red areas near the edges represent cold dust detected by the Herschel Space Telescope (70 microns), and the white star field was observed by the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicate ...

(3.6 microns). These observations suggest that parts of the nebula formed separately, contributing to its distinctive swan-like shape.

Gallery

File:The VST captures three spectacular nebulae in one image.jpg, alt=Omega Nebula (left), Eagle Nebula (center), and Sharpless 2-54 (right)., 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