Lagoon Nebula
Encyclopedia
The Lagoon Nebula is a giant interstellar cloud
in the constellation
Sagittarius
. It is classified as an emission nebula
and as an H II region
.
The Lagoon Nebula was discovered by Guillaume Le Gentil
in 1747 and is one of only two star-forming nebula
e faintly visible to the naked eye from mid-northern latitudes. Seen with binoculars
, it appears as a distinct oval
cloudlike patch with a definite core. A fragile star cluster
appears superimposed on it.
or a telescope
, human vision
having poor color sensitivity at low light levels. The nebula contains a number of Bok globule
s (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296. It also includes a funnel-like or tornado
-like structure caused by a hot O-type star that emanates ultraviolet light, heating and ionizing gases on the surface of the nebula. The Lagoon Nebula also contains at its centre a structure known as the Hourglass Nebula (so named by John Herschel
), which should not be confused with the better known Hourglass Nebula
in the constellation of Musca
. In 2006 the first four Herbig-Haro object
s were detected within the Hourglass, also including HH 870. This provides the first direct evidence of active star formation by accretion within it.
Interstellar cloud
Interstellar cloud is the generic name given to an accumulation of gas, plasma and dust in our and other galaxies. Put differently, an interstellar cloud is a denser-than-average region of the interstellar medium. Depending on the density, size and temperature of a given cloud, the hydrogen in it...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Sagittarius
Sagittarius (constellation)
Sagittarius is a constellation of the zodiac, the one containing the galactic center. Its name is Latin for the archer, and its symbol is , a stylized arrow. Sagittarius is commonly represented as a centaur drawing a bow...
. It is classified as an emission nebula
Emission nebula
An emission nebula is a cloud of ionized gas emitting light of various colors. The most common source of ionization is high-energy photons emitted from a nearby hot star...
and as an H II region
H II region
An H II region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place. The short-lived, blue stars forged in these regions emit copious amounts of ultraviolet light, ionizing the surrounding gas...
.
The Lagoon Nebula was discovered by Guillaume Le Gentil
Guillaume Le Gentil
Guillaume Joseph Hyacinthe Jean-Baptiste Le Gentil de la Galaisière was a French astronomer.-Biography:...
in 1747 and is one of only two star-forming nebula
Nebula
A nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...
e faintly visible to the naked eye from mid-northern latitudes. Seen with binoculars
Binoculars
Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...
, it appears as a distinct oval
Oval
An oval is any curve resembling an egg or an ellipse, such as a Cassini oval. The term does not have a precise mathematical definition except in one area oval , but it may also refer to:* A sporting arena of oval shape** a cricket field...
cloudlike patch with a definite core. A fragile star cluster
Star cluster
Star clusters or star clouds are groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds of thousands of very old stars which are gravitationally bound, while open clusters, more loosely clustered groups of stars, generally contain less than...
appears superimposed on it.
Characteristics
The Lagoon Nebula is estimated to be between 4,000-6,000 light years from the Earth. In the sky of Earth, it spans 90' by 40', translates to an actual dimension of 110 by 50 light years. Like many nebulas, it appears pink in time-exposure color photos but is gray to the eye peering through binocularsBinoculars
Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...
or a telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
, human vision
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
having poor color sensitivity at low light levels. The nebula contains a number of Bok globule
Bok globule
Bok globules are dark clouds of dense cosmic dust and gas in which star formation sometimes takes place. Bok globules are found within H II regions, and typically have a mass of about 2 to 50 solar masses contained within a region about a light year or so across...
s (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296. It also includes a funnel-like or tornado
Tornado
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
-like structure caused by a hot O-type star that emanates ultraviolet light, heating and ionizing gases on the surface of the nebula. The Lagoon Nebula also contains at its centre a structure known as the Hourglass Nebula (so named by John Herschel
John Herschel
Sir John Frederick William Herschel, 1st Baronet KH, FRS ,was an English mathematician, astronomer, chemist, and experimental photographer/inventor, who in some years also did valuable botanical work...
), which should not be confused with the better known Hourglass Nebula
Hourglass Nebula
The Engraved Hourglass Nebula is a young planetary nebula situated in the southern constellation Musca about 8,000 light-years away from Earth. It was discovered by Annie Jump Cannon and Margaret W. Mayall during their work on an extended Henry Draper Catalogue...
in the constellation of Musca
Musca
Musca is one of the minor southern constellations. The constellation was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman and it first appeared on a 35-cm diameter celestial globe published in 1597 in Amsterdam by...
. In 2006 the first four Herbig-Haro object
Herbig-Haro object
Herbig–Haro objects are small patches of nebulosity associated with newly born stars, and are formed when gas ejected by young stars collides with clouds of gas and dust nearby at speeds of several hundred kilometres per second...
s were detected within the Hourglass, also including HH 870. This provides the first direct evidence of active star formation by accretion within it.
See also
- New General CatalogueNew General CatalogueThe New General Catalogue of Nebulae and Clusters of Stars is a well-known catalogue of deep sky objects in astronomy. It contains 7,840 objects, known as the NGC objects...
- Messier objectMessier objectThe Messier objects are a set of astronomical objects first listed by French astronomer Charles Messier in 1771. The original motivation of the catalogue was that Messier was a comet hunter, and was frustrated by objects which resembled but were not comets...
- List of Messier objects
- List of nebulas
External links
- Breaking Waves in the Stellar Lagoon — ESA/HubbleHubble Space TelescopeThe Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
Photo Release - Messier 8, SEDS Messier pages
- NightSkyInfo.com - M8, the Lagoon Nebula
- Messier 8, Pete's Astrophotography Gallery
- Astronomy Picture of the Day (APOD): Lagoon Nebula http://antwrp.gsfc.nasa.gov/apod/ap050803.html