The Trifid Nebula (catalogued as Messier 20 or M20 and as NGC 6514) 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 north-west of Sagittarius in a star-forming region in the Milky Way's Scutum-Centaurus Arm. It was discovered by

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 ...

on June 5, 1764.Messier 20
/ref> Its name means 'three-lobe'. The object is an unusual combination of an

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 ...

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s, an

emission nebula An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star. Among the several different types of emissio ...

(the relatively dense, reddish-pink portion), a reflection nebula (the mainly

NNE The points of the compass are a set of horizontal, Radius, radially arrayed compass directions (or Azimuth#In navigation, azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east ...

blue portion), and a

dark nebula A dark nebula or absorption nebula is a type of interstellar cloud, particularly molecular clouds, that is so dense that it obscures the visible wavelengths of light from objects behind it, such as background stars and emission or reflection nebu ...

(the apparent 'gaps' in the former that cause the trifurcated appearance, also designated Barnard 85). Viewed through a small

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 ...

, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers. The most massive star that has formed in this region is HD 164492A, an O7.5III star with a mass more than 20 times the

mass of the Sun 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 ...

. This star is surrounded by a cluster of approximately 3100 young stars.

Characteristics

The Trifid Nebula was the subject of an investigation by astronomers using the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

in 1997, using filters that isolate emission from

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, and ...

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

ized

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

atoms, and doubly ionized

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

atoms. The images were combined into a false-color composite picture to suggest how the nebula might look to the eye. The close-up images show a dense cloud of dust and gas, which is a

stellar nursery Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space

full of embryonic stars. This cloud is about away from the nebula's central star. A stellar jet protrudes from the head of the cloud and is about long. The jet's source is a young stellar object deep within the cloud. Jets are the exhaust gasses of star formation and radiation from the nebula's central star makes the jet glow. The images also showed a finger-like stalk to the right of the jet. It points from the head of the dense cloud directly toward the star that powers the Trifid nebula. This stalk is a prominent example of

evaporating gaseous globule An evaporating gas globule or EGG is a region of hydrogen gas in outer space approximately 100 astronomical units in size, such that gases shaded by it are shielded from ionizing UV rays. Dense areas of gas shielded by an evaporating gas globule ...

s, or 'EGGs'. The stalk has survived because its tip is a knot of gas that is dense enough to resist being eaten away by the powerful radiation from the star. In January 2005,

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, f ...

discovered 30 embryonic stars and 120 newborn stars not seen in

visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

images. It is centered about 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 ...

. Its

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

is 6.3.

Details and features

File:Trifid.nebula.arp.750pix.jpg, The Trifid nebula. The outlined area is enlarged right. File:Trifid.nebula.jet.arp.750pix.jpg, Hubble image of a stellar jet in the Trifid nebula. File:Cross-fade video comparing views of the Trifid Nebula in visible and infrared light.ogg, This video sequence compares a new view of the Trifid Nebula in infrared light, from the VVV VISTA survey with a more familiar visible-light view from a small telescope. File:Triffid Nebula.jpg, The Trifid nebula. File:Trifid Nebula Upclose.jpg, Trifid Nebula Upclose

References

External links

Spitzer IR Trifid discoveries

SEDS Messier pages
Trifid Nebula at ESA/Hubble
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Trifid Nebula at Constellation Guide
{{Sky, 18, 02, 23, -, 23, 01, 48, 9000 Carina–Sagittarius Arm H II regions Messier objects NGC objects Sagittarius (constellation) 17640605 Articles containing video clips Star-forming regions

Characteristics

Details and features

See also

References

External links