North America Nebula
Encyclopedia
The North America Nebula (NGC
7000 or Caldwell 20) is an emission nebula
in the constellation
Cygnus
, close to Deneb
(the tail of the swan and its brightest star
). The remarkable shape of the emission nebula
resembles that of the continent of North America
, complete with a prominent Gulf of Mexico
. It is sometimes incorrectly called the "North American Nebula"http://www.nasa.gov/mission_pages/spitzer/news/spitzer20110210.html.
; but its surface brightness is low, so normally it cannot be seen with the unaided eye. Binoculars
and telescope
s with large fields of view (approximately 3°) will show it as a foggy patch of light under sufficiently dark skies. However, using a UHC filter, which filters out some unwanted wavelength
s of light, it can be seen by the naked eye under dark skies. Its prominent shape and especially its reddish color (from the hydrogen
Hα emission line) show up only in photographs of the area.
Cygnus's Wall is a term for the "Mexico and Central America part" of the North America Nebula. The Cygnus Wall exhibits the most concentrated star formation
s in the nebula.
The North America Nebula and the nearby Pelican Nebula
, (IC 5070) are in fact parts of the same interstellar cloud
of ionized hydrogen
(H II region
). Between the Earth and the nebula complex lies a band of interstellar dust that absorbs the light of stars and nebulae behind it, and thereby determines the shape as we see it. The distance of the nebula complex is not precisely known, nor is the star responsible for ionizing the hydrogen so that it emits light. If the star inducing the ionization is Deneb
, as some sources say, the nebula complex would be about 1800 light years distance, and its absolute size (6° apparent diameter on the sky) would be 100 light years.
The nebula was discovered by William Herschel
on October 24, 1786, from Slough
, England
.
New General Catalogue
The 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...
7000 or Caldwell 20) is 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...
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....
Cygnus
Cygnus (constellation)
Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross...
, close to Deneb
Deneb
Deneb is the brightest star in the constellation Cygnus and one of the vertices of the Summer Triangle. It is the 19th brightest star in the night sky, with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous nearby stars...
(the tail of the swan and its brightest star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
). The remarkable shape of the 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...
resembles that of the continent of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, complete with a prominent Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
. It is sometimes incorrectly called the "North American Nebula"http://www.nasa.gov/mission_pages/spitzer/news/spitzer20110210.html.
General information
The North America Nebula is large, covering an area of more than four times the size of the full moonMoon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
; but its surface brightness is low, so normally it cannot be seen with the unaided eye. 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...
and 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...
s with large fields of view (approximately 3°) will show it as a foggy patch of light under sufficiently dark skies. However, using a UHC filter, which filters out some unwanted wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s of light, it can be seen by the naked eye under dark skies. Its prominent shape and especially its reddish color (from the hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
Hα emission line) show up only in photographs of the area.
Cygnus's Wall is a term for the "Mexico and Central America part" of the North America Nebula. The Cygnus Wall exhibits the most concentrated star formation
Star formation
Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. As a branch of astronomy star formation includes the study of the interstellar medium and giant molecular clouds as precursors to the star formation process and the study of young...
s in the nebula.
The North America Nebula and the nearby Pelican Nebula
Pelican Nebula
The Pelican Nebula is an H II region associated with the North America Nebula in the constellation Cygnus. The gaseous contortions of this emission nebula bear a resemblance to a pelican, giving rise to its name...
, (IC 5070) are in fact parts of the same interstellar cloud
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...
of ionized hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
(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...
). Between the Earth and the nebula complex lies a band of interstellar dust that absorbs the light of stars and nebulae behind it, and thereby determines the shape as we see it. The distance of the nebula complex is not precisely known, nor is the star responsible for ionizing the hydrogen so that it emits light. If the star inducing the ionization is Deneb
Deneb
Deneb is the brightest star in the constellation Cygnus and one of the vertices of the Summer Triangle. It is the 19th brightest star in the night sky, with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous nearby stars...
, as some sources say, the nebula complex would be about 1800 light years distance, and its absolute size (6° apparent diameter on the sky) would be 100 light years.
The nebula was discovered by William Herschel
William Herschel
Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...
on October 24, 1786, from Slough
Slough
Slough is a borough and unitary authority within the ceremonial county of Royal Berkshire, England. The town straddles the A4 Bath Road and the Great Western Main Line, west of central London...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
.
External links
- The North America Nebula (NGC 7000) at the astro-photography site of Mr. T. Yoshida.
- NASA APOD: The North America and Pelican Nebulae (June 30, 2009)
- NASA APOD: The North America Nebula (May 1, 2000)
- NASA APOD: The North America Nebula (June 6, 1996)
- NGC7000
- starpointing.com – Central part of the North America Nebula: The Great Wall]
- project-nightflight.net – DSLR image of the North America Nebula