سديم أمريكا الشمالية
| سديم انبعاثي | |
|---|---|
| H II region | |
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This image layout reveals how the appearance of the North America nebula can change dramatically using different combinations of visible and infrared observations.
| |
| بيانات الرصد: حقبة J2000.0 | |
| الصعود المستقيم | 20h 59m 17.1s |
| الميل | +44° 31′ 44″ |
| المسافة | 1,600 ± 100 س.ض. (675 ± 30 pc) |
| القدر الظاهري (V) | 4 |
| الأبعاد الظاهرة (V) | 120 × 100 arcmins |
| الكوكبة | Cygnus |
| تسميات | NGC 7000, Sharpless 117, Caldwell 20 |
سديم أمريكا الشمالية (North America Nebula ؛ NGC 7000 أوCaldwell 20) هوemission nebula in the constellation Cygnus, close to Deneb (the tail of the swan and its brightest star). The remarkable shape of the nebula resembles that of the continent of North America, complete with a prominent Gulf of Mexico. It is sometimes incorrectly[بحاجة لمصدر] called the "North American Nebula".
معلومات عامة
The North America Nebula is large, covering an area of more than four times the size of the full moon; but its surface brightness is low, so normally it cannot be seen with the unaided eye. Binoculars and telescopes 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 wavelengths of light, it can be seen without magnification 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.
The portion of the nebula resembling Mexico and Central America is known as the Cygnus Wall. This region exhibits the most concentrated star formation.
The North America Nebula and the nearby Pelican Nebula (IC 5070) are 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 1,800 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, from Slough, England, on October 24, 1786 or by his son John Herschel before 1833.
معرض صور
Amateur photo
Infrared view of the nebula
سديم أمريكا الشمالية.
NGC 7000 is one of the well-known nebulae in Cygnus
انظر أيضاً
- Pelican Nebula
المراجع
- ^ "NASA/IPAC Extragalactic Database". Results for NGC 7000. Retrieved 2006-10-17.
- ^ Shevchenko, V. S.; Grankin, K. N.; Nel'Nikov, S. Yu. (1988). "The structure of RSF أربعة CYG B - Regions of star formation from an unusual point of view". Astronomicheskii Zhurnal. 65: Nov.–Dec. 1988, p. 1230–1243. In Russian. Bibcode:1988AZh....65.1230S. ISSN 0004-6299.
- ^ "New View of Family Life in the North American Nebula". NASA. Retrieved 23 February 2012.
- ^ "NGC 7000 – North America Nebula". SEDS – Students for the Exploration and Development of Space, The Messier Catalogs. Retrieved 25 August 2017.
وصلات خارجية
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مشاع الفهم فيه ميديا متعلقة بموضوع North America Nebula. |
- 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
- سديم أمريكا الشمالية on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
