Mgławica Ślimak

NGC 7293
Ilustracja
Mgławica Ślimak – zdjęcie z Europejskiego Obserwatorium Południowego z 2009 r.
OdkrywcaKarl Ludwig Harding
Data odkryciawrzesień 1823
Dane obserwacyjne (J2000)
GwiazdozbiórWodnik
Typplanetarna
Rektascensja22h 29m 38,55s
Deklinacja–20° 50′ 13,6″
Odległość714+88−68 ly[1] (219+27−21 pc)
Jasność pozorna mgławicy7,3[2]m
Rozmiary kątowe16' (średnica halo 28')[2]
Charakterystyka fizyczna
Wymiary2,87 ly (0,88 pc)
Jasność absolutna6,58m
Szacowany wiek10 600 lat
Alternatywne oznaczenia
NGC 7293, PK 36-57.1, ESO 602-PN22, CS=13.5

Mgławica Ślimak (również NGC 7293) – mgławica planetarna znajdująca się w konstelacji Wodnika, oddalona o około 714 lat świetlnych. Jest jedną z najbliższych Ziemi mgławic planetarnych i została odkryta przez Karla Ludwiga Hardinga we wrześniu 1823 roku[3]. Od 2003 w internecie czasem nazywano tę mgławicę „Okiem Bożym”[4]. Mgławica ta rozciąga się na 2,5 roku świetlnego. Jej wiek ocenia się na mniej więcej 10 600 lat.

Mgławica planetarna NGC 7293 „Ślimak” w różnych zakresach fal: w ultrafiolecie (GALEX), przedstawionym jako niebieski, oraz w podczerwieni (Spitzer, WISE)


Zobacz też

Przypisy

  1. Hugh C. Harris i inni. Trigonometric Parallaxes of Central Stars of Planetary Nebulae. „The Astronomical Journal”. 133 (2), s. 631-638, 2007. DOI: doi:10.1086/510348 (ang.). 
  2. a b SEDS: NGC 7293, Mgławica Ślimak (ang.)
  3. Courtney Seligman: NGC 7293 (ang.). Celestial Atlas. [dostęp 2015-11-30].
  4. The Eye of God (ang.). snopes.com, 2006-07-05. [dostęp 2013-04-29].

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Helix Nebula - Unraveling at the Seams.jpg
A dying star is throwing a cosmic tantrum in this combined image from NASA's Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX), which NASA has lent to the California Institute of Technology in Pasadena. In death, the star's dusty outer layers are unraveling into space, glowing from the intense ultraviolet radiation being pumped out by the hot stellar core.

This object, called the Helix nebula, lies 650 light-years away, in the constellation of Aquarius. Also known by the catalog number NGC 7293, it is a typical example of a class of objects called planetary nebulae. Discovered in the 18th century, these cosmic works of art were erroneously named for their resemblance to gas-giant planets.

Planetary nebulae are actually the remains of stars that once looked a lot like our sun. These stars spend most of their lives turning hydrogen into helium in massive runaway nuclear fusion reactions in their cores. In fact, this process of fusion provides all the light and heat that we get from our sun. Our sun will blossom into a planetary nebula when it dies in about five billion years.

When the hydrogen fuel for the fusion reaction runs out, the star turns to helium for a fuel source, burning it into an even heavier mix of carbon, nitrogen and oxygen. Eventually, the helium will also be exhausted, and the star dies, puffing off its outer gaseous layers and leaving behind the tiny, hot, dense core, called a white dwarf. The white dwarf is about the size of Earth, but has a mass very close to that of the original star; in fact, a teaspoon of a white dwarf would weigh as much as a few elephants!

The glow from planetary nebulae is particularly intriguing as it appears surprisingly similar across a broad swath of the spectrum, from ultraviolet to infrared. The Helix remains recognizable at any of these wavelengths, but the combination shown here highlights some subtle differences.

The intense ultraviolet radiation from the white dwarf heats up the expelled layers of gas, which shine brightly in the infrared. GALEX has picked out the ultraviolet light pouring out of this system, shown throughout the nebula in blue, while Spitzer has snagged the detailed infrared signature of the dust and gas in yellow A portion of the extended field beyond the nebula, which was not observed by Spitzer, is from NASA's all-sky Wide-field Infrared Survey Explorer (WISE). The white dwarf star itself is a tiny white pinprick right at the center of the nebula.

The brighter purple circle in the very center is the combined ultraviolet and infrared glow of a dusty disk circling the white dwarf (the disk itself is too small to be resolved). This dust was most likely kicked up by comets that survived the death of their star.

Before the star died, its comets, and possibly planets, would have orbited the star in an orderly fashion. When the star ran out of hydrogen to burn, and blew off its outer layers, the icy bodies and outer planets would have been tossed about and into each other, kicking up an ongoing cosmic dust storm. Any inner planets in the system would have burned up or been swallowed as their dying star expanded.

Infrared data from Spitzer for the central nebula is rendered in green (wavelengths of 3.6 to 4.5 microns) and red (8 to 24 microns), with WISE data covering the outer areas in green (3.4 to 4.5 microns) and red (12 to 22 microns). Ultraviolet data from GALEX appears as blue (0.15 to 2.3 microns).
Helix Nebula.jpg
Autor: European Southern Observatory, Licencja: CC BY 4.0
This colour-composite image of the Helix Nebula (NGC 7293) was created from images obtained using the the Wide Field Imager (WFI), an astronomical camera attached to the 2.2-metre Max-Planck Society/ESO telescope at the La Silla observatory in Chile. The blue-green glow in the centre of the Helix comes from oxygen atoms shining under effects of the intense ultraviolet radiation of the 120 000 degree Celsius central star and the hot gas. Further out from the star and beyond the ring of knots, the red colour from hydrogen and nitrogen is more prominent. A careful look at the central part of this object reveals not only the knots, but also many remote galaxies seen right through the thinly spread glowing gas. This image was created from images through blue, green and red filters and the total exposure times were 12 minutes, 9 minutes and 7 minutes respectively.