NGC 6946

Galaxie
NGC 6946
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Aufnahme mithilfe des Nicholas U. Mayall Telescope
AladinLite
SternbildKepheus
Position
Äquinoktium: J2000.0, Epoche: J2000.0
Rektaszension20h 34m 52,3s[1]
Deklination+60° 09′ 14″[1]
Erscheinungsbild
Morphologischer TypSAB(rs)cd / Sy2 / HII[1]
Helligkeit (visuell)9,0 mag[2]
Helligkeit (B-Band)9,7 mag[2]
Winkel­ausdehnung11,5′ × 9,8′[2]
Positionswinkel57°[2]
Flächen­helligkeit14,0 mag/arcmin²[2]
Physikalische Daten
Rotverschiebung0,000160 ± 0,000007[1]
Radial­geschwin­digkeitheliozentrisch: (48 ± 2) km/s[1]
Hubbledistanz
H0 = 73 km/(s • Mpc)		(18 ± 5) · 106 Lj
(5,45 ± 1,471) Mpc [1]
Durchmesser90.000 Lj[3]
Geschichte
EntdeckungWilhelm Herschel
Entdeckungsdatum9. September 1798
Katalogbezeichnungen
NGC 6946 • UGC 11597 • PGC 65001 • CGCG 304-006 • MCG +10-29-006 • IRAS 20338+5958 • Arp 29 • GC 4594 • H IV 76 • h 2084 •

NGC 6946 (Arp 29) oder auch Feuerwerksgalaxie ist eine Balken-Spiralgalaxie vom Hubble-Typ SAB(rs)cd im Sternbild Cepheus an der Grenze zum Sternbild Cygnus am Nordsternhimmel.

Die Galaxie liegt nahe unserer galaktischen Ebene, daher wird das Licht, das von NGC 6946 zu uns kommt, durch Gas und Staub aus unserer Galaxie stark abgedunkelt. Dies erschwert die Beobachtung dieser Galaxie und ihrer Mitglieder und besonders auch die Bestimmung ihrer Entfernung. Insbesondere soll aus den Supernova-Beobachtungen deren Entfernung bestimmt werden, wozu neben der scheinbaren Helligkeit und der absoluten Helligkeit auch die (in diesem Fall schlecht messbare) interstellare Extinktion bekannt sein muss. Eine im Jahre 1997 veröffentlichte Berechnung ergab eine fotometrische Distanz von 6,4 Megaparsec (21 Mio. Lichtjahren)[4]. Andere Messungen ergaben Werte zwischen 4,1 und 10,5 Megaparsec[5]. NGC 6946 führt die Statistik der Supernovahäufigkeiten in den letzten hundert Jahren mit einer Anzahl von zehn an.

Halton Arp gliederte seinen Katalog ungewöhnlicher Galaxien nach rein morphologischen Kriterien in Gruppen. Diese Galaxie gehört zu der Klasse Spiralgalaxien mit einem ausgeprägten Arm (Arp-Katalog).

Das Objekt wurde am 9. September 1798 vom deutsch-britischen Astronomen Friedrich Wilhelm Herschel entdeckt.[6]

Literatur

  • König, Michael & Binnewies, Stefan (2019): Bildatlas der Galaxien: Die Astrophysik hinter den Astrofotografien, Stuttgart: Kosmos, S. 103

Weblinks

Literatur

  • Jeff Kanipe und Dennis Webb: The Arp Atlas of Peculiar Galaxies – A Chronicle and Observer’s Guide, Richmond 2006, ISBN 978-0-943396-76-7

Einzelnachweise

  1. ↑ a b c d NASA/IPAC EXTRAGALACTIC DATABASE
  2. ↑ a b c d e SEDS: NGC 6946
  3. ↑ NASA/IPAC
  4. ↑ Sharina, M. E., Karachentsev, I. D., & Tikhonov, N. A. (1997): Photometric distance to the galaxy NGC 6946 and its companion. In: Pis'ma v Astronomicheskii Zhurnal 23, S. 430
  5. ↑ Zitiert aus Bonnarel, F., Boulesteix, J., & Marcelin, M.: Morphology of the ionized gas in the spiral galaxy NGC 6946
  6. ↑ Seligman

Auf dieser Seite verwendete Medien

NGC6946 - Noao-ngc6946kpno.jpg
Autor/Urheber: Credit: KPNO/NOIRLab/NSF/AURA/T.A. Rector (University of Alaska Anchorage)/H. Schweiker (WIYN), Lizenz: CC BY 4.0
Spiral Galaxy NGC 6946


This image was obtained with the wide-field view of the Mosaic Camera on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory on September 5th, 2008. The face-on spiral galaxy NGC 6946 is fueled by the births and deaths of brilliant, massive stars. Over the past century, eight supernovae have exploded in the arms of this galaxy, making NGC 6946 the most prolific known galaxy for supernovae during the past 100 years. It was observed in the filters U (violet), B (blue), V (green), I (orange) and H-alpha (red). North is left, East is down.

Credit:

KPNO/NOIRLab/NSF/AURA/T.A. Rector (University of Alaska Anchorage)/H. Schweiker (WIYN)
NGC6946 Galaxy from the Mount Lemmon SkyCenter Schulman Telescope courtesy Adam Block.jpg
Autor/Urheber: Ngc1535, Lizenz: CC BY-SA 4.0
Deep exposures of Galaxies

using the 0.8m Schulman Telescope at the Mount Lemmon SkyCenter

Credit Line & Copyright Adam Block/Mount Lemmon SkyCenter/University of Arizona
Fireworks Galaxis Sig08-008.jpg
Image Credit: NASA/JPL-Caltech/R. Kennicutt (U. of Ariz./Inst. of Astr., U. of Cambridge) and the SINGS Team

Instrument: IRAC, Spitzer Space Telescope

Wavelength: 3.6 (blue), 4.5 (green), 5.8-8.0 (red) microns
Caldwell Catalogue.jpg
Autor/Urheber: Roberto Mura, Lizenz: CC BY-SA 3.0
Caldwell Catalogue objects.
Caldwell 12 - 2.jpg
Autor/Urheber: NASA Hubble, Lizenz: CC BY 2.0
A spectacular spiral: octopus-like arms of stellar icy blue whipping around a glowing marmalade nucleus like water rushing toward a drain. This is Caldwell 12, a mid-sized spiral galaxy that resides on the border of the constellations Cepheus and Cygnus in our night sky. Caldwell 12’s beauty isn’t its only claim to fame. An unprecedented ten supernovae have been observed in the galaxy’s spiral arms since 1917, making it a popular object for both scientists and amateur astronomers alike. Unfortunately, its location (obscured behind lots of Milky Way dust) as well as its somewhat small size (about 50,000 light-years across) don’t do much to help its luminosity (at magnitude 9.7). This means it can be particularly difficult to spot in the night sky, and when found, can often appear hazy rather than with stark, well-defined spiral arms.

Caldwell 12’s high propensity to produce supernovae has helped earn it the nickname of the Fireworks galaxy. Around the nucleus of Caldwell 12 is a tight, glowing ring, which scientists believe has been manufacturing stars for nearly 20 million years, acting as a stellar factory to fuel the galaxy. Astronomers can learn more about star birth, death, how galaxies formed and came to be with the help of galaxies like Caldwell 12.

Also known as NGC 6946, Caldwell 12 was discovered by astronomer William Herschel in September of 1798. At 15 million light-years away, the Fireworks galaxy is one of the closest known galaxies to the Milky Way outside of the Local Group (a collection of gravitationally bound galaxies that includes our own).

The Fireworks galaxy is best viewed in the late summer in the Northern Hemisphere. In the Southern Hemisphere it’s a late-winter object, but only those close to the equator will have a good view of it. Through a telescope in clear, dark skies, the galaxy appears as a bright nucleus with a soft halo.

This mosaic image, showing a little more than half of Caldwell 12, was made mostly from exposures taken with Hubble’s Advanced Camera for Surveys (ACS) and supplemented with observations from the Wide Field and Planetary Camera 2 (WFPC2).The ACS observations were taken as part of a study of the centers of nearby spiral galaxies and star formation within them. The WFPC2 observations helped identify sources for some of the supernovae observed in the Fireworks galaxy.

Credit: NASA, ESA and L. Ho (Peking University); Processing: Gladys Kober (NASA/Catholic University of America)

For more information about Hubble’s observations of Caldwell 12, see:

hubblesite.org/contents/news-releases/1999/news-1999-10.html

For Hubble's Caldwell catalog site and information on how to find these objects in the night sky, visit:

www.nasa.gov/content/goddard/hubble-s-caldwell-catalog