NGC 4945

Image-data was acquired by Thorsten Brandes in Namibia/Hakos with the equipment of Johannes Schedler in May 08.

Also available at NASA website.

Date: May 2008 - seeing 8/10; transp. 9-10/10

Scope: 140 TEC corrected (Flattener)

CCD: ST 11k L:6x10min; R,G,B, 2x 10min (1x1) AstroDon filters

1 Master Dark. Color weight RGB=1.4-1-1 (Maxim)

Image acquisition: Thorsten Brandes

Scope and Mount credits: Johannes Schedler

Processing: Stargazer-Observatory


 
 

NGC 4945, aka PGC 45279 is a considerable large galaxy of the southern night skies. Located in the constellation Centaurus, 4945 renders a galaxy - tpye Sbc, meaning it holds a barred core-region. Measuring 19.8 by 4 arc minutes, this galaxy is a wonderful object for easy visual observation, as it shines in a magnitude of 9m3, since it is only some 13 Mio LY away from earth.

Similar to NGC 6946 of the northern hemisphere, the information about that very galaxy has to penetrate huge masses of intergalactic dust, hence swallowing serious amount of light, and detailled information. Nevertheless, 4945 is a highly investigated galaxy, as it is known for 2 characteristics:

1) Being a star-burst galaxy. This type of galaxy gives birth to giant masses of young stars and star-populations, yielding to strong emmissions of light, making it an even more bright object. Many galaxies undergo such a phase in a status post colliding with another galaxy or after close encounters with other galaxies. The rate of forming stars in such galaxies is so high that if it was sustained, reserves of gas utilized for creating stars was totally consumed in a blink of the time, a galaxy usually exists! This is mainly the reason why star-burst events are assumed to be temporary. (also see NGC 4490, NGC 4449, M82).

and 2) At the same time 4945 is also a socalled Seyfert-galaxy (Type II). This makes her a galaxy with an extremly active and luminous bright core in terms of enormous emissions in spectra of hydrogen, helium, nitrogen, and oxygen. What makes these emission-lines so typical for Seyfertgalaxies, is the Doppler-broadening in these specific lines, indicating the high velocity of the energy, being emitted at some 4000 km/sec. The reason for the immense emmission is fabled to be a super-massive black hole, as the phenomenon takes place associated to an accretion-disk surrounding such black hole.

Seyfert galaxies have been among the most intensively studied objects in astronomy, primarily because they are thought to be nearby, low-luminosity versions of the same phenomenon observed in quasars.

 

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