Astro Images

Visual Magnitude: 10.9
Size: 4.4' X 3.4'
Distance: 100 million light years
Discoverer: unknown

Visual Description: NGC7974 is probably the best barred spiral galaxy in the northern hemisphere and, at a visual magnitude of 10.8, is bright enough to be visible in modest telescopes. Orientated almost face-on, an 8 inch (20cm) telescope shows a cigar shaped object about 4 arc-minutes long by 1 wide, running almost due north-south. This is NGC7974's prominent bar and averted vision shows some mottling in it, possibly due to the dust lanes in the bar. However the two spiral arms, which emanate from each end of the bar, requires more appature. A 16 inch reveals the western arm but even in this telescope the eastern one is still invisible. The nucleus is however obvious and looks like a 12th magnitude star. NGC 7974 is very easy to find, being 3 degrees due south of Alpha Pegasi (Markab).

NGC 7974 is a classical barred galaxy, almost face-on with the spiral arms winding out from a very prominent bar. As a result NGC 7974 has been extensively studdied in order to understand bar formation. Also in its favour is its isolation from other galaxies and its morphology is therfore due solely to itself rather than any galactic interactions. So understand NGC 7974 and take a large step to understanding barred spirals. To do this it is necessary to study its interstellar material ( and NCG 7974 has plenty ) as well as just its stars. Laine et al. (1988 & 1999) used radio telescopes primarily to detect emissions from CO (carbon monoxide molecules), which are easier to observe than H-alpha but are believed to be accurate tracers of it. CO emissions were detected only in the dust lane that runs the length of the bar. Results indicate that the motion of the molecular gas is circular in the circum-nuclear region but outside this there is a strong radial velocity, inward towards the nucleus. Laine and Gottesman (1997) proposed that the more prominent western arm was the result of a minor merger. Rozas et al. (1999) on the other hand examined NGC 7974 in H-alpha light detecting over 1,000 H-II regions with only a small number in the bar.

Seeing Conditions: Seeing was very poor (very humid and hazy). Because the seeing was very poor, longer than normal exposures were needed.

Telescope: Meade 10" LX200 Optical Tube Assembly
Focal Length: 2500 mm (f10)
Mount: Takahashi NJP 160
Camera: Starlight XPress MX916
Exposure: 8-15minute exposures stacked (added).
Other: S.T.A.R 2000 Autoguider

Image Processing: subtracted dark frames from each exposure. Stacked 8-15 minute exposures (added) and then sharpened with a hi-pass filter.

Astro Images

doug@dougsastro.net

Copyright(c) 2007 Doug Sanqunetti. All rights reserved