Designations: M108, NGC3556
Object Type: Spiral Galaxy
Constellation: Ursa Major
RA: 11h 11m .5
Dec: 55 deg 40m
Visual
Magnitude: 10.0
Size: 8.7m X 2.2m
Distance: 46 million light
years
Discoverer: Pierre Mechain 1781-1782
Visual Description: M108 is a tiny
spiral galaxy by astronomical standards, only about one twentieth the mass of
M31. Although we see the galaxy nearly edge on, the central bulge is all but
absent. Whatever shines in the nuclear region is masked by turbulent eddies of
dark matter lining the galaxy's highly fore-shortened arms. The nucleus might
have also depleted itself long ago, or it has only periodic bursts of energetic
activity that keeps it going. Brilliant regions of star formation among the
obscuring matter look like signal flares burning in a storm.
Visible in
binoculars as a faint gray streak only two moon diameters (1deg) northwest of
the Owl Negula (M97), or just 1 degree southeast of Merak (Beta Ursae Majoris),
M108 is an interesting spiral. With its highly wrinkled texture, this
10th-Magnitude system looks as if it is the shed skin of M82 - a galaxy with a
similar demeanor - left here to dry. Even at 23X in a 4-inch, M108's elongated
(8'.7) and highly mottled disk can be recognized. Moderate and high powers are
needed to show its haphazard array of dark lanes, superposed stars, and
irregularly bright nebulous patches, which look like they have been pasted
together by a three-year-old. At 130 X one prominent, kinked, dark channel runs
along the galaxy's northern rim. More difficult is a long dust lane that follows
the southern edge of the galaxy. A beautiful, though delicate, fan of material
sprays westward from a faint knot embedded in the western half of M108, and a
misty breath of galactic haze shines feebly beneath a 13th magnitude star in the
eastern falf. A fainter glow connects that dim patch to the pseudo-nucleus- a
fairly bright foreground star near the galaxy's invisble heart. The real
challenge is to see the 14th-magnitude bead immediately southwest of that
central pip.
Seeing Conditions:
Humidity was high so
transparancy was not great. seeing was steady
Telescope: Meade 10" LX200 Optical Tube
Assembly
Focal
Length: 2500 mm X .63 focal
reducer
Mount: Takahashi NJP 160
Camera:
Starlight XPress
MX916
Exposure:
8 15-minute exposures
Other: STV Autoguider
Image Processing: Images were stacked and sharpened with a hi-pass filter.
The Visual description of the M108 Galaxy was writen by Steven James O'Meara in the book "The Messier Objects" by Stephen James O'Meara. Page. 279. ISBN number 0-521-55332-6.
Copyright(c) 2007 Doug Sanqunetti. All rights reserved
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