M100 Spiral Galaxy and It's Neighbors in Virgo


Copyright 2008 Hap Griffin

M100 is a spectacular example of what is know as a "Grand Design Spiral Galaxy".  It is a member of the relatively nearby Virgo cluster of galaxies and is one of the brightest face-on spirals visible to us, evidenced by the fact that it was one of the earliest of its class first cataloged in 1781.  There are approximately 2500 galaxies in the Virgo cluster and it along with our local group of galaxies make up what is known as the Virgo Supercluster.  M100 has special significance in modern cosmology in that it contains a number of variable brightness stars called Cepheid Variables.  These giant stars vary in brightness over a period of 1 to 100 days and provide a "standard candle" of brightness reference since their absolute brightness is closely related to their variability period, and can thus be used to very accurately determine the distance to galaxies that contain them.  In 1994, the Hubble Space Telescope was used to study the Cepheid's in M100 and determine very accurately that it's distance is 56 million light years.  This value was used to refine the value of Hubble's Constant which is used to determine the age of the Universe based on its expansion rate.

With the mass of 160 million suns, M100 is  less massive than our own Milky Way galaxy, but is more expansive, being over 150,000 light years in diameter.  It lies at a distance of 60 million light years.

Several of M100's neighbor galaxies can be seen in this image, the most conspicuous of which is spiral galaxy NGC 4312 at its lower left.  Closer in and at the 12 o'clock position is the irregular galaxy GSC 1445 and at the three o'clock position, NGC 4323.  Several other irregular galaxies can be spotted towards the bottom of the frame.

Date/Location:    February 9, 2008     Griffin/Hunter Observatory    Bethune, SC
Instrument:    Canon 40D Digital SLR (modified) through Orion 10" Newtonian w/ Baader MPCC
Focal Ratio:   F /4.7
Guiding:    Auto through Orion ED-80 w/ SBIG ST-401 on an AP-1200 mount
Conditions:    Visually clear
Weather:    42 degrees 
Exposure: 156 minutes total @ ISO 800 (52 x 3 min exposures)
Filters:    Baader UV/IR Block internal to camera
Processing:    Focused and captured with ImagesPlus V3.0.  RAW to TIFF conversion, frame calibrations, auto frame alignment, frame stacking, Digital Development, scaling and JPEG conversion with ImagesPlus V3.5a.  Finished in Photoshop CS2.