M100
NGC 4321
UGC 7450
PGC 40153
Galaxy
Coma Berenices
Class: SAB(s)bc
RA: 12h 22m 55.0s
DEC: +15? 49’ 25”
Mag: 9.3
Size: 7.5’ x 6.3’
Sometimes I’m amazed that when I start searching for an OOTW, I come across an object that I would have bet my last dollar another OOTW author already scooped it up. As I began researching my notes this week looking for a worthy object, I thought I’d give M100 a quick search – only assuming it was already chosen. Boy, was I surprised when after 550+ OOTW’s, M100 had never made an appearance. Until now.
M100 in Coma Berenices is another stunning example of a grand-design galaxy. Maybe one of the best. As a refresher, a "grand-design" galaxy refers to a specific type of spiral galaxy that exhibits 2 prominent, well-defined spiral arms extending from a central nucleus. These spiral arms are often tightly wound and exhibit a symmetrical and organized structure, giving the galaxy an elegant and “grand” appearance. Think of some of the most beautiful ‘face-on’ galaxies we all love such as M51, M101 or M74.
Discovered alongside M98 & M99, M100 was first observed by French astronomer and comet hunter Pierre Méchain on March 15th, 1781. Charles Messier observed all 3 objects a month later on April 13th, 1781 and added them to his now famous catalog. However, it wasn't until the early 20th century that astronomers identified M100 as a captivating spiral galaxy nestled within the Virgo Cluster, located approximately 55 million light-years away.
M100 hit mainstream media in 1993 when a blurry image of it was first publicly released by NASA. M100 was one of the Hubble Space Telescopes very 1st targets after HST’s 1990 launch into orbit. Unfortunately, a severe and unexpected case of spherical aberration of Hubble’s primary mirror proved the image – and subsequently the telescope itself - worthless when M100 came back to Earth so blurry, you’d think someone smeared Vaseline on the optics. But, and as NASA usually does, engineers at NASA devised a solution (COSTAR) and after a 1993 servicing mission, repaired Hubble bringing the telescope to the condition everyone expected. NASA rereleased an image of M100 showing the dramatic difference the repair made to the optics of Hubble.
During this time of year, M100 is visible in the western sky, setting a couple of hours after local midnight. Located 8.3? east of Leos’ Denebola, M100 is in the southern portion of Coma Berenices. Let’s be honest, there probably isn’t much I can say about its visual appearance that many of DSF’s seasoned observers haven’t already seen. Reports online reveal amateurs having observed M100 as a small, circular glow in scopes as small as 4 inches with the arms only revealing themselves in the 10 to 12inch aperture range and beyond. In larger scopes with good conditions, M100 begins to come into its own providing the observer with a bright condense core with two opposing spiral arms extending in easterly and westerly directions from the core. In my 25”, I’ve made mention of a thin, diffuse glow that encompasses the entire galaxy. Like so many objects, M100 is best observed with larger aperture, higher magnification (250x and above) and clear, dark skies.
As possible challenge objects, much smaller and fainter NGC 4322 and NGC4328 lie nearby.
Next time you’re out, give M100 a chance. It’s well placed shortly after sunset in the western sky. But be sure to give it a go sooner rather than later. If you miss your chance this late in the season, you may just have to wait until next spring to view this beautiful grand-design object!
As always, give it a go and let us know!
M100 Before_After.jpg
HST Before & After
M100 HST WFC3.jpg
HST WFC3
eso-m100.jpg
M100 - ESO
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