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View Full Version : Object of the Week June 18th, 2023 - M100



Dragan
June 20th, 2023, 03:43 PM
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!

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HST Before & After

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HST WFC3

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M100 - ESO

lamperti
June 20th, 2023, 06:14 PM
With an 18" at 286x, I had to "... put M-100 out of the field since it is distracting. NGC 4328 was a faint, roundish, even glow."

Raul Leon
June 20th, 2023, 08:11 PM
Hi, here's my observation from 6/4/2016: Ngc 4321 aka Messier 100 is a galaxy in Coma Berenices ; magnitude:9.3 ; size: 7.5' x 6.3' ; beautiful, bright face on ; bright central nucleus, shows spiral pattern and mottled texture surrounding the halo ; galaxy is surrounded by triangle of stars. Ngc 4328 is small roundish glow nearby. I used a 10mm Ethos at 198x with my 14.5 Starstructure f/4.3 5164

cloudbuster
June 21st, 2023, 09:46 AM
I saved M100 for observation on the Roque de los Muchachos (La Palma), because being a face-on galaxy it needs all transparancy that it can get. It appears very large and therefor I chose to sketch it with a 10mm eyepiece. It’s almost round, but slightly flattened. The bright and small core strongly contrasts with the surrounding nebulosity. Two arms are seen with effort, especially the one above and left. Apart from the core, the nebulosity is pretty uniform in brightness. As a bonus, two small and dim galaxies can be seen; NGC 4328 without much effort and NGC 4322 which is a bit dimmer, with AV. Sketched with a 16" Sumerian Alkaid @181x

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Martijn

Don Pensack
June 22nd, 2023, 02:07 PM
It is a quite impressive galaxy even with a smaller aperture.
My notes from an 203mm scope in 1995:
"large, roundish-oval, face-on spiral, outer areas diffuse like M51, very impressive!!!, bright stellar core, mottling in arms regions, irregular edge outline, best magnification 145x"
My first view of this was in 1963 with a 108mm reflector, so it is visible in quite small apertures.
It really comes alive around 200x in my 318mm reflector. It is up there with M51 and M101 and M74 as Dragan suggested.
I was looking at nearby NGC4312 in May (very nice nearly edge-on in same low power field as M100) when I moved over to M100 and almost needed sunglasses. It is really bright for a face-on spiral.
A great OOTW.

Steve Gottlieb
June 22nd, 2023, 10:19 PM
A couple of observations -- one with my 18-inch and the second with Mr. Lowrey's 48-inch.

18" (5/15/10): very bright, large, ~4.0-4.5' diameter, sharply concentrated with a very bright round core. Spiral structure was evident at 220x with a spiral arm attached on the southwest side of the core region. This arm sweeps east on the south side, heading in the direction of a mag 14 star just off the southeast end of the galaxy, but bending north. On the north side off of the core, a portion of the inner spiral arm is visible oriented E-W and extending to the northwest of the core region.

48" (4/18/15): stunning view of this gorgeous spiral at 375x and 488x. M100 was sharply concentrated with an intensely bright circular nucleus. Two prominent, high contrast arms (fairly narrow) each rotated ~270° and could be clearly traced to within 1' of the center. The south and north outer tips of the arms are between 5.5'-6' apart with the overall size ~6'x5'.

One arm begins off the WNW side of the core with a bright mottled section angling nearly north-south for ~25". This section contains multiple HII sites NGC 4321:[HK83]220/223/229/230 from Hodge and Kennicutt's 1983 "An Atlas of H II regions in 125 galaxies". The arm curls clockwise around the south side. A small (~8" dia.) HII knot (#160/171/172) is within this arm, 1.0' S of center. Just to the east [1.5' SE of center] is a brighter, mottled section that contains a close pair [18" separation] of compact HII knots (#110 and #69/87). The surface brightness of the arm abruptly drops as it shoots due north on the east side of the halo for ~3'. The arm dims further as it curves west on the northeast side of the outer halo and ends just southeast of mag 15 star situated 2.9' NNW of center.

The second arm begins ~1' SE of center as a thicker, much brighter region. The Hodge-Kennicutt Atlas catalogues numerous HII designations in this region, but none stood out individually. The arm sharply narrows and rotates clockwise around the north side of the core towards the west. It passes just south of two mag 15.5 stars, where there is a slightly brighter mottled section containing HII regions #252/253. The arm dims significantly as it heads south on the west side of the halo. Finally, it weakens further and spreads out at the end on the southwest side of the galaxy [2.6' from center].

Howard B
June 23rd, 2023, 03:13 AM
I have a couple of observations of M100 as well - first with the 28-inch and second with Jimi's 48-inch - and on the same night as Steve's observation:

28-inch f/4 (February 20, 2009):
"a terrific view of this large and subtle spiral galaxy. The core is a small, bright oval with delicate spiral arms twirling away. Two small blobs were seen nearby [NGC's 4322 and 4328] 253x, 21.40 SQM."
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48-inch f/4 (April 18, 2015):
"Holy cow, what a great view! Spiral arms wrapping 180 degrees and more around the core, and two close companion galaxies. More than anything, it was a beautiful sight. 375x, 488x [no SQM]"
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Uwe Glahn
June 26th, 2023, 07:18 PM
Very nice face-on spiral. With mid size aperture difficult to resolve. I found an older sketch with my former 16" from 2006 with the supernova SN2006x included.

sketch: 16", 129x-225x, Nelm 6m0+
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home (http://www.deepsky-visuell.de/Zeichnungen/M100_SN2006X.htm)