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| Spring Supplemental - M51 - Whirlpool Galaxy |
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Frank Barrett's image of M51 (Click on image for larger view)
M51, also known as the Whirlpool Galaxy or NGC 5194/5195, is a spectacular object to observe. With a magnitude of 8.4, it is easy to spot in almost any telescope and even in binoculars. With larger apertures, however, more details details can be seen within it.
M51 was discovered by Charles Messier in 1774, but the spiral nature of it was not recognized until Lord Rosse trained his leviathan 72-inch reflector on it from his observatory in Birr Castle, Ireland in 1845. It was still thought to be a spiral nebula until modern astrophotography revealed its true nature.
Though its companion, NGC 5195, is a separate galaxy, its long interaction with the main galaxy has affected M51's spiral arms. The smaller companion has passed through the main galaxy at least twice and is currently slightly behind M51, as seen from Earth. Visually, in smaller apertures, two bright spots can be seen with one being a bit larger and brighter than the other; however, they are both connected within the glow.
M51 is part of the small M51 galaxy group that includes M63 (the Sunflower Galaxy), NGC 5023, and NGC 5229. The Whirlpool Galaxy lies somewhere between 15 and 37 million light years from Earth. Observations/Drawings/Photos
Roger Ivester: LVAS Member from North Carolina
The spring supplemental Observers Challenge object is NGC 5194 (M51) and its smaller companion, NGC 5195, which lies only 4' to the north. All observations were made from my moderately light-polluted backyard in Boiling Springs, North Carolina.
Both galaxies can be easily seen with a 60mm scope under a dark sky and good transparency. The appearance is that of two faint nebulae, both with brighter cores, each having a stellar nucleus, with faint mostly-round halos.
A 4" refractor presents NGC 5194 as having a brighter well-concentrated middle and a stellar nucleus. The eastern-most part of the halo has a brighter rim and curves from the south edge toward the north. The western halo appears similar, but is not as bright, nor nearly as concentrated. NGC 5195 appears mostly round with a brighter middle, and also with a stellar nucleus, which seems to be a bit more intense in brightness than the nucleus of the larger NGC 5194.
When observing NGC 5194 with a 10" reflector, the spiral arm on the western edge becomes very pronounced, and the overall texture begins to hint at spiral structure. A mag. 13.5 star can be seen just off of the western edge of the core, and a fainter mag. 14 star sits just below. A mag. 13.7 star can be seen on the eastern edge of the halo. NGC 5195 is presented as smaller, but again with a brighter stellar nucleus as compared to the larger NGC 5194.
 Click on image for larger view
The sketch was made using a 10" reflector at a magnification of 190X. Due to the poor conditions as of late, I picked a sketch from April 1994 and duplicated it as close as possible. This sketch was made on a 5 X 8 note card, using a combination of different graphite drawing pencils. The colors have been inverted using a scanner, and there are also some changes in contrast and brightness.
Fred Rayworth: LVAS Member from Las Vegas
I had two opportunities to look at this great galaxy pair for the spring supplemental. Once in May and the other in June. Below is a summary of the two observations.
I saw it both times from Redstone Picnic Area on the North Shore Road of Lake Mead, Nevada. On May 15, 2010, what started as a bad night (clouds moving in before sunset) opened up after dark and became the best observing night of 2010, so far. The sky was pristine, at least wherever I looked. There was no wind and I remained in a T-shirt the whole night.
At first glace, I was wowed by the stunning detail I saw in the galaxy pair. At 70X, it was small, a pair of bright cores with the larger one having just the hint of spiral arms. At 101X, more details came out as the spiral arms started to show mottling and more structure. At 220X, it was the best. As the spiral arms spread out from the bright and large non-stellar core, I spotted individual lumps of nebulosity and what may have been some globular clusters embedded within. A faint bridge connected to NGC 5195. As for NGC 5195, the core seemed almost as bright as that of M51, but the surrounding glow was much smaller and just a tad oval. It had no other shape and I thought it to be distinctly of the elliptical variety. It was quite a contrast to the extended spiral arms of M51. Overall, I got the impression that M51 was spinning so fast, it threw a large chunk off to the side and it was still connected. This is not likely the case, but it set my imagination wild.
  Click on images for larger view
Upon a return visit on 05 June, 2010, the skies weren't quite as nice, there was an erratic breeze blowing, and I was tired the moment I got there. Still, I had a great time and had a chance to try a new 4.7mm eyepiece (390X) on it.
At 70X, 101X, and 220X, I observed the same details as the last time though they were not quite as distinct. When I tried 390X, the image filled the field. Both cores looked equally bright, though M51 was a bit larger. The spiral arms washed out so that only the brightest clumps were visible, vaguely giving it a spiral appearance. The bridge between M51 and NGC 5195 was gone. Though the new eyepiece gave a nice 82° field of view, the magnification was just too high for the conditions and didn't add much. Overall, they looked like a pair of bright cores with "something" around one of them.
Rob Lambert: LVAS Member from Las Vegas
In doing research for the Spring Supplemental Challenge, I was really surprised by the number of differing estimates regarding M51's distance, its size, and its brightness. Differences varied from 15 million light years to the more accepted 37 million light years. Estimates of its size varied from 50,000 light years to over 100,000 light years. Estimates of its luminosity ranged from 10 billion suns to over 160 billion suns. It's amazing that estimates can vary this greatly.
From this observer's standpoint, M51 is one of the most intriguing objects of the night sky. It's always a favorite of the public at our Education Outreach events. The Mallincam is able to reveal much detail in M51's structure.
 Click on image for larger view
Both M51 and its companion, NGC 5195, located to its north, have very bright cores. M51 has a definite fairly well defined spiral structure while the companion appears to be somewhat irregular, probably from the destructive interaction with M51. The Whirlpool has two tightly wound spiral arms that appear to originate opposite each other on the east and west sides of the core. Both arms wrap more the 360 degrees around the galaxy. The arm that originates on the west gradually thins out and fades into space on the south side of the galaxy, while the eastern originating arm reaches out and seems to encompass NGC 5195. There is an obvious dust lane interior to the arm that forms the bridge between the two galaxies. The dust lane makes NGC 5195 appear to be below the bridge, which is supported by some of the research observations I reviewed in preparing to observe this object. Other dust lanes are obvious throughout both arms, but are most noticeable in the eastern originating arm. There also appear to be some knots of stellar activity in the portion of the arm directly between the two galaxy cores; again most likely due to the interaction of the the two galaxies.
M51 and its companion will continue to be a favorite of mine. I look forward to observing and sharing the intriguing views of this beautiful spiral galaxy.
Jim Gianoulakis: LVAS member from Las Vegas
The 51st entry in Charles Messier's famous catalog is perhaps the original spiral nebula--a large galaxy with a well defined spiral structure also cataloged as NGC 5194. Over 60,000 light-years across, M51's spiral arms and dust lanes clearly sweep in front of its companion galaxy, NGC 5195. Not far in the sky from the handle of the Big Dipper, they officially lie within the boundaries of the small constellation Canes Venatici.
 Click on image for larger view
This image is composed of a stack of 22 light frames and 32 dark frames combined and stacked using DeepSkyStacker. Levels and curves applied in Photoshop.
Dr. James Dire: LVAS member from North Carolina (www.wildwoodpines.org)
M51 is an 8.4 magnitude face-on spiral galaxy in the northeast corner of the constellation Canes Venatici. The galaxy is best found by starting at the star Alkaid (end of the Big Dipper handle) and going 3.5° southwest. The galaxy is approximately 7.8" by 6.6" in size and has great surface brightness for a face-on spiral galaxy. I have seen this galaxy in all size telescopes, the largest being a 25" Newtonian at 8,000 ft in Colorado's Pike National Forest. In that behemoth scope, the spiral arms jumped out like a photograph.
  Click on images for larger view
My first image of M51 was taken with a Canon 30DSLR camera attached to a Stellarvue 102mm apochromatic refractor at f/6.3 . The exposure was 30 min. The second image was taken with a 190mm f/5.3 Maksutov-Newtonian using an SBIG ST-2000XCM CCD exposed for 40 min. Both images were shot at the Wildwood Pines Observatory in Earl, NC.
M51 has two spiral arms coming out of the galactic bulge, each branching off into more arms. Detailed structure in the galaxy can be seen in either image, including the bridge of stars connecting M51 to its companion spiral galaxy, NGC 5195.
NGC 5195 is also a face-on spiral galaxy less than half the size and brightness of M51. However both galaxies' cores have similar surface brightness and are just as easy to spy visually.
Frank Barrett: LVAS friend from North Carolina (www.celestialwonders.com)
Frank took an outstanding photo of M51 on 2/20/2010 from his observatory in Gastonia, North Carolina. His image was selected to be the spotlight image of this month's Challenge Object (see photo at top of page). He used a Meade 10" LX200R with a 2800mm focal length @ f/11. His exposure time was 2.5 hrs luminance and 1.5 hrs color with a SBIG STL-11000M camera. His mount was a Losmandy G11 with Ovision worm upgrade.
Buddy L. Barbee: LVAS friend from North Carolina
Friday, March 6, 2010 was forecast to be the second clear night of three after a front and rain had come through my area. My club, the Forsyth Astronomical Society, had a public observing session planned for Saturday night. I met up with two other members of the club to do some observing. They used their 10" Dob and I used my 4" refractor. The sky was beautifully clear, but the night was very cold.
I've observed M51 many times over the years with many different telescopes. On this night I chose to use my TeleVue 102mm refractor (a wonderful instrument) with a 13mm Nagler eyepiece for a magnification of 67X. When previously observing M51 with my C11 on a great night, I have seen what appears to be the bridge between M51 and its companion. With my larger telescopes, which include a 10" Dob, a 6" Meade AR6 refractor and an ETX125 PE, I have been able to see spiral structure and the appearance of a faint doughnut around the galaxy core. I was surprised to see something different this time. There was the bright core of the galaxy surrounded by a faint halo. Then I saw what appeared to be segments of spiral arms on each side of the galaxies' core. NGC 5194, the companion galaxy, was also visible. This was one of my best views that I can remember having of M51.
 Click on image for larger view
(Buddy sent his observations and a drawing which can be seen on his log sheet above).
Steve Davis: LVAS friend from North Carolina
I was playing over the weekend and got this image with an AP130 @ f/8. Not much, but thought everyone might find it interesting. It's just been stacked (8X5 min) and stretched. I didn't have time to mess with it much.
 Click on image for larger view
Now I want to put the CN212 on it and see what happens. I need a new camera.
Editor's Note: Notice the background galaxies that are visible in Steve's image south (right) of M51. You may need to view the larger image to see them.
Other Notable Observations:
James Mullaney, Celestial Harvest: 300-Plus Showpieces of the Heavens for Telescope Viewing and Contemplation Whirlpool/Question-Mark Galaxy: Visible in 3” as "two very unequal nebulae nearly in contact. M-51 is typically disappointing in less than a 6”. The spiral arms can be seen in an 8” with averted vision on a dark night. Yet, it took Lord Rosse's 72” speculum metal-mirror to first recognize them. This fact provides a perfect illustration of Sir William Herschel's famous dictum that "When an object is once discovered by a superior power an inferior one will suffice to show it afterwards!" The Whirlpool can be glimpsed in binoculars on a dark night. Burham’s Celestial Handbook, Vol 1, by Robert Burnham, Jr. M-51 is a Sc type spiral. A good pair of binoculars will show it on a dark night and a 2" lens will show a core with a halo. More details pop out at larger apertures. In 12", the spiral coils begin to resemble the familiar photographs. The Night Sky Observer’s Guide, Vol 2, Spring & Summer, George Robert Kepple and Glen W. Sanner In 8" to 10" scopes, has a well concentrated, mottled halo that suddenly brightens through the core to a stellar nucleus. The bridge to NGC-5195 is undetectable. In 12" to 14" scopes, it has a large diffuse halo containing a well-concentrated core. Spiral arms are visible with averted vision. In 16" to 18" scopes, the halo contains a clockwise spiral structure of two arms arcing almost completely around the core. The spiral arms are mottled and laced with dark lanes. Observing Handbook and Catalogue Of Deep-Sky Objects, by Christian Luginbuhl and Brian Skiff, Cambridge University Press In 6cm (2.4”), spiral component is mottled and extensive, but well-defined halo with little brightening toward the center, then a suddenly brighter core and stellar nucleus. In 15cm (6”), is difficult to tell which galaxy is brighter. No bridge visible. 25cm (10”) shows the arms clearly, brought out by dark patches N and SW of center. In 30cm (12”) the east arm is brighter, unwinding clockwise. Core is optically "deep," glowing like an unresolved globular cluster. |
