The weather really made our Observer's Challenge even more so for April. Cloud cover and moving storm fronts on our dark sky nights in the Las Vegas area delayed or prevented the observing of NGC 4889 and the Coma Berenices Galaxy Cluster. We've posted the reports of our friends and members that were able to observe this interesting galaxy cluster, but we'll certainly update our report with other observations, if our Challenge participants are able to observe this object during the month of May. Please check out the reports below of our participants that were able to observe the cluster during the month of April.

 

Dr. James Dire's image of NGC 4889 and nearby galaxies

 

NGC-4889, also known as Caldwell 35, is a super-giant Class-4 elliptical galaxy in the Coma Berenices Galaxy Cluster.  It is the brightest member of the group and lies approximately two hundred and fifty million light years away.  With a relatively dim magnitude of 11.4, it is sometimes drowned out by the glare from the nearby mag 7 star, Beta Comae Berenices, especially if the sky conditions are not good.  Nearby is the second brightest galaxy in the group, NGC-4874 at mag 12.6.

 

Observations/Drawings/Photos

Roger Ivester: LVAS Member from North Carolina

 

My favorite deep-sky objects have always been galaxies. The April challenge object, NGC-4889 is the brightest galaxy in the Coma cluster. This elliptical galaxy glows rather faintly at mag. 11.4 and can be difficult if conditions are not very good. All of my observations were from my moderately light-polluted backyard located in Boiling Springs, North Carolina, which is in the foothills region of the western part of the state. I used two telescopes for my observations, including a 10” f/4.5 reflector and a 4” f/9.8 refractor. The following observations were made over a three night period with the seeing and transparency both being rated as fair to poor. The naked eye limiting magnitude for these nights averaged 5.0 to 5.5, which can be normal for this time of the year due to higher humidity, and haze.

 

With the 10”, NGC-4889 at 143X was presented as faint, slightly elongated with an orientation of E-W. A bright stellar nucleus could be seen with averted vision, but could not be held constantly. A faint and also elongated halo surrounded this galaxy, and was fairly easy to see. I also observed this galaxy with the 4” refractor, which presented NGC-4889 as elongated with a brighter and more concentrated middle, but without a stellar nucleus.

 

The second brightest galaxy of the Coma cluster is NGC-4874, and is located less than 10’ away from NGC-4889, toward the west.

 

NGC-4874 is especially difficult, being located south of a bright mag. 7 star which causes significant glare.  NGC-4874 shines at a fainter mag. 11.9, and the surface brightness is fairly low, with a mostly even texture, without any central brightening. Wanting to see more, I decided to borrow a 13 mm Nagler from a local observatory for a trial. When using the Nagler eyepiece with the 10”, it gave a magnification of 87X. I was very surprised to see that the glare was completely eliminated as compared to the views of the four-element eyepiece from the previous night. The 13 mm did not have any internal reflections and much greater detail was now visible when using this eyepiece. The view of NGC-4874 was now presented as mostly round, very little concentration, an even texture with a faint, but very subtle brighter core. I noted that the background in the larger field of the 13 mm was much darker and also the bright mag. 7 star was no longer distracting.

 

Roger's sketch of NGC 4889

 

I also observed both galaxies with my 4” refractor, and to my surprise, NGC-4874 was actually easier to see than with the 10”. The glare of the mag. 7 star was far less with the refractor as compared to the much larger reflector, when using the four-element eyepiece with internal reflections, as discussed in the previous paragraph. The contrast of the much smaller refractor was superior, and fainter detail could be observed. When observing with the 4”, NGC-4874 appeared mostly round, very soft and even texture, a very faint halo, with no central brightness being noted. I was not able to use the 13 mm Nagler with the refractor due to time constraints the following night.

 

 

Fred Rayworth: LVAS Member from Las Vegas, Nevada

 

 

I observed this galaxy the same night I spotted the March challenge objects, in early April with my 16” f/4.5 Meade LightBridge and 26mm Q-70, 17mm and 8mm Hyperion eyepieces. However, the sky conditions were horrible to the east that night. Besides some kind of haze that was in the sky, two derrick barges out in the middle of Lake Mead were covered with spotlights and lit up the sky worse than the moon would have. Those lights caused a glow that at first didn’t seem that bad until I tried to find any galaxies in the Coma Berenices/Virgo/Leo part of the sky. Before I concentrated on NGC-4889, I succeeded with a couple of brighter galaxies in Ursa Major and Leo and barely saw objects at mag. 10, despite the sky appearing dark above the glow coming off the lake.

 

Fred's sketch of NGC 4889

 

After much hunting and pecking, I only found NGC-4889 because I knew exactly where to look. It took several passes before I spotted it and could see almost nothing with direct vision. With averted vision, I  spotted an oval shape that didn't look quite right. At 220X it showed a slight lump to one side which may have been NGC-4886. What bothered me was that it shouldn’t have looked like an oval, being an elliptical galaxy. I was expecting a rounder shape or at least a fatter oval with a fuzzy glow like a distant globular cluster. I took my bearings again to make sure the star was Beta Comae Berenices and looked again, saw the same thing. NGC-4874 which should have been clearly visible right next to it was not there at all. After looking at photographs, I recognized the star patterns and positively identified the area. On a better night, I  should have seen multiple galaxies in the field of view. This was a shock after seeing so much detail in the March object which was in the skyglow of Las Vegas. My sketch reveals an empty field of stars except for the oblong lumpy fuzz of NGC-4889 and NGC-4886.  I even doubted the lump I  saw was really NGC-4886 as it is much fainter than NGC-4874. However, it is also much smaller and concentrated so that may be why I was able to spot it.

 

 

Dr. James Dire: LVAS Member from North Carolina

 

 

Galaxies tend to group into galaxy clusters. Many are found throughout the heavens. Perhaps one of the most impressive galaxy clusters is the Coma Cluster in the constellation Coma Berenices. The Coma Cluster contains approximately 1,000 galaxies located roughly 300 million light years away. The cluster can be found approximately one-quarter of the way along the line from the mag. 4 star Beta Comae Bernices to the mag. 4 star Gamma Comae Bernices.

 

My cluster image is centered on NGC-4889, the brightest galaxy in the cluster. NGC-4889 is a not-so-impressive mag. 11 elliptical galaxy that is roughly half the size of our Milky Way home. NGC-4889 is not only the brightest member of the cluster, but it is also located near the center of the cluster from our perspective. My image spans the inner 1° field of view around NGC-4889. There are several Milky Way stars in this field of view. The brightest is mag. 7 HD112887.

 

Jim's labeled NGC 4889 with companion galaxies

 

Most of the faint objects in the image are galaxies. I estimate that 200-300 galaxies are visible in this 3 hr exposure taken with a 190mm f/5.3 Maksutov-Newtonian astrograph with an SBIG ST-2000xcm CCD camera. It was taken on May 4 - 6, 2010 at the Wildwood Pines Observatory. The faintest galaxies in the image are approximately mag. 19. The image is actually 40’ X 30’ in size. Light leaving a galaxy on the left edge of this image takes 3,500,000 years to travel to a galaxy on the right edge of the image

.

 

Frank Barrett: LVAS Friend from North Carolina (www.celestialwonders.com)

 

 

How many galaxies can you count in Frank’s image below?  The two brighter galaxies are NGC-4889 and NGC-4874.

 

Frank's image of NGC 4889

 

On 3/19/2010, I took this image from my observatory in Gastonia, North Carolina. I used a Meade 10” LX200R, with a2,800mm focal length giving it an f/11 focal ratio. My exposure was 400 min. with an SBIG STL-11000M camera. My mount was a Losmandy G11 with an Ovision worm upgrade.

 

Other Notable Observations

 

David J. Eicher, Galaxies and The Universe, An observing guide from Deep-Sky magazine, The Coma Berenices Galaxy Cluster by Brian Skiff - The brightest galaxies in the Coma cluster are NGC-4889, just east of the center of the cluster, and NGC-4874, slightly fainter, 9.2' away to the west.  Both are visible in the 5” refractor at medium power.  NGC-4874 is more difficult to view, appearing as a poorly-concentrated roughly circular patch. A mag. 12.5 star lies 2' southwest. A mag. 7 star only 6.5' north of the galaxy interferes with viewing here and in larger apertures.  With the 12.5”, NGC-4874 is about 1.5' across and roughly circular, but many tiny galaxies nearby make for a seemingly irregular outline. The outer regions have a moderate even concentration. The core arises in a slight, sharp condensation 20" across, but there is no distinct nucleus.

 

Tom Lorenzin, 1000+ The Amateur Astronomer's Field Guide to Deep-Sky Observing - NGC-4889; 11.5M; 3' X 2' extent; soft oblong with brighter center; mag. 14 star 40" N of core.

 

Burham’s Celestial Handbook, Vol 2, by Robert Burnham, Jr. - Brightest member of a very remote and very rich cluster of galaxies. NGC-4889 is a giant elliptical system of mag. 13. The red shift of the galaxy is near 4250 miles per second. A survey by F. Zwicky (1957) identified 804 galaxies brighter than mag. 16.5 within 160’ of the cluster’s center, and 29, 951 galaxies brighter than mag. 19.0 within 6º.

 

Observing Handbook and Catalogue Of Deep-Sky Objects, by Christian Luginbuhl and Brian Skiff, Cambridge University Press - NGC-4889 is the brightest object in the Coma cluster of galaxies. It is distinctly brighter than NGC-4874, 9.2' W, in 15 cm (6”) at 75X. The 1.'5 halo is evenly and well concentrated to a faint stellar nucleus. At times it seems elongated E-W, but a mag. 13.5 star 1' SE may be influencing this. 30 cm (12”) shows a 1' X 0'.6 core elongated E-W; here this seems due mostly to a very faint galaxy, eg A1257 + 28, superimposed on the W side only 28" from the center.

 

References

(Submitted by Fred Rayworth and Roger Ivester)

David J. Eicher, Galaxies and The Universe, An observing guide from Deep-Sky magazine, The Coma Berenices Galaxy Cluster by Brian Skiff

Tom Lorenzin, 1000+ The Amateur Astronomer's Field Guide to Deep-Sky Observing

Burham’s Celestial Handbook, Vol 2, by Robert Burnham, Jr.

Observing Handbook and Catalogue Of Deep-Sky Objects, by Christian Luginbuhl and Brian Skiff, Cambridge University Press