Tuesday, May 21, 2013

Galaxies galore and a departing comet

Finally after a long period where either the weather was bad or I was able to observe only at home, an opportunity came to observe my favorite kind of object from darker skies than I see at home, galaxies. While there I also took a look at the now departing comet 2011L4PANSTARRS and a elusive globular cluster. My original plans were to observe from a nearby state park, but when I arrived there it was clear that was not possible so I went to another site accessible to me. I took the 15-inch there along with my full array of eyepieces and filters. Upon arrival during the deepening twilight, I quickly set up the telescope and got down to the business at hand, observing and sketching deep sky objects. I also made use of the Sky Commanders, whose accuracy allows me to spend more time observing than searching for objects.
After a having a look at the crescent moon and Jupiter low in the western sky, comet PANSTARRS was the first object I looked at and sketched that night. Venus was also visible, but since it just emerged from superior conjunction and was very low in the sky I did not look at it that night. Now deep in the northern sky in Cepheus, PANSTARRS is a pale shadow of what it was when it came into view last March. Shining at eighth magnitude, it was still a nice object for a telescope, resembling a lopsided or interacting spiral galaxy with an off-center nuclear region. Closer inspection showed the coma was fan shaped, and there was no sign of a tail evident. The comet was low in the sky and the observing site was far from being what would be called very dark. I'll follow it as long as I can since it will remain near Polaris for the next six weeks or so before it heads south again and fades out of sight.
M-65 is a Sb-type spiral galaxy in Leo that is currently undergoing a supernova called SN2013am, but my hopes of seeing it faded when it became clear it was heavily obscured by dust clouds in the galaxy. The galaxy itself shines at magnitude 9.3 and has a length of 10 arc-minutes, large for a galaxy. As a consequence, it was not evident when I looked at it, but the bright nucleus and subtle hints of spiral structure were visible. It was impressively large in the field of view at 227X. This is definitely one of the finest galaxies visible in the spring sky from the northern hemisphere for almost
 any telescope from a good site.
Only some 38 arc-minutes away from M-65 is M-66, another spiral galaxy in orbit around M-65. This disturbed Sb spiral shines at 9th magnitude but is slightly smaller at 8.7 arc-minutes long. Both are visible together at lower power through the 15-inch, and in smaller telescopes the larger but fainter edge-on spiral galaxy NGC-3628 can be seen with M-65 and M-66. Unlike the nicely symmetrical M-65, M-66 shows irregularities in it's disk. I can see hints of a "crab claw" like spiral arm on one side and a smaller spiral arm on the other side of the bright nuclear bulge. While I did not sketch it, I did take a look at NGC-3628, whose dust lane was very apparent, and so was it's distorted, long, box like shape. It was brighter than I had ever seen it through a smaller telescope. I plan to sketch this one before it gets too near the Sun to see. Together with M-65 and NGC-3628, these galaxies form the Leo Triplet, one of the best examples of a galaxy trio for small telescopes.
Ursa Major like Virgo is a galaxy hunter's playground, with hundreds of NGC and IC galaxies that can be seen with amateur telescopes from dark sites. I started with the oval elliptical NGC-2639, which showed nothing else other than a steady brightening towards the center. It was bright and small, which made it easy to find even though it shines at magnitude 11.8. The small apparent size of two arc-minutes enables it to punch through sky glow and haze easily.
Longer but narrower than NGC-2639, NGC-2654 is a bright edge on lenticular or spiral galaxy with an apparent size of 4.3 arc-minutes and a magnitude of 11.8. It's precisely edge-on and shows a bright core. This galaxy unlike many edge-on systems has a high surface brightness and is therefore not a difficult object from less than truly dark sites. Like NGC-2639, this galaxy is also circumpolar from most of the northern hemisphere, and therefore can be seen just about any time of year.

NGC-2793 is another small but fairly bright elliptical galaxy in Ursa Major. Shining at magnitude 11.7, this somewhat oval shaped system has a small but bright inner core, no doubt swarming with billions of older yellow and red stars with a super massive black hole lurking at the center. This galaxy is not however circumpolar. A quite easy object for the 15-inch and no doubt someone from a moderately dark site will find it with an 6 or 8-inch telescope due to the fairly high surface brightness that stems from both it's small apparent size of 2.2 arc-minutes and the stars being densely packed like a giant globular cluster. Indeed, it resembles an unresolved globular cluster through the telescope. Like most ellipticals, this galaxy is otherwise featureless other than the bright inner core.
After moving on from the abundant galaxies near Ursa Major's nose, I turned my attention to Hydra the water snake and her rich array of galaxies. Hydra like Ursa Major is a great constellation to find all kinds of galaxies, from dwarf systems just beyond our local group to massive and very remote galaxies that will test the largest of amateur telescopes to their limit. NGC-3091 is the largest and brightest member of a small group of galaxies. Another much smaller and fainter member was visible, NGC-3096. NGC-3091 itself is an elliptical galaxy which is about 2.2 arc-minutes across and shines at 11th magnitude. NGC-3096 is much fainter at about 13th magnitude and appears as a minuscule oval glow. The three other PGC galaxies that also are in the same vicinity I did not see, probably because the skies were not dark and clear enough, but they can be seen with a 10-inch or even smaller telescopes from a dark site.
The interacting pair of galaxies in neighboring Sextans the Sextant has a distant companion I was unaware of until this spring, so I took the opportunity to see if it would be observable. Sure enough just to the west of the tenth magnitude galaxies NGC-3166 and NGC-3169, NGC-3156 appeared as an small oval shaped object with a brighter center. It was surprisingly visible despite the sky glow it had to compete with. It's about 12th magnitude and has an apparent magnitude of about two arc-minutes.
Leo has an embarrassment of riches when it comes to galaxies, so many bright ones are found there that there are others that are passed over such as NGC-3162 in Leo's neck. Not a match for M-65, M-66 or any of the other three Messier galaxies, this oval galaxy is not terribly hard for an 8 or 10-inch under less than perfect skies. This spiral galaxy is about three arc-minutes across and shines at magnitude 11.6. The nuclear region was bright and slight mottling seemed to be in the disk, but I wasn't sure what I saw until I looked at a photo of the galaxy after returning home for the night.
This bright elliptical galaxy NGC-3585 adorns southern Hydra, which seems to have an abundance of elliptical systems in her borders. Very bright with a bright core, this galaxy is visible in small telescopes as an oval shaped 10th magnitude object. The apparent size is three arc-minutes, and other than the brightening towards the very center, this galaxy is otherwise quite featureless.
Unlike all the other NGC galaxies observed that night, NGC-3621 is larger and or brighter than all of the NGC galaxies previously described. Shining at 10th magnitude with a length of 10 arc-minutes, this galaxy looks both larger and fainter than NGC-3585 even though both have the same overall magnitude. This Sc class spiral displays a brighter nuclear region and a very large glowing disk around it. It resembles M-33 tilted closer to edge-on than face on as that galaxy appears to us. The disk was quite faint and seems patchy, and in photos there are numerous star formation regions present. It's also nicely set in a kite shaped asterism of foreground stars which belong to the Milky Way. Although it was hindered by the sky glow, this would be a magnificent spiral galaxy that is equal to many Messier and indeed superior to some in size, brightness and visible structure from a dark site. NGC-3621 was a nice find given most galaxies in Hydra are much fainter and smaller.
At last midnight came and went, and I was beginning to grow tired as dew began to drench everything including the telescope. So I decided to chase one last object before packing up and going home. The globular cluster NGC-5053 frustrated me even though the nearby and much brighter M-53 is easy to see even from home. I finally succeeded in finding it from the airstrip once before with the 15-inch, and from a roadside field I succeeded again.  Both M-53 and NGC-5053 are within 2,000 light years of each other, but they are in independent orbits around the center of the Milky Way. While M-53 is small, rich in stars and quite bright, NGC-5053 is the opposite. It has five times fewer stars than M-53, and it's stars are spread out across 10.5 arc-minutes and the whole cluster shines at magnitude 10. These factors dilute the cluster's light so much it appears as a round, dim, hazy glow peppered with faint glimmers of it's very brightest stars. It was almost like a miniature version of Bernice's Hair, which refers to a famous queen who lived in the early third century A.D. in what is today Benghazi Libya. Famed for her beauty and long blond hair, she sacrificed it as an offering to the Gods to ensure her husband's safe return from a war. NGC-5053 and M-53 are a great opportunity to demonstrate that globular clusters are not alike.

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