Astronomerica Home

Sunday, April 19, 2009

Fun in Ursa Major

I spent some real quality time in Ursa Major last Friday night (April 17). It was one of those nights that we rarely get around here- exceptionally clear with excellent seeing. And it wasn't even that cold! Motored up to the Blue Ridge foothills, arriving around 10 p.m. thinking the Boy Scouts were already camping there, but discovering it was six more members of my astronomy club instead. So we had a great time observing, I being the last to leave as usual, around 2:30 a.m. I was using my usual 10-inch dob reflector.

I started out in Ursa Major to check out 13.5 mag Type II supernova SN 2009dd in NGC 4088. The galaxy is an 11.1 mag spiral with well-defined arms, although well-tilted to our view. It's cataloged as Arp 18 due to a large, somewhat detached piece at the end of NE arm. The supernova is so close to the nucleus that if you didn't know, you'd think it was the nucleus. Here's an image showing how tough it is to tell. And here's an SDSS image of the galaxy without the supernova. Who would've known?

NGC 4088

I was really getting some nice detail on all the objects, not just because the sky was so good, but I had also just cleaned the mirror. The collimation I did indoors with the cheshire eyepiece was spot on and I didn't even need to tweak it. You don't need fancy barlowed laser collimators, my friends. In fact (ascending soapbox) there's a lot of overkill in the equipment department these days. You don't need all the fancy expensive gear that some proponents find so essential. Get back to basics and you'll have a whole lot more fun (descending soapbox).

NGC 4088 did show the supernova well in the 10-inch and in the other larger scopes gathered there. I could make out the detached section of the galaxy in the 10, as well as a lot of subtle mottling and lumpiness in the spiral arms. The supernova appeared just slightly offset to the SW from the exact nucleus, which would have been hard to tell were the seeing less than excellent.

Nearby is galaxy NGC 4085 (12.4 mag). It appeared about 1/4 of the size of 4088 in the scope, thin, with an ENE-WSW orientation. It has a brighter core, not quite stellar, and some clumpiness to the arms. Better in 150x or higher.

Well, I looked around the area in my charting program and saw lots of other galaxies to feast on, and truth be told, I never did really make it out of this area in Ursa Major except for a quick look at Saturn and a late foray into the Virgo Cluster, although I later realized I had in fact strayed into Canes Venatici without knowing it. After all, there are no borders in space, at least none that I've been able to discern.

Next up was NGC 4100 (11.0 mag), a fat, roughly N-S oriented, cigar-shaped spiral with a stellar core and some clumps along both arms. There seemed to be a slightly sharper dropoff in brightness along the eastern edge.

At that point I was getting pretty cocky (or maybe just lazy) and left the barlow in to hop around to nearby galaxies in 104x, wandering over into Canes Venatici. A little over a degree to the NE is NGC 4157 (11.1 mag), another edge-on but thinner and longer than both 4088 and 4100. 4157 was host to its own supernova back in 1937. That one was the first discovered by Fritz Zwicky with his 18-inch Schmidt telescope at Mount Palomar designed specifically to find and study supernovae. Zwicky and Walter Baade had only a few years earlier written some pioneering papers on the existence of supernovae. So this galaxy has its own little place in history.

Move not quite half a degree from NGC 4157 to the NE and you'll find the 13.3 mag galaxy NGC 4187. It appeared round with a nearly stellar core surrounded by a very small brighter glow and a larger dim outer shell.

Some other galaxies I bumped into along the way:

UGC 6992 (14.7 mag): A very soft, smooth and diffuse oval patch with only a very slightly brighter middle. An SDSS image of NGC 6992 (13.5' x 10'):

UGC 6992

NGC 4026 (10.7 mag): Nice big, bright core with thin arms on either side. In this scope and in my 4.5 inch six years ago, I got the sense that this galaxy really should have a thin dark lane running across its length, but alas that's just an illusion. See what you think. It really ought to have one.

After a break, I took a look at Saturn, which is showing a noticeable tilt to the rings, with the gaps visible on either side of the planet's disk now.

Back in Ursa Major again:

M97, the Owl Nebula: The "eyes" were really coming out well tonight. SE eye is darker w/ and w/o the filter. Glimpses of the central star <5% of time at about 250x especially when zooming in and out slightly. Kept sensing a tiny bright knot or star on SW edge, but there's nothing in particular there in any images. Maybe a slight knot or bulge breaking the symmetry of the edge.

M108 - The star that is often mistaken for the core of the galaxy was unmistakably not a part of galaxy because it stood out so sharply. Knots and details in both arms.

UGC 3594 (14.7 mag galaxy) - Picked it up pretty quickly. Best in about 180x. Round patch visible about 70% of time. Something stellar or sharper in there, possibly its core. Here's an Aladin Previewer image:

UGC 3594

UGC 6228 (15 mag) - Couldn't pick it up. I could see a 14.4 mag star nearby but no sign of the galaxy.

NGC 3530 (13.8 mag) - Easy. Compact, bright core, E-W elongation.

NGC 3517 (13.0 mag) - Actually a bit harder than 3530. Brightens toward the center but not as much, and it was hard to get a shape on it. A little larger than 3530, too. I couldn't really discern the little elongated galaxy visible on its northern edge in the linked SDSS image.

Heading toward Beta UMa, NGC 3499 (14.0 mag): Very small w/ stellar core with fuzz around it. Vague hint of thin elongation NW-SE. Linked SDSS Image shows a dust lane roughly in that orientation.

The other six people had all left by this time (1:45).

So it was time to make a dent in the Virgo cluster:

NGC 4608 (11.1 mag) - round, bright, with a not quite stellar core.

NGC 4596 (10.7 mag) - bright center, almost-stellar with extensions to WSW and ENE. These are actually the ends of the bar and I'm not even seeing the rest of the glow beyond that. The bar only extends about halfway out to the edge in the linked SDSS image.

IC 3608 (15.0 mag) - no luck. Would be a nice one if I could see it. This SDSS image is zoomed in to about 5' x 4', making it appear larger than it would in the standard 13.5' x 10' SDSS image on this site to show the fine detail:

IC 3608

NGC 4567-8, the Siamese Twins (11.5 and 11.2 mag)- I can make out two galaxies in 104x easily. Soft glows both. The orientations are clear. 4568 is a little more brightly concentrated. The core is visible in 4567 but 4568 is just brighter in the central oval area.

NGC 4564 (11.2 mag) - Very close to the Siamese Twins. SW-NE elongation with a bright core and dim, stubby arms.

M58 (10.1 mag) - like a larger, brighter version of NGC 4596. Bar in the same orientation (SW-NE). Very slight hints of mottling in the glow.

NGC 4550/4551 (11.6 and 11.9 mag) - 4550 is brighter, more elongated (N-S). They are angled at about 120 degrees to each other, although 4551 is less elongated, just slightly SW-NE. 4550 has an elongated brighter core with a stellar point toward the center; 4551 has a more diffuse core.

M89 (9.8 mag) - A big, bright, round elliptical. Core gets much brighter and drowns out any stellar point that might be in there.

Finished up at 2:24 with the Moon rising in about half an hour. The wind had been picking up in intensity throughout the night. The temperature was in the upper 40s or slightly warmer with no dew, so I could use the mirror fan to improve the seeing.

Just as I was packing up I spotted a nice -5 mag fireball below Saturn in the west- just happened to look up at the right time! A great way to end the night.