Arp 247 is a pair of interacting galaxies; IC 2339 and IC 2338, left to right and top to bottom. A common arm connects them on the west side. At least Arp seems to say this when he says: "Spirals have common arm, N spiral arm continues NE." The latter comment seems to refer to the southern arm of IC 2339 that goes north and continues as a faint tidal streamer far beyond the galaxy. He seems to have missed a similar streamer going mostly west and a bit north on the other side. It is fainter and out of his image. Apparently he didn't know it was there. It is classed under his category: Galaxies (not classifiable as S or E); Appearance of fission. Odd but his comment calls them spirals then he puts them in a class saying they aren't identifiable as spiral or elliptical! I see several problems here. One is that while the arm may appear "common" to both galaxies this is likely a perspective issue and if seen at a different angle one is likely in front of the other and we are seeing an overlapping of two separate arms. Since colliding galaxies can merge but not split as they are already separate objects this might be fusion but certainly not fission. Or is he referring to that tidal arm as splitting off? We now know these almost always collapse back into the merging galaxies though some stars may never return, most do. At least in the simulations I've seen or run.

Redshift data on both galaxies shows virtually the same radial velocity which translates to a distance of just over a quarter of a billion light-years. This strengthens the idea they will merge in the future. Or already have and the light just needs a quarter of a billion years to get here to tell us. Actually due to the expansion of the universe it will take a bit longer that that to reach us through the ever growing universe. The pair is part of what is known as the Cancer cluster. The main part of the cluster is well out of my field of view to the west south west.

IC 2339 is classed as a SB(s)c pec galaxy while IC 2338 is SAB(s)cd pec. I've not mentioned much about classification so let me go into more detail here. SB(s)c can be broken down to SB indicating a barred spiral, one whose bar is straight, if it curved some it would be SAB. The (s) means the arms that come off the bar go only one way, If they had gone both left and right from the bar then it would be (r) for ring even if that ring was far from complete. The c indicates how loosely or tightly wound the arms are. Tightly wound gets an "a" very loose gets a "d". Pec of course means peculiar so it sort of fits the previous classification or is thought it did before something happened to it like running by this other galaxy. IC 2338's classification as SAB means the bar is somewhat curved, not straight in that the spiral part that comes off the arms is a gradual transition rather than a sharp one as in SB class. (s) has been covered and the cd means it is more loose than a c class but not as loose as a d class. And of course, it is specular due to its run in with IC 2339. This is a somewhat over simplification of the de Vaucouleurs classification. Hubble's class would be simply SBc and SBcd. It has fewer divisions. Just is it spiral or elliptical or a spindle. If spiral does it have a bar and then how loosely the arms are wound. Elliptical galaxies are given a number, 1-5 depending on how elliptical they are 1 being a sphere. Spindles are just S0 in Hubble's system. Those that don't fit any of this are called irregular. De Vaucouleurs adds a class Sm which could be called a messed up spiral. Too messed up for the normal spiral classes but still recognizable enough not to be an irregular. The Magellanic Clouds would be such an example and is the reason for the m to denote this class. For a good link on all of this and a lot more (big PDF file) see: http://www.astro.ufl.edu/~vicki/galaxies/Lecture2.ppt There was a much better pdf version but it seems to have vanished to be replaced with the ppt file of the same URL except for the ppt extension.

The large galaxy above Arp 247 is IC 2341, an S0 galaxy also about a quarter billion light years away so a member of the Cancer cluster. The Sc spiral down and left of IC 2341 is LEDA 142820, a 16th magnitude spiral in the Cancer cluster.

Toward the upper left corner is a round smudge of a galaxy with a faint star on its SW side. identifying it is a big mystery. SIMBAD says it is [OBC97] C04-1 an Im galaxy of 17th magnitude about 370 million light-years away. If I'd have stopped there all would be well. But I checked NED. It gives three different objects at this location, each a second of arc or so different but all within the glow I show and none correspond with the star. One agrees with SIMBAD but two don't. One of these is [OBC97] C03-5, a low surface brightness galaxy. SIMBAD shows it a bit under a minute of arc SW at a location nothing is seen on their image as well as mine yet it too is listed as 17th magnitude. It appears NED has decided this is an error and has moved it to coincide with the first location but with no classification or red shift data. But NED also says it is SDSS J082432.97+212706.2. SIMBAD says it doesn't exit yet when asked for the coordinates of it, it knows of them. In any case the SDSS puts its red shift far lower than [OBC97] C04-1, right in line with it being a member of the Cancer cluster! And the public thinks astronomy is an exact science.

The Sloan image can be found at:
http://astronomerica.awardspace.com/SDSS-5/IC2338.php
Arp's image:
http://nedwww.ipac.caltech.edu/level...ig_arp247.jpeg

There are 10 asteroids in the image, which was taken last January but just recently processed. One of the asteroids is unknown to the Minor Planet Center. This marks the third one I've "found" months after I took the image and thus it remains "lost in space" until someone who checks their data nightly and thus can follow up on it comes across it in the future. I do need to look at these the next morning. I've been saying that for a couple years. I've made an annotated image identifying the asteroids, all but one which just gets a red question mark. All the action is happening in Cancer a couple degrees NW of M44. I've also attached a 2x enlargement of just Arp 247.

14" LX200R @ f/10, L=4x10', RGB=2x10'x3, STL-11000XM, Paramount ME

Image with less compression:
http://www.spacebanter.com/attachmen...tid=2638&stc=1

Rick

Attached Images

	ARP247L4X10RGB2X10X3MERGE-7.jpg (144.2 KB, 18 views)
	ARP247L4X10RGB2X10X3MERGE-ID.jpg (123.5 KB, 27 views)
	ARP247L4X10RGB2X10X3CROP200.jpg (62.3 KB, 36 views)

I admire the research hours you're putting in, doggedness must be as important as having the mathematics in your line of work, RickJ.
The rich irony, though, of those ephemeral asteroids intruding into view - probably exaxctly what A.N. Other would jump under a bus for.

Those are asteroids? It's impressive you can keep track. They look like globby galaxies what with their bright colours and all.

Glom,
The asteroids are colorless streaks in the image. Most tilt up to the right as they are following the plane of our solar system though they can deviate from that as does 1998 CN, the brightest one. They are either above or below the ID. I put them below unless a star is in the way as happened several times in this image forcing me to put the name above the asteroid's streak. The streak due to their orbital motion during the 40 minutes of luminosity exposure. The brightest sometimes show up in the RGB as well as short colored streaks. In this case only 1998 CN shows shows these to the left of the bright white streak. Since the asteroids are moving they show up white in the image as they have moved before the color filters can be used. The color is very faint as it only colors noise in the luminosity image or a star it passes over in the case of 1998 CN.

I don't keep track of them. I let the Minor Planet Center do that. When I find one in the image I just note its position and time then ask the MPC for what asteroid was at that exact position at that exact time. With nearly a half million known asteroids I don't try to keep up!

Rick

Once again great job on the tiny distant galaxies. And the asteroids add an interesting touch.

__________________
My Astrophotography Gallery
Solar System Imaging Simulator

Now I see it... I think.

If you are having trouble seeing them, they are quite obvious on my monitor, then your monitor isn't adjusted correctly for astro images and is blocking the dim objects in everyone's images. You should see all levels in the calibration strip I've attached. If the top or bottom levels run together as a large black or white area your monitor needs adjustment.

Rick

Attached Images

calibration_strip_h.jpg (2.5 KB, 6 views)

Maybe it's better on this monitor. I wouldn't say all of them are obvious. 1998 CN is very visible though.

You know, if one of your lost asteroids turns out to be a doomsday rock, we'll all blame you.

__________________
You can't really tell the difference between drunken rambling and sober blogging.

Dang, my secret's out!


On a slightly different note:
This part of northern MN is rife with the 2012 crapola. Even a local doctor believes it. I've been asked many times by my wife's customers about it and when I tell them it is a load of male cattle manure I'm accused of being part of the conspiracy. ARGH!

Some days I get so much of it I'd almost welcome a doomsday smack, just to be rid of them. But then I think of the grandkids.

Rick

But think of how smug you'll feel in 2013. I suggest you prepare your extravagant gloating ceremony now.