Object name: ARP256

Designation(s): ARP256, PGC 001224, PGC 001221,

Arp 256 consists of two interacting galaxies; MCG -02-01-051/PGC 001224 (lower) and MCG -02-01-052/PGC 001221 (upper) at a distance of about 355 million light years. Arp classed them as; Galaxies not classifiable as S or E; Appearance of fission. Using standard galaxy classification the upper one is classed as SBc pec while the lower as SBb pec? So both are considered barred spirals. One note says of the upper galaxy; "It is possible that it alone consists of two overlapping galaxies." Hubble has taken an excellent image of this pair, it is at: I'm not sure if it answers the question about it being two galaxies or not. That blue knot between the cores of the two galaxies may be a third galaxy. It carries a redshift that is a bit higher than either of the two galaxy cores. It is about the same as the smaller area of blue stars north of the core of the upper galaxy. Thus there seems to be an overlay of blue stars with a slightly greater redshift (by about 40 to 80 km/s). Whether this is a separate system I don't know. More likely the difference is just due to rotation of the galaxy in a plane tilted a bit away from us. The lower galaxy MCG-02-01-051 has a very interesting tidal tail to the west and in the Hubble image, it too has some of these super hot blue stars that may really be related to the other blue stars rather than the galaxy itself. Note how wild its core is as seen by Hubble.

The entire field is rather interesting and contains one of the most distant galaxies I've ever imaged directly, It's the distance of quasars, not galaxies. Per NED it's redshift puts it a bit over 10 billion light-years away! Did galaxies large enough to shine at 20th magnitude exist in a 3.5 billion year old universe? That seems pushing it, though Hubble has shown large galaxies coming together far faster than we had expected. There's one "but" in this. Seems the redshift distance has been determined photometrically rather than spectroscopically. Thus there's room for a very large error if some assumptions are wrong. The galaxy is directly below Arp 256 near the bottom of the page. Many more distant galaxies and a couple quasars (one quasar candidate is even further away than the galaxy but not by much. There are two asteroids in the image as well. Rather than try to point all this out I've just attached a second annotated image. Quasars are noted with a q in front of the distance. The other distances are for galaxies.

This pair is located at the western end of Cetus the Whale and thus is rather low in my sky reducing my ability to see fine detail. The image is a bit fuzzier than I'd like because of this.


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