Object name: MRK273

Designation(s): MRK273, IC0921, IC926, IC929, IC930, ID931, IC932, IC934, IC936, IC937, UC938, ABELL1783,

Markaryan 273 is a well studied but mostly ignored by amateurs galactic merger in progress located in Ursa Major about 3 degrees northwest of M101. Redshift puts it about 516 million light-years distant. The core shows two nuclei one second apart. Far beyond my resolution this night. They consist of very different age stars. One of the merging galaxies is thought to have been unusually gas rich. A note at NED indicates there\'s a ring of star formation some 100 kpc (326,000 light-years) in diameter thanks to all the gas. I measure the southern plume as being some 144,000 light-years long though a note at NED puts it at 130,000. The difference may be due to the distance estimate used. As with all my redshift distances I used NED\'s 5 year WMAP calculator. I measure the northeastern fainter plume as being even longer at 165,000 light-years. Since they aren\'t 180 degrees apart I find the distance between their endpoints to be 103.7\" of arc which works out to 259,000 light-years. The merging galaxies are considered very strong in all wavelengths from radio well into the ultraviolet. It is classed as an ultraviolet excess object, an IR source and a radio source. All but the gamma ray astronomers have put a lot of time into studying this object. There is a lot of information at NED on this galaxy, far too much for me to cover. Those interested can go to NED and look up MRK 273 and click on the notes link in the list of links at the upper right of the page. Several other galaxies with the same redshift as MRK 273 are in the area a few of which are in the frame.

I placed the galaxy well to the north of the center of the field to also pick up the core of the Abell 1783 galaxy cluster. This cluster\'s core consists of quite a few IC galaxies all of which are listed in NED as; \"Identification as IC 0nnn is not certain.\" SEDS says of these; \"Unidentified at the place given, or type unknown, in Ursa Major.\" Due to this, I\'ve listed them with a question mark in the annotated image. The cluster\'s distance is about 920 million light-years. All the IC galaxies in this cluster were discovered in 1892 by Edward Barnard. He was a very careful observer so how these identifications became so questionable I don\'t know. With a radius of 35 minutes of arc MRK 273 is within the cluster but lies only about half as far away so the two are unrelated. All these IC galaxies were discovered by Edwin Barnard in June 1802. How such a careful observer came up with uncertain data I don\'t know. IC 936 may be a duplicate of IC 934 according to Seligman, if so what is the other one and which is the correct whatever IC number is used? It\'s all very confusing. Other IC galaxies credited to Barnard this night are just out of the image to the south. None of the identifications is certain, hence the question mark in the annotated image.

Well below MRK 0273 is the strange galaxy ASK 300802. Is that a plume going to the north-northeast or is it a separate galaxy? I consulted the Sloan image and couldn\'t tell. But according to NED, they say it is a star! Try as I may, I can\'t turn a fuzz patch into a star. So it is a mystery object, plume or separate galaxy but certainly not a star.

The frame contains several very blue star-like objects that appear to be quasars but aren\'t so listed at NED. Instead, they are listed as BLAGN (Broad Line Active Galactic Nuclei. Since they appear very quasar-like and are as bright as quasars I also show them as (Q?) in the annotated image. If a galaxy had a catalog designation that wasn\'t just its position I\'ve shown that but if it is listed only by its coordinates I\'ve just listed it as G followed by its distance. If a galaxy was in the IC but had no distance data it is listed with na where the distance would have been shown if it had been available. I\'ve listed NED\'s classification of the object if given after its catalog name or \"G\" when available.

To show the faint northeastern plume of MRK 0273 I\'ve stretched the image more than normal which also helps to show the noise in the image due to my short exposure time. I\'d planned much more time but, as usual, this year, the weather conditions made that impossible. I had to fight for what little I got.

Also, the F7 star just east of MRK 273 sent horrid reflections all across the frame. The multitude of overlapping donuts it created was a major processing pain and cost me some faint detail. More time would have made those reflections even worse.

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