This object is a pair of galaxies located in the constellation of Bootes at a declination of +23 degrees. In his Arp catalog, Dr. Arp classified this object into the category of Spiral Galaxies with Low Surface Brightness Companions on Arms.

The large galaxy is NGC 5829, a distorted face-on spiral located 150 million light years away. This magnitude 14 galaxy spans 1.7 arc-minutes in our apparent view, which corresponds to a diameter of 80,000 light years.

The smaller galaxy to the upper right is IC 4526. Even though it seems that it is an interacting companion, data shows that it is 0.6 billion light years away. So Dr. Arp was not correct in his assertion that they are interacting. IC 4526 is a magnitude 17 galaxy which spans 1.7 arc-minutes in our apparent view, corresponding to a diameter of 80,000 light years. If IC 4526 was at the same distance as NGC 5829, it would only be 20,000 light years in diameter, which wouldn’t make sense for a galaxy with such a structure. So I believe that the distance estimates are correct and that these galaxies are not interacting.

I love the chaotic look of both galaxies. NGC 5829 is a strong 2 arm grand spiral and is virtually undisturbed in the inner region. But as soon as each arm takes 1 half turn out from the core, the fun begins. To the left of the core appears to be a characteristic straight segment of a Vorontsov-Velyaminov row. Both arms deteriorate into a wide star stream by the time a full rotation is reached. Star clusters are seen in the outer arm, caused by a disturbance of some sort. None of the galaxies in this image are at the same distance, so perhaps the culprit has already been absorbed into this galaxy.

The more distant galaxy, IC 4526, appears to be equally distorted. It looks like the letter “d”, with a faint star stream to the right of the core. I like how these right star streams of both galaxies look so similar.

The largest 5 galaxies at the center of this image also form the 73rd entry in the Hickson catalog. In addition to the 2 galaxies of Arp 42, the other 3 galaxies are small spirals seen a bit to the opper left, upper right, and lower right. The lower right galaxy is the furthest away at 1.3 billion light years.