Hickson 61 (HCG 61) is a group of four galaxies located in the constellation Coma Berenices, and sometimes referred to as the Box Galaxies. The four galaxies in this group show no trace of interaction.
The galaxy NGC 4169 in the southwest corner is of the compact type S0, the intermediate stage between a spiral galaxy and a barred spiral galaxy. We look at it from the side, because its axis of rotation is inclined by 70 degrees to our line of sight. The escape speed in relation to the local group is around 3800 km/s. With a Hubble constant of 75 km/s/Mpc, this means a distance of around 170 million light-years.
In the case of the elongated galaxy NGC 4173 in the northern corner, we look exactly at the edge, which makes it difficult to determine its type, but most likely it is of type SBd or Scd. NGC 4173 is moving away at a speed of only 1000 km/s, which equates to a distance of only 43 million light-years. So it doesn’t seem to belong to the group, but it was still included by Paul Hickson. NGC 4173 is also a bit out of line because of its low surface brightness.
NGC 4174 at the southern corner is by far the smallest of the four galaxies, but still much brighter than NGC 4173. In this spiral galaxy, too, we are almost looking at the edge, because the angle between the axis of rotation and the viewing direction is about 72 degrees. It shows the same escape speed as NGC 4169, so also the same distance.
The galaxy NGC 4175 in the west of the group of four is a spiral galaxy of type S or Sb, roughly like M 31. The angle of inclination is 86 degrees, so we are almost looking at the edge. Its escape speed is somewhat higher with about 3900 km/s relative to the local group, which equates to a distance of 170 million light-years.
