Based on a recessional velocity of 7427 km/sec, NGC 5550 is about 330 million light years away. Given that and its apparent size of 1.2 by 0.8 arcmin, it is about 115 thousand light years across.

With NGC 5566 and 5569, comprises Arp 286, a trio of gravitationally interacting galaxies (though as noted in its discussion, NGC 5569 may not actually be interacting with the other two galaxies). Based on a recessional velocity of 1730 km/sec, NGC 5560 is about 80 million light years away. Since it appears to be gravitationally interacting with NGC 5566 and 5569, they should all be at about the same distance. A comparison of the redshift-based and redshift-independent distance estimates for the galaxies suggests an approximate distance for the trio of 70 million light years. Presuming that is correct, NGC 5560's apparent size of 3.7 by 0.7 arcmin would imply that it is about 75 thousand light years across.

Per Dreyer, NGC 5564 is "extremely faint, small, probably = Marth 279". Ironically, it is indeed a duplicate observation, but of Marth 278 (= NGC 5554), not Marth 279 (= NGC 5563).

With NGC 5560 and 5569, comprises Arp 286, a trio of gravitationally interacting galaxies. Based on a recessional velocity of 1505 km/sec, NGC 5566 is about 70 million light years away, in good agreement with redshift-independent distance estimates of 65 to 85 million light years. Given that and its apparent size of 6.6 by 2.2 arcmin, NGC 5566 is about 135 thousand light years across.

Below, an ultraviolet image of the galaxies shows where hot, bright young stars have recently formed within them. The central bar of NGC 5566 does not show up in this image because it consists of older, cooler stars; but the ring of stars around the nucleus, and the extensive star formation in the arms are obvious, as is the distortion of NGC 5560 by its gravitational interaction with the larger galaxy. There is similar evidence of accelerated star formation throughout NGC 5569, so despite a much greater uncertainty in its distance, it is probably a physical part of Arp 286. (Image credit: NASA, JPL-Caltech, GALEX)

With NGC 5560 and 5566, comprises Arp 286, a trio of gravitationally interacting galaxies. Based on a recessional velocity of 1780 km/sec, NGC 5569 is about 83 million light years away, in poor agreement with a redshift-independent distance estimate of 55 million light years. Still, the two values bracket the approximate distance of its "companions", and if it is part of a physically interacting trio it must be at about that same distance. As shown in the GALEX image of NGC 5566 (which see), there is strong evidence of accelerated star formation in NGC 5569, so it probably is interacting with the other galaxies, and is equally likely to be at their distance of about 70 million light years. Given that and its apparent size of 1.7 by 1.4, NGC 5569 should be about 35 thousand light years across.

Based on a recessional velocity of 1640 km/sec, NGC 5584 is about 75 million light years away, in good agreement with redshift-independent distance estimates of 65 to 90 million light years (the most recent and presumably most accurate value, based on measurements of over 600 Cepheid variable stars, is 72 million light years). Given that and its apparent size of 2.45 by 1.65 arcmin, the galaxy is about 50 thousand light years across. It is listed in NED as an isolated galaxy (not a member of any known group or cluster).