NGC 520 - Arp 157
NGC 520 is a colliding pair of galaxies located at a distance of 105 million light-years in the constellation "Pisces". It is the second brightest
disturbed galaxy pair in the sky after the famous "Antennae" galaxies.
The collision started about 300 million years ago, which also initiated a strong starburst phase, in which an especially large number of stars
were formed.
The main component is seen directly from the side (EdgeOn), that's why it appears fainter to us. The second component is brighter, but also
low in mass and especially low in gases like hydrogen. A dark line of dust seems to separate the two galaxies, at least in appearance. In long
exposure images, two tidal tails can be seen extending far out into the surrounding space. This may have resulted in an object called "UGC 957,"
which strongly resembles a dwarf galaxy.
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Although the object is listed as having a brightness of 12.2mag, NGC 520 appeared fainter than expected in my 20" f/3.2 telescope.
At a magnification of 270x, all the exciting details showed up. The northwestern part (upper right) was brightest, the other part was much fainter.
The dust lane in between was also very faint and could only be glimpsed with averted vision. The tidal tails were extremely difficult and could
only be glimpsed but not steadily held. All in all a really exciting object, but not easy.
