Is this a single galaxy, or a merger of two galaxies? NGC 520, a galaxy composed of stars, gas and dust, is thought to contain the remnants of two separate disk galaxies. In detailed images provided by the Hubble Space Telescope, the most striking feature of NGC 520 is the intricately intertwined ribbon of dust hanging vertically down the spine of the colliding galaxies. A similar scene could occur if our Milky Way galaxy collides with its larger neighbor Andromeda (M31) in a few billion years. The current shape of NGC 520 is the result of a galaxy collision that began about 300 million years ago. This galaxy, also known as Arp 157, is located about 100 million light-years away, is more than 100 thousand light-years across and can be seen through a small telescope in the direction of the constellation Pisces. Although the stars in NGC 520 are moving at high speeds, the distances between them are so great that this pair of colliding galaxies will not change visibly in our lifetime.

September 7, 2021 Astronomy Photo of the Day (NASA APOD)

Image Source: NASA, ESA, Hubble; Processing and Copyright: William Ostling (The Astronomy Enthusiast)