Also known as "NGC 772", the galaxy Arp 78 spans about 200,000 light-years. You'll notice that it has an elongated outer spiral arm made up of dust lanes and young, bluish star clusters.
This distorted spiral arm, which seems to "run away" from the rest of the galaxy, is probably the result of gravitational tidal interactions between Arp 78 and its neighbor NGC 770, which appears in the upper right corner in relation to the larger spiral.
The galaxy NGC 772 shines in the center of the image accompanied by several stars of the Milky Way, which appear with their yellowish tones.
Galaxy NGC 772 and the Milky Way
It may not seem like it, but this galaxy has some features in common with the Milky Way — for example, the two are accompanied by so-called satellite galaxies, those that orbit the main galaxy closely and remain gravitationally linked to them.
In the case of Arp 78, one of its satellite galaxies is NGC 770, a spiral-type galaxy that can be partially observed in both Earth's hemispheres, during certain times of the year. The Milky Way is accompanied by different satellite galaxies, the largest of which is the Large Magellanic Cloud, about 163,000 light-years from us.
On the other hand, there are also several differences between the two. One is that NGC 772 is a peculiar spiral galaxy , with a different structure, shape or composition than expected. Furthermore, it does not contain a group of stars at its center that forms a kind of bar, something common in many known galaxies.
Source: APOD
Galaxy Arp 78, with its spiral arm distorted by gravitational interactions (Image: Reproduction/Josep Drudis)
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