APOD: 2022 March 24 - Arp 78: Peculiar Galaxy in Aries

Good morning, Rallypoint, and welcome to the March 24th Astronomy Picture of the Day (APOD): "Arp 78: Peculiar Galaxy in Aries." If you've ever wondered why telescopes find their way to the tops of mountains, today's APOD is a good example of why that is. Arp 78 (NGC 772) is an unbarred spiral galaxy almost twice the size of our Milky Way, and lies some 100-130 million light years away in the constellation Aries. This portrait of Arp 78 was taken from the Gemini North telescope atop Mauna Kéa in Hawai'i.

Galaxies are 'peculiar' for one of two reasons: 1) they interact with another galaxy, or 2) have an active galactic nucleus. In this case, Arp 78 has a partner galaxy (NGC 770) that is above and to the right of this splendid close up. Gravitational 'tides' are believed to be responsible for the pronounced spiral arms we see. Two supernovae were detected in Arp 78 in 2003.