APOD: 2026 September 30 – Arp 78: Peculiar Galaxy in Aries
The post APOD: 2026 September 30 – Arp 78: Peculiar Galaxy in Aries appeared first on NASA Science .
On September 30, 2026, the Astronomy Picture of the Day (APOD) featured the peculiar galaxy Arp 78, located in the constellation Aries. This enormous spiral galaxy, also known as NGC 772, spans 200,000 light-years across. What makes Arp 78 unique is its prominent, outer spiral arm that is overdeveloped due to galactic-scale gravitational tides. This arm runs along sweeping dust lanes and is lined with young blue star clusters.
The striking appearance of Arp 78 is enhanced by its interaction with a brighter companion galaxy, NGC 770, which is seen directly below the larger spiral. The gravitational forces between these two galaxies have caused NGC 770 to take on a fuzzy, elliptical shape, in contrast to the spiky foreground Milky Way stars. Embedded within faint star streams revealed in the deep telescopic exposure are the remnants of this cosmic dance.
Arp 78 and its companion NGC 770 continue to captivate astronomers with their intriguing features, making them a fascinating subject for study and observation.
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