APOD: 2026 September 30 – Arp 78: Peculiar Galaxy in Aries
NASA’s Astronomy Picture of the Day features the peculiar spiral galaxy Arp 78, located 100 million light-years away in the constellation Aries, showcasing its distorted spiral arms and interactions with a companion galaxy.
The NASA Astronomy Picture of the Day (APOD) for September 30, 2026, presents Arp 78, a peculiar spiral galaxy situated in the constellation Aries. This island universe lies approximately 100 million light-years beyond the Milky Way, spanning an enormous 200,000 light-years across. The image highlights its prominent outer spiral arm, which appears overdeveloped due to gravitational interactions with nearby galaxies.
Arp 78, also cataloged as NGC 772, features sweeping dust lanes and clusters of young blue stars along its distorted spiral structure. The galaxy’s unusual shape is attributed to tidal forces generated by interactions with its brightest companion, NGC 770, a more compact elliptical galaxy visible below the larger spiral in the image.
The detailed telescopic exposure reveals faint star streams surrounding Arp 78, evidence of past gravitational encounters. These streams contrast with the sharp, spiky appearance of foreground stars from the Milky Way, which populate the image’s foreground. The galaxy’s elliptical companion, NGC 770, exhibits a fuzzy, elongated shape typical of such systems.
APOD’s submission process for future images has been updated, with new guidelines available via the APOD Submissions page. The daily feature continues to showcase captivating astronomical phenomena, offering insights into the dynamic processes shaping galaxies across the universe.