NASA's Astronomy Picture of the Day highlights Arp 78, a peculiar spiral galaxy located in the constellation Aries.
Key facts
- •Arp 78 is located in the constellation Aries, about 100 million light-years from the Milky Way.
- •The galaxy measures 200,000 light-years in diameter.
- •Gravitational interactions with the companion galaxy NGC 770 are believed to cause the overdeveloped spiral arm.
- •The image features dust lanes and young blue star clusters within the spiral arm.
NASA has featured the peculiar spiral galaxy Arp 78, also known as NGC 772, as its Astronomy Picture of the Day for September 30, 2026. Located within the constellation Aries, the galaxy sits approximately 100 million light-years away from the Milky Way.
By the numbers
Characteristics of Arp 78
Arp 78 spans 200,000 light-years across and features a prominent, overdeveloped outer spiral arm. This arm is marked by sweeping dust lanes and clusters of young blue stars, which astronomers attribute to galactic-scale gravitational tides.
Interaction with NGC 770
The galaxy's structure is influenced by its interaction with a smaller, compact companion galaxy called NGC 770, which is positioned directly below the larger spiral. Deep telescopic imaging reveals faint star streams between the two, highlighting the contrast between the elliptical appearance of NGC 770 and the surrounding foreground stars of the Milky Way.
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This article was independently rewritten by ManyPress editorial AI from reporting originally published by NASA Breaking News.
