Deep-Sky Dreams: NGC 3718 and NGC 3729

Interacting galaxies NGC 3718 (left) and NGC 3729 form an unusual pair of challenging objects to observe in the constellation Ursa Major. Credit: SAFIY14

Key Takeaways:

• NGC 3718 is a distorted spiral galaxy about 65 million light-years away.
• NGC 3729, a nearby galaxy, likely distorted NGC 3718.
• Both NGC 3718 and NGC 3729 are barred spiral galaxies.
• Hickson Compact Group 56 is a group of interacting galaxies much farther away (425 million light-years).

Key takeaways sponsored by The Space Store

Ursa Major and its Big Dipper asterism are loaded with terrific galaxies. Two strange galaxies that inhabit this area may be found below the southern edge of the dipper. NGC 3718 (Arp 214) is a distorted barred spiral lying about 65 million light-years away. It glows at magnitude 10.6, spans 2.9’ by 2.3’, and is characterized by a strong S shape, a prominent dust bar encircling its hub, and an intensely bright, concentrated nucleus. 

NGC 3718 displays warping believed to have been caused by interaction with its neighbor, NGC 3729, which lies about 150,000 light-years from its neighbor. 

NGC 3729 is a barred spiral lying approximately 65 million light-years away, glowing at magnitude 11.0, spanning 2.8’ by 1.8’, and representing a garden-variety barred spiral structure.

South of NGC 3718 is another unusual object, the odd interacting galaxy group known as Hickson Compact Group 56, which consists of a chain of distant galaxies lying some 425 million light-years away.