Snapshot: Astronomers spy a strong-arming galaxy

The outstretched arm of this peculiar spiral is the result of a cosmic handshake between neighbors.
By | Published: April 6, 2022 | Last updated on May 18, 2023
International Gemini Observatory/NOIRLab/NSF/AURA; Image processing: T.A. Rector (University of Alaska Anchorage), J. Miller (Gemini Observatory/NSF’s NOIRLab), M. Zamani & D. de Martin

The stunning spiral galaxy NGC 772 might look like it’s extending a cosmic hand in this image taken by the Gemini North telescope in Hawaii. But in reality, its extra-long arm is distorted thanks to an ongoing interaction with a nearby dwarf galaxy known as NGC 770 (not pictured). The gravitational tug-of-war has morphed NGC 772 into its unusual shape, making it an obvious entry for the Atlas of Peculiar Galaxies.

Nestled within the constellation Aries the Ram, NGC 772 resides some 100 million light-years from Earth. Its unique, lopsided look earned the galaxy a spot as the 78th entry in astronomer Halton Arp’s Atlas of Peculiar Galaxies, a catalog of 338 galaxies with — you guessed it — peculiar shapes. Entries in this tome, created in 1966, include: M66, a distorted spiral galaxy; the Antennae galaxies (NGC 4038/NGC 4039), an interacting pair with distinct tidal tails; and the Tadpole galaxy (Arp 188), which sports a bright head and a long tapered body. And these are just a few of the magnificently bizarre galaxies scattered throughout our universe.