This image of the spiral galaxy Arp 184/NGC 1961 was taken by the Hubble Space Telescope. (Image credit: ESA/Hubble & NASA, J. Dalcanton, RJ Foley (UC Santa Cruz), C. Kilpatrick)
What is it: Arp 184 (NGC 1961)
Location: 190 million light years away in the constellation Camelopardalis.
When published: April 29, 2025.
Why it matters: What if a galaxy had just one spiral arm?
According to Space.com, our solar system sits at the edge of one of the Milky Way's supposed four spiral arms, but not all galaxies have this structure. The latest image from NASA's Hubble Space Telescope shows an unusual galaxy called NGC 1961 that has only one — a single, wide, star-studded spiral arm that appears to extend toward us when viewed at an angle.
It may seem like an impressive prospect, but that’s just what Hubble captures in terms of its location on its orbital path around Earth. On the far side of the newly acquired galaxy, beyond the swirls of stars and dust around the bright core, there’s no equally spectacular spiral arm; instead, we see just a few wisps of gas and stars. The image is also available as a panoramic video, a zoomable version, and a 15-megapixel download.
Full version of the image.
Its single spiral arm has long led to NGC 1961 being known as Arp 184 and earning it a place in the Atlas of Unusual Galaxies, a catalogue of galaxies that are neither perfectly symmetrical spirals nor smooth spherical ellipticals. First published in 1966 by American astronomer Halton Arp, the atlas includes 338 galaxies with unusual shapes, many of which are interacting with other galaxies. Other objects in the atlas are dwarf galaxies that are in motion.
There’s another reason Hubble is targeting Arp 184/NGC 1961. Over the past four decades (in 1998, 2001, 2013, and 2021), four known supernovae—powerful explosions of dying stars—have occurred there. It’s exceptionally rare to see a supernova in action, so galaxies with such a proven track record are prime targets for study.
Arp 184/NGC 1961 was discovered by German-British astronomer William Herschel in 1788, just seven years after his discovery of the planet Uranus – the first planet discovered in modern times.
According to space observations
Sourse: www.livescience.com
