
science & techESA/Hubble
A lopsided spiral galaxy 190 million light-years away shows one lone arm reaching toward Earth
Hubble has photographed Arp 184, also called NGC 1961, a spiral galaxy about 190 million light-years away in the constellation Camelopardalis. Unlike a typical spiral, it is viewed at a skewed angle and has one broad, star-speckled arm stretching toward us, while its far side has only faint wisps of gas and stars. The galaxy earned its name from the Atlas of Peculiar Galaxies, compiled by astronomer Halton Arp in 1966, which lists 338 galaxies that are neither clearly elliptical nor clearly spiral. Many of them are interacting with neighbours, and some are dwarf galaxies with no well-defined structure. The image combines data from three short Hubble Snapshot programmes. One of them targeted Arp 184 for its odd shape, while the galaxy is also a good supernova hunting ground, having hosted four known supernovae in the past three decades.
Hubble's Snapshot programme fills short gaps in its schedule, and this image shows how that spare time yields striking results. Catalogues like Arp's show that galaxies come in far more shapes than the textbook categories suggest, and interactions between galaxies are a major way their shapes change.
Halton Arp's atlas was a catalogue of galaxies that did not fit the standard elliptical and spiral classes.
ESA/Hubble · CC BY 4.0
Image: ESA/Hubble & NASA, J. Dalcanton, R. J. Foley (UC Santa Cruz), C. Kilpatrick
