Two peculiar spiral galaxies are found in the latest image released by the Hubble Space Telescope. The two galaxies, known collectively as Arp 303, are about 275 million light-years from Earth. IC 563 is the oddly shaped galaxy at lower right, while IC 564 is a flocculent spiral at upper left.
Fittingly, these two strange galaxies are part of the Atlas of Peculiar Galaxies, which is a catalog of unusual galaxies produced by astronomer Halton Arp in 1966. He collected a total of 338 galaxies for his atlas, which was originally published in 1966 by the Institute of California Tech.
What Arp wanted to do in his catalog was to provide examples of the different kinds of peculiar structures found among galaxies. While most of the catalog entries consist of individual galaxies, some of the objects were entered as interacting galaxies and others as galaxy groups.
Interacting galaxies are often distorted in shape, while galaxy groups are simply gravitationally bound together, but not necessarily close enough to induce major structural changes.
Although the two galaxies in Arp 303 are not exceptionally close to each other, they do appear distorted. Therefore, Arp entered Arp 303 as “unclassified”. Objects 298–310 in his atlas are considered unclassified and are mostly pairs of interacting galaxies.
Since the Hubble Space Telescope can zoom in on individual galaxies with its multiple instruments, this image is actually created from two separate Hubble observations of Arp 303. The first used Hubble’s Wide Field Camera 3 (WFC3) to study the lumpy star of the pair. -region formation in infrared light. The Hubble team said that galaxies like IC 563 and IC 564 are very bright at infrared wavelengths and host many bright regions of star formation.
The second observation was taken with Hubble’s Advanced Camera for Surveys (ACS) to take a quick look at bright and interesting galaxies in the sky. The observations filled in the gaps in the Hubble archive and searched for promising candidates that Hubble, the James Webb Space Telescope, and other telescopes could study further.