Astronomers using the NASA/ESA Hubble Space Telescope and NASA’s Spitzer Space Telescope have produced this vivid image of a distant pair of interacting galaxies known as Arp 142.
This composite image shows two interacting galaxies, known collectively as Arp 142. NGC 2936, once a standard spiral galaxy, and NGC 2937, a smaller elliptical, bear a striking resemblance to a penguin guarding its egg. The blue streak at the top of the image is an unrelated background galaxy, UGC 5130. Image credit: NASA-ESA / STScI / AURA / JPL-Caltech.
The Arp 142 pair is located in the southern constellation Hydra, approximately 326 million light-years away.
It is a member of the Arp catalog of peculiar galaxies observed by astronomer Halton C. Arp in the 1960s.
The ‘penguin’ part of the pair, NGC 2936, was probably once a relatively normal-looking spiral galaxy, flattened like a pancake with smoothly symmetric spiral arms.
Rich with newly-formed hot stars, seen in visible light from Hubble as bluish filaments, its shape has now been twisted and distorted as it responds to the gravitational tugs of its neighbor. Strands of gas mixed with dust stand out as red filaments detected at longer wavelengths of infrared light seen by Spitzer.
The ‘egg’ of the pair, NGC 2937, by contrast, is nearly featureless.
The distinctly different greenish glow of starlight tells the story of a population of much older stars.
The absence of glowing red dust features informs us that it has long since lost its reservoir of gas and dust from which new stars can form.
While NGC 2937 is certainly reacting to the presence of its neighbor, its smooth distribution of stars obscures any obvious distortions of its shape.
Eventually these two galaxies will merge to form a single object, with their two populations of stars, gas and dust intermingling.
This kind of merger was likely a significant step in the history of most large galaxies we see around us in the nearby Universe, including our own Milky Way Galaxy.
Above the pair, an unrelated, lone, bluish galaxy, inconsistently cataloged as UGC 5130, appears to be an elongated irregular or an edge-on spiral. Located 230 million light-years away, this galaxy is much closer to us than the colliding pair, and therefore is not interacting with them.
