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Epic galaxy merger imaged by Hubble Space Telescope

Out in the depths of space, collisions of enormous objects can occur on an almost unimaginable scale. Entire galaxies can collide, with two galaxies merging into one object and producing a storm of star formation as clouds of dust and debris from each galaxy are shoved together and fuel the birth of new stars.

One such galaxy merger has been captured by the Hubble Space Telescope, which snapped this image of the galaxy merger CGCG 396-2. Located 520 million light-years from Earth in the Orion constellation, the two galaxies have become so enmeshed they are considered one object, of an unusual type called a multi-armed galaxy merger.

This NASA/ESA Hubble Space Telescope observation has captured the galaxy CGCG 396-2, an unusual multi-armed galaxy merger which lies around 520 million light-years from Earth in the constellation Orion.
This NASA/ESA Hubble Space Telescope observation has captured the galaxy CGCG 396-2, an unusual multi-armed galaxy merger that lies around 520 million light-years from Earth in the constellation Orion. ESA/Hubble & NASA, W. Keel

This merger was originally spotted by volunteers using the Galaxy Zoo citizen science project. Members of the public were invited to help comb through Hubble data and classify different types of galaxies that could be seen in the images, to create a catalog of galaxy types.

“The Galaxy Zoo project originated when an astronomer was set an impossibly mind-numbing task; classifying more than 900,000 galaxies by eye,” the European Space Agency writes. “By making a web interface and inviting citizen scientists to contribute to the challenge, the Galaxy Zoo team was able to crowdsource the analysis, and within six months a legion of 100,000 volunteer citizen astronomers had contributed more than 40 million galaxy classifications.”

Since the project began in 2007, it has expanded to include galaxy mergers as well as different types of objects like supernovae. It has also resulted in contributions to more than 100 scientific journal articles and inspired other citizen science programs which also run on the Zooniverse platform.

Once many galaxies had been classified, a public vote was held to decide which of these objects should be observed in further depth, and CGCG 396-2 was a winner. It was imaged by the Advanced Camera for Surveys instrument on Hubble to create the image you see above.

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