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Hubble Reveals a River of Star Formation

A bright star at image center, above it are two galaxies merging with bright blue star forming regions. a stream of blue-white stars trails off to the bottom of the image just left of center to another dwarf galaxy at the bottom of the image.
NASA, ESA, and J. Charlton (Pennsylvania State University); Image processing: G. Kober (NASA Goddard/Catholic University of America)

This newly revised NASA Hubble Space Telescope image of the Hickson Compact Group 31 (HCG 31) of galaxies highlights streams of star-formation as four dwarf galaxies interact. The bright, distorted clump of young blue-white stars (top-right of center) is NGC 1741. Although it appears to be a single galaxy, NGC 1741 is actually a pair of colliding dwarf galaxies. Another dwarf, cigar-shaped galaxy to the pair’s right joins their dance with a thin, blue stream of stars that connects the trio. HGC 31’s fourth member is revealed by a stream of young blue stars that point to the galaxy (bottom-left of center) and indicate its interaction with the other three. The bright object in the center of the image is a star situated between Earth and HCG 31.

Dwarf galaxy encounters are normally seen billions of light-years away, and therefore occurred billions of years ago, but HCG 31 is located some 166 million light-years from Earth, relatively close by cosmic standards. The newly revised image emphasizes star-forming regions spurred by the quartet’s gravitational dance. The color blue represents visible blue light and showcases young, hot, blue stars, while the color red represents near-infrared light.

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