Why does the tidy, compact spiral galaxy NGC 470 on the right look so different to its neighbour NGC 474, a shell elliptical galaxy spreading out vastly and fuzzily in concentric rings of stars?

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At least 10% of elliptical galaxies in our Universe have this diffuse, shell-like structure, but the reasons are unknown.

The shells may be ‘ripples’ following a merger with a smaller galaxy, or – since spiral galaxies make up around 72% of the galaxies that have been observed – are they overcoming their wispier cousins?

It may be that NGC 470 has been exerting a powerful gravitational pull on NGC 474 for millennia, slowly pulling it apart.

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Observatory Very Large Telescope

Release date 6 January 2020

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Image credit ESO

Authors

Jane Williamson science journalist and writer
Jane WilliamsonScience journalist

Jane Williamson is BBC Sky at Night Magazine's Production Editor.