Mature, shapely, and with some beautiful bars

Distant galaxy give clues to the structure of the Milky Way.

NGC 7773, as seen by Hubble: spiral, mature and barred.

ESA/Hubble & NASA, J. Walsh

It’s difficult to know what your home looks like if you don’t, or can’t, leave it.

Take the Milky Way, for instance. Astronomers think it is a barred spiral galaxy, a bit like this one, which is called NGC 7773, which is about 392 million light years away. They can’t be sure, though, mainly because no human-made imaging vessel has thus far escaped the galaxy, turned around and taken a snap.

This image of NGC 7773, taken by NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 (WFC3), reveals the existence of a series of luminous bars – they appear orangey-brown in this instance.

Astronomers think that the bars develop as galaxies mature, and comprise star-forming material slowly being pulled into the centre of the system.

The Milky Way is a spiral, and quite old, as galaxies go, so it is reasonable to suspect it also contains bars. It might be a very long time indeed, however, before the photographic material exists to prove the contention.

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