In today's image, we see one of the nearer clusters of galaxies known as the Hydra cluster. Galaxies tend to group in to large structures like clusters, then superclusters, and finally great filaments. This leaves much of the universe as relatively empty voids.

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This Podcast is an authorized New Media Mirror Site for APOD. You can access the image and website directly at: Astronomy Picture of the Day. You can use the archive link below the image to select the photo corresponding to the date of this podcast.

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