In today's image, we see a photographic plate of the Andromeda Galaxy marked by Edwin Hubble one hundred years ago with the identification of variable stars. This discovery led to an increase in our understanding of the size of the universe showing that Andromeda was not a nebula within our galaxy but actually another galaxy or island universe of its own.

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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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