Scientists who mapped a donut-shaped region of the sky (pictured) with a balloon-borne telescope called ARCADE say they've picked up an unmistakable radio signal coming from beyond our Milky Way galaxy. Sorry, but it's probably not E.T. broadcasting. One theory is that ARCADE detected faint radiation left over from the universe's first mega-stars, which all collapsed during the first billion years of time as we know it. The energy transmitted by their long-ago supernovae might be reaching us in the form of these transmissions. Or it might be caused by ultra-massive black holes in other galaxies. Get the full story over at New Scientist.

Illustration via NASA/ARCADE