February 22, 2001
Somewhere between the Big Bang and this birthday, the universe learned how to make kindness, curiosity, humor, memory, and hope.
3C294: Distant X-Ray Galaxy Cluster
Birthday · February 22, 2001
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APOD published February 22, 2001. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
Large clusters of galaxies are the most massive objects in the universe. Astronomers now realize that a hallmark of these cosmic behemoths are gas clouds with temperatures of tens of millions of degrees that pervade the clusters and radiate strongly in x-rays. This Chandra Observatory image centered on a radio galaxy cataloged as 3C294 indeed reveals the telltale hot x-ray gas in an hourglass shaped region surrounding the dominant galaxy and shows the presence of a massive galaxy cluster in the distant universe. Here the picture is color-coded by x-ray energy, red for low, green for medium, and blue for high energy x-rays. The cluster associated with 3C294 is 10 billion light-years away making it the most distant x-ray galaxy cluster ever detected. Objects at that extreme distance existed when the universe was young, a mere 20 percent of its present age. Impressively, this observation demonstrates that even at those early times massive clusters of galaxies were already present.