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Looking deep into the sky—and, by extension, far back in time—astronomers have spotted a curious space blob that existed when the universe was only 800 million years old, about 6 percent of its present age.
Masami Ouchi, a fellow at The Observatories of the Carnegie Institution in Pasadena, Calif., who led the research reported in the May 10 issue of the Astrophysical Journal, says that the luminous gas cloud, which spans some 55,000 light-years (about half the diameter of the Milky Way), is unique for its time. "There are no extended objects found at such an early epoch," he says. Other known objects in its class, called Lyman-alpha blobs, are from somewhat more recent history, Ouchi says—at least two billion to three billion years after the big bang.
Lyman-alpha blobs are an astronomical mystery that may be primordial galaxies. "The consensus is that these are enormous protogalaxies, which over the course of time will yield very massive old galaxies such as we see in the local universe," says Dan Smith, a postdoctoral researcher at Liverpool John Moores University in England. Smith, who was not involved in the study, calls the detection of such an early Lyman-alpha blob "a very exciting result."
But as of now, it is not known what Lyman-alpha blobs are or what causes them to glow. Resolving the proposed explanations for these early objects could shed light on how galaxies such as the Milky Way take shape. Some theories hold that Lyman-alpha blobs are formed by inflows of cold streams of gas, a mechanism that Smith points out has recently been suggested by some researchers as the dominant mode of galaxy growth. Other explanations posit that the blobs' gas emits radiation due to heating by an active galactic nucleus harboring a churning object such as a supermassive black hole or by an accelerated phase of star formation known as a starburst.
The Lyman-alpha blob has been dubbed Himiko, after a queen in ancient Japan. "I found the name of Himiko is very suitable," Ouchi says, "given the fact that this object was discovered in an ancient universe [by] the Subaru Telescope," which is operated by the National Astronomical Observatory of Japan.