The Blob That Didn't Eat the Universe
It’s hard to resist an astronomy discovery when it’s called a blob, even if the precise name is the Lyman-Alpha blob. In a paper being published this afternoon in Astrophysical Journal, astronomers are announcing that they spied such an object—thought to be an enormous body of gas that may be the precursor to a galaxy—dating from when the universe was a mere 800 million years old. Stretching for 55,000 light years (approximately the radius of our Milky Way galaxy’s disk), this Lyman-Alpha blob has astronomers scratching their heads.
Named Himiko for a legendary Japanese shaman queen, the blob is not the largest such object ever discovered. That honor goes to a Lyman-Alpha blob reported in 2006 and thought to be the biggest object in the universe. Instead, this one is notable because it is so far away, and in cosmic terms far away = long ago. “The farther out we look into space, the farther we go back in time,” says astronomer Masami Ouchi of the Observatories of the Carnegie Institution , who led the international team that made the discovery: because light travels at a finite velocity, it takes time for light from objects in space to reach the eyes of Earthlings or their telescopes, which means we are seeing the blob as it was near the dawn of time, when the universe was barely 6 percent of its current age of 13.7 billion years. That means light from Himiko has been traveling toward us for 12.9 billion years, which is equivalent to saying we are seeing it was it was 12.9 billion years ago.
And that makes astronomers a bit uneasy. Whether the blob is ionized gas powered by a supermassive black hole, a primordial galaxy, the collision of two young galaxies or a single giant galaxy with a mass of 40 billion Suns—all of which are on the table—it’s too big for its age. As Ouichi puts it, “I have never imagined that such a large object could exist at this early stage of the universe’s history. According to . . . Big Bang cosmology, small objects form first and then merge to produce larger systems. This blob had a size of typical present-day galaxies when the age of the universe was about 800 million years old.” In fact, other blobs had the decency to wait to show up, appearing when the universe was 2 to 3 billion years old. No extended blobs had been found from when the universe was younger, until Himiko, which means astronomers need to scurry back to the drawing boards to figure out how an object this massive managed to grow up so fast.