A mysterious glowing “blob” in outer space has puzzled astronomers for more than 15 years. Now, a team of researchers says it has uncovered the secret behind the blob’s eerie light.
The blob was first spotted back in the late 1990s by Chuck Steidel, an astronomer at Caltech, and some colleagues. They were observing a bunch of galaxies in the distant reaches of the universe, he recalls, “but we also saw these big blotchy things.”
At first, they thought they had somehow accidentally screwed up the images. But then they realized they had actually discovered strange, glowing clouds of hydrogen gas.
They were huge — about 10 times the Milky Way in diameter — making them some of the largest known objects in the universe.
Steidel’s team named these mysterious objects Lyman-alpha blobs. The “Lyman-alpha” part of the name just refers to the wavelength of light they emit. And the “blob” part was supposed to be tongue-in-cheek, says Steidel, “like the blob from outer space or something like that.”
He and other astronomers just couldn’t understand what made the blobs glow.
“There was no obvious source that could be illuminating that blob,” says Steidel.