The blob is one of the biggest and most mysterious objects in our universe. Discovered 16 years ago by researchers at Cal Tech's Palomar Observatory, the gargantuan object glows 10 times bigger than the Milky Way.
At first, the scientists thought the blob in their data was a fluke. Then they identified more of the mysterious blotches and realized they'd detected something new: glowing clouds of hydrogen gas 11.5 billion light years from Earth. The scientists called the clouds "Lyman-alpha emitters," for the particular wavelength of light that emanates from them, and named the original discovery "Lyman-alpha blob 1." But having a name didn't get the researchers any closer to figuring out what the blobs were, or what made them glow.
So a slew of astronomers went to the Atacama Large Millimeter/Submillimeter Array (ALMA) — a collection of 66 radio telescopes in the desert of northern Chile — to try and peer inside Lyman-alpha blob 1.
According to a recent report in the Astrophysical Journal, the blob contains two young galaxies generating new stars at a feverish pace. Their activity lights the cloud of gas surrounding them, creating the blob's characteristic diffuse glow.
"Think of a streetlight on a foggy night," lead author Jim Geach, an astronomer at the University of Hertfordshire, said in a statement. "You see the diffuse glow because light is scattering off the tiny water droplets. A similar thing is happening here, except the streetlight is an intensely star-forming galaxy and the fog is a huge cloud of intergalactic gas. The galaxies are illuminating their surroundings.”
The findings can help astronomers understand how galaxies form and evolve. Researchers believe the two galaxies at the center of the Lyman-alpha blob are in their earlier stages of development, spitting out at least 100 sun-size stars per year. Eventually, they'll probably merge into a single, elliptical galaxy.
Note that because this blob is 11.5 billion light years away, all this stuff already happened; we just haven't seen it yet because the light has to travel such a long distance to get to us.
"We are seeing a snapshot of the assembly of that galaxy 11.5 billion years ago," co-author Dave Clements said in a statement.
If the same kind of activity is powering other Lyman-alpha emitters that scientists have seen, then these blobs could be the birthplaces of the most massive galaxies in the universe.
“Unveiling the galaxies shrouded in LAB-1 did more than just put to bed the long-standing issue of the gas cloud’s glow,” said Desika Narayanan, a researcher at Haverford College in Pennsylvania and also a co-author of the paper. “It provided a rare opportunity to see how young, growing galaxies behaved when the universe was quite young.”