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September 22, 2016

Star and galaxy birth causes giant space blobs’ intense glow

by John_A

A team of scientists have unraveled the secret behind lyman-alpha blobs and their intense glow. These massive clouds of hydrogen gas baffled astronomers from the time they first found out about their existence. A scientist named Charles Steidel discovered Lyman-alpha blob 1 or LAB-1, called as such because it’s first of its kind we’ve ever seen, in 2000. In an effort to get to the bottom of things, a team led by Jim Geach, an astrophysicist from the University of Hertfordshire in the UK, took a closer look at the massive structure.

With the help of the Atacama Large Millimeter Array of radio telescopes and the European Southern Observatory’s Very Large Telescope (VLT), the team found that LAB-1, which is thrice the size of the Milky Way, has two large galaxies in its center. They also found that the two are surrounded by a number of smaller galaxies, based on their observations using the Hubble Space Telescope and the Keck Observatory in Hawaii.

Now, here’s the important part: the two bigger galaxies are in midst of birthing one star after another. And thanks to cosmic materials from the smaller ones, stars are forming within the duo at a rate of over 100 times that of our own galaxy. All the ultraviolet light given off by this rapid star formation is what’s making the blob shine brightly.

Geach explained:

“Think of a streetlight on a foggy night — 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.”

Since LAB-1 is 11.5 billion light-years away, the team believes we’re seeing the early stages of the formation of a gigantic elliptical galaxy — the two in its center are bound to merge — that will become the heart of a cluster. The light from Lab-1 that reaches us today was from 11.5 billion years ago, after all, shortly after the Big Bang. Astronomers now believe that the biggest galaxies in the universe form within bright, colossal blobs, just like Lab-1.

Source: Atacama Large Millimeter/Submillimeter Array, Arxiv (PDF)

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