Scientists Reveal the Secret of the Giant Space Blob

Wednesday, 21 September 2016 - 1:10PM
Astronomy
Space
Wednesday, 21 September 2016 - 1:10PM
Scientists Reveal the Secret of the Giant Space Blob
A weird, greenish blob in the sky near the Aquarius constellation has puzzled astronomers since its discovery in 2000—what was making all of that light? Why was it green? The blob was the first of its kind, and was appropriately called LAB-1 for "Lyman-Alpha Blob #1." The "Lyman-Alpha" part of the name comes from the kind of radiation it gave off, generated by electrons changing energy states. Other LABs have been discovered since 2000, but LAB-1 was one of the largest and definitely the most studied. Now, we know what it is. And the answer is mind-blowingly awesome.

LAB-1 is a star factory.

Blob

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According to a release by the ESO (European Southern Observatory):  

 

Opening quote
A team of astronomers, led by Jim Geach, from the Centre for Astrophysics Research of the University of Hertfordshire, UK, has now used the Atacama Large Millimeter/Submillimeter Array's (ALMA) unparallelled ability to observe light from cool dust clouds in distant galaxies to peer deeply into LAB-1. This allowed them to pinpoint and resolve several sources of submillimetre emission [2].

They then combined the ALMA images with observations from the Multi Unit Spectroscopic Explorer (MUSE) instrument mounted on ESO's Very Large Telescope (VLT), which map the Lyman-alpha light. This showed that the ALMA sources are located in the very heart of the Lyman-alpha Blob, where they are forming stars at a rate over 100 times that of the Milky Way.

Closing quote


It turns out LAB-1 is a giant cloud of hydrogen gas stretching hundreds of thousands of light years, with two huge galaxies contained within it. These two galaxies are almost colliding with each other, and they're undergoing a "frenzy of star formation." But that's not all: around these two galaxies are a swarm of smaller galaxies, who appear to be projecting material inward, giving the whole process more fuel to run. The faint light we see from the blob (which took 1.5 billion years to reach us) is actually UV radiation whose wavelength has stretched out so much that it's actually visible...and green. Here's how scientist Jim Geach (one of the authors on the new study on LAB-1) describes it:

Opening quote
"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."
Closing quote


That is, quite possibly, the coolest thing ever. Here's a handy image from the ESO's release, which explains the whole thing a bit more:




What makes this discovery important is that it gives astronomers some insight into galaxy formation, one of the most complicated processes in the universe. What's going on in LAB-1 could serve as a model for how galaxies behave, grow, and function, and the radiation from all that star formation allows astronomers to see it happen. Compared to galaxies, making stars is easy.
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