Breakthrough: The Entire Sky Is Faintly Glowing At Wavelengths Invisible To The Human Eye

Tuesday, 02 October 2018 - 1:25PM
Astronomy
ESA
Tuesday, 02 October 2018 - 1:25PM
Breakthrough: The Entire Sky Is Faintly Glowing At Wavelengths Invisible To The Human Eye
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YouTube: ESA/Hubble & NASA, ESO/ Lutz Wisotzki et al.
An international team of astronomers have discovered that the entire sky – perhaps the entire universe – is faintly glowing at wavelengths invisible to the human eye. The breakthrough came using the ESO's Very Large Telescope coupled with the MUSE instrument also on deck.

This spectral "glow" is called a Lyman-alpha emission and it originates in vast clouds of hydrogen as their electrons shift to a higher energy level. It's an established phenomenon – but we had no idea of the scope or magnitude until now. That blue you see flooding across the entire image represents these glowing clouds of hydrogen. It's everywhere.

"Realizing that the whole sky glows in optical when observing the Lyman-alpha emission from distant clouds of hydrogen was a literally eye-opening surprise," said Kasper Borello Schmidt, an astronomer on the team.

The area of the sky researchers were examining had been mapped by the Hubble telescope in 2004, when the equipment spent 11 days trained on a single set of coordinates. This prolonged observation brought thousands of previously invisible galaxies to light but was technologically incapable of revealing the Lyman-alpha emissions we see today. The MUSE instrument – which stands for Multi Unit Spectroscopic Explorer – was able to look deeper beneath the surface of these galaxies thanks to its ability to separate and record light into wavelengths for analysis.

Since this light has to travel vast distances to reach Earth, what we are seeing today is a window into the distant past offering clues to what our universe looked like in its infancy. The next step will be to take targeted measurements with more sensitive equipment.

Hydrogen is the most plentiful element in space and its precession frequency – roughly, subatomic movement to the strength of the magnetic field – is what's known as the "hydrogen line." This radio frequency falls in a relatively quiet area of the spectrum and, as such, has been singled out as the most likely frequency for establishing intergalactic communication. The most famous SETI signal was discovered on the hydrogen line frequency, and remains unexplained to this day.

One needn't make contact with an alien civilization to appreciate the wonder inherent to our universe. Themiya Nanayakkara, another researcher on the team, may have put it best when she said, "Next time you look at the moonless night sky and see the stars, imagine the unseen glow of hydrogen: the first building block of the universe, illuminating the whole night sky."

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