Observed: The Day the Universe Lit Up

By Corey S. Powell | March 19, 2013 3:06 pm

Although it was born in the fireball brilliance of the Big Bang, the universe spent much of its infancy in the dark. Clouds of primordial particles expanded and cooled forming atoms–hydrogen, mostly that were opaque to light. Galaxies did not yet exist. Even stars did not yet exist. These are known as the cosmic Dark Ages. That era is shrouded in mystery, since scientists literally cannot see what was happening then.

Then gravity did its work. Gas collapsed into bright stars, larger clumpings of matter collected into proto-galaxies, and the universe  began to light up. Astronomers have worked out the general theory of how this probably happened. Now at last they are seeing it for real, due to data coming from the brand-new Atacama Large Millimeter/submillimeter Array, or ALMA.

First light: The red blobs are newly discovered, extremely distant galaxies that are forming new stars at a furious rate. They are invisible to ordinary telescopes but easily detectable to ALMA. The blue objects are relatively nearby galaxies, whose gravity is magnifying the radiation from the faraway ones (Credit: ALMA/ESO/NRAO/NAOJ, J. Vieira et al.)

My friend Govert Schilling has written a great explainer about what ALMA is and how it works. This telescope array in Chile’s Atacama desert  is a remarkable tool for exploring deep space–so remarkable that it has just yielded groundbreaking work on the Dark Ages even while it is still under construction.

Aiming 16 of its dishes at a series of distant galaxies, ALMA picked up faint millimeter-wave emission–shorter than FM radio waves, longer than the infrared rays from a heat lamp–from carbon monoxide molecules in those galaxies. Carbon monoxide is significant for two reasons. First, it is the second-most common molecule in the universe, behind molecular hydrogen; it therefore produces a relatively strong signal. But more important, carbon monoxide radiates especially in the locations where new stars are being born. When an infant galaxy begins forming stars, the carbon monoxide floodlights suddenly switch on.

FIve distant “starburst” galaxies observed by ALMA. These images are composite views from ALMA (red) and the Hubble Space Telescope (blue). ALMA detects invisible microwave radiation, which is depicted as red for clarity. Each red splotch is a newborn galaxy as bright as 10 trillion suns. (Credit: ALMA/ESO/NRAO/NAOJ, J. Vieira et al.)

These baby galaxies are very difficult to see in visible light. They tend to be shrouded in gas and dust, keeping the Dark Ages out of sight and making them undetectable to conventional telescopes. The radiation from carbon monoxide can still get through, however. That’s because the carbon monoxide “shines” by giving off radiation with a wavelength of 3 millimeters (about 1/10th of an inch), about 5,000 times as long as visible light. Such long waves basically jump right over bits of dust and continue on their way to us. Ordinary telescopes cannot detect such waves. The Hubble Space Telescope cannot see such waves. But ALMA can.

Which bring us back to ALMA’s mind-bending new discovery. A team of astronomers led by Joaquin Vieira, a post-doc at
 Caltech, zeroed in on 26 suspected distant galaxies. ALMA detected strong carbon monoxide emission in 23 of them–the telltale sign of a galaxy bursting with newborn stars. Moreover, by measuring how the radiation had been stretched by the expansion of the universe, Vieira and his colleagues were able to calculate the distances to these starburst galaxies and found that they were substantially farther away than expected. Most of them were about 12 billion light years away, meaning we are seeing them as they were 12 billion years ago.

Since the observable universe is just 13.7 billion light years old, these galaxies were lighting up the Dark Ages when the universe was less than 2 billion years old–a billion years earlier than astronomers expected. The most distant of the galaxies detected by ALMA were fully aglow with stars when the universe was just 1 billion years old.

Gravitational lens–a natural magnifier–helps ALMA see much deeper into space. Radiation from a distant galaxy (red) is bent and amplified by the gravity of a nearer galaxy (blue-white). This effect made the galaxies look up to 22 times brighter to ALMA.
(Credit: ALMA, L. Calçada, Y. Hezaveh et al.)

OK, let’s step back for a moment and think about what that really means. The first chapters of cosmic history must have been extremely eventful, going from Big Bang to fog to Dark Ages to first stars to full-fledged galaxies in just the first 7% of the age of the universe. The first chapter of ALMA’s history is pretty impressive too. In its very first week of active operation, ALMA is already revealing new details about about the early history of galaxies like our Milky Way, and about the remarkable path that led from a soup of atomic particles to the sun, the Earth, and to you.

I can’t wait to see what ALMA will tell us next.

Follow me on Twitter: @coreyspowell

  • http://www.facebook.com/people/David-Vognar/2407164 David Vognar

    How fascinating! Great work.

  • http://www.facebook.com/people/Juliann-Henneman/1814446294 Juliann Henneman

    Hi Corey….isn’t the “Fireball Brillance of the Big Bang” an outdated descriptor for the event?

  • coreyspowell

    [author] I think “fireball brilliance” is still a reasonable way to convey something that was, by its nature, fundamentally unobservable. In the moments after the Big Bang, the universe was a dense soup of particles and photons, at an exceedingly high temperature. To me, that counts as a brilliant fireball, even if there was no outside vantage from which you could witness it. And of course there was nobody around to witness it from the inside, either. The problem here is that we are attempting to describe events and conditions that lie far outside the range of human experience, and hence far outside the range of language as well.

  • Cguy

    Apparently, not you, you idiot.

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Out There

Notes from the far edge of space, astronomy, and physics.

About Corey S. Powell

Corey S. Powell is DISCOVER's Editor at Large and former Editor in Chief. Previously he has sat on the board of editors of Scientific American, taught science journalism at NYU, and been fired from NASA. Corey is the author of "20 Ways the World Could End," one of the first doomsday manuals, and "God in the Equation," an examination of the spiritual impulse in modern cosmology. He lives in Brooklyn, under nearly starless skies.

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