The Big Bang Afterglow is known as the Cosmic Microwave Background (CMB). Discover how combining CMB data with galactic observations is unlocking the secret of galaxy formation.
I’ve run into counterfeit currency a couple of times. In one case, when I was a travelling consultant, I came home from Nashville with a dodgy US fifty-dollar bill. My credit union sent it off to Ottawa to have it tested, and it turned out to be genuine.
Another time, I handed a cashier a Canadian fifty-dollar bill in a shop, and he insisted that it was counterfeit. I knew that it wasn’t, so I left my purchases on the counter and took back the bill.
I spent it at a competitor’s store. The clerk held the bill up to the light saying, “Nope, there’s nothing wrong with this fifty at all.”
HOLDING A BANK NOTE UP TO THE LIGHT
That technique of holding a banknote up to the light lets you see watermarks or unique markings on it. Having a backlight often reveals detail you can’t detect under ambient light.
Now scientists at Cornell University and Berkeley Labs have applied a similar technique to solve a much greater puzzle. They’re using the afterglow from the Big Bang to find the material that makes galaxies form in our Universe.
In 1964, Bell Labs tested a brand new six-metre radio antenna in Holmdel, New Jersey. They needed it to receive signals reflected from Echo balloon satellites.
TWO PEOPLE IN CHARGE WERE ARNO PENZIAS AND ROBERT WILSON
The two people in charge of the project were Arno Penzias and Robert Wilson. They knew that the signals they were looking for were very faint, so they did everything humanly possible to eliminate any kind of earth-based interference.
Despite their efforts, they started picking up a mysterious residual noise. It was 100 times stronger than they had thought any background interference could be. They received the signal no matter where they pointed their antenna. They were virtually certain it wasn’t coming from the Earth, the Sun or even the Milky Way Galaxy.
Even so, they wanted to rule out any local sources for this odd static. For example, they shooed some nesting pigeons away from the antenna and cleaned off their droppings.
KEPT RECEIVING THE SAME MICROWAVE BACKGROUND SIGNAL
No matter what they tried, they kept receiving the same microwave background signal. Penzias and Wilson were confident that they had ruled out every source other than something beyond our galaxy.
While all this was going on, Robert H. Dicke, Jim Peebles and David Wilkinson at Princeton University were working on a related idea. They had determined that the Big Bang should have released a tremendous amount of radiation.
Because of the time and distance involved, it would be red-shifted into the microwave frequency range by the time that radiation reached Earth. The Princeton team didn’t know it at the time, but that’s precisely what Penzias and Wilson were detecting.
RADIATION FROM THE BIG BANG RED-SHIFTED INTO MICROWAVES
Penzias found out about the hypothesis on which the Princeton team was working. They wrote back and forth, and eventually, Dicke came out to visit the Bell Labs antenna.
Dicke published a paper along with Peebles, Wilkinson, and P.G. Roll. Their findings showed that the strange signal that Penzias and Wilson discovered was the background radiation from the Big Bang.
At that time, scientists were divided about whether the Universe had a beginning or not. Many scientists still supported the Steady State Theory as opposed to the Big Bang Theory.
SIGNAL BECAME KNOWN AS THE COSMIC MICROWAVE BACKGROUND (CMB)
Penzias and Wilson’s signal became known as the Cosmic Microwave Background (CMB). Their discovery tipped the scales favouring the Big Bang Theory, which is today’s standard model in cosmology.
This week, the Cornell research team published their study in the journal Physical Review D. The investigators are using the CMB to make new discoveries. They want to understand how galaxies form from enormous gas clouds called proto-galaxies.
When scientists consider protogalaxies’ characteristics and then do the math, it seems that nothing but stars should form instead of galaxies. That’s not what happens.
LESS THAN 10% OF A GALAXY’S GAS FORMS INTO STARS
For reasons that scientists don’t yet understand, less than 10% of a galaxy’s gas forms into stars. The research team is determined to explain why the process is so inefficient.
Emmanuel Shaan is a postdoctoral fellow at Berkeley Labs and a co-author of the study. Returning to my counterfeiting escapades, Dr. Shaan explained, “It’s like a watermark on a banknote. If you put it in front of a backlight, then the watermark appears as a shadow.
“For us, the backlight is the cosmic microwave background. It serves to illuminate the gas from behind, so we can see the shadow as the CMB light travels through that gas.”
NO WAY TO DIRECTLY OBSERVE THE PROCESS
The reason scientists have difficulty explaining how galaxies form because they have no way to directly observe the process. The process takes place over billions of years, so any individual galaxy at which an astronomer looks will always be at one fixed point in the evolutionary process.
Cosmologists can only survey a wide range of galaxies and then determine the process’s steps from the entire sample. This new approach combines two sets of data to provide a proxy of the backlight technique.
The team took data from the Atacama Cosmology Telescope (ACT) showing the effects of the CMB. Then, they overlaid data from what cosmologists call the Sunyaev-Zel’dovich effects. These measure the heat and motion of the medium that surrounds galaxies and galaxy clusters.
MOTIONS OF THE GAS INSIDE A PROTO-GALAXY
Using these combined calculations, the team can observe the motions of the galactic medium. They’ve been able to determine some parameters about galaxy formation, and their work is ongoing.
The Universe has a remarkable capacity for self-organization. This is one of the striking things about the story behind its ongoing evolution.
REMARKABLE CAPACITY FOR SELF-ORGANIZATION
Every culture needs an origin story, and in western culture, our story is based on science. Our creation story won’t be fully satisfying until scientists unravel how galaxies form, organize themselves into stars and evolve.
The study’s lead author is Stefania Amodeo, a postdoctoral researcher at Cornell. She concluded by explaining the value of the study’s results. “There is uncertainty on the formation of stars within galaxies that theoretical models are unable to predict. With this work, we are providing tests for galaxy formation models to comprehend galaxy and star formation.”
We always have more to learn if we dare to know.
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