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Wednesday, May 25, 2022

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X-ray light pulses out in rings from a neutron star in the Circinus X-1 star system. (Credit: NASA's Chandra X-ray Observatory) X-ray light pulses out in rings from a neutron star in the Circinus X-1 star system. (Credit: NASA's Chandra X-ray Observatory)

Hunting the Original Star Stuff

SDSU astrophysicist Fridolin Weber will present his research on “Big Bang matter” at this year’s Albert W. Johnson lecture.
By Michael Price

“It’s kind of mind-boggling. If things had happened just a little differently in the early universe, we wouldn’t be here.”

Every atom in every molecule of your body was born in a single spectacular, 2000-billion-degree Kelvin explosion some 13.8 billion years ago. But the Big Bang also produced exotic forms of matter that lasted only fleeting seconds before blinking out of existence. Fridolin Weber searches the universe for these elusive particles that can only exist in extreme astronomical conditions, such as inside the hearts of super-dense neutron stars. The San Diego State University theoretical astrophysicist will present findings from his galactic hunt on Friday, April 7, at the annual Albert W. Johnson Lecture.

Weber’s quarry is the quark, an elementary particle that constitutes matter’s most fundamental building block. Quarks are bound up in composite particles like protons and neutrons and are generally not found in nature by themselves. The exception is inside neutron stars, which are incredibly dense remnants of massive stars blown apart by supernova explosions. Composed primarily of neutrons, they are only 24 kilometers (15 miles) or so in diameter, yet are twice as massive as our sun.

That amount of mass packed into a relatively miniscule area creates extraordinary density at the star’s core, squeezing atomic nuclei so tightly that fundamental particles like quarks can exist freely. It’s the closest parallel to conditions immediately after the Big Bang that we know of in our universe.

“We want to understand what happened in the moments and minutes after that gigantic explosion,” Weber said. “We turn to neutron stars to see if we can detect the astrophysical signature of this ‘Big Bang matter.’”

Weber and his colleagues trawl data from enormous radio telescopes scattered around the world. They’re looking for distortions in radio waves emitted by stars that are characteristic of neutron stars’ unusually high temperatures. Right now, astrophysicists know of about 2,000 neutron stars in the sky, but Weber expects that number to grow to more than 30,000 in the coming years as telescopes and computing technology improve.

Just because you’ve found a neutron star doesn’t mean you’ve found quarks, though. Once a good candidate is located, Weber looks for a secondary pattern.

A neutron star is a magnetically charged sphere that radiates energy over time, causing it to “spin down,” like a spinning figure skater with outstretched arms. At the same time, the star is becoming denser and denser. Finally, the theory goes, the density will become so great that the atomic nuclei within the star’s core will break apart, forming quarks. This briefly makes the star “spin up” again—the figure skater pulling in her arms—before the quarks dissipate and the star resumes spinning down. Astrophysicists like Weber can detect this “spin down, spin up, then spin down again” pattern, allowing them to indirectly rewind the universe to its very beginning.

“These quarks would exist as plasma, which would have existed in the first couple of minutes after the Big Bang,” he said.

It’s easy to get lost in the fine-grained data and details needed to study complex astrophysics, but when Weber steps back from all that and considers the connection every single molecule in the universe shares with that single celestial moment, he’s humbled.

“It’s kind of mind-boggling,” he said. “If things had happened just a little differently in the early universe, we wouldn’t be here."

Weber’s lecture, “Searching for Big Bang Matter in Stars,” will take place at 3 p.m. on Friday in Storm Hall West, Room 11. For more information, visit the Albert W. Johnson University Research Lectureship website.