University of Delaware researchers helping solve the mystery of neutrinos

Jessica Bies | The News Journal

Show Caption Hide Caption Solving the mystery of 'ghost particles' An IceCube spokesman and other experts explain the observations that led to identifying the source of high-energy neutrinos and cosmic rays.

University of Delaware researchers are part of an international team of scientists that recently discovered what appears to be the source of cosmic neutrinos, ghostly subatomic particles that can travel in a straight line for billions of light years, passing unhindered through galaxies, stars and anything else in their path.

“This is the smoking gun,” said Thomas K. Gaisser, a professor of physics and astronomy at the University of Delaware. “Active galaxies have long been thought to be a likely source of the highest-energy particles in nature.

"But in order to make the generalization, we have to see another one. Or several others."

Scientists at the IceCube Neutrino Observatory at the South Pole discovered a single neutrino, commonly referred to as a "ghost particle," in September and traced it to a blazar galaxy nearly 4 billion light-years away, in the constellation Orion, Gaisser said. Scientists refer to the galaxy as "Texas," a play on its scientific name, TXS 0506+056.

The finding was published in a pair of studies in the journal Science. Researchers from UD, who in 2016 received $750,000 to maintain and operate IceTop, an array of sensors at the surface of the larger IceCube project, also helped deploy the system that detected the neutrino.

Encompassing a cubic kilometer of deep, pristine ice a mile beneath the surface at the South Pole, the massive particle detector is composed of more than 5,000 light sensors — on a grid that is several football fields wide.

When a neutrino interacts with the nucleus of an atom, it creates a secondary charged particle, which in turn produces a characteristic cone of blue light that is detected by IceCube and mapped. The clear, dark ice makes the interaction easier to catch.

"This is the first evidence that we have of an active galaxy emitting neutrinos, which means we may soon start observing the universe using neutrinos to learn more about these objects in ways that would be impossible with light alone," said study co-author Marcos Santander, a University of Alabama astronomer.

Gaisser said the discovery was a bit of a surprise.

Equipped with a nearly real-time alert system, IceCube broadcast the coordinates of the Sept. 22 neutrino alert to telescopes worldwide for follow-up.

Observatories, including NASA’s orbiting Fermi Gamma-ray Space Telescope and the Major Atmospheric Gamma Imaging Cherenkov Telescope in the Canary Islands, detected a flare of high-energy gamma rays associated with the blazar, a convergence of observations that convincingly implicated the far-off galaxy as the most likely source.

Blazars are giant, oval-shaped galaxies thought to have spinning supermassive black holes at their center that blast out radiation — including light. When the galaxy is oriented so that the jets of energy exiting the black hole are pointed toward Earth, the observations become even more dramatic, according to the Kavli Institute for Particle Astrophysics and Cosmology, or KIPAC.

Observing a blazar is a bit like looking down the barrel of the most powerful gun in the universe, according to KIPAC's website.

“It wasn’t in the list of potential sources we were looking at,” Gaisser told the campus news service, UDaily. “This one never popped up before.”

Neutrinos, which are difficult to detect, are extremely tiny particles and are among the most abundant in the universe. They don’t interact much with anything and travel close to the speed of light.

In fact, trillions of neutrinos just flew through your body while you read the previous two sentences.

They also don't have an electrical charge and are unaffected by even the most powerful magnetic field. Because they rarely interact with matter and have almost no mass they are often referred to as "ghost particles."

From the South Pole: Tracking neutrinos University of Wisconsin-Madison's Albrecht Karle talks about pinpointing the source of a neutrino.

Scientists said the recently-published journal articles may hold the key to some of the biggest mysteries about the universe, including why matter won out over antimatter soon after the Big Bang.

"Now that we've identified a real source, we'll be able to focus in on other objects like this one to understand more about these extreme events billions of years ago which set these particles racing towards our planet," said Gary Hill of the University of Adelaide in Australia.

The IceCube Collaboration, with over 300 scientists in 49 institutions from around the world, runs an extensive scientific program that has established the foundations of neutrino astronomy.

Gaisser said the next step will be making the IceCube sensor array bigger, increasing the likelihood of neutrinos hitting it and interacting with matter here on Earth.

But expanding IceCube is a lengthy process that involves drilling 1.5-mile-deep holes into the ice for the sensors to be lowered into. Weather conditions can greatly impact the work.

“There was one season where we (drilled) 20," Gaisser said. "The first season we got one.”

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A bigger sky for Delaware astronomers

Interested in astronomy?

The night sky just got a lot bigger for local stargazers thanks to a new partnership with the Southeastern Association for Research in Astronomy, or SARA, which gives researchers and astronomers from the University of Delaware and nearby Mount Cuba Astronomical Observatory access to three far-flung telescopes.

They are situated in so-called “dark-sky” areas at Kitt Peak, Arizona, Cerro Tololo, Chile, and La Palma on the Canary Islands off the coast of Spain.

At each location, there are few city lights or other bright distractions. The telescopes also sit more than a mile higher than instruments at Mt. Cuba, which is about 260 feet above sea level.

And, no, researchers won't have to fly thousands of miles to use the telescopes.

They can be accessed and controlled over the internet. Because the telescopes are located in different time zones, the new partnership also extends the viewing day at UD and makes it possible to track stars through more than one hemisphere.

UD now has eight full-time astronomy professors and offers a bachelor's degree in the subject, according to UDaily. SARA telescopes provided some of the data used in IceCube's recently-published papers on neutrinos, and several UD research projects rely on the SARA network.

Visit UDaily to find out more.

USA Today reporters Doyle Rice and Katharine Lackey contributed to this story. Contact Jessica Bies at (302) 324-2881 or jbies@delawareonline.com. Follow her on Twitter @jessicajbies.

Looking for more education news? Visit delawareonline.com/education. Submit story ideas at delonline.us/2i2tugB.