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New detector will fly over Antarctic ice to find energetic particles from space


Sometimes a question is so big that it takes a continent to answer it.

University of Chicago physicist Abby Vieregg is leading an international experiment that essentially uses Antarctic ice as a giant detector to find extremely energetic particles from space. Recently approved by NASA, the $ 20 million project will build an instrument to fly over Antarctica in a balloon, launched in December 2024.

“We are looking for the most energetic neutrinos in the universe,” said Vieregg, associate professor in the physics department. “They’re made in the most energetic and extreme places in the cosmos, and these neutrinos offer unique insight into those places. Finding one or more of them could allow us to learn completely new things about the universe.

The international collaboration of 12 institutions will build a radio detector attached to a high-altitude balloon, which will be launched by NASA and travel over Antarctica at 120,000 feet, in search of neutrino signals. The revolutionary project is called PUEO, short for Payload for Ultrahigh Energy Observations. (It shares its name with the only living owl native to Hawaii, where the previous PUEO experience originated.)

‘A beautiful way to look at the universe’

Neutrinos are often called “ghost” particles because they very rarely interact with matter. Billions pass harmlessly through your body every second.

Because they can travel enormous distances without being distorted or deflected, neutrinos can serve as unique clues to what is happening elsewhere in the universe, including cosmic collisions, galaxies, and black holes where they are. created.

“Neutrinos are a great way to look at the universe because they travel unhindered in space,” Vieregg said. “They can come a long way, and they’re not scrambled along the way, so they indicate where they’re coming from.”

Scientists have detected a few neutrinos from outer space entering Earth’s atmosphere. But they believe there are even more neutrinos that carry extraordinarily high energies – several orders of magnitude higher than even particles accelerated at the Large Hadron Collider in Europe – and have never yet been detected. These neutrinos could tell us about the most extreme events in the universe.

That is to say if you can catch them.

These neutrinos interact so rarely with other forms of matter that Vieregg would have to build a huge detector the size of a country to catch them. Or she can use one that already exists: the ice sheet atop Antarctica.

“The ice cap is perfect – a homogeneous, dense, radiolucent block that spans millions of square kilometers,” Vieregg said. “It’s almost like we designed it. “

If one of these highly energetic neutrinos passes through Earth, it is possible that it collides with one of the atoms inside the Antarctic ice sheet. This collision produces radio waves which pass through the ice. This radio signal is what PUEO would detect when it hovers over Antarctica.

To do this, he needs very, very special equipment.

The next generation

PUEO is the next generation of a mission called ANITA, based at the University of Hawaii, which flew over Antarctica aboard NASA balloons four times between 2006 and 2016 to search for similar neutrinos. PUEO, however, will have a much more powerful detector.

The new detector harnesses the power of an old trick of astronomy, a technique called interferometry, which combines signals from multiple telescopes. PUEO is dotted with radio antennas, and a central data acquisition system will merge and analyze these signals to create a stronger signal.

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