Antarctic Balloon Seeks Highest-Energy Neutrinos, Results Still Blind
University of Chicago astrophysicist Abby Vieregg describes PUEO, a NASA balloon that used Antarctic ice as a detector; analysis remains blinded.
The story in focus
A NASA balloon mission called PUEO flew 40 kilometers above Antarctica to search for the highest-energy neutrinos, using the continent's radio-transparent ice as a detector. University of Chicago astrophysicist Abby Vieregg said the flight lasted 23 days and yielded 50 to 60 terabytes of data, analyzed blind until the end.
- PUEO is a NASA balloon mission carrying antennas about 40 kilometers (120,000 feet) above the Antarctic ice sheet
- The flight lasted 23 days, ending in January, and produced roughly 50 to 60 terabytes of data
- Analysis is done blind, so results on whether any neutrinos were detected are only known at the end
A balloon over a continent-sized detector
Abby Vieregg, a University of Chicago professor of physics and astronomy and astrophysics, described PUEO, the Payload for Ultra High Energy Observations, on the Big Brains podcast published October 9. The mission is a set of antennas on a NASA balloon flying roughly 40 kilometers, or 120,000 feet, above the Antarctic ice sheet.
The approach relies on glacial ice being radio transparent and dense enough to give neutrinos a chance to interact. The team watches the ice from above for those interactions, effectively using the entire Antarctic continent as its detector. Vieregg said the mission is designed to look for the highest-energy astrophysical neutrinos.
Flight and data
The team arrived in Antarctica in early November, declared flight readiness in mid-December and launched in December. Vieregg said the mission was terminated in January after 23 days, about what the team expected.
The campaign involved a team of 16 people, and the balloon facility hosted two payloads that year, which she described as a normal number. Vieregg said roughly 50 to 60 terabytes of data were collected. She noted she had returned home before launch and watched it from a hotel room in Christchurch, New Zealand, while graduate students and postdocs ran operations.
Blind analysis and what counts as a detection
Results will not emerge gradually. Vieregg said analyses in particle physics are usually done blind when searching for something unseen, so the team characterizes backgrounds systematically before asking whether any neutrinos appeared.
She said no one has observed neutrinos at these energies, and a few events from different sources would be a big deal. Neutrinos are called ghost particles because they are uncharged and interact only weakly, passing through matter and space largely unnoticed. Vieregg said high-energy neutrinos from dense, energetic engines such as accreting black holes can reach observers even when dust blocks ordinary light, potentially mapping those central engines. She also cited the 2026 Nobel Prize in Physics as recognition for high-energy neutrino research.
Why does the PUEO team wait until the end to know if it detected neutrinos?
Vieregg said the analysis is done blind, as in nearly all particle physics searches. Researchers systematically characterize backgrounds in data before asking whether any neutrino events are present.
Sources & further reading
- Neutrino hunters: Searching for ghostly particles in Antarctic ice, with Abby Vieregg - Podcast ↗news.uchicago.edu
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