In 2021, the IceCube detector in Antarctica caught a high-energy neutrino — event IC 210922A. Neutrinos are among the most elusive particles in the Universe: no charge, almost no mass, they pass through matter with barely any interaction. Tracing where a specific neutrino came from is like hunting a ghost.
After the alert, dozens of telescopes scanned the relevant patch of sky — no gamma-ray burst, no supernova, no obvious source. But a few days later, a team led by Yuji Urata spotted an extraordinarily bright distant galaxy using the JCMT and SMA submillimeter telescopes in Hawai'i. It was nicknamed "Shadow Blaster."
Follow-up observations with ALMA and Gemini North revealed the details. The galaxy is ~11 billion light-years away and sits behind a powerful gravitational lens — a massive foreground galaxy amplifies its brightness from 2.7 to 33 trillion solar luminosities in infrared.
The key twist: Shadow Blaster shows no signs of an active black hole. The neutrino was likely born in the galaxy's ultra-dense core, where gas and dust are so compressed that intense star formation acts as a natural particle accelerator. Previously, neutrino sources were thought to be mainly black hole jets.
If confirmed, Shadow Blaster would be the first individual dusty star-forming galaxy directly linked to a high-energy neutrino. And such galaxies may be very common — estimates suggest they could contribute up to 20% of the total cosmic neutrino background.