There’s a new way to look at the universe — using high-energy particles called “neutrinos” — thanks to the work of Drexel Astrophysicist Naoko Kurahashi Neilson, PhD, and her colleagues on the IceCube Collaboration.
In July 2018, the Collaboration released two papers in Science magazine that describe a high-energy neutrino event. Detected on September 22, 2017 via the IceCube particle detector at the South Pole, the incident coincided with the direction and time of a gamma-ray flare from a blazar. Blazars are giant, oval-shaped galaxies theorized to have spinning, supermassive black holes at their center that blast out radiation, including light.
“A lot of people thought blazars emitted neutrinos, but no one ever saw it,” Neilson says.
The second paper, for which Neilson served as lead author, reviewed the previous nine-and-a-half years of IceCube neutrino observations. The data showed strong evidence of other neutrinos coming from that specific blazar, which can be seen in the night sky just off the left shoulder of Orion.
The discovery identifies the first-known source of high-energy neutrinos, which can provide a glimpse into how far-away galaxies are formed and even how they evolved, Neilson says.
“All of astronomy is light. You see a star because photons — which are light — hit your eyes,” she says. “It’s all different frequencies of light.”
Right now, Neilson says, “everything we know about astronomy is photons.” Getting better acquainted with neutrinos — where they come from, especially — opens up a whole new range of what’s possible to see and understand.
“If I shine a light on a table, you won’t see the light on the other side because the table blocks it,” she explains. “But if I had a neutrino flash- light, the light would go right through and you could see it on both sides, because neutrinos can’t be blocked by anything.”
The IceCube team is now working to build upon their latest discovery.
“We’re trying to look for more neutrino sources and more correlations between neutrinos and photons,” Neilson says.