Recently, new data figuratively unearthed from the physical Earth’s most ice-laden continent, Antarctica, brought more verification for a neutrino sighting that occurred not so long ago. This is significant because it marks a new kind of astronomy that studies the universe indirectly by means of neutrinos.
WHAT IS A NEUTRINO, AND WHAT DOES IT DO?
Neutrinos are massless high-energy subatomic particles generated by radioactive decay in black holes, large exploding stars, e.g. supernovas, and the unimaginably bright and high-energy cores of galaxies, or, as the late physicist F. Reines would say, neutrinos are “the most tiny quantity of reality ever imagined by a human being.” The recent study detected 21 ultra-high-energy muons, which are secondary particles generated when neutrinos mock chance by interacting with other particles around them. Their presence is direct confirmation of astrophysical neutrinos from cosmic neighborhoods both familiar, and far, far away.
Known as the IceCube Collaboration, the scientific team hailed this new data as an “unequivocal signal” for astrophysical neutrinos, whose histories, having met stars, planets, galaxies, magnetic fields, and clouds of interstellar dust, limn the universe by their compound effect on the more malleable proton particles that’ve tread cross their path.
WHY ARE NEUTRINOS NEWS, IF THEY’RE SO UBIQUITOUS?
If these high-energy neutrinos are created deep within the bowels of the cosmos’ most violent and active phenomena, and are excited to energy levels surpassing even our own record-holding Large Hadron Collider by a factor exceeding one million, the information such particles may hold would be absolutely indispensable to scientists. Recent observation of these particles was carried out with thousands of optical sensors resting in the murky abyssal depths beneath the Antarctic ice of the South Pole. But they sensors were actually pointed, down, through the Earth to monitor the Northern Hemisphere’s sky.
WHY ARE WE LOOKING AT THE GROUND TO SEE SPACE? WHAT?
The Earth’s body actually filters out a good deal of background muons generated upon cosmic rays’ impact with our atmosphere. By amassing instruments amidst a cubic kilometer of Antarctic ice, the IceCube team of scientists were able to make a detector covering a great enough volume to capture a neutrino collision’s rare signature. When this occurs, a muon is created, leaving a trail of Cherenkov light that accurately traces the trajectory of the passed neutrino. Called “optical sonic booms,” these collisions are sensed by optical sensors that compose the IceCube detector array, and can theoretically reveal the source of the neutrino.
MAPPING THE UNIVERSE
Neutrinos observed from the IceCube Observatory showed identical scans to those seen while the observatory captured neutrinos from the Southern Hemisphere. Albrecht Karle from UW-Madison thinks that this suggests that many of the potential sources for high-energy neutrinos have origins beyond the Milky Way. He added that if there are a significant number of sources in our own galaxy, the IceCube detector would register more activity when scanning across the plane of our galaxy.
“The plane of the galaxy is where the stars are. It is where cosmic rays are accelerated, so you would expect to see more sources there. But the highest-energy neutrinos we’ve observed come from random directions,” added Karle. “It is sound confirmation that discovery of cosmic neutrinos from beyond our galaxy is real.”
