November 21, 2013
Discovery Of Cosmic Neutrinos Signals New Era Of Astronomy
[ Watch the Video: Cosmic Neutrinos Observed By IceCube Observatory ]
Lee Rannals for redOrbit.com - Your Universe Online
Astronomers working with the IceCube Neutrino Observatory in Antarctica have announced that they have, for the first time, observed 28 very high-energy particle events, leading them to conclude that "the era of neutrino astronomy has begun.”
Cosmic neutrinos are nearly massless particles that stream to Earth at the speed of light from outside our solar system. This observation, published in the journal Science, will allow scientists to learn about the nature of astrophysical phenomena that occurs millions to billions of light years away from Earth.
"The sources of neutrinos, and the question of what could accelerate these particles, has been a mystery for more than 100 years. Now we have an instrument that can detect astrophysical neutrinos. It's working beautifully, and we expect it to run for another 20 years,” Gregory Sullivan, who led the team from University of Maryland, said in a statement.
Between May 2010 and May 2012, the IceCube detector at the South Pole captured a total of 28 neutrinos with energies greater than 30 teraelectronvolts (TeV). Two of the neutrinos had an energy of more than 1,000 TeV, which is more than the kinetic energy of a flying bug.
"This is the first indication of very high-energy neutrinos coming from outside our solar system," said Francis Halzen, principal investigator of IceCube and the Hilldale and Gregory Breit Distinguished Professor of Physics at the University of Wisconsin-Madison.
Until now, scientists have only seen low-energy neutrinos that originate in Earth’s atmosphere, from farther out within the solar system, and from a nearby supernova known as 1987A. The team is now working on pinpointing where these high-energy neutrinos are coming from outside of our solar system.
"The universe is transparent to neutrinos," stated Tom Gaisser, the Martin A. Pomerantz Chair of Physics and Astronomy at the University of Delaware. "Are they remnants from supernovae, did they emanate from gamma ray bursts, or were they accelerated from an accreting black hole? We do not have conclusive information about their origin yet."
Billions of neutrinos pass through Earth every second, rarely interacting with matter because they have no electrical charge. The majority of these subatomic particles originate either in the sun or in Earth’s atmosphere. Cosmic neutrinos have long been theorized to provide insight into the powerful cosmic objects from which they originate.
"This is an important observation," Gaisser says. "It means that somewhere in the universe, there are high-intensity sources near a 'central engine,' and lots of collisions are occurring to produce the neutrinos."
IceCube was designed to measure the flux, or rate, of high-energy neutrinos, and also to try and identify some of their sources. The observatory is composed of 5,160 digital optical modules suspended like beads on a necklace along 86 strings embedded in about a half cubic mile of ice beneath the South Pole. IceCube detects neutrinos through the tiny flashes of blue light, called Cherenkov light, produced when tiny particles interact in the ice.
"IceCube is a wonderful and unique astrophysical telescope – it is deployed deep in the Antarctic ice but looks over the entire Universe, detecting neutrinos coming through the Earth from the northern skies, as well as from around the southern skies," Vladimir Papitashvili of the National Science Foundation (NSF) Division of Polar Programs said in a statement.
The 28 events recorded so far are too few to point to any one location, but IceCube will be able to detect more cosmic neutrinos to help reveal a clearer picture. Sullivan said that waiting for these to arrive is like waiting for a long exposure photograph. The more measurements that fill in a picture, the more it reveals the point of origin of these phenomena.