HAWC Gamma-ray Observatory reveals new look at the very-high-energy sky
"HAWC gives us a new way to see the high-energy sky," said Jordan Goodman, professor of physics at the University of Maryland, and U.S. lead investigator and spokesperson for the HAWC collaboration. "This new data from HAWC shows the galaxy in unprecedented detail, revealing new high-energy sources and previously unseen details about existing sources."
HAWC researchers presented the new observation data and sky map April 18, 2016, at the American Physical Society meeting.
The new sky map shows many new gamma ray sources within our own Milky Way galaxy. Because HAWC observes 24 hours per day and year-round with a wide field-of-view and large area, the observatory boasts a higher energy reach especially for extended objects. In addition, HAWC can uniquely monitor for gamma ray flares by sources in our galaxy and other active galaxies, such as Markarian 421 and Markarian 501.
In a region of the Milky Way where researchers previously identified a single gamma ray source named TeV J1930+188, HAWC identified several hot spots, indicating that the region is more complicated than previously thought.
"Studying these objects at the highest energies can reveal the mechanism by which they produce gamma rays and possibly help us unravel the hundred-year-old mystery of the origin of high-energy cosmic rays that bombard Earth from space," said Goodman.
HAWC--located 13,500 feet above sea level on the slopes of Mexico's Volcan Sierra Negra--contains 300 detector tanks, each holding 50,000 gallons of ultrapure water with four light sensors anchored to the floor. When gamma rays or cosmic rays reach Earth's atmosphere they set off a cascade of charged particles, and when these particles reach the water in HAWC's detectors, they produce a cone-shaped flash of light known as Cherenkov radiation. The effect is much like a sonic boom produced by a supersonic jet, because the particles are traveling slightly faster than the speed of light in water when they enter the detectors.
|The complete array of HAWC detector tanks is seen here in Dec. 2014 |
[Credit: HAWC Collaboration]
"Unlike traditional telescopes, with HAWC we have now an instrument that surveys two-thirds of the sky at the highest energies, day and night," said Andres Sandoval, Mexico spokesperson for HAWC.
HAWC exhibits 15-times greater sensitivity than its predecessor--an observatory known as Milagro that operated near Los Alamos, New Mexico, and ceased taking data in 2008. In eight years of operation, Milagro found new sources of high-energy gamma rays, detected diffuse gamma rays from the Milky Way galaxy and discovered that the cosmic rays hitting earth had an unexpected non-uniformity.
"HAWC will collect more data in the next few years, allowing us to reach even higher energies," said Goodman. "Combining HAWC observations with data from other instruments will allow us to extend the reach of our understanding of the most violent processes in the universe."
Source: University of Maryland [April 18, 2016]