Credit: HAWC Collaboration
The Water Telescope
Observing the highest energy radiation produced by the Universe requires novel techniques and quite a bit of ingenuity. Orbiting satellite observatories like the Compton Gamma-Ray Observatory, AGILE, INTEGRAL, Swift, and the Fermi Gamma-Ray Space Telescope observe high energy sources by looking at the shadows that they cast, or by converting radiation to matter and plotting the tracks the particles make. Other observatories like HESS and VERITAS actually use the earth's atmosphere to detect and track incoming high energy photons from deep space. The High-Altitude Water Cherenkov Gamma-Ray Observatory (HAWC) is perhaps one of the most unusual of these high-energy observatories. HAWC, located on the side of the Sierra Negra volcano near Puebla, Mexico at an altitude of 4100 meters, uses 300 large corrugated steel tanks four meters high and 7.3 meters in diameter, each containing four photomultiplier tubes, sophisticated light detectors. High energy photons and charged particles entering the water tanks produce a special kind of blue light called Cherenkov radiation in a cone about 41 degrees wide which can be detected by the photomultipilier tubes. HAWC covers about 15 degrees of the sky instantaneously, while the rotation of the earth allows HAWC to scan a good portion of the sky. The image above shows HAWC's high-energy Gamma-Ray image of about two-thirds of the entire sky taken during 340 days of operation between November 2014 and November 2015. To help guide the eye, common constellations and asterisms are noted on the image. Sources in the Milky Way are prominent, as are the extragalactic active galaxies Markarian 421 and Markarian 501.
Published: September 26, 2016
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Page Author: Dr. Michael F. Corcoran
Last modified Monday, 03-Oct-2016 11:10:40 EDT