Milagro (the Spanish word for miracle) was a ground-based water Cherenkov radiation

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

situated in the

Jemez Mountains The Jemez Mountains are a group of mountains in Rio Arriba, Sandoval, and Los Alamos counties, New Mexico, United States. Numerous Puebloan Indian tribes have lived in the Jemez Mountains region since before the Spanish arrived in New Mexico. T ...

near

Los Alamos, New Mexico Los Alamos is an census-designated place in Los Alamos County, New Mexico, United States, that is recognized as the development and creation place of the atomic bomb—the primary objective of the Manhattan Project by Los Alamos National Labora ...

at the

Fenton Hill Observatory Fenton Hill Observatory is an astronomical research facility operated by Los Alamos National Laboratory in the Jemez Mountains of New Mexico, about west of Los Alamos. The site is home to several astronomical experiments and observatories spanning ...

site. It was primarily designed to detect

gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...

s but also detected large numbers of

cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...

s. It operated in the

TeV TEV may refer to: * Transient Earth Voltage: a term for voltages appearing on the metal work of switchgear due to internal partial discharges * TeV, or teraelectronvolt or trillion electron volt, a measure of energy * Total Enterprise Value, a ...

region of the spectrum at an altitude of 2530 m. Like conventional telescopes, Milagro was sensitive to light but the similarities ended there. Whereas "normal" astronomical telescopes view the

universe The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. Acc ...

in visible light, Milagro saw the universe at very high energies. The light that Milagro saw was about 1 trillion times more energetic than visible light. While these particles of light, known as photons, are the same as the photons that make up visible light, they behave quite differently due to their high energies. A cosmic ray or high-energy gamma ray striking an atom in the upper atmosphere generates a cascade of particles known as an air shower. This cascade of particles are traveling near the speed of light and generate Cherenkov radiation as they pass through the atmosphere and the water in the Milagro experiment. The photons of Cherenkov radiation are detected by an array of detectors or

photomultiplier tubes Photomultiplier tubes (photomultipliers or PMTs for short) are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum. They are members of the class of vacuum tubes, more speci ...

which send a signal to a recorder. The data from the recorder can then be used to determine the energy and direction of the cosmic or gamma ray. The Milagro experiment used 700 sensitive light detectors submerged in the pond plus another 200 detectors arrayed around the pond. The Milagro Experiment stopped taking data in April 2008 after seven years of operation. There is a follow up experiment called the

High Altitude Water Cherenkov Experiment The High Altitude Water Cherenkov Experiment or High Altitude Water Cherenkov Observatory (also known as HAWC) is a gamma-ray and cosmic ray observatory located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an altit ...

(HAWC) located near the

Large Millimeter Telescope The Large Millimeter Telescope (LMT) ( es, Gran Telescopio Milimétrico, or GTM) -officially Large Millimeter Telescope Alfonso Serrano ( es, Gran Telescopio Milimétrico Alfonso Serrano)- is the world's largest single-aperture telescope in its f ...

at the

Sierra Negra Sierra Negra (also, and perhaps more properly, Cerro La Negra) is an extinct volcano located in the Mexican state of Puebla, close to the border with Veracruz. At officially above sea level, it is the fifth-highest peak in Mexico. Sierra Ne ...

volcano,

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

, which is expected to be 15 times more sensitive. In November 2008 Milagro published the surprising result of observing cosmic ray anisotropy.

Footnotes

External links

Milagro homepage at Los Alamos National LabThe University of Maryland HAWC pageLos Alamos observatory fingers cosmic ray 'hot spots'
Cosmic-ray experiments Gamma-ray telescopes {{observatory-stub

See also

Footnotes

External links