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Radio
map of the galaxy Messier 87 and the powerful jets of material
coming out from the central black hole.
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Radio
astronomers have pioneered systems for interferometry. This technique
combines the signals from several instruments in a manner that allows
them to act as a single "virtual telescope," one with
a huge effective diameter equaling the distance between the most
widely separated telescopes. The greater the diameter of a telescope,
the more detail it can see. An example is the Very Large Array (VLA)
of movable radio telescopes near Socorro, New Mexico, with an effective
diameter of up to 27 kilometers. Building on the VLA's success,
the Expanded Very Large Array (EVLA) will create an array of radio
dishes with 10 times the VLA's sensitivity and angular resolution.
The EVLA will have a thousand times the VLA's capability for making
spectroscopic observations at different radio wavelengths. The expansion
will involve replacement of the current detectors,computers, and
software to improve sensitivity. In a second stage of the expansion,
as many as eight new antennas will be built. Interconnected by fiber-optic
links, the new and old dishes will allow the EVLA to study the cosmos
with an angular resolution comparable to that of the Next Generation
Space Telescope (NGST) and of the Atacama Large Millimeter Array
(ALMA). These three instruments will complement one another by providing
high-resolution views of the cosmos in the spectral domains of radio,
millimeter (radio waves with the shortest wavelengths), and infrared
wavelengths.
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Location
of VLA and the additional antennas constituting the EVLA.
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Still
finer angular resolution will come from the Advanced Radio Inter-ferometry
between Space and Earth (ARISE) initiative. ARISE combines a radio
telescope 25 meters in diameter, orbiting in space, with the existing
Very Long Baseline Array (VLBA) of radio telescopes. ARISE will
enable the study of explosive events, such as the jets ejected from
the matter orbiting a supermassive black hole. It will have a precision
that may be good enough to explain how and why these ejections occur.
And it may be able to reveal how the ejection of matter leads to
the production of an enormous quantity of radio emissions. But a
system with even the finest angular resolution cannot observe faint
sources unless it can collect sufficient amounts of radiation. To
observe the faintest radio sources in the cosmos, radio astronomers
from around the world are planning the Square Kilometer Array (SKA)
of radio telescopes, which will cover a total area of one square
kilometer. The SKA will have hardware and software capable of simultaneously
analyzing the signals detected in each of the huge number of telescopes
in the array. The SKA will effectively function as a single radio
dish even larger than 1 kilometer in diameter, possessing 10 times
the collecting area of the 300-meter radio telescope near Arecibo,
Puerto Rico. The SKA will be able to observe the clouds of gas that
formed the precursors of galaxies 12 to 14 billion years ago, as
well as gas within distant galaxies. The Astronomy and Astrophysics
Survey Committee recommends that, during this decade, resources
be provided for the U.S. contribution to the technology development
required for the SKA, which will be by far the most sensitive radio
instrument ever built.
Visit
the Official EVLA Site
Visit
the Official ARISE Site
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