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Topic Name: Forty-year-old telescope is still a galactic explorer
Category: Telecommunication
Research persons: Bob Brown
Location: GPO Box 404, Hobart Tasmania 7001, United States
Details
Most 40-year-old electronic systems have long since been consigned to the
scrap heap. But astronomers who use the giant 305-metre Arecibo radio telescope
in Puerto Rico say it still offers unique capabilities, despite a review panel
that last year urged the National Science Foundation to cut its support. The
radio dish – the largest in the world – is needed to test general relativity and
theories of galactic evolution, its supporters say.
"We're very hopeful about the future," says Bob Brown, director of the National
Astronomy and Ionosphere Center, which operates Arecibo. Brown was speaking
after a recent meeting in Washington, DC, US, discussing the cutting-edge
astronomy that can still be done with the observatory.
Although not movable, Arecibo's biggest strength is its size – it is three times
wider than the world's second-biggest dish, the steerable 100-metre Robert C
Byrd Green Bank Telescope in West Virginia. Its size makes it extremely
sensitive to radio waves at any given instant in time, allowing it to detect
speedy changes in faint objects, or compare many points across the sky.
Testing Einstein
That sensitivity keeps it in demand – astronomers submit requests for three to
four times more observing time than is available. When the centre of the galaxy
comes into its field of view, that demand climbs to nine times more time than is
available.
Arecibo is famed historically for discovering pulsars. Now astronomers want to
take advantage of its high sensitivity to detect changes in the timing of pulses
from these dense, spinning stars.
Such observations could reveal how the stars are rippling the fabric of
space-time around them by emitting gravitational waves as they rotate –
providing a test of Einstein's theory of general relativity, which predicts the
phenomenon. "That kind of science is unique to Arecibo," and important to
physics as a whole, says Brown.
The Washington meeting also discussed plans to map the distribution of
intergalactic hydrogen across the sky. Earlier surveys sought to measure the
amount of hydrogen linked to nearby galaxies, but the new survey will look in
areas where no galaxies are present.
About Researchers: Bob Brown
GPO Box 404, Hobart Tasmania 7001
Phone 03 6224 3222 or 1300 133 251
Fax 03 6224 2999
Asteroid hunt
The goal is to see if large amounts of unconsolidated hydrogen gas are
primordial remnants of the Big Bang, or were stripped from galaxies that were
interacting with each other as they evolved. The answer will have a big impact
on astronomers' understanding of
galactic
evolution, Brown says.
Arecibo is also crucial for asteroid researchers, as one of only two planetary
radars in the world. Radar observations are the best way to characterise the
orbits of asteroids that could potentially strike Earth.
Arecibo can observe asteroids at twice the distance of the only other planetary
radar, on NASA's 70-metre Goldstone antenna in California, US, although
Goldstone can observe more of the sky because it is fully steerable.
Related Online Links:
http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/fr_1/fr_1_gal.html
http://www.theregister.co.uk/2007/07/03/galactic_starburst/
http://www.intergalactichydrogen.com/
http://www.h2go.info/about.html
http://www.tricoat.com/goldstone/goldstone_antenna_coatings.htm
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