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Tuning Up the Arecibo Dish

A new seven-pixel radio ‘camera’ installed on the 300-meter Arecibo radio dish two years ago this April has brought extraordinary new sensitivity to the huge radio telescope. Called the Arecibo L-Band Feed Array (ALFA), the system of detectors is being used to image large areas of sky at a much faster rate than before, while searching for tricky time-variable phenomena like pulsars. The latter are rapidly spinning neutron stars that are the result of supernovae.

Where the Arecibo upgrade impacts interstellar flight studies is in what it may tell us about some of the most crucial subjects in cosmology. Stephen Torchinsky, who is the former ALFA project manager, has this to say:

“ALFA is going to discover probably 1,000 new pulsars that we haven’t seen yet,” said former ALFA project manager Stephen Torchinsky. “The expectation is that we’re going to find some exotic objects. We could use these systems to test the limits of the theory of relativity — and at the most extreme cases, to find gravitational waves.”

ALFA is a a cluster of seven cooled dual-polarization feeds, a fiber-optical transmission system, and digital back-end signal processors that will significantly broaden Arecibo’s capabilities. One key study that it will enable is a survey of extragalactic objects. This includes a search for radio targets in distant hydrogen clouds, with the expectation that Arecibo will detect some 20,000 galaxies at distances up to 750 million light years.

And out of that work we are likely to learn a great deal about dark matter. High on astronomers’ lists is the discovery of dark galaxies, those widely hypothesized objects believed to consist largely of dark matter and hydrogen gas but few — if any — stars. Scientists at Cornell University are creating a computer system to manage the data that may help us understand these elusive structures, which would be invisible to optical telescopes.

The word at Arecibo is that the ALFA changes aren’t entirely for the good, in that ALFA science has become such a hot ticket that individual proposals may have a harder time finding acceptance. But the creation of huge archival databases that will sharpen our knowledge of exotic matter and help us probe fundamental theories of the universe seems a tradeoff worth making.