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News Release 05-015

Arecibo Begins Search for Dark Galaxies

New receiver increases the radio telescope's sensitivity by seven times

ALFA soars

As seen looking up from the big Arecibo dish, ALFA soars toward its new home.
Credit and Larger Version

February 7, 2005

Fitted with a new compound eye, the Arecibo radio telescope in Puerto Rico last week began a multiyear effort to survey all the galaxies in a large swath of sky out to a distance of 800 million light years—a survey that may well uncover the often-theorized, but never-seen, "dark galaxies."

If they do exist, dark galaxies, would be vast clumps of primordial hydrogen and helium gas that have drifted through the universe for 10 billion years or more, but for some reason have never been able to turn that gas into stars. As such, they would account for at least some of the mysterious cosmic "dark matter," which makes itself known only by its gravitational effects on the ordinary, star-rich galaxies. Certainly the dark galaxies would have been missed by previous astronomical surveys, most of which were restricted to optical and infrared light; the cold hydrogen and helium of a dark galaxy would shine only at radio wavelengths—Arecibo's specialty. 

Funded by the National Science Foundation and operated by the  the National Astronomy and Ionosphere Center at Cornell University, the 305-meter-wide Arecibo Observatory telescope is the world's largest and most-sensitive single-dish radio telescope. Last year, its sensitivity was further boosted by the Arecibo L-Band Feed Array (ALFA): essentially a seven-pixel camera that will allow astronomers to collect data about seven times faster than before. The the survey project starting today has thus been dubbed ALFALFA, for Arecibo Legacy Fast Alfa Survey.




Media Contacts
M. Mitchell Waldrop, NSF, (703) 292-8070,
David Brand, Cornell University, (607) 255-3651,

Program Contacts
Richard E. Barvainis, NSF, (703) 292-4891,

Principal Investigators
Riccardo Giovanelli, Cornell University, 607-255-6505,

Related Websites
The NAIC Web site:
The ALFA Web site:
A Cornell press release on ALFA:
Cornell University press release on the survey:

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The ALFA receiver in its new home.
The ALFA receiver (hanging from cable) enters the Gregorian dome high above the Arecibo dish
Credit and Larger Version