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Foreword by Walter Cronkite  
Introduction - The National Science Foundation at 50: Where Discoveries Begin, by Rita Colwell  
Internet: Changing the Way we Communicate  
Advanced Materials: The Stuff Dreams are Made of  
Education: Lessons about Learning  
Manufacturing: The Forms of Things Unknown  
Arabidopsis: Map-makers of the Plant Kingdom  
Decision Sciences: How the Game is Played  
Visualization: A Way to See the Unseen  
Environment: Taking the Long View  
Astronomy: Exploring the Expanding Universe
Science on the Edge: Arctic and Antarctic Discoveries  
Disaster & Hazard Mitigation  
About the Photographs  
About the NSF  
Chapter Index  
Astronomy: Exploring the Expanding Universe

New Tools, New Discoveries

Much of astronomy involves the search for the barely visible—a category that describes the overwhelming majority of objects in the universe, at least for the time being. One of today's most effective tools for detecting what cannot be seen is Arecibo Observatory in Puerto Rico, the site one of the world's largest and most powerful telescopes for radar and radio astronomy. Operated by Cornell University under a cooperative agreement with NSF, the Arecibo telescope collects extraterrestrial radio waves of almost imperceptible intensity in a 1,000-foot-wide dish. This telescope, used by scientists from around the world, is a dual-purpose instrument. About three-quarters of the time, the telescope detects, receives, amplifies, and records signals produced by distant astronomical objects. The rest of the time, it measures reflected radio signals that were transmitted by its antenna. The signals bounce off objects such as planets, comets, and asteroids, allowing researchers to determine each object's size and motion.

Arecibo Radio Telescope - click for detailsIt was at Arecibo in 1991 that Alexander Wolszczan of Pennsylvania State University discovered the first three planets found outside our solar system. With support from NSF, Wolszczan discovered these planets by timing the radio signals coming from a distant pulsar—a rapidly rotating neutron star—7,000 trillion miles from Earth in the constellation Virgo. He saw small, regular variations in the pulsar's radio signal and interpreted them as a complicated wobble in the pulsar's motion induced by planets orbiting the pulsar. Two of the planets are similar in mass to the Earth, while the mass of the third is about equal to that of our moon. It is unlikely that any of these newly discovered planets support life, because the tiny pulsar around which they orbit constantly bombards them with deadly electromagnetic radiation. Wolszczan's work helps astronomers understand how planets are formed, and his discovery of planets around an object as exotic as a pulsar suggests that planets may be far more common than astronomers had previously thought.

Magnetar Computer Rendering - click for details In 1995, four years after Wolszczan's discovery, two Swiss astronomers announced that they had found a fourth new planet, orbiting a star similar to the Sun. Two American astronomers, Geoffrey Marcy and Paul Butler, confirmed the discovery and, the following year, announced that their NSF-supported work culminated in the discovery of another two planets orbiting sun-like stars. Using an array of advanced technologies and sophisticated analytic techniques, Marcy, Butler, and other astronomers have since discovered four more extrasolar planets. An especially astonishing discovery was made in 1999 by two independent NSF-supported teams of the first multi-planet system-other than our own-orbiting its own star. At least three planets were found by Marcy, Butler, and others to be circling the star Upsilon Andromedae, making it the first solar system ever seen to mimic our own.

By August 2000, the number of extrasolar planets had topped 50, and more such sightings were expected. Based on the discovery of these planets, it seems as if the Milky Way is rife with stars supporting planetary systems.

PDF Version
Voyage to the Center of the Sun
New Tools, New Discoveries
At the Center of the Milky Way
The Origins of the Universe
The Hunt for Dark Matter
Shedding Light on Cosmic Voids
Visualizing the Big Picture
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