Don't touch that dial

POSTED 10 JULY 1997

it's not a walkman

As an astronomer in the thriller Contact, Jodie Foster listens to the universe with giant radio telescopes. She's searching for extraterrestrial intelligence -- hoping against hope to hear a police scanner, a summer TV rerun or a cellular modem squawking "We're here!"

We're pleased that Hollywood -- the last word on terrestrial intelligence -- is interested in radio telescopes. With their giant antennas vacuuming signals from millions of light years away, these outsize dishes are dynamite radio receivers.

But most radio telescopes are not listening for mysterious radio signals from extraterrestrials -- or Howard Stern, either. Instead, they are making images of cosmic cataclysms near the center of galaxies. Unlike visible light, radio waves can pass right through dust and gas that usually hide galactic centers.

Thus radio telescopes can take pictures of some bizarre goings-on: black holes, active galactic centers, and gamma ray bursters.

Because radio waves are long, you need a big antenna to make detailed pictures from them. Until recently, the largest radio telescope was the Very Long Baseline Array. The VLBA took data from 10 telescopes stretched from Hawaii to the Virgin Islands, and was, in effect, a 5,000-mile-wide instrument.

In February, that mammoth spyglass was expanded to about 17,000 miles across with the launching of HALCA, a Japanese satellite carrying a small radio antenna. As with the VLBA itself, data from the dishes are assembled at one location (with a technique called "interferometry") and processed into images.

How can radio waves make images? Because, like visible light, they are electromagnetic waves. Although our eyes can't see them, radio waves can be computer-manipulated into images.

The satellite has brought a phenomenal increase in resolving power. "The amount of fine detail seen in an object depends on the size of the radio telescope," says Bob Dickman, the National Science Foundation's program manager for radio astronomy. Radio-wave interferometry, he adds, "is achieving the highest resolution ever attained in any sort of astronomy."

Still not impressed? Then consider this: images from the VLBA-satellite combination are expected to be about 100 times as detailed as visual-light images from the Hubble Space Telescope.

LEFT: There's little detail in this VLBA image of a quasar, just hints of action at the top and left.
RIGHT: The image from VLBA and the satellite shows the quasar's mass at lower right and a jet of particles at the top left. So this quasar is one of those energetic oddities that spew huge jets of matter.
Images by National Radio Astronomy Observatory, Socorro, N.M.

What does this improvement mean in visual terms? We were hoping you'd ask, so we rounded up two images of a quasar 6.5 billion light years distant. Quasars are enormously bright, distant and ancient light sources. Nobody knows exactly why they're so powerful. This quasar is seen as it appeared when the universe was about half its present age.

Greater resolution, Dickman emphasizes, is vital to astronomy because it shows more details, and "details are clues to origins. We have been looking at galaxy cores and quasars for a long time but we don't fully understand the processes. The key to what is happening is the core, near the central engine." That's because the "engine" -- whether it's a black hole or some equally bizarre object -- drives the entire galaxy.

And as radio astronomers peer through the gas and dust toward the weirdo energy sources powering many galaxies, more surprises are about the only certainty.

PS Jodie: Did you know The Why Files already covered the search for unearthly brains?

-- David Tenenbaum


	RELATED WHY FILES: Orbital advertising Lost and spaced? Discovery of a planet Are you talkin' to me? Jodie Foster in the movie "Contact". ©1997, Warner Bros.		POSTED 10 JULY 1997 Call her the glamour nerd: As an astronomer in the thriller Contact, Jodie Foster listens to the universe with giant radio telescopes. She's searching for extraterrestrial intelligence -- hoping against hope to hear a police scanner, a summer TV rerun or a cellular modem squawking "We're here!" We're pleased that Hollywood -- the last word on terrestrial intelligence -- is interested in radio telescopes. With their giant antennas vacuuming signals from millions of light years away, these outsize dishes are dynamite radio receivers. But most radio telescopes are not listening for mysterious radio signals from extraterrestrials -- or Howard Stern, either. Instead, they are making images of cosmic cataclysms near the center of galaxies. Unlike visible light, radio waves can pass right through dust and gas that usually hide galactic centers. Thus radio telescopes can take pictures of some bizarre goings-on: black holes, active galactic centers, and gamma ray bursters. Bigger is better Because radio waves are long, you need a big antenna to make detailed pictures from them. Until recently, the largest radio telescope was the Very Long Baseline Array. The VLBA took data from 10 telescopes stretched from Hawaii to the Virgin Islands, and was, in effect, a 5,000-mile-wide instrument. In February, that mammoth spyglass was expanded to about 17,000 miles across with the launching of HALCA, a Japanese satellite carrying a small radio antenna. As with the VLBA itself, data from the dishes are assembled at one location (with a technique called "interferometry") and processed into images. How can radio waves make images? Because, like visible light, they are electromagnetic waves. Although our eyes can't see them, radio waves can be computer-manipulated into images. The satellite has brought a phenomenal increase in resolving power. "The amount of fine detail seen in an object depends on the size of the radio telescope," says Bob Dickman, the National Science Foundation's program manager for radio astronomy. Radio-wave interferometry, he adds, "is achieving the highest resolution ever attained in any sort of astronomy." Still not impressed? Then consider this: images from the VLBA-satellite combination are expected to be about 100 times as detailed as visual-light images from the Hubble Space Telescope. LEFT: There's little detail in this VLBA image of a quasar, just hints of action at the top and left. RIGHT: The image from VLBA and the satellite shows the quasar's mass at lower right and a jet of particles at the top left. So this quasar is one of those energetic oddities that spew huge jets of matter. Images by National Radio Astronomy Observatory, Socorro, N.M. Pictures never lie What does this improvement mean in visual terms? We were hoping you'd ask, so we rounded up two images of a quasar 6.5 billion light years distant. Quasars are enormously bright, distant and ancient light sources. Nobody knows exactly why they're so powerful. This quasar is seen as it appeared when the universe was about half its present age. Greater resolution, Dickman emphasizes, is vital to astronomy because it shows more details, and "details are clues to origins. We have been looking at galaxy cores and quasars for a long time but we don't fully understand the processes. The key to what is happening is the core, near the central engine." That's because the "engine" -- whether it's a black hole or some equally bizarre object -- drives the entire galaxy. And as radio astronomers peer through the gas and dust toward the weirdo energy sources powering many galaxies, more surprises are about the only certainty. PS Jodie: Did you know The Why Files already covered the search for unearthly brains? -- David Tenenbaum

			Credits \| Feedback \| Search ©1997, University of Wisconsin, Board of Regents.