Gigantic New Scope Probes Far Reaches of Universe
A radio telescope here that is powerful enough to read the lettering on a dime a mile away has been so successful that it is being expanded into a 5,000-mile network that will in effect turn the Earth into a huge antenna.
The present instrument, consisting of 27 dish antennas scattered around an ancient New Mexico lake bed, is by far the most powerful radio telescope in the world, but the expansion that is under way is expected to eclipse the remarkable scientific discoveries that have been made here since the facility went into full operation five years ago.
When completed, the expanded network will give astronomers clear images of electromagnetic activity in the far reaches of the universe.
Those images, according to Peter Napier of the National Radio Astronomy Observatory, will be the astronomical equivalent of “reading a newspaper in San Francisco while you are standing in Washington, D.C.”
Nearly every object in the universe emits radio waves in varying degrees of intensity, and modern radio telescopes can intercept those waves and convert that electromagnetic energy into visual images that look like photographs that are called radiographs or maps.
The Very Large Array, completed in 1980 at a cost of $78 million, uses 27 dishes, each 82 feet in diameter, tied together through computers so that the entire system acts as a single antenna. The dishes are situated along a Y-shaped railroad network and can be moved close together for greater sensitivity to weak radio waves or far apart for greater resolution and sharper images. At their greatest extension, the dishes comprise an antenna 21 miles in diameter.
When it was under construction, astronomers thought they could produce a map every few hours, but advances in computer technology have shortened that time dramatically.
500 Maps a Day
“It turns out you can make 500 maps a day here,” said Richard Perley, a staff scientist. Because of faster computers, “you can now observe for one minute and do as well (as had been expected) in 12 hours.”
The computers catalogue billions of bits of data collected by the antennas and translate the data into visual images. And while recent advances have made the instrument far more efficient than had been anticipated, faster computers that are now on the market could make it even far more effective, Perley said.
The radio telescope, he added, “is now producing at a fraction of its potential rate.”
The National Science Foundation, which funds the telescope, is considering adding a supercomputer that would maximize the instrument’s effectiveness.
Preliminary work has already been financed to add 10 dishes scattered from Hawaii to Puerto Rico and as far north as Washington state. They would work in concert with the array, in effect using the face of the Earth as a huge antenna. That is expected to turn this sleepy little New Mexico community into one of the premier astronomical centers of the world.
The facility here is one of a host of new astronomical instruments helping scientists learn more about the basic forces that drive the universe. And it will be joined in the near future by even more sophisticated tools, including a space telescope that is scheduled to be placed in permanent orbit next year by the space shuttle.
The field of ground-based optical astronomy is also booming because of breakthroughs in mirror technology that will permit the construction of huge telescopes. Caltech broke ground earlier this month for what will be the largest optical telescope in the world, the 400-inch Keck Telescope on top of an extinct volcano in Hawaii.
All of these instruments should pay rich dividends in humanity’s quest for understanding of the origins of life, astronomers believe.
In the meantime, however, the Very Large Array about 50 miles west of here continues turning out images that have astounded many of the hundreds of astronomers who have come here to make the instrument work its magic.
“It’s been a gold mine,” said Mark Morris, a UCLA astronomer who has used the array to achieve some major scientific breakthroughs. “Every time we sneeze we see new details” in areas of the universe that had been hidden from view.
Morris and Farhad Yusef-Zadeh of Columbia University are probing the center of our galaxy, the Milky Way, an area that is uniquely suited for radio astronomy. Optical telescopes cannot see the galactic center because light waves are blocked by galactic dust.
‘Interstellar Smog’
“It’s like trying to look through 30,000 light years of interstellar smog,” Morris said. That dust, caused by giant stars expelling their atmosphere, has left the center of the galaxy “essentially opaque.”
“We can only see about one-tenth of the distance to the center” using optical telescopes, he said.
Radio waves, which are of much longer wavelengths than light waves, are not impeded by stellar dust, and Morris and Yusef-Zadeh have produced a series of images that have yielded the strongest evidence yet that the center of the galaxy has a powerful magnetic field. The dramatic images show a “very energetic” plasma of gases and dust “acting with the magnetic field,” Morris said.
The plasma looks like a fireball with plumes of energy following paths controlled by an unseen force, which Morris believes to be a magnetic field much like the Earth’s “but 100 billion times larger.” The plumes are at least 150 light years long. (A light year is the distance light travels in a year, about 6 trillion miles.)
Search for Black Hole
In one area of the “fireball” is a small spot that Morris and other astronomers believe to be a black hole, an object so dense that its gravity traps even the light generated by its violent activity. That is why no one has ever seen a black hole, and mountains of recognition await the astronomer who proves whether one even exists.
That proof is beyond the scope of even the Very Large Array, but the expansion of the system could yield the kind of resolution that would allow astronomers to produce radio images of the tiny speck that is believed to be the black hole at the center of the Milky Way.
The theory behind the expanded network has already been tested by temporarily pairing the Very Large Array with other radio telescopes around the world, but real progress requires a dedicated facility that would be available for related studies year after year. That has led the National Science Foundation to finance the first legs of the expanded network, called the Very Long Baseline Array.
Under that program, additional antennas will be built in Massachusetts, Iowa, Texas, Arizona, Washington, Puerto Rico, Hawaii, California’s Owens Valley, and New Mexico. The antennas and the Very Large Array will all be focused on the same subjects at precisely the same time, and the data they collect will be recorded and fed into a computer.
Because of the distance between the disks, the end product will include samples of radio waves striking anywhere on the side of the Earth facing the target, and that should yield images of extraordinary clarity.
Precise Measurements
The system, which could be in operation as early as 1990, according to Napier, would also be able to make precise measurements of the distance between the antennas, possibly documenting the speed of continental drift. Napier said the antennas should be able to pinpoint movement of as little as one quarter-inch.
Other practical uses could be to pinpoint the location of a spacecraft, for example.
However, it is the more exotic side of the system that appeals to astronomers like Morris. Radio astronomy could unlock many secrets of the universe by permitting scientists to study areas that are invisible to optical instruments.
“There’s so much new stuff here,” Morris said. The new stuff, he said, is helping scientists understand the dynamic forces of the Milky Way and may eventually reveal the exact nature of the galactic center, a dream harbored by astronomers for many years.
“We need to know what the beast is really like,” Morris said.
