Telescopes to Gauge ‘Big Bang’ : Space: An unmanned rocket is fired aloft so NASA can measure radiation unleashed with the creation of the universe. Five orbiting observatories may help physicists explain the forces of nature.
Piercing through the early morning California sky on a tail of flame, the National Aeronautics and Space Administration’s last unmanned, expendable rocket soared into space at 6:34 a.m. Saturday.
The 116-foot-tall Delta rocket carried with it the first of five orbiting astronomical observatories that NASA will launch during the next decade, a $150-million space telescope that is designed to study the afterglow of the creation of the universe.
The 19-foot-long, 5,000-pound Cosmic Background Explorer (COBE), which resembles nothing so much as an outsized badminton shuttlecock, is designed to sweep the night skies from its 559-mile-high circular orbit. It will measure the faint microwave radiation that cosmologists believe is the last remnant of the so-called “Big Bang,” the cataclysmic explosion 15 billion years ago in which all matter was created.
COBE is expected to provide new information about the precise sequence of events during the first milliseconds of the universe’s existence and shed new light on physicists’ efforts to develop a “grand unified theory” that will embrace and explain the four forces of nature. Freed from the interference caused by the Earth’s atmosphere, it will be able to see the universe with a sensitivity never before possible.
The five new space telescopes “are going to provide us with an unprecedented, unbelievable view of the universe,” said NASA’s Larry Caroff, program scientist for the COBE project. “We will see things we haven’t even imagined. . . . This is going to shake up the world of science.”
Saturday’s launch will be followed in March by the orbiting of the Hubble Space Telescope, an optical telescope of unprecedented power that will be carried into space aboard the shuttle Discovery. The shuttle also will launch the Gamma Ray Observatory in June and the Advanced X-Ray Astrophysics Facility in 1997.
The decade of activity will be capped in 1999 when the Space Infrared Telescope Facility will be launched by another unmanned rocket, this one provided by a private company.
The Delta launch “is a milestone,” said Peter Eaton, a NASA rocket official. From now on, NASA will launch only manned shuttles and perhaps an unmanned cargo shuttle that is now on the drawing board. Launches that require an expendable rocket will be handled by the Air Force or private contractors.
COBE, which has been under development for 15 years, was originally scheduled to be launched by the shuttle after shuttle operations began at Vandenberg, the only U.S. site from which satellites can be safely launched into polar orbit.
When shuttle facilities at Vandenberg were mothballed after the 1986 Challenger explosion, the launch was shifted to a Delta rocket. That meant that the satellite had to be redesigned because the unmanned rocket has less cargo capacity than the shuttle.
One consequence of the redesign is that the satellite will carry only about 600 quarts of liquid helium, the super-cold (minus 456 degrees Fahrenheit) fluid that is used to cool the satellite’s sensitive radiation detectors. With that amount, researchers expect COBE to operate for no more than two years, which would allow it to make four complete surveys of the heavens.
COBE will be studying what cosmologist John C. Mather calls “the most important ‘fossil’ available”--the remnants of microwave radiation left over when the universe sprang into existence.
This radiation permeates the cosmos, glowing feebly in the spaces among stars and among galaxies, making up in abundance what it lacks in intensity. “It’s 99% of all the radiant energy in the universe,” said Mather, of NASA’s Goddard Space Flight Center in Greenbelt, Md. The stars, which on a clear night seem to overwhelm the sky, account for a mere 1% of the universe’s total radiance.
Although sophisticated and expensive radio telescopes are necessary to perceive the faint cosmic radiation through the Earth’s atmosphere, television watchers see evidence of the radiation in the static on unused television channels.
The “Big Bang” is perhaps one of the most difficult physics concepts for laymen to accept. Its chief assumption is that 15 billion years ago, all matter in the universe was compressed into an unimaginably dense sphere no larger than a tennis ball.
This ball contained not atoms, not even protons and neutrons, but only the simplest particles from which all others are produced--quarks, leptons, photons, electrons, neutrinos, axions, photinos, a veritable zoo of exotic species, each accompanied by its antimatter analog.
The ball exploded at a temperature of trillions of degrees, launching all the matter on the expansionary course it continues to follow today.
Within the first millionth of a second after the explosion, quarks and other exotic particles combined to form protons and neutrons. Immediately after they were formed, most of them were annihilated in collisions with antiprotons and antineutrons, releasing their energy in the form of light waves.
It is this light, now spread ineffably thin by the continued expansion of the cosmos, that astrophysicists hope to study with COBE. Its faint glow corresponds to a temperature of just 2.5 degrees above absolute zero (minus 455 degrees Fahrenheit).
During this cosmic annihilation, a small amount of matter survived to form the universe we know today, an amount so small that there are a billion particles of light--photons--for every proton and electron in the universe, Mather said.
That matter condensed to form everything from the largest galaxies to the smallest grains of interstellar dust.
But it is in this condensation where cosmologists run into their primary problem with the “Big Bang” theory.
For stars and other matter to condense from the gaseous cloud formed in the “Big Bang,” there must have been small irregularities in the density of primordial matter as it expanded outward. These irregularities would act like “seeds” around which more matter would condense in exactly the same manner that dust particles, pollen, and other objects in the atmosphere serve as seeds to trigger the condensation of raindrops.
If such irregularities existed, they would have left a permanent imprint on the cosmic background radiation, perturbing light waves in a manner that should still be detectable today.
But researchers have been unable to find any traces of such irregularities. Everywhere they look in the sky, the microwave radiation appears to have exactly the same temperature and density.
Just last week, astrophysicist Anthony C. S. Readhead and his colleagues at Caltech’s Owens Valley Radio Observatory reported in the Astrophysical Journal the results of the most sensitive survey of cosmic radiation yet.
In 174 days of viewing between 1984 and 1987, they studied 24 different sectors of the sky and found, to one part in 60,000, no differences in density.
“These results raise serious questions about our theories of the universe,” Readhead said. In particular, they focus attention on how galaxies were able to condense.
To get around this problem, cosmologists have postulated the existence of large amounts of “dark matter” made up of nearly undetectable material called non-baryonic matter. Cosmologists now argue that 90% to 99% of the universe is composed of this invisible material.
They speculate that variations in the density of dark matter were responsible for the condensation of primordial material. And because the dark matter interacts so weakly with light, existing telescopes are not sensitive enough to detect the slight variations in cosmic background radiation caused by it.
But COBE is expected to change all that.
The idea of dark matter is not as much of an ad hoc construction as it might appear. While cosmologists were contemplating the origins of the universe, physicists have been trying to develop a grand unified theory, the so-called “theory of everything” that ties together the four fundamental forces of nature--gravity, electromagnetism, and the strong and weak forces that bind the atom together--into one neat equation.
As they have worked on their theories, the physicists have independently arrived at the idea that the universe must be filled with non-baryonic matter--an apparent indication that the cosmologists are on the right track.
But researchers want to see traces of the dark matter. Readhead’s detectors are sensitive enough, he said, that they should have shown variations of density attributable to neutrinos. Because he saw no variations, he added, the dark matter must be composed primarily of some other non-baryonic particles, such as the still hypothetical axions and photinos.
The detectors on COBE are three times as sensitive as those used by Readhead. And with that sensitivity, Mather said, they should finally be able to measure the minute density variations caused by these mysterious, elusive particles.
