Originally created 04/11/98

Orbiting telescope peers into the dark zone



A new orbiting telescope that looks at the cosmos with technology akin to night-vision goggles promised to give astronomers their first looks at the most mysterious part of the universe, wrote Jim Wilson in an article in the May issue of Popular Mechanics, the so called dark zone.

This region earns its sinister name because it cannot be viewed using current telescopes. The universe has been expanding since the "big bang" set things in motion about 15 billion years ago. Light from the most distant parts of the universe has taken the longest to reach Earth, so the deeper astronomers peer into space, the older the light is that they see. The light from the most distant objects is a window on the most distant past.

But there is a gap in what researchers can currently view. The Hubble Space Telescope has returned images of galaxies as they formed some 2 billion to 4 billion years after the big bang (theory). Instruments aboard COBE, the Cosmic Background Explorer, have peered back even farther, to within 300,000 years of creation.

"The dark zone is a gap in the history of our universe that holds the secrets of its evolution," says NASA astronomer Peter Stockman. "How did these seeds (seen by COBE) condense into the stars and galaxies observed by Hubble?"

In the most basic chemical sense, we trace our ancestry to this unexplored time. All elements heavier than helium were manufactured in stars. After the big bang, hydrogen and helium condensed into stars. Then thermonuclear reactions converted these light elements into heavier elements, including carbon, oxygen and nitrogen, the building blocks of life. Sorting things out is complicated by the well-known Doppler effect.

"Light from these first stars is shifted by the expansion of the universe into the near- and mid-infarred, hence the ability of Hubble to find them," explains Stockman.

To see the light radiated from the dark zone requires technology comparable to a pair of orbiting night-vision goggles. Yet to be formally named, the proposed instrument's working designation is the "next generation space telescope," or NGST.

Like Hubble, NGST will spend its life in orbit. But this is where the similarities end. While Hubble detects light across a wide range of frequencies -- from ultraviolet down through visible light and partway into near-infarred -- NGST will concentrate on the near- and mid-infarred parts of the electromagnetic spectrum.

Radiation in this region has a wavelength from 1 to 20 microns. Since the human eye is tuned to the 0.35- to 0.8-micron region, the light is invisible. NGST will convert this infared radiation first into electronic data and then into images visible to the human eye.

Thus equipped, NGST will make it possible for astronomers to see the infarred-shifted light coming from near the edge of the universe and also peer through the dust that obscures most of the star-forming regions in nearby galaxies.

"Much of the universe is hidden from our view by dust. Although each dust grain is tiny -- less than the width of a human hair -- it is remarkably effective at scattering and absorbing visible and ultraviolet light," says Stockman.

If all goes well, GNST will launch in 2007. To overlap with the mission, NASA is considering extending Hubble's life to 2010.

What happens when NGST arrives on-orbit is anyone's guess. "We have many different and conflicting predictions of what we'll see when NGST begins sending its images to Earth," Stockman says. "That we don't know the outcome is why it is such a great science."