If you want to learn more about some of the hottest, most violent objects in the universe, you'll have to launch yourself beyond the curtain of Earth's atmosphere and pack telescopes tuned to light frequencies no one has ever looked at before.
That's just what two Maryland astronauts -- Dr. Samuel T. Durrance of Lutherville and Dr. Ronald A. Parise of Silver Spring -- plan to do Thursday aboard the shuttle Endeavour, on their second mission with the Astro ultraviolet observatory.
Dr. Durrance, 51, is the oldest crew member and an astrogeophysicist and research scientist at the Johns Hopkins University. Dr. Parise, 43, is an astronomer and senior scientist with Computer Sciences Corp. in Silver Spring.
Three ultraviolet telescopes aboard Endeavour will give astronomers their best look yet at hundreds of ultraviolet targets -- from the moon to Jupiter's auroras, newborn and dying stars, powerful galaxies and quasars billions of light years from Earth.
Astronomers are still studying data from the first Astro mission in December 1990, said Hopkins physics professor Dr. Arthur F. Davidsen, principal investigator for the Hopkins Ultraviolet Telescope (HUT), one of Astro's three telescopes.
Despite a balky pointing system that cut that mission's observations in half, the effort yielded a bounty of scientific discoveries.
"It's amazing," he said. "We've published 50 papers on Astro 1 results already, just from HUT. There have been probably 100 papers altogether from Astro 1. And there is still information here that someone, a graduate student perhaps, could . . . find discoveries in."
Astro 2, planned for 16 days, would be twice as long a Astro 1, and the longest shuttle flight ever, Dr. Parise said.
Flying with HUT will be the Ultraviolet Imaging Telescope (UIT), developed by the Goddard Space Flight Center in Greenbelt, and the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE), built by the University of Wisconsin at Madison.
HUT's spectrographs will analyze starlight for clues to the physics and chemistry of its sources. The UIT will photograph the targets, looking for structures that are not apparent in visible light. WUPPE (pronounced "whoopie") will study the polarization ultraviolet light for clues to the geometry of the sources and the material the light has traversed.
Targets on the $445 million mission include the youngest and oldest stars in the galaxy.
With stars, Dr. Davidsen said, "middle age is pretty quiet and subdued, and nothing much is changing. So the exciting part we're still trying to figure the details of is the birth of stars and their death throes."
Newborn stars and dying "white dwarf" stars are extremely hot. That makes them glow brightly in the ultraviolet (UV) band of the electromagnetic spectrum, which lies between those of visible light and X-rays. UV light is nearly invisible to telescopes on the ground.
Other UV targets include certain large galaxies with massive "black holes" at their core -- collapsed matter with the mass of up to a billion suns. Their intense gravitation draws in nearby gas, which heats to 100,000 degrees and emits ultraviolet radiation before being swallowed.
The 1,700-pound, 12-foot-long HUT is uniquely designed to reveal the nature of these extra-hot objects because it "sees" in the most energetic bands of UV light. Those frequencies are inaccessible to other observatories, including the Hubble Space Telescope.
"It's like having a radio that can tune in to stations that are off the end of the regular dial," Dr. Davidsen said. Improved optics make HUT three times more sensitive than in 1990.
The Hopkins astronomers' biggest quarry on Astro 2 will be intergalactic helium -- the "ash" left over from the creation of the universe.
"This is the most difficult thing by far we are trying to do," Dr. Davidsen said.
Theory suggests that the space between the galaxies should contain atomic hydrogen and helium -- the two lightest and simplest elements in the universe -- which condensed from cooling subatomic particles just minutes after the Big Bang.
Much of it later condensed into stars and galaxies. But "there ought to be some left over even today, because we can't really imagine the formation of galaxies was 100 percent efficient," Dr. Davidsen said.
"It's very possible there is more matter in intergalactic gas than in all the galaxies we can see," he said. "It's part of the missing mass question" which has long baffled astronomers.
They have estimated the mass of all the bright objects they can see, and found too little to provide the gravitation needed to hold together all those galaxies and clusters of galaxies. Most of what's there must be too dark to see. But what is it?
If they can find and calculate the amount of invisible hydrogen and helium, then they'll have an idea of how much matter is still missing. That material might consist of a variety of exotic subatomic particles.