Hubble Team Off for Sights Unseen
Why mess with success?
It’s been three years since astronauts turned the crippled Hubble Space Telescope into the most powerful astronomical instrument ever--a telescope that has dazzled astronomers by detecting the faintest galaxies ever seen, chronicling a comet’s collision with Jupiter and revealing Pluto’s surface.
This is what the astronauts will be fiddling with when they return to Hubble this week. “We’d hate to have anything go wrong,” said Steve Maran, an astronomer at NASA’s Goddard Space Flight Center in Greenbelt, Md.
So why take the risk? Because a refurbished Hubble could open our eyes to the universe in new and astonishing ways.
By replacing two of the telescope’s four instruments, astronauts will change Hubble’s character as an astronomical observatory, turning a telescope designed to detect and characterize extremely faint points of light into one better able to make detailed images and analyses of complex structures.
So in addition to being able to make out the faintest of stars, Hubble will be able to find order in some pretty messy parts of the universe. The telescope will be better than ever for peering into the hearts of galaxies, probing the dense dust clouds where young stars are born and studying the debris left by massive stellar explosions.
“It’s going to give a whole new set of abilities to the telescope,” said Robert Kirshner, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “What you’ll see as a result of this is there’s a whole different kind of science coming out.”
The main goal of the current Hubble mission is to swap two instruments already in the telescope for state-of-the-art replacements. This being NASA, all four gizmos have ponderous names that reduce to undecipherable acronyms.
STIS, the space telescope imaging spectrograph, is basically the telescope’s color vision. It can look at a distant planet or gas cloud and generate a detailed analysis of its hue, giving astronomers a remarkable number of clues about what chemical elements are present in the object, how fast it’s moving and how far away it is.
STIS is an improvement on the instruments it will replace, the Goddard high-resolution spectrograph (GHRS) and the faint object spectrograph (FOS). Those instruments could only analyze the color of one point at a time. But STIS can analyze the colors along a stripe, making it a faster and more versatile instrument for looking at objects such as supernova remnants, the expanding balls of debris left behind after a star’s violent demise.
“We’d like to understand how the stars blow up in some detail,” Kirshner said. “This is the kind of instrument that’s going to let you do that.”
The other new instrument, NICMOS, will expand the colors that Hubble can detect into the infrared wavelength, just beyond the red end of the visible light spectrum. That wavelength is well suited to seeing the most distant astronomical objects, as well as newborn stars and other things that tend to be hidden in dusty clouds.
“When stars are formed, or new planets are formed, or even when new galaxies are formed, they’re usually surrounded by wombs of dust,” said Rodger Thompson, an astronomer at the University of Arizona at Tucson.
The old Hubble couldn’t see through dust. But infrared light goes through dust the way X-rays go through flesh, so the new-and-improved Hubble will be able to study regions like the Eagle nebula, where stars are forming amid giant clouds that look like columns of sooty smoke.
NICMOS will also be good at looking deep into the universe, making Hubble even more sensitive to objects that existed during the universe’s infancy. In the last year or so, astronomers using mostly ground-based telescopes have detected hundreds of galaxies from that era. The galaxies are so far away that their light has taken most of the universe’s history to reach Earth, so they appear as they were billions of years ago, when the universe was less than half its current age.
When viewed through earthbound telescopes, those galaxies don’t look like much. But astronomers expect Hubble’s new NICMOS instrument--a.k.a. the near-infrared camera and multi-object spectrometer--to reveal those galaxies in some detail.
“We have this impression that the fainter and more distant galaxies are kind of peculiar looking, that many of them do not fall into the nice neat categories of spirals and ellipticals that we see today,” said Mark Dickinson, an astronomer at the Space Telescope Science Institute in Baltimore.
NICMOS may determine whether that impression is correct. If it’s not, then the neat, spiral- and elliptical-shaped galaxies that are common today may have formed early in the universe’s history and stayed pretty much the same for billions of years. But it’s more likely that the first galaxies were peculiar-shaped and then either were superseded by or developed into the stately galaxies that are common today.
“Maybe we’ll find that when we look in the infrared these things will look fairly normal,” Dickinson said. “In fact, I think that they won’t end up looking normal.”
While Dickinson and his colleagues are peering deep into the universe, black-hole hunters hope to use the new Hubble to bag their quarry right in the intergalactic neighborhood. Last month at a meeting of the American Astronomical Society, researchers reported that they’ve found a black hole in the center of nearly every galaxy where they’ve looked. What’s more, the size of the matter-gobbling void is roughly correlated to the size of the galaxy it’s in.
That suggests that the formation of black holes and their host galaxies may have had something to do with one another, said Douglas Richstone, a professor at the University of Michigan at Ann Arbor. He and his colleagues expect that they’ll be able to investigate that possibility in a Hubble project designed to examine black holes in about 50 relatively nearby galaxies.
“We’re salivating,” Richstone said. “This is going to be fun.”
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Helping the Hubble
Two minor refurbishments during this month’s space mission should improve the Hubble telescope’s ability to make detailed images of faraway galaxies.
(1) Space telescope imaging spectrograph (STIS)
(The Hubble’s color vision--It can detect the color of a distant planet or other body.)
Replaces two spectrographs that can only analyze the color of one point at a time.
(2) Near-infrared camera and multi-object spectrometer (NICMOS)
(Expands viewing distance through infrared wavelengths.)
Replaces a lens that prevents the Hubble from seeing through dusty clouds.
How it works
(3) Light entering telescope bounces off (4) primary and (5) secondary mirrors, then shines on science instruments through a hole in the center of the primary mirror.
