Picturing Space: The Hubble Space Telescope
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TOM BEARDEN: At first glance, the image doesn’t look like much: Smudges of light on a black background. But to astronomers, it was a revelation. This 1995 image, called the “deep field,” is a picture of a tiny piece of the night sky taken by a genuine time machine, the Hubble Space Telescope.
The points of light aren’t merely stars; they’re incredibly distant galaxies, vast collections of billions of stars. Why call Hubble a time machine? Because the light it’s seeing from these galaxies has been traveling toward the Earth for some 10 billion years. So this picture shows the universe not as it is today, but how it looked back then, the earliest image of the universe anyone had ever seen.
Astronomer Steven Beckwith says the deep field is crucial evidence of how the universe grew.
STEVEN BECKWITH: It’s the same as studying a person, as a person evolves from birth to maturity. If you want to understand that evolution, you have to look at the different stages and compare the different stages. The big bang theory predicted it and explained many other observations. But no one had actually seen that happening with the light from stars and galaxies before the Hubble deep field.
TOM BEARDEN: Beckwith is now in the process of traveling back even further. Sometime in February, the Space Telescope Science Institute, which he heads, will release a final image of the so-called “ultra deep field.” Light from that image is so faint and so distant that Hubble will have to orbit the Earth 412 times, an extremely long time exposure to collect enough light to make an image.
TOM BEARDEN: So, over that 400 hours, you’re collecting photons that began their journey billions of years ago –
STEVEN BECKWITH: About 14 billion years ago, a little less than that. The universe, we believe, is 13.7 billion years old, and we hope to look back 13 billion light-years.
TOM BEARDEN: In the decade since its flawed optics were corrected, Hubble has given the world images such as new stars forming from clouds of pre-stellar dust, and old stars dying in pinwheels of glowing gas. Hubble’s controllers are busy 24/7, since there are nine times as many experiments that want to use the telescope as can be accommodated.
But Hubble is closing in on the end of its planned service life. It is supposed to be decommissioned in 2010. Hubble was designed to observe and record both the visible and the ultraviolet ends of the light spectrum.
Scientists and engineers are now building Hubble’s successor, called the James Webb Space Telescope. Webb is designed to view both visible and infrared light, which is the part of the spectrum that best shows the oldest and farthest-away galaxies. As space scientist John Trauger put it to an audience at the Jet Propulsion Laboratory in Pasadena, Calif., scientists hope Webb will be able to see the universe’s first light.
JOHN TRAUGER: It will look at fields like the Hubble deep field, but it will now see things that are hidden in dust.
TOM BEARDEN: Trauger’s lecture drew a more-than-respectable crowd on a chilly and drizzly Thursday night, testimony to the reaction that millions of people have had to the often spectacular images Hubble has produced.
CAB BURGESS: The ones that show the birth of stars really get my interest — just wondering what’s really going on there, you know? Is there the touch of God or something? You know, it seems really kind of mystical.
RANDY HALE: They hit me as an artist. I’ve always … I’ve got them on my computer. I look at them all the time. They’re just amazing to me. They look like they have life in them to me. I mean, you know, gives you hope about the universe out there.
TOM BEARDEN: Webb, which is named after NASA’s second administrator, is supposed to launch around 2011, folded up to fit inside an unmanned European Ariane rocket. It will be sent to a point about a million miles further from the sun than the Earth. Once there, it will automatically unfold a massive, flexible, multilayered sun shield the size of a tennis court. Then the secondary mirror. Then the main light collector, the primary mirror built in 18 individual segments. Engineers at NASA’s optical testing lab are now fine tuning controls for the segmented mirror. The project’s senior scientist says it will be the biggest mirror in space.
JOHN C. MATHER: It’s about 20 feet across, so it’s huge. It’s way, way bigger than the Hubble which is only 2.4 meters across, or about 7 feet. We wanted it to be bigger yet. But when we found out how much work it takes to make those mirrors, we said, OK, we don’t want to wait that long and we don’t have that much money, so we’d rather have one sooner and have it now and working.
TOM BEARDEN: The theory is that after the big bang, the brand-new universe was composed of only light elements like hydrogen; the first stars forged heavier elements in the nuclear fusion of their cores. When they grew old, they often exploded, casting those elements out into space, where they formed new stars, and eventually our sun and planet Earth. Scientists believe the very elements of which human beings are made came from ancient stars.
Alan Dressler at the Carnegie Observatories in Pasadena says Webb should be able to see back to the time when the heavier elements like carbon, nitrogen and oxygen were being formed.
ALAN DRESSLER: We know the universe didn’t start with that material; the stars made it. We want to see how the first generations of stars were born, how they made the materials that would allow planets to be built, and then provided the raw materials for life to start. This program even includes looking at the nearest few hundred stars to the Earth to see if they have Earth-like planets themselves, and whether there’s life on those planets as well.
TOM BEARDEN: But while many scientists look forward to Webb, many others are worried about losing Hubble, particularly those experimenting in the ultraviolet spectrum, which Webb doesn’t see. Others worry that there might be a long gap between the demise of Hubble and the launch of Webb. Webb’s launch date has already slipped twice. Mike Shull at the University of Colorado is worried that such a gap could seriously damage the entire field of study. He’s concerned about the future of students like Catherine Boone, who’s about to launch her first telescope experiment aboard a small rocket.
MICHAEL SHULL: We could live with a year gap, but if it were three or four or five years, that would be a disaster.
TOM BEARDEN: Why?
MICHAEL SHULL: Well, if you stopped doing science for three or four years, just like if you stopped practicing a sport, you know, the field would no longer have the vigor; new students wouldn’t go into it.
TOM BEARDEN: Dressler is sympathetic but pragmatic.
ALAN DRESSLER: I think in order to make those new telescopes a reality, it’s going to be necessary at some point to turn the Hubble Space Telescope off and go on to other things. So it will mean a loss of some capabilities for a while until those capabilities are improved for the future.
TOM BEARDEN: Those who worry about losing Hubble have even more immediate concerns. In the past, Hubble has depended on shuttle launched servicing missions to make fixes and install improved instruments.
The final planned servicing mission was to have occurred next year. It was supposed to install the cosmic origins spectrograph, an instrument designed by Shull’s colleagues to help him to search for dark matter, the mysterious substance now thought to hold the whole universe together.
A distinguished panel of scientists has called for yet another servicing mission to extend Hubble’s life to 2020, but the space shuttle Columbia accident has thrown everyone’s plans into disarray. NASA officials say very clearly that in the future, shuttle flights must be planned to allow the vehicle to reach a safe haven at the international space station, or to be able to make repairs in space. The problem is, shuttles can’t reach Hubble’s orbit and still have enough fuel to reach the station. And astronauts can’t yet repair the shuttle in orbit.
Ed Weiler is NASA’s chief of space science.
TOM BEARDEN: So is talk of an added servicing mission premature?
EDWARD J. WEILER: In my opinion, it’s very premature, because right now my major goal is to make sure we get another servicing mission. Talking about whether we have one five or six or seven or eight years from now is a bit premature.
TOM BEARDEN: Servicing missions are expensive, $600 million to $1 billion, not even counting the cost of launching the shuttle. Supporters of the Webb telescope are worried that efforts to prolong Hubble’s life might siphon off money from Webb and other science programs.
TOM BEARDEN: Is there a potential for a turf war here?
ALAN DRESSLER: It’s not surprising that people who are as passionate about what they do as scientists want to hold onto the tools and the ability to do the things that they love to do, and feel they’re making progress. And it’s also not surprising that they tend to be more passionate about the things they do than perhaps what their other astronomer colleagues are doing. So it does look like a bit of a turf war between different groups.
EDWARD J. WEILER: If the shuttle could fly safely for the next 20 or 30 years, and we had the money to pay for it, you could probably get good science out of Hubble for 20 years. When do you judge that good science isn’t good enough because it’s taking money away from something that might produce great science? That’s an awfully difficult line to draw, and that’s why we have broad community advisory groups, because I don’t want to make that kind of decision.
TOM BEARDEN: The decisions now being made about Hubble, Webb, and all the other instruments now on the drawing boards will greatly affect the direction of astronomy and astrophysics in decades to come. The ironic reality is that for astronomers to have the tools to look at galaxies billions of years in the past, they also have to look closely at decisions made here on Earth in the very near future.