Hubble Successor Under Way, Will See Even Farther

John Pickrell
for National Geographic News
June 8, 2004

Launched in 1990, the orbiting Hubble Space Telescope has captured the public imagination by beaming back unprecedented images of countless astronomical wonders. Left alone, however, the Hubble's battery and gyroscopes will likely fade by 2007, making the telescope useless.

After much public outcry over the telescope's planned demise, NASA is now considering a space shuttle-based or robotic tune-up mission. Perhaps even more important, the U.S. space agency has something much more impressive up its sleeve: the next major space telescope, already in the early stages of construction.

Hubble vs. The Next Generation

Scheduled for launch in 2011, the James Webb Space Telescope (JWST) could be powerful enough to "see" objects 400 times fainter than those visible with Earth-based telescopes—potentially snagging a peek at objects 15 billion light-years away.

By contrast, the Hubble can see objects 60 times fainter than those visible with Earth-based telescopes.

Objects 15 billion or so light-years away are so distant that light emitted from them shortly after the big bang is only now reaching us. This means that the JWST should be able to see even farther "back in time" than the Hubble can.

To get an idea of how far 15 billion light-years is, consider that light from the sun—93 million miles (150 million kilometers) away—takes just eight minutes to arrive at Earth.

The JWST (named for NASA's second chief administrator) is a joint project of NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA). Though the project is NASA led, its most important imaging instrument is being built in Europe. The consortium is scheduled to launch the telescope from French Guiana in one of the ESA's Ariane 5 rockets.

Astronomers will use the telescope to observe the birth of galaxies, the physics of star and planet formation, and even the early evolution of the universe.

The JWST will be more powerful than the Hubble in a number of ways. Its 21-foot-wide (6.5-meter-wide) main mirror will have ten times the light-collecting power of the Hubble's.

The JWST will also carry three different types of cameras, all tuned to detect infrared light, which is invisible to the human eye. In contrast, the Hubble was equipped to capture mostly visible light and ultraviolet parts of the spectrum.

All objects produce infrared light, or heat radiation. This means that scientists can use infrared cameras to detect cool, faint objects, which emit very little of their light in the visible parts of the spectrum.

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