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Sunday, November 25, 2007

space telescopes of tomorrow

What space telescopes of tomorrow will see
Webb Space Telescope to launch in 2013.
Giant-sized telescopes such as Hubble, Spitzer and Chandra offer unprecedented views of the cosmos, but astronomers are eager to put more powerful tools into orbit around the Earth.

Without the extra help, said Rachel Somerville, an astronomer at the Max Planck Institute for Astronomy in Germany, it may be impossible to resolve some of the universe's greatest mysteries.

"We need better observations to make our models better," Somerville said, noting her search to understand galaxy formation and mysterious quasars. "... If you just put theorists in a room for the next 15 years with the biggest supercomputer you can find, it will never happen."

NASA expects the James Webb Space Telescope to launch in 2013, and many scientists are already pondering their future observations of tiny extrasolar planets, elusive black holes and distant galactic arms.

Somerville and other astronomers laid bare their sky-watching hopes — including telescopes beyond JWST — at the recent Astrophysics 2020 conference, sponsored by Johns Hopkins University and held at the Space Telescope Science Institute in Baltimore.

Galactic details
JWST will boast a segmented mirror nearly 21 feet (6.4 meters) in diameter, which has seven times the light-collecting area of Hubble. Somerville thinks the sensitive infrared observatory will be crucial for understanding galaxy formation.

If you don't have a high enough resolution, galaxies you're trying to observe are going look like fuzzy blobs," Somerville said. "Seeing the star-filled arms of galaxies in detail, for example, can tell us how some galaxies evolved."

And the higher the resolution, the further a telescope can see back in time, as light can take millions or billions of years to reach Earth.

While Somerville said NASA's next "great observatory" will deliver unprecedented views of galactic arms, she thinks the telescope could use some help to speed along other cosmic discoveries.

Helper telescopes
"JWST has a big mirror and is very sensitive, but it has a postage-stamp sized camera sensor. You can see very, very deep into the universe, but you can only see this much at a time," she told, drawing the sensor size in the air with her hands.

"That takes a long time. If you have a smaller-diameter telescope with a lot of sensors, you can see much more of the sky at one time."

She explained that while such "wide-field" telescopes would not be as sensitive as JWST, such high-sensitivity telescopes could step in to observe interesting areas in greater detail. "It narrows your playing field and, ultimately, saves you a lot of time," Somerville said.

Saving that time should help astronomers find objects of interest faster and rapidly expand scientific knowledge.

Beyond JWST
Somerville, however, isn't the only one with big ideas. Wes Traub, an astronomer and project scientist for several proposed planet-finding NASA missions, would like to see extrasolar planets in greater detail than ever before.

Traub and his colleagues envision blocking out the blinding light of distant stars with giant occulters, or "solar shades," to observe planets around stars with future space telescopes.

"There are many, many planets to be found," Traub said. If the solar shade idea takes off, he explained, astronomers could block the intense glare of a planet's star and precisely measure light reflecting off the planet. In effect, astronomers could look for life-nurturing compounds such as water, methane and oxygen on the planet.

"If we can image a planet with just one pixel on a detector ... we could characterize its surface and search for life," he said. If NASA approves such a mission in the next decade, JWST may be the first telescope to take such measurements.

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