NASA's Wide-field Infrared Survey Explorer, or WISE, is chilled out, sporting a sunshade and getting ready to roll. NASA's newest spacecraft is scheduled to roll to the pad on Friday, Nov. 20, its last stop before launching into space to survey the entire sky in infrared light.
WISE is scheduled to launch no earlier than 14:09 UTC on Dec. 9 from Vandenberg Air Force Base in California. It will circle Earth over the poles, scanning the entire sky one-and-a-half times in nine months. The mission will uncover hidden cosmic objects, including the coolest stars, dark asteroids and the most luminous galaxies.
"The eyes of WISE are a vast improvement over those of past infrared surveys," said Edward "Ned" Wright, the principal investigator for the mission at UCLA. "We will find millions of objects that have never been seen before."
The mission will map the entire sky at four infrared wavelengths with sensitivity hundreds to hundreds of thousands of times greater than its predecessors, cataloging hundreds of millions of objects. The data will serve as navigation charts for other missions, pointing them to the most interesting targets. NASA's Hubble and Spitzer Space Telescopes, the European Space Agency's Herschel Space Observatory, and NASA's upcoming Sofia and James Webb Space Telescope will follow up on WISE finds.
"This is an exciting time for space telescopes," said Jon Morse, NASA's Astrophysics Division director at NASA Headquarters in Washington. "Many of the telescopes will work together, each contributing different pieces to some of the most intriguing puzzles in our universe."
Visible light is just one slice of the universe's electromagnetic rainbow. Infrared light, which humans can't see, has longer wavelengths and is good for seeing objects that are cold, dusty or far away. In our solar system, WISE is expected to find hundreds of thousands of cool asteroids, including hundreds that pass relatively close to Earth's path. WISE's infrared measurements will provide better estimates of asteroid sizes and compositions -- important information for understanding more about potentially hazardous impacts on Earth.
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WISE will uncover many "failed" stars, or brown dwarfs, in infrared light. This diagram shows a brown dwarf in relation to Earth, Jupiter, a low-mass star and the sun. Stars with less mass than the sun are smaller and cooler, and hence much fainter in visible light. Brown dwarfs are the smallest and coolest of stars. They have less than eight percent of the mass of the sun, which is not enough to sustain the fusion reaction that keeps the sun hot. These cool orbs are nearly impossible to see in visible light, but stand out when viewed in infrared. Their diameters are about the same as Jupiter's, but they can have up to 80 times more mass and are thought to have planetary systems of their own.
Credit: NASA/JPL-Caltech/UCB
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WISE in the clean room at Ball Aerospace & Technologies Corp., in Boulder, Colo.
Credit: NASA/JPL-Caltech/Ball
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An engineer loads hydrogen gas into WISE, in a clean room at the Vandenberg Air Force Base, Calif. The hydrogen is cooled and frozen inside a Thermos-like bottle, called the cryostat, which keeps the science instrument cold. This allows WISE to see the infrared glow of space objects without picking up its own heat.
Credit: NASA/JPL-Caltech/Space Dynamics Lab
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The image on the left shows an infrared view of the center of our Milky Way galaxy as seen by the 1983 Infrared Astronomical Satellite (IRAS), which surveyed the whole sky with only 62 pixels. The image on the right shows an infrared view similar to what WISE, will see. Thanks to improvements in infrared detector technology, WISE has four million pixels. The picture on the right was taken by the Midcourse Space Experiment (MSX) in the late 1990s. MSX only imaged a portion of the sky. WISE will map the entire sky with a similar resolution and sensitivity. IRAS was a joint project between the United States, United Kingdom and the Netherlands. MSX was a project of the Ballistic Missile Defense Organization.
Credit: NASA/JPL-Caltech/IRAS/MSX
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Astronomers think there are roughly as many brown dwarfs as regular stars like our sun, but brown dwarfs are often too cool to find using visible light. These tiny orbs are similar to stars but they are cooler and less massive. They lack the mass to fuse atoms at their cores and shine with starlight. Using infrared light, WISE will find many dozens of brown dwarfs within 25 light years of the sun. These two pictures show simulated data before and after the WISE mission (stars are not real). The simulated picture on the left shows known stars (white and yellow) and brown dwarfs (red) in our solar neighborhood. The picture on the right shows additional brown dwarfs WISE is expected to find. One of these newfound brown dwarfs could even be closer to us than our closest known star, Proxima Centauri, which is four light-years away.
Credit: AMNH/Caltech/UCB
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This infrared view of the whole sky highlights the flat plane of our Milky Way galaxy (line across middle of image). WISE will take a similar infrared census of the whole sky, only with much improved resolution and sensitivity. The image was compiled using data from several past missions: the Infrared Astronomical Satellite, a joint project of the United States, United Kingdom and the Netherlands; NASA's Cosmic Background Explorer; and the Two-Micron All-Sky Survey, a NASA, National Science Foundation and University of Massachusetts project.
Credit: NASA/JPL-Caltech/IRAS/2MASS/COBE
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This diagram shows a bird's eye view of our asteroid belt, which lies between the orbits of Mars (red) and Jupiter (purple). WISE will see hundreds of thousands of asteroids with diameters larger than 3 kilometers (1.9 miles). The green dots represent populations of asteroids -- yellow illustrates the populations WISE is expected to see. Populations of near-Earth objects -- comets and asteroids with orbits that pass relatively close to Earth's path around the sun (blue) -- are shown in red. WISE is expected to detect about 1,000 near-Earth asteroids.
Credit: NASA/JPL-Caltech
"With infrared, we can find the dark asteroids other surveys have missed and learn about the whole population. Are they mostly big, small, fluffy or hard?" said Peter Eisenhardt, the WISE project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
WISE also will find the coolest of the "failed" stars, or brown dwarfs. Scientists speculate it is possible that a cool star lurks right under our noses, closer to us than our nearest known star, Proxima Centauri, which is four light-years away. If so, WISE will easily pick up its glow. The mission also will spot dusty nests of stars and swirling planet-forming disks, and may find the most luminous galaxy in the universe.
To sense the infrared glow of stars and galaxies, the WISE spacecraft cannot give off any detectable infrared light of its own. This is accomplished by chilling the telescope and detectors to ultra-cold temperatures. The coldest of WISE's detectors will operate at below 8 Kelvin, or minus 445 degrees Fahrenheit.
"WISE is chilled out," said William Irace, the project manager at JPL. "We've finished freezing the hydrogen that fills two tanks surrounding the science instrument. We're ready to explore the universe in infrared."
