SCIENCE : SILENT? -UNIVERSE'S- SPITZER

SPITZER Space Telescope spotted extraordinary wonders in its 16 years. But now, this sharp eye on the universe closes.

Last week, NASA's Spitzer space telescope signed off and went silent. But even during its final days of operations, the spacecraft was making one-of-a-kind observation.

The telescope, the size of a family sedan, follows Earth in its orbit around the sun, but trails 158 million miles behind. Lately, it has gazed out with its infrared eyes, taking sensitive measurements of fine cosmic dust that pervades the space between planets in the solar system.

The resulting imagery will enable researchers to better understand our local celestial neighborhood, while informing models of worlds circling other stars and giving insight into the early universe.

Since it was launched on August 25, 2003, Spitzer has provided unique contributions to science. It gave us new views of distant galaxies, newborn stars and nearby exoplanets, as well as of asteroids, comets and other objects in our solar system.

Its infrared cameras have observed the universe in a light imperceptible ti human eye senses, providing otherwise unattainable visions of the sky.

''There is no field of investigation that has not been touched by Spitzer,'' said Daniela Calzetti, an astronomer at the University of Massachusetts, Amherst, who used the telescope to study galactic evolution.

Among the highlights of Spitzer's 16-plus years of discovery
.-  Finding a never-before-seen ring around Saturn;
.-  Determining the the point in cosmic history - 10 billion years ago - when star formation peaked;
.-  And, as part of its most famous finding discovering four of the seven Earth-size planets spinning close around the star known as Trappist-1.

''It's really the end of an era, particularly for me,'' said Heather Knutson, an astrophysicist at the California Institute of Technology who, as a graduate student, used the telescope to map high speed winds on a hot Jupiter-size exoplanet.

''Spitzer has been around for as as long as I've been doing science, I don't remember a time without it.''

The end of a spacecraft mission always provides a a moment for reflection. But Spitzer's conclusion is particularly challenging for infrared astronomers, and many wish it it wasn't yet time to say goodbye.

''From a purely technical point of view, we could continue to operate it,'' said George Helou, also an astronomer at Caltech who was part of NASA review into whether the telescope should continue to operate.

The telescope has been part of NASA's Great Observatories program which includes the well known Hubble Space Telescope, the still-orbiting Chandra X-ray Observatory and the retired Compton Gamma Ray Observatory.

Although Spitzer's components are aging, some scientists have suggested that the observatory is in overall great condition and that it could be kept around for at least . another year.

The World Students Society thanks author Adam Mann.