In images from the Sloan Digital Sky Survey, asteroids (circled in green) appear to move over time. Galaxies like NGC4517A, at lower right, don't. *
Photo: Sloan Digital Sky Survey * In 1930, a young astronomer named Clyde Tombaugh found Pluto. He did it with a high tech marvel called a blink comparator; he put two photographs of the same patch of sky taken on different nights into the contraption and flipped back and forth between them. Stars would stay fixed, but objects like comets, asteroids, and planets moved.
Astronomers have since traded photographic plates for massive digital images. But Tombaugh's method — take a picture of the sky, take another one, compare — is still used to detect fast-changing stellar phenomena, like supernovae or asteroids headed toward Earth.
True, imaging the entire sky, and understanding those images, won't be easy. The first telescope that will be able to collect all that data, the Large Synoptic Survey Telescope, won't be finished until 2014. Perched atop Cerro Pachón, a mountain in northern Chile, the LSST will have a 27.5-foot mirror and a field of view 50 times the size of the full moon seen from Earth. Its digital camera will suck down 3.5 gigapixels of imagery every 17 seconds. "At that rate," says Michael Strauss, a Princeton astrophysicist, "the numbers get very big very fast."
The LSST builds on the most ambitious attempt to catalog the heavens so far, the Sloan Digital Sky Survey. Operating from a New Mexico mountaintop, the SDSS has returned about 25 terabytes of data since 1998, most of that in images. It has measured the precise distance to a million galaxies and has discovered about 500,000 quasars. But the Sloan's mirror is just one-tenth the power of the mirror planned for LSST, and its usable field of view just one-seventh the size. Sloan has been a workhorse, but it simply doesn't have the oomph to image the entire night sky, over and over, to look for things that change.
The LSST will cover the sky every three days. And within the petabytes of information it collects may lurk things nobody has even imagined — assuming astronomers can figure out how to teach their computers to look for objects no one has ever seen. It's the first attempt to sort astronomical data on this scale, says Princeton astrophysicist Robert Lupton, who oversaw data processing for the SDSS and is helping design the LSST. But the new images may allow him and his colleagues to watch supernovae explode, find undiscovered comets, and maybe even spot that killer asteroid.
Related The Petabyte Age: Sensors everywhere. Infinite storage. Clouds of processors. Our ability to capture, warehouse, and understand massive amounts of data is changing science, medicine, business, and technology. As our collection of facts and figures grows, so will the opportunity to find answers to fundamental questions. Because in the era of big data, more isn't just more. More is different.
