Computer rendering shows LSST as it should appear when completed in 2014. In a relentless
campaign of 30-second views, the telescope will open a movie-like window on
heavenly bodies that change or move on rapid timescales:
exploding supernovas, hazardous asteroids, and objects in the distant Kuiper belt.
Image courtesy of Todd Mason, Mason Productions INC./LSST Corporation
As evening blankets Cerro Pachon, a remote and arid peak in northern Chile, a giant eye begins its vigil. Two metal shutters at one end of a large building on the summit slide apart like the lids of a waking dragon, revealing a squat, almost spherical structure of steel and glass. Once the shutters are fully open, the electronic eyeball turns skyward and begins to gaze in one direction, but only for 30 seconds. Then, having seen all it needs, it shifts its attention to another patch of sky.
The giant eye is connected to a giant brain, a computer of enormous speed and capacity. Most of the billions of things this eye sees each night are starlike specks or gauzy smudges of light. They may seem vague or inconsequential, but no matter; the brain remembers everything, storing each image for future recall. The brain is thinking, too. All through the night, even while waiting for the next image to arrive, it is comparing what it has just seen with stored images of the same part of the sky to see if anything has changed. It recognizes and records these changes in a vast electronic logbook. The brain notes worlds the size of Pluto, slowly moving through the dim vastness at the edge of the solar system. It notes distant stars winking out momentarily as an orbiting planet blocks the light. Every few minutes it catches the flash of a supernova, a star blowing itself into oblivion in a far-off galaxy. It keeps track of hundreds of thousands of asteroids, including a few that might be on a collision course with Earth. When a particularly interesting or distressing object appears, it sends messages to subscribing astronomers around the world.
While this scenario is futuristic, it is not a work of fiction. A unique collaboration of researchers in academia and the private sector is currently at work to make this giant eye a reality. The team’s project, the Large Synoptic Survey Telescope, or LSST, stands poised to radically alter the way that scientists study the sky. Once the telescope is up and running, around 2014, astronomers will maintain continuous automated surveillance of the heavens, calling up images of the sky with no more effort than the click of a mouse.
In the broadest sense, the goal is to make the greatest-ever digital map of the sky, according to Zeljko Ivezic, the University of Washington astronomer charged with coordinating LSST’s science initiatives. The largest sky survey to date contains about 300 million sources of light. LSST will blow that away, capturing some 10 billion stars, galaxies, and other objects, including some that are one-hundredth the brightness of anything detectable in a survey of the sky today. “This will be the first survey in the history of astronomy that will catalog more objects in the sky than there are people on Earth,” Ivezic says.
Yet making history’s most complete star map is just the beginning. Instead of rendering a static picture like other such maps, LSST will capture the sky in motion, a kind of time-lapse cinematography of the cosmos. “We’ll compare the images we get tonight with all the accumulated images of the same part of the sky on other nights and look for what’s there now that wasn’t there before. This is how we are going to find killer asteroids and a few million other solar system objects,” Ivezic says. “It will be the greatest movie ever made.”
That movie will capture much that changes in the universe, both near the Earth and far away. “What is remarkable is the ability to do a lot of different kinds of science all at once, from investigating the profound unsolved problems of cosmology to probing the evolution of the solar system and the structure of the Milky Way,” says Christopher Stubbs, a Harvard University astronomer who sits on the project’s board. When LSST’s data are made available online, moreover, “everyone, even high schoolers, will be able to use it to make astronomical discoveries,” Stubbs says. “It will mean a revolution in the sociology of doing science.”
LSST’s lofty goals helped attract the attention of one of the legends of the computer industry, engineer Wayne Rosing, who spearheaded development at Apple and Sun Microsystems. He signed on as an LSST partner in 2005. “The LSST pushes the envelope in every respect, and I hope that I can contribute in many ways,” he says. But that is only part of what attracts partnerships with giant corporations like Google. If you already provide access to much of the digital information on planet Earth, it’s just good business to stake a claim to the rest of the universe when you get the chance.
A New Way to Study the Sky
The Large Synoptic Survey Telescope represents a giant leap from the technology of today. Even the renowned Keck Observatory in Hawaii and the orbiting Hubble Space Telescope are basically snapshot cameras, shifting their gaze fitfully around the sky like hyperactive schoolchildren, doling out precious slots of observing time to a long succession of researchers. With such scarcity, astronomers must carefully choose the objects that interest them and propose projects to a “time allocation committee” of their peers, who judge whether the project merits a place on the telescope’s overloaded schedule. The lucky astronomer who passes muster gets to spend a few hours or a few nights pointing the telescope at the designated objects, collecting data for the next year of desk work back home.
As a result of this catch-as-catch-can process, modern telescopes monitor the heavens only incompletely, a bit here and a bit there. The data they collect are distributed through professional journals and preserved on the hard drives of astronomers scattered around the globe. That is fine as far as it goes, but according to Anthony Tyson, a physicist at the University of California at Davis and now the director of the LSST project, it will not be possible to answer the great questions in astronomy and cosmology without a technological breakthrough. For more than a century, engineers have been building bigger and bigger mirrors to collect as much light as possible, but that misses an essential part of the problem. Instead of bigger mirrors, Tyson says, “we need something that goes wider, deeper, and faster than any instrument” we have today. In other words, LSST—a movie camera to the stars.
