Mapping the Solar System and the Milky Way
LSST will also keep a close eye on conditions closer to home, tracking objects within our galaxy and solar system, including asteroids and comets that could someday collide with Earth. To find immediate threats, Tyson says, it is necessary to differentiate incoming objects from bodies locked in place in the asteroid belt. “Each faint asteroid must be captured in many separate exposures for computers to distinguish it from numerous other asteroids and then piece together its orbit,” he explains. Right now, planetary scientists are searching for hundreds of potentially threatening asteroids approaching Earth. LSST would allow us to locate many more and determine their trajectories with precision, giving us time to intervene if one is on a deadly course.
With its keen eye for anything that moves, LSST should also reshape our understanding of the solar system as a whole by discovering millions of new objects, mostly in its shadowy outer realms. Astronomers like Michael Brown of Caltech have been pushing current telescopes to the limit trying to locate new bodies in the Kuiper belt (a vast population of small bodies orbiting the sun past Neptune) and beyond. Thought to consist of remnants from the formation of the solar system, the Kuiper belt will be analyzed in greater detail than ever before possible through the LSST’s relentless scrutiny. Discoveries may include planets the size of Mars or larger, but lying much farther from the sun than Pluto.
The LSST will also help reveal the life history of the Milky Way, Ivezic says. “Roughly speaking, our galaxy looks like a pizza pie with an orange in the center—that’s the galactic bulge—and then there is a very tenuous halo around the pie,” he explains. “We don’t know much about most of those stars in the halo, because they are so faint. We can see only halfway to the edge of the galaxy, but the closer you get to the edge, the more information you can gain about how the galaxy was formed. We think it was formed by cannibalizing nearby smaller galaxies.” The idea is that the bigger the Milky Way grows, the more new galaxies it could attract, growing larger still.
The theoretical engine of this growth turns out to be complex: New galaxies get pulled in and stretched around the halo like strings of spaghetti, maintaining the signature of their independent origin; galaxies closer to the central bulge get mixed up with other old structures, losing the hallmarks of their original form. To validate this mechanism as real, astronomers will use the LSST to see more of the halo. “For the first time, we will be able to see the stars all the way to the edge of the Milky Way,” Ivezic says. “Not only will we see them as points of light, but we will also be able to measure their motion across the sky. From their colors, we’ll be able to estimate their chemical composition. Putting all this together will tell us a lot about the formation and evolution of the Milky Way.”
Heaven’s Dream team
Building a machine with such ambitious goals requires a large, dedicated team. Project director Tyson became involved through a long-standing interest in mapping dark matter by measuring the effects of gravitational lensing, the process by which matter bends light. His ambitious research hit a roadblock during the 1990s due to the pernicious effects of local distortions. Frustrated, Tyson realized he needed a totally new type of telescope, one that could take wide-field images of the deepest universe in a matter of seconds. Nothing like that existed at the time.
One day in 1998 Tyson received a call from noted optical designer Roger Angel, director of the Steward Observatory Mirror Lab at the University of Arizona, who had heard about Tyson’s needs. Angel, it so happened, had already worked out the design for a wide-angle telescope that might do the job. The two started talking up the idea among their colleagues, and within a few years the concept of a survey telescope like LSST was firmly implanted in the astronomical community.
Good ideas are a dime a dozen, though, while real telescopes are expensive. Funding for astronomy is far more limited than that available for cancer research, say, and compared with most other fields of science, the number of professional astronomers is astonishingly small (the membership of the American Astronomical Society would just about fit into Radio City Music Hall). Though its estimated cost of $400 million is considerably less than the $2 billion-plus sticker for the Hubble Space Telescope, LSST is an expensive project—quadruple the cost of each of the Keck telescopes.
Yet support for the telescope kept growing. In 2000 about a hundred enthusiastic scientists and engineers convened in Aspen, Colorado, and formed the LSST collaboration. Then, in 2001, the National Academy of Sciences’ “decadal survey” of astronomy—a summary of the field’s primary goals for the next 10 years—listed a survey telescope as a high priority for the field. In 2003 the most interested players formalized a public-private LSST Corporation, able to solicit private donations and grants. The group submitted a proposal to the National Science Foundation, soon garnering a seed grant of $15 million to support preliminary design.
