Astronomers poised to apply novel way to look for comets beyond Neptune

Lawrence Livermore National Laboratory astronomers are major partners in a scientific collaboration that will conduct an extremely novel search for small, comet-like bodies in the outer solar system using four half-meter telescopes. The work was described today at the winter meeting of the American Astronomical Society.

Rather than look for the light reflected directly by these objects (as is customary astronomy practice), this project will search for those very rare moments when one of these objects passes between the telescopes and a nearby background star. This brief “eclipse” lasts less than a second, but will allow the scientists to study objects that are much too faint to be seen in reflected sunlight, even with the largest telescopes.

This work was presented today by Sun-Kung King, on behalf of the TAOS Project (TAOS: Taiwanese-American Occultation Survey) and by Matthew Lehner of the University of Pennsylvania. King is an astronomer from the Institute of Astronomy and Astrophysics of the Academia Sinica in Taiwan. Lawrence Livermore National Laboratory scientists have played a key role in the design and building of the telescopes and are members of TAOS.

The region probed by TAOS is known as the Kuiper Belt, and sometimes as the Edgeworth-Kuiper Belt, after the two scientists who independently proposed its existence more than 50 years ago. There were only two objects (Pluto and its moon Charon) known in this region until the 1990s, when a flood of exciting discoveries of new bodies was started by David Jewitt (at the

University of Hawaii) and Jane Luu (then at UC Berkeley). Despite hundreds of discoveries later, much more remains unknown.

All theories of this region predict that there are many more small objects than large objects. Conventional telescope searches principally find objects that are larger in diameter than about 100 kilometers. An ambitious program with the Hubble Space Telescope may find objects as small as 10 kilometers in size. The scientists in TAOS believe they will be able to extend this lower limit to about 3 kilometers. It is believed there are billions of objects this small in the outer solar system.

“The TAOS survey will provide data on remnants of our early solar system and early planet formation,” said Kem Cook, a TAOS astronomer who works at Livermore’s Institute for Geophysics and Planetary Physics. “It will provide us insight into how the solar system evolved. We’ll be looking at the smallest objects than anyone else has seen.”

Current observations and theories can say very little about regions many times farther from the sun than Neptune. TAOS is unique among astronomical surveys in its ability to probe these great distances. TAOS is able to do this because it does not rely on reflected sunlight.
These small objects are thought to be directly related to the new comets that wander into the planetary system. Composed of dust and ice, they begin to evaporate when they come closer to the sun, producing the spectacular and beautiful tails that astronomers believe are the oldest objects in the solar system, which makes them especially interesting.

“The small objects we will detect are much too faint to be seen directly, even by the largest telescopes in the world,” King said. “We will find them silhouetted against the background stars, which will make it possible for us to detect them.”

TAOS will consist of four telescopes (only half a meter in diameter), which will be used to monitor up to 2,000 stars. The telescopes will operate in the central highlands of Taiwan.

The optical performance of the TAOS telescopes proved difficult to achieve in a compact design.

“We depended on LLNL precision engineering, optical design and fabrication capabilities to build these telescopes,” Cook said. “Without that expertise we would not have been able to build the TAOS telescopes.”

The TAOS collaboration is made up of: King, A. Wang, C.Y. Wen, S.Y. Wang, and T. Lee from the Academia Sinica’s Institute of Astronomy and Astrophysics in Taiwan; C. Alcock, R. Dave, J. Giammarco and Lehner from the University of Pennsylvania; Cook, S. Marshall and R. Porrata from the Lawrence Livermore National Laboratory; W.P. Chen and Z.W. Zhang from the National Central University in Taiwan; Y.I. Byun from Yonsei University in South Korea; J. Lissauer from NASA’s Ames Research Center; and I. De Pater, C. Liang and J. Rice from UC Berkeley.

TAOS is funded by the Academia Sinica and the National Central University, which receive support from the Ministry of Education and the National Science Council in Taiwan; by the Korean Research Foundation in South Korea; and by NASA at the University of Pennsylvania and the Lawrence Livermore National Laboratory.

Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy’s National Nuclear Security Administration.