Harvard-Smithsonian Center for Astrophysics|
The CfA Almanac Vol. XIII No. 2, July 2000
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For the third time since it was established in 1992, the Smithsonian Astrophysical Observatory (SAO) has won the Secretary's Award for Excellence in Safety, Large Facility Category.
Kathleen Entler, accompanied by CfA Safety Officer Karen Lawley, accepted the award on behalf of Director Irwin Shapiro and the SAO staff at a ceremony in Washington June 6. The citation read by the Secretary noted that SAO "has a very successful, proactive safety program... designed to respond to problems quickly and effectively, and to coordinate efforts and expend resources necessary to prevent safety hazards from recurring. All SAO staff have an active role in the program--including the Director, Safety Coordinator, Safety Office, three safety committees, central administration, lab supervisors, facility management, and employees..."
The Secretary's Award For Excellence in Safety was created to recognize the Smithsonian Institution museum or facility that best exemplifies the high standards established for the Smithsonian in the areas of safety, fire protection, and environmental management. The award consists of a permanent traveling trophy, a director's plaque, a safety coordinator's plaque and cash prize. Awards are presented in both a large and a small facility category.
According to a Sky and Telescope article written on the 100th anniversary of that historic experiment, "During the 10 years that [William and George Bond] conducted photographic experiments at Harvard, they obtained some 70 daguerreotypes and between 200 and 300 wet collodion plates on the moon, stars, and planets.... Not until dry plates came into use [in the 1880s] was celestial photography actively resumed at Harvard."
Building on the progress that scientists have made in unlocking the secrets of the universe, a new report from the National Research Council of the National Academies maps out the priorities for investment in astronomy research over the next decade. The highest priority is given to the Next Generation Space Telescope, an instrument that will be far more advanced than the Hubble telescope and should dramatically increase our understanding of how the first stars and galaxies formed billions of years ago and how stars and planets form today. The report also cites several other projects that have the greatest promise for providing more knowledge.
Four CfA-based (or originated) initiatives, Constellation-X, VERITAS, EXIST and the South Pole Submillimeter Telescope (SPST) were among those tabbed as vital astronomical programs for the start of the new millennium.
Constellation-X, a proposed successor to the Chandra X-ray Observatory, was named as the premier instrument in the quest to understand black holes. The project would consist of several powerful x-ray telescopes, working in unison while orbiting in space, to simultaneously observe distant objects.
Also cited in the report under the "Moderate Initiatives" category, VERITAS was recognized for its potential to study the very-high-energy, and still poorly understood, gamma rays that permeate space. Proposed to be built at SAO's Whipple Observatory in Amado, AZ, by a consortium of scientific institutions, VERITAS (which stands for "Very Energetic Radiation Imaging Telescope Array System") will have seven, 10-meter-diameter, optical telescopes used as a high-resolution array to detect the faint signatures left by cosmic gamma rays hitting the top of the Earth's atmosphere. SAO's Trevor Weekes, who pioneered this ground-based technique of observing gamma rays, will serve as the principal investigator for the project.
The Energetic X-Ray Imaging Survey Telescope (EXIST), which was also cited among the "Moderate Initiatives," would map the sky in the critically important hard-X-ray band of the spectrum, a region that connects the predominantly thermal (X-ray) and nonthermal (gamma-ray) universe. Designed to be attached to the International Space Station, EXIST has been approved for study as a NASA New Mission Concept, with Josh Grindlay as principal investigator.
The South Pole Submillimeter Telescope (SPST) has its origins in a 10-meter-diameter antenna described by an international consortium including scientists from SAO, the Max-Planck Institute for Radioastronomy, the California Institute of Technology, the University of Arizona, the University of Cologne, Carnegie Mellon University, and the University of Chicago. Although unclear who will actually build and operate the SPST, it is recommended to be installed at the National Science Foundation's Amundsen-Scott South Pole Station and made available to the international community on a proposal basis.
Although the Chandra X-ray Observatory is the source of most of the news from the CfA's High Energy Astrophysics Division, and usually the objects studied are among the oldest and most distant in the Universe, HEAD's Paul Gorenstein and colleagues from both the CfA and the Smithsonian Institution have played key roles in a space project a little closer to the present time and a little nearer to home.
New data from NASA's Near Earth Asteroid Rendezvous (NEAR) mission indicate asteroid Eros may be a primordial relic left over from the solar system's formation. Using the X-ray/Gamma-ray Spectrometer (XGRS) on the NEAR Shoemaker spacecraft, scientists will spend the remainder of the mission collecting data from other parts of Eros to determine if their latest findings are consistent across the approximately 34-kilometer-long asteroid. If they are, studying Eros should help scientists understand how the rocky planets evolved.
The NEAR team, which includes Gorenstein and Misha Petaev of the CfA's Planetary Division, gathered the information after a powerful explosion on the Sun zapped Eros with X rays on May 4. The half-hour solar flare caused elements on Eros' surface to emit X rays and instruments on NEAR Shoemaker analyzed the intensity of X-rays produced by the asteroid at different wavelengths, thus obtaining a fingerprint of the asteroid's chemical composition.
"Analysis of X-rays from an area roughly 6 kilometers across on Eros indicates that it has an elemental composition similar to the most primitive rocks in the solar system, the chondritic meteorites," says Jacob Trombka of NASA's Goddard Space Flight Center.
"Chondrites are the building blocks of terrestrial planets," says Tim McCoy of the Smithsonian Institution's National Museum of Natural History, a participating scientist on the XGRS team. "If more data confirm Eros is primordial, Eros will be a link between the chondrite meteorites found on Earth and the history of the solar system's formation. With Eros, we could be looking at the structure of the solar system during a time no longer recorded on Earth."
Astronomers and geologists believe chondrites formed from the nebula of gas and dust that comprised the nascent solar system. Collisions between these dust particles eventually formed larger bodies, called planetesimals, which then collided under the influence of their mutual gravity to form planets. Asteroids are relics of this earliest period in solar system history. The gravitational tugs exerted on asteroids by Jupiter likely kept a large planet from ever forming in the main asteroid belt. Even today, collisions continue and fragments of asteroids occasionally fall to Earth as meteorites.
The most primitive meteorites, called chondrites, are a homogeneous mixture of heavy and light materials--a sign that the asteroid from which they originated was never subjected to melting. The process of heating and cooling that changes the nature and distribution of these materials is referred to as differentiation. If Eros is undifferentiated, like the chondritic meteorites that fall to Earth, it probably never was exposed to intense heating. In contrast, asteroids that were extensively melted have a layered structure-like that of the Earth-resulting from the separation of materials of different density. Heavy materials, like nickel-iron metal, tend to sink to the center while lighter materials, composed mostly of silicon and oxygen, rise to the surface. If Eros were composed mostly of light materials, it would probably be a fragment from near the surface of a larger body, while an abundance of heavy materials would point to the origin of Eros as the core of a larger, broken-up asteroid.
The latest XGRS data show the surface of Eros does not have an excess of heavy or light materials, and that the relative abundance of elements is similar to that in chondrites. This indicates that the particular region observed during the solar flare on May 4 is undifferentiated and likely primordial.
Interestingly, Gorenstein, who is actively engaged in analyzing the Eros data, points out that the XGRS instrument is more or less a copy of the Apollo X-ray Fluorescence Spectrometer designed by some of the current HEAD staff while they were at American Science and Engineering in the late 60's. Only the packaging has changed, he says.
Also interesting, says Gorenstein, is the nature of the experiment. The analysis and mapping of the asteroid's chemical composition by resolving the outgoing fluorescence X-rays created by the incoming solar X-rays is essentially the same type of experiment--only to be performed upon the Moon-- that Riccardo Giacconi used to justify the 1962 rocket flight that resulted in the discovery of the first cosmic X-ray sources and the X-ray background.
"The Moon experiment was, of course, hopeless," says Gorenstein, "considering the five-minute rocket flight and the distance from the Moon. But the other results gave birth to modern x-ray astronomy."
In a final HEAD connection, Gorenstein notes that the lunar X-ray experiment was repeated successfully nine years later from Apollo 15 and 16, when he served as a co-investigator, and the technique is now being applied with equal success to the study of Eros.
The complete multi-institutional NEAR XGRS team includes members from Goddard Space Flight Center, the University of Arizona, Cornell University, and Max Planck Institute for Chemistry, and participating scientists from the Smithsonian Institution National Museum of Natural History, Harvard-Smithsonian Center for Astrophysics, Los Alamos National Laboratory, University of California at Berkeley, University of California at San Diego, and Computer Sciences Corporation.