1996 TL66, che scattered Kuiper Belt can extend at least as far 

 as — 150 AU. From discovery statistics, CfA scientists and col- 

 leagues elsewhere infer that the scattered Kuiper Belt consists 

 of —10,000 objects like TL66, with a total estimated mass of 

 — 0.5 Ms. Although this mass estimate is uncertain by a fac- 

 tor of several, there is no doubt that the solar system is substan- 

 tially populated to the 200 AU range. The origin of the scattered 

 Kuiper Belt is as yet uncertain, but a plausible hypothesis is 

 that it consists of Uranus-Neptune region planetesimals scat- 

 tered outward by planetary embryos, perhaps as part of the 

 process that formed the Oort Cloud. It may then be possible, 

 for the first time, to use direct observations to constrain the 

 mass of the outer solar nebula and the mass of the Oort 

 Cloud. By analogy with our solar system, dust disks around 

 other stars might be generated by unseen Kuiper Belt objects. 



The Ultraviolet Coronagraph Spectrometer (UVCS) on 

 board the Solar Heliospheric Observatory (SOHO) measured 

 particle velocity distributions in the inner solar corona along 

 lines of sight in polar coronal holes that correspond to unex- 

 pectedly high kinetic temperatures. The observed properties 

 can be understood only in terms of a physical process that 

 hears and/or accelerates heavier ions more than lighter ones 

 and preferendally in directions perpendicular ro the magnetic 

 field. Outflow speeds of coronal material were found ro reach 

 values of about 200 km/s at 2 solar radii from Sun center. 

 Although the velocity distributions in equatorial streamers 

 are not so broad as those found in coronal holes, their means 

 are much higher than expected and they also display anisotro- 

 pics, albeit at greater heights. It appears that the ion-cyclotron 

 process may also be important in those structures. Compari- 

 sons of coordinated UVCS spectroscopy with white-light 

 imagery and radio scintillation measurements show that the 

 slow-speed solar wind flows from the tips of streamers, while 

 the fast solar wind appears to fill the rest of the extended 

 corona. An abundance depletion of heavy ions relative to 

 photospheric values in streamers is consistent with depletions 

 observed in the slow-speed wind. In addition, UVCS measure- 

 ments of line intensities and profiles in coronal mass ejections 

 are providing important diagnostics for detailed study of the 

 physical and dynamical parameters of the ejected plasma. 



Theoretical Astrophysics 



The Theoretical Astrophysics Division engages in a broad 

 range of research covering most topics of interest in astro- 

 physics. One piece of work that caused much excitement was 

 the development of a new method to analyze type la super- 

 nova light curves that gives more accurate relative distances 

 to galaxies than was previously possible. The estimate ob- 

 tained for the Hubble Constant is 63 ± 6 km/s/Mpc. The 

 precise Hubble diagrams provided by this method have also 

 been used to constrain the motion of the local group and, 

 wich sufficient future observations, promise to provide a meas- 

 urement of the cosmic deceleration parameter. 



Theoretical studies of accretion disks show that, for suffi- 

 ciently low accretion rates, inward advection can become 



more imporrant than radiation as the energy transport 

 mechanism, leading to what is called an advection-dominated 

 flow. For an accretion disk around a black hole, this process 

 may allow the energy generated in the flow to be swallowed 

 by the hole before it can radiate away. Advection-dominated 

 flows have been used to provide a natural explanation for the 

 otherwise puzzling low X-ray luminosities from disks around 

 some black hole candidates, for example, during the low 

 states in X-ray transient sources. 



Conservation Analytical Laboratory 



Lambertus van Zelst, Director 



The Conservation Analytical Laboratory (CAL) is the 

 Smithsonian's specialized facility dedicated to research and 

 training in the area of conservation, analysis, and technical 

 study of museum collection and related materials. Conserva- 

 tion and preservation research seeks to increase our under- 

 standing of the mechanisms that affect the preservation of 

 materials in museum collections, in order to formulate im- 

 proved exhibit, storage, and other use conditions, as well as to 

 develop, test, and improve treatment technology. In collections- 

 based research, objects from museum collections and related 

 materials are studied to increase their contextual information 

 value and address questions in archaeology, art history, etc. 

 Several of these research programs are conducted in collabora- 

 tion with other institutions, notably the National Institute 

 for Standards and Technology (NIST) in Gaithersburg and the 

 Carnegie Institution of Washington, where CAL staff can 

 have access to special equipment not available within the 

 Smithsonian Institution. 



Chemical characterization of archeological materials and 

 the raw materials from which they were made serves to iden- 

 tify objects with the source from which the raw material was 

 procured. Thus, one may draw conclusions regarding trade 

 and exchange patterns and political and economical relation- 

 ships. For trace element characterization of ceramics, CAL 

 researchers applied neutron activation analysis at a special 

 facility maintained and operated in collaboration with NIST, 

 in studies involving archaeological ceramics from various 

 Maya and Southwest sites. International recognition of CAL's 

 expertise in this field is reflected in its role in a new coordin- 

 ated research program, sponsored by the International Atomic 

 Energy Agency (IAEA), on Applications of Neutron Activa- 

 tion Analysis in Latin American Archaeological Research. Seven 

 research teams from six Latin American countries partici- 

 pate in this three-year program, with CAL providing 

 coordination in research design, analytical protocols, and 

 standardization. Other CAL researchers used lead isotope 

 analysis to characterize the metal ore sources for traditional 

 Nigerian bronzes. In studies of historic and prehistoric tech- 



6- 



