The study of the circumstellar disks out of which planets form will benefit greatly from the high spatial resolution of GSMT, fitted with high-contrast instrumentation so that the faint disks do not get lost in the glare of their parent stars, and there is complementary coverage of wavelengths with JWST and ALMA. Resonant structures and gaps within a disk that may be caused by gravitational perturbations due to planets will be imaged in optical, infrared, and submillimeter radiation, allowing a complete picture of the structure and composition of these disks to be derived.

Frontiers of Knowledge

The hunt is on to elucidate the nature of dark matter first identified by astronomers more than 70 years ago. If it comprises supersymmetric particles, then there are hopes that they will be seen directly at particle accelerators like the Tevatron and the Large Hadron Collider (LHC). They may also be seen directly at one of the many different types of underground detectors being built. However, it is also possible that they will be identified indirectly by the gamma rays that are produced through annihilation or decay processes in distant dark matter concentrations. A new ACTA would be roughly 10 times more sensitive than existing facilities and able to further constrain the nature of dark matter. ACTA could also check that the highest-energy photons do, indeed, travel at the speed of light.

Another potential contribution to fundamental physics will come from microwave background observations using future CMB telescopes combined with probes of structure formation, which can provide an upper limit to the sum of the masses of the three flavors of neutrino with higher sensitivity than can be done with ongoing laboratory experiments. More detailed information may also emerge on the individual particle masses.

A third possible contribution is to nuclear physics. Neutron stars can be thought of as giant atomic nuclei, and understanding how their radii change with the mass is of fundamental importance for nuclear physics and complements what is being learned from collisions of heavy ions. These astronomical measurements are becoming possible using radio and X-ray telescopes.

Turning to chemistry, with the advent of ALMA and CCAT in particular, an explosion in the variety of detected interstellar and circumstellar molecules is expected. A better understanding of the chemistry of these molecules will provide new information about stellar evolution and galaxy formation and evolution.


On the basis of the input from the community, the priority science identified by the SFPs, the prioritized conclusions of the PPPs, and the results of the indepen-

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