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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.
RECOMMENDED PROGRAM OF ACTIVITIES
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 independent costing and technical evaluation,
the committee developed the ranked program described below for ground-based and spaced-based
astronomy in the United States. In each category, the discussion proceeds with ranked large and ranked
medium priorities followed by unranked smaller priorities. A large space activity is one with total cost
estimated to exceed $1 billion; a medium space activity is one with total cost estimated to lie in the range
$0.3 billion to $1 billion. A large ground-based activity is one with total cost of construction and
acquisition of capital assets estimated to exceed the threshold for the NSF’s MREFC program (currently
$135 million in FY2010 for projects from the Directorate for Mathematical and Physical Sciences); a
medium ground-based activity is an initiative for which the total cost would fit into the Mid-Scale
Innovations Program range, $4 million to $135 million as defined by this committee. The committee has
not ranked the core-sustaining activities described in Chapter 5 except in the sense that it has
recommended funding augmentations to some relative to the current levels of support. The committee’s
priorities have varied degrees of relevance to DOE, NASA, and NSF, as some projects are envisioned as
being supported by more than one agency.
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