Science with the GBT
The Robert C. Byrd Green Bank Telescope is a unique and powerful telescopenan, used by hundreds of visiting scientists each year. Over the next 10-20 years the GBT will contribute to our understanding in areas as diverse as the detection of gravity waves, the formation of stars, galaxies and galaxy clusters, the origin of life, the composition of the planets and their satellites, and the scientific principles that govern the Universe. The telescope’s strength is its flexibility, sensitivity, and sky coverage, allowing for rapid response to new and innovative scientific ideas over three decades of frequency. Its discoveries have a high impact. Although the most important science may come from projects not yet conceived, there are a number of key science areas in which the GBT will excel over the coming decade.
As the premier telescope for pulsar observations worldwide, the GBT is the central instrument of the NANOGrav collaboration’s efforts to detect gravitational radiation. Direct detection of gravitational waves through pulsar timing will open a completely new window on physical processes in the Universe and confirm this fundamental prediction of general relativity. In the coming years the GBT’s sensitivity will also be exploited to make the most sensitive search yet for pulsars around the black hole at the Galactic Center. The periodic signals from any detected pulsars will provide unique probes of the space-time, plasma, and dark matter around the central black hole. Precise timing of radio pulsars by the GBT can be used as well to derive information on the nature of matter at the highest densities, densities that exceed those of atomic nuclei and which cannot be studied in any other fashion. Finally, measurements of atomic and molecular lines at high redshift will continue to place stringent limits on possible temporal variation of fundamental physical constants in early epochs of the Universe.
Stellar Birth and Evolution:
There are many mysteries about star formation. It occurs on the scale of a solar system, but can be triggered by events at the scale of a galaxy, through density waves, tidal encounters, AGN activity, feedback from earlier star formation, and cloud collisions. Advances in our understanding of star formation require observations on all angular scales. The wide-area, high sensitive mapping capability of the GBT is a necessary complement to the detailed high-resolution data provided by ALMA, the EVLA, and other interferometers. The GBT is ideally suited for measuring physical conditions in infrared-dark clouds, the likely progenitors of stellar clusters. With its high sensitivity to extended, low surface brightness emission, the GBT can determine the temperature, density, turbulence, velocity field and magnetic field on scales from tens of pc to the sub-pc level. By measuring the properties of molecular clouds in galaxies, both nearby and distant, the GBT can link large-scale processes with star formation in a necessary complement to local studies. The GBT is also well suited for studies of spinning dust, an important probe of early stellar systems and protoplanetary disks.
Origin of Life:
How did life come to be on Earth? This question is as old as humanity, and the answer will require research across many fields, from biology and chemistry, to physics and astronomy. The GBT has had a leading role in this research, detecting many new organic molecules in space through its ability to measure weak, spatially extended spectral lines over a wide range of frequency. The GBT will become an increasingly important facility as its capabilities are extended into the lower part of the 3mm band, outside the current ALMA coverage and in a region of the spectrum where no large radio telescope operates. Interstellar molecular clouds are host to chemical reactions that occur under conditions of temperature and density not accessible in terrestrial laboratories. Studies of chemistry in clouds give fundamental information on the nature of the chemical bond in gases and on surfaces, over time scales not achievable on Earth. The GBT will measure interstellar chemical processes and their variation throughout the Milky Way, determine the characteristics of pre-biotic chemistry in star-forming regions, and study the components necessary for the formation of life. The observation may shed light on the provocative question of the connection, if any, between organic chemistry in space and life on Earth. With wide-field cameras the GBT will allow rapid imaging of cometary molecules, revealing the content of the building materials of the Solar System.
Galaxies Across Cosmic Time:
The numerous and diverse instruments on the GBT give insight into galaxies at all redshifts. By measuring the properties of hot gas in galaxy clusters via the Sunyaev-Zel'dovich effect to detecting cold dust at high redshift, the GBT probes the evolution gas and dust in the Universe on large-scales across cosmic time. Measurements of nuclear black hole masses, with the GBT as a single instrument and as part of the HSA, contributes to the understanding of the role of mergers in galaxy evolution. Surveying the raw material of star formation in CO, HCN, and HI, reveals the flow of baryons in and around galaxies and the processes by which galaxies evolve. The GBT was used to discover H2O masers in M31 providing targets for astrometry for proper motion studies. It will survey thousands of galaxies for their HI content, rotation, and mass. It can detect HI emission an order of magnitude fainter than any other telescope revealing patterns of interaction and accretion in nearby systems.