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Astrophysics Research This is an exciting time for astrophysics worldwide, and Hopkins astrophysicists are leaders in many of the hottest areas, from cosmology to planets. Prof. Chuck Bennett is Principal Investigator (PI) of the Wilkinson Microwave Anisotropy Probe (WMAP), a NASA satellite launched in 2001 and continuing to return the most detailed maps ever made of the tiny fluctuations in the cosmological microwave background. From a careful study of their character, his team has been able---for the first time ever---to measure accurately the age of the Universe (13.7 Gyr), as well as provide much tighter constraints on many other important cosmological parameters, such as the curvature of the Universe, its mean density, the Hubble constant, etc. A false color image of the intensity of the CMB; typical fluctuation scales Delta T/T are ~10^{-5} How galaxies formed from an initially smooth distribution of matter is another topic of worldwide interest in which Hopkins astrophysicts are actively engaged. Prof. Alex Szalay is a leading theorist of cosmological large-scale structure. He is at the forefront in creating and using large-scale surveys of distant galaxies to learn how and when galaxies were put together, and how the extraordinary features in their distribution (from groups of galaxies to super-clusters) were formed. "Adolescent" galaxies (galaxies only a few Gyr old) have a propensity for dramatic behavior. Just about all good-sized galaxies acquire super-massive black holes at their centers, and when they are young, so much matter is accreted onto these black holes that the power output can easily be 100 times as great as that of all the stars in the host galaxy. Both Prof. Tim Heckman and Prof. Julian Krolik are widely-recognized experts in the study of these strange objects (called "quasars" or "active galactic nuclei"), with Heckman approaching the issue from an observational point of view and Krolik concentrating on theoretical aspects. Using the Chandra X-ray Observatory to obtain some of the deepest images of the X-ray sky ever made, University Professor (and Nobel Laureate) Riccardo Giacconi and Prof. Colin Norman have recently shown that the diffuse X-ray background is in fact made by huge numbers of these active galaxies. Data from the Chandra spacecraft and other X-ray telescopes is also the basis for Principal Research Scientist Tahir Yaqoob's work on supermassive black holes in galactic nuclei. Chandra Deep Field South (false-color); bluer sources have "harder" X-ray spectra NGC 5135 in visible light (ground-based)
NGC 5135 in visible light (HST) NGC 5135 in the UV (HST) NGC 5135 in X-rays (Chandra) Closer to home, we find that the interstellar medium of galaxies is often rich with molecular gas. In some circumstances, naturally-occurring masers can form, producing extremely bright and collimated beams of radiation. Prof. David Neufeld is an expert in all aspects of molecular astrophysics, and uses molecular diagnostics to elucidate the properties of astronomical systems from planets and comets to stellar atmospheres to molecular clouds. Prof. Steven Beckwith, former Director of the Space Telescope Science Institute, has long been a leader in using infrared observations to probe molecular clouds in order to reveal the new stars being created within them. Characterizing diffuse UV emission has long been a goal of Prof. Richard Henry's work. The last decade has seen an explosion of interest in the formation of planetary systems, now that we can detect dozens of extra-Solar planets as well as conduct detailed studies of many of our own Solar System's planets through a variety of space experiments. A number of Hopkins astrophysicists are deeply involved in these efforts, developing new techniques for detecting extra-Solar Planets (Prof. Holland Ford), studying the atmospheres and magnetospheres of other planets in our Solar System (Prof. Warren Moos), and analyzing cometary spectra (Prof. Paul Feldman). Virtually all the matter in the Universe is ionized, and magnetic fields are ubiquitous in ionized gases. Two of the most important unsolved physics problems in astrophysics are the origin and growth of these magnetic fields and what happens when oppositely-directed fieldlines reconnect. These problems are at the center of Prof. Ethan Vishniac's work. Another fundamental problem in the physics of astrophysics is the role of magneto-hydrodynamic processes in accretion (for example, onto black holes) and in the generation of relativistic jets. Krolik, Norman, and Vishniac are all pursuing this problem, using techniques ranging from large-scale general relativistic MHD simulations to analytic models. Magnetic fieldline structure in both the accretion disk surrounding a black hole and its outflow, superimposed on logarithmic color contours of gas density. JHU astrophysicists are also among the world's leading developers of new astronomical tools. We are a member of the Sloan Digital Sky Survey, an effort, now near complete, to image a quarter of the sky and obtain spectra for a million galaxies, 100,000 quasars, and sundry stars and other interesting objects. For that project, Paul Feldman and Alan Uomoto built the spectrograph, while Alex Szalay designed the data archive. Based on that experience, Alex Szalay has become one of two Co-PIs of the National Virtual Observatory, a project that will merge the electronic databases of a large number of astronomical surveys. Lastly, Hopkins has long been one of the principal centers for developing instrumentation for space astronomy. As mentioned before, Chuck Bennett led the effort to build the WMAP satellite. Warren Moos is the PI (and Research Professor Bill Blair is the Deputy PI) for the Far Ultraviolet Spectroscopic Explorer (FUSE), a spacecraft still operating, six years after its launch in summer, 1999. Observers using FUSE can study hot astronomical plasmas in objects all the way from our Solar System to nearby hot stars to supernova remnants to starburst galaxies to quasars. Holland Ford is PI of the Advanced Camera for Surveys (ACS), the principal camera (and at the moment, only functioning instrument) on the Hubble Space Telescope. We expect that our group will continue to be a center for this sort of activity as NASA and other agencies look toward future projects such as the Joint Dark Energy Mission. |
