Talks & Events
Special Seminars: 2011
Origins of Stars and Planets: 2020 Vision(s)
Despite recent setbacks, the next decade should still see the realization of two revolutionary capabilities in astrophysics: the launch of the James Webb Space Telescope and (hopefully) first light for at least one Extremely Large Telescope (such as the GMT or the E-ELT). Both of these will make fundamental contributions towards understanding the origins of stars (like our Sun) and planetary systems (like our own), and thus our place in the Universe. I will compare and contrast these facilities from the perspective of star and planet formation, with a focus on the direct detection of extra-solar planets as a critical test for theories of planet formation and evolution (based on extrapolation from current work).
The Small Star Opportunity to Find and Characterize Habitable Planets
One of the most exciting aspects of the field of exoplanets is the push towards the detailed study of habitable planets. Although most attention in this area is focused on Sun-like stars and has a time-horizon of decades, low-mass stars offer a real opportunity for the detection and atmospheric characterization of such planets in the near-future. I will describe work to overcome the technical challenges to making these kinds of observations for planetary systems around low-mass stars. I will also present results from two studies that utilize the power of low-mass stars: a planet search sensitive to potentially habitable planets and the first atmospheric characterization of a "super-earth" type planet. I will conclude with a look ahead at how similar observations with future instruments could yield the detection of biologically relevant molecules in the atmosphere of a potentially habitable planet around a low-mass star by the end of the decade.
Within the rapidly evolving field of exoplanets, super-Earths stand out as exceptional objects. They do not exist in our solar system, but they bear a relation to the terrestrial planets and icy satellites and thus constitute a new laboratory to test ideas. Remarkably, a subset of them may be habitable, making them interesting planets to characterize. In addition, the recent detections of the first three transiting low-mass planets mark the beginning of a prosperous field. The first generation of data arriving now is masses and radii, and in this context I will present results, challenges and future venues for inferring the composition and early evolution of these planets. Looking into the future, within the next decade we expect to have measurements of a coarse spectrum, which may provide a window into the understanding of the dynamics of the interior and thermal evolution of these potentially habitable planets.
Seeing Other Solar Systems in the Making: Direct Imaging and Spectroscopy of Planets and Planet-Forming Disks
In this talk, I will describe new results on direct imaging and spectroscopy of young planets and planet-forming disks around other stars that provide a context for the evolution of the solar system's planets. First, I will discuss why direct imaging is both essential for characterizing planets around other stars and will explain the observing and image processing techniques that have proven successful for direct imaging. Second, I will present new science results from directly imaging gas giant planets around nearby, young stars, in particular the multi-planet system HR 8799. My data reveal a newly-detected, 4th planet orbiting at ~15 AU; my analysis shows that the HR 8799 planets have unique atmospheric properties, specifically thicker/denser clouds not found in other substellar objects and not predicted from standard atmosphere models. I will also present new detections of other young planets and images of planet-forming disks showing strong evidence for hitherto unseen planets. Starting next year, the Gemini Planet Imager instrument, with which I'm involved, will spatially resolve numerous planet-forming disks, provide a sensitive probe of the atmospheric evolution of over 100 soon-to-be imaged massive gas giants, and require facilities like Magellan for follow up. Finally, by the end of this decade, the University of Chicago-supported Giant Magellan Telescope will image and probe the atmospheric evolution of even lower-mass planets, potentially including young Earths.
Observing Planet Formation in Nearby Circumstellar Disks
Circumstellar disks are an integral part of the star formation process and the sites where planets are formed. Understanding their evolution is crucial for planet formation theory. Disks evolve through various physical processes, including accretion onto the star, grain growth and dust settling, dynamical interactions, and photoevaporation. In this talk, I will review our current understanding of the evolution of protoplanetary disks and the constraints they provide on planet formation processes. I will present results from our work on the so-called "transition" circumstellar disks, aiming to identify the sites of ongoing giant planet formation (i.e., the ultimate planet formation laboratories!). I will also discuss the prospects for detailed studies of these fascinating objects with the Atacama Large Millimeter Array (ALMA) as well as for the direct detection of forming planets with current and future instrumentation.
Planetary Systems from Kepler
On Feb. 2, the Kepler space mission released its first 4 months of data on all targets, as well as a series of papers on statistical results on transiting exoplanets. Perhaps the biggest surprise is the great abundance of candidate multiple-planet systems; out of 997 targets with a candidate transiting exoplanet, 170 of them hosted multiple candidates. I describe the dynamics (stability, transit timing variations) and architecture (resonances, inclinations) of these new planetary systems. Dynamics allows us to confirm that some of these systems are indeed planetary (Kepler-9, Kepler-11), and continued monitoring of these and other systems (the ultra-compact KOI-500, the coorbital KOI-730) will challenge and refine theories of the formation of planetary systems.
Characterizing Magnetized Turbulence in Molecular Clouds and Galaxies
While Submillimetre polarimetry of dust emission is arguably the most common observational tool to probe magnetic fields in molecular clouds, it has mainly been used to provide a measure of their geometry and their strength through the so-called Chandrasekhar-Fermi technique. The usefulness and accuracy of this technique are however hampered by observational biases, such as the signal integration along the line of sight and across the telescope beam. I will show how it is possible to account and correct for this effect, and significantly improve results obtained with the Chandrasekhar-Fermi equation. I will also discuss how an extension of this analysis can lead to a complete characterization of the magnetized turbulence power spectrum in molecular clouds and Galaxies (using polarization of synchrotron emission). I will present examples showing measurements of the turbulent energy dissipation scale due to ambipolar diffusion,and of the anisotropy of the magnetized turbulent power spectrum
The GMT Integral-Field Spectrograph (GMTIFS): What It Can Do for You!
The GMT Integral-Field Spectrograph (GMTIFS) is one of six potential first-light instruments for the 25m-diameter Giant Magellan Telescope. The Australian National University has completed a Conceptual Design Study for GMTIFS. I will summarize the sciences cases for GMTIFS, and describe the instrument capabilities and design. GMTIFS will be the work-horse adaptive-optics instrument on GMT. It will address a wide range of science from epoch of reionization studies to forming galaxies at high redshifts, to star and planet formation in our Galaxy, and studies of the Solar system. These are largely the science case for Laser-Tomography Adaptive Optics on the telescope. I will describe why you will want to routinely use LTAO with GMTIFS for your science in the 2020s.
Accretion, jets and winds: High-energy emission from young stellar objects
Young stars form by contraction from large molecular clouds, they accrete mass from their environment. In the stage of classical T Tauri stars (CTTS) they are surrounded by an accretion disk, in which planet formation takes place. At this time, there are three possible mechanisms to power X-ray and UV emission: First, a corona similar to main-sequence stars, second, an accretion shock when infalling matter from the disk hits the star and, third, wind and collimated jets.
I will present X-ray and UV observations that tell us about the physical conditions in the emission regions and show that all three mechanisms can be observed, albeit to a different degree in different objects.