Weekly Calendar of Events

OCTOBER 27 - 31, 2014


Noon: Solar, Stellar, and Planetary Sciences Division Seminar. "Leveraging the Power of a Planet Population: Compositions, Mass-Radius Relation, and Host Star Multiplicity of Kepler's Super-Earths," Angie Wolfgang, University of California, Santa Cruz. Pratt Conference Room.

Abstract: The Kepler Mission has found thousands of planetary candidates with radii between 1 and 4 times that of Earth. These planets have no analogues in our Solar System, providing a potentially revolutionary opportunity to assess planet formation and evolution processes for a new planetary population. By coupling theoretical work with sophisticated statistical modeling, we place quantitative constraints on the distribution of physically relevant properties, such as planet compositions, while accurately incorporating the large uncertainties and biases in the Kepler data. We first apply this framework to the composition distribution of Kepler's sub-Neptunes: assuming an internal structure consisting of a rocky core with a hydrogen and helium envelope, we find that these envelopes are most likely to be ~1% of these planets' total mass with an intrinsic scatter of +/- 0.5 dex. Our results do not produce a one-to-one relationship between super-Earth masses and radii. Accordingly, we derive a probability density function that incorporates the intrinsic scatter in planetary masses at a given radius, which provides dynamical studies a more appropriate means to map Kepler radii to masses. Finally, we present first results from our campaign to detect stellar companions to Kepler super-Earth host stars using the laser guide star adaptive optics systems at Lick Observatory, and discuss implications for the orbital evolution of this entirely new class of planets.

Noon: Seamless Astronomy Colloquium. "The Knowledge Infrastructure of Astronomy," Christine Borgman, University of California, Los Angeles. Phillips Auditorium.

Abstract: Big data, data-intensive science, and eScience are contemporary terms to describe research fields that generate, manipulate, and manage large volumes of data. Astronomy was among the first data-intensive fields, hence many other domains wish to learn from the experience of astronomers. Their knowledge infrastructure -- an ecology of people, practices, technologies, institutions, material objects, and relationships -- has accumulated over millennia. Over the last several decades, the practice of astronomy has transitioned from analog to digital technologies. In turn, the broad adoption of common tools, standards, and technologies has enabled astronomers to construct infrastructure components such as the Astrophysics Data System (ADS), the Strasbourg Astronomical Data Center (CDS), the NASA Extragalactic Database (NED), the Virtual Observatory, and data archives for missions such as Chandra, Hubble, and the Sloan Digital Sky Survey. While far from complete or seamless, the knowledge infrastructure for astronomy provides more comprehensive access to scientific publications and data than do most other scientific domains. This talk is drawn from continuing research by the Knowledge Infrastructures project on scholarship in astronomy (Borgman, Sands, Golshan, Darch, & Traweek, in progress) and a forthcoming book (Borgman, 2015).

  • Borgman, C. L. (2015). Big Data, Little Data, No Data: Scholarship in the Networked World. Cambridge MA: MIT Press.
  • Borgman, C. L., Sands, A. E., Golshan, M., Darch, P., & Traweek, S. (in progress). Building blocks of the night sky: Creating a knowledge infrastructure for astronomy.

Speaker: Christine L. Borgman, Professor & Presidential Chair in Information Studies at UCLA, is the author of more than 200 publications in information studies, computer science, and communication.


1:00 pm: Institute for Theory and Computation (ITC) Seminar. Speakers: Ilse Cleeves, University of Michigan, and Andreu Font-Ribera, Lawrence Berkeley National Laboratory. Pratt Conference Room.


3:00 pm: Radio and Geoastronomy Division Talk. "Statistical Analysis of Turbulence in the ISM," Erik Bertram, Universitat Heidelberg. Room M-340, 160 Concord Avenue.

Abstract: Understanding the dynamics of molecular clouds (MCs) is an important task in astrophysics. It is still a great debate which physical processes regulate star formation. Beyond self-gravity, the radiation field, magnetic fields and a complex thermodynamic and chemical evolution, several studies in the past have shown that turbulent motions play an important role for controlling the star formation process. Characterizing interstellar turbulence is therefore very important for understanding star formation. In this talk I will give an overview of different statistical methods commonly used to characterize turbulent flows in MCs and present their theoretical background. In this context, I will also present some new results of a statistical analysis of simulated MCs with time-dependent chemistry and a radiative transfer post-processing and briefly discuss the impact of different physical effects (chemistry, optical depth effects, mean density, ...) on the statistics.

4:30 pm: Special ITAMP Colloquium. "An Alternative to Laser Cooling," Prof. Mark Raizen, University of Texas, Austin. Tea served at 4:00 pm after short student talk. Jefferson 250, Harvard University.

Abstract: We are developing new approaches to the control of atomic motion. The starting point is the supersonic beam, an ultra-bright source of atoms. We use pulsed magnetic fields to stop the beam, and now have realized an adiabatic slower. We further cool the atoms using a one-way wall, a direct realization of the historic thought experiment of Maxwell's Demon, proposed by James Clerk Maxwell in 1871. We do not rely anywhere on the momentum of the photon but rather the photon entropy. This toolbox of new methods is an alternative to laser cooling, with much better predicted performance in terms of generality, flux of ultra-cold atoms, and phase-space density. I will discuss the application of these methods to basic science, nanoscale materials, and medicine.


11:00 am: Institute for Theory and Computation (ITC) Colloquium. "Clustered Star Formation and Stellar Feedback," Prof. Chris Matzner, University of Toronto. Pratt Conference Room.

Abstract: I will discuss the creation and implications of star clusters. Star formation is usually a collective process, with many stars forming in close proximity. Clustering dramatically alters the nature of stellar energy feedback, while the stars form, as well as afterward. Embedded star clusters form in an interplay between stellar feedback and mass accretion from the environment: both effects stir turbulence in the cluster forming gas, while star-driven outflows counteract the accumulation of matter -- possibly ending cluster formation and determining the cluster's fate. Photo-ionization, radiation force, and winds then conspire to clear channels for the effective output of supernova energy into the galactic environment, enhancing the role of supernovae in the galaxy-scale regulation of the star formation rate.

4:00 pm: Colloquium. "Microlensing Takes Off," Prof. Andrew Gould, The Ohio State University. Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: After 50 years of dreaming about it, space-based microlensing observations are now underway. A Spitzer Pilot Program is yielding "microlens parallaxes" for dozens of lenses, opening the prospect of routine mass and distance measurements for the cool planets probed by microlensing as well as determining the Galactic distribution of planets. Analogous observations by Kepler will measure the mass function of free-floating planets. WFIRST microlensing observations will, as advertised, "complete the planetary census" but they will do an immense amount of astrophysics as well. WFIRST parallaxes will be 100 times better than GAIA, with 1M below 0.3 microarcsec and 40M below 4 microarcsec. WFIRST will produce 1M astroseismic measurements, precision orbits of 1000 KBOs beyond the break at r=26.5, and much else. I discuss how microlensing's take off builds on rapid ground-based developments.


12:30 pm: Radio and Geoastronomy Division Lunch Talk. "Mapping the Ionization Environment of Protoplanetary Disks," Ilse Cleeves, University of Michigan. M-340, 160 Concord Avenue.

Abstract: The ionization state of protoplanetary disks fundamentally affects their physical properties (i.e., MRI driven turbulence) and chemical compositions. In the densest gas, near the disk midplane, cosmic rays (CR) and short-lived radionuclide (SLR) decay are thought to be the primary ionizing agents. However, the incident CR flux in the circumstellar environment is unknown and may be highly modulated due to winds and/or magnetic fields. We present models of CR exclusion by winds and SLR ionization including loss factors. We find the molecular ion chemistry is particularly sensitive to the assumed ionization environment and that resolved observations with ALMA will be able to "map out" individual ionizing sources. Finally, we present new SMA data of TW Hya, which, combined with existing ALMA data and detailed modeling provides an interesting new picture of the ionization state of the closest gas-rich planet forming disk.


October 28-29, 9:00 to 5:00 pm: Einstein Postdoctoral Fellows will present highlights of their recent work on high energy astrophysics, gravity, and cosmology. Dr. Paul Green is organizing the symposium. For more information, contact him at pgreen@cfa.harvard.edu or at 617-495-7057. Light refreshments will be available. The detailed program and list of speakers can be found at: http://cxc.harvard.edu/fellows/program_2014.html. Phillips Auditorium.

The Calendar is prepared by the Web Services Group. Entries may be submitted via email to weekly_cal@cfa.


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