Weekly Calendar of Events

SEPTEMBER 15 - 19, 2014


12:30 pm: CfA AstroStat Talk. "Big Computing and Computer-Aided Discovery in Astronomy," Victor Pankratius, MIT/Haystack. Room 706, Science Center.

Abstract: Next-generation astronomy needs to handle rapidly growing data volumes from ground-based and space-based telescope networks. In radio astronomy for instance, the current generation of antenna arrays produces data at Tbits per second, and forthcoming instruments will expand these rates much further. Human scientists are thus becoming increasingly overwhelmed when attempting to opportunistically explore Big Data. As real-world phenomena at various wavelengths are digitized and mapped to data, the scientific discovery process essentially becomes a search process across multidimensional data sets. The extraction of meaningful discoveries from this sea of data therefore requires highly efficient and scalable machine assistance to enhance human contextual understanding. Computer-Aided Discovery uses automation in a new way to match models and observations and support scientists in their search. The NSF-supported computational infrastructure currently being developed at MIT Haystack opens up new possibilities to answer questions such as: What inferences can be drawn from an identified feature? What does a finding mean and how does it fit into the big theoretical picture? Does it contradict or confirm previously established models and findings? How to test hypotheses and ideas effectively? To achieve this, scientists can programmatically express hypothesized scenarios, constraints, and model variations. Using programmable crawlers in a cloud computing environment, this approach helps delegate the automatic exploration of the combinatorial search space of possible explanations in parallel on a variety of data sets.

1:00 pm: Institute for Theory and Computation (ITC) Seminar. Speakers: Will Dawson, Lawrence Livermore National Lab/UC Davis, and Caroline D'Angelo, University of Leiden. Topics: To be announced. Pratt Conference Room.

1:30 pm: Seamless Astronomy Colloquium. "Hackable User Interfaces and the Future of Data Analysis in Astronomy," Chris Beaumont, CfA. Phillips Auditorium.

Abstract: The tools we use to investigate data affect the way that we do science -- we are constantly (if subtly) drawn towards questions that are easily answered by our analytical and software tools, and comparatively discouraged from research directions that are less-well matched to these tools. A crucial skill that most scientists learn early in their careers is how to identify the most fruitful scientific questions, given the current state of analysis techniques. However, some of us are drawn to to the problem from the other side -- how might we build new tools to answer different classes of questions, and how would this shape scientific research? This talk will explore that question, by sketching some general limitations to our current tools. In particular, we currently live with a strong dichotomy between code-driven and interactive workflows. While GUI-based tools offer more fluidity for common tasks, code-driven workflows offer greater expressiveness and reproducibility. These are complementary strengths, but switching between different workflows is extremely cumbersome. Inspired by this, we have been building Glue (http://glueviz.org) as a "hackable user interface" to bridge this gap. Glue lets users easily build interactive, linked-view visualizations to drill down into high-dimensional datasets. At the same time, it is designed to be easily and deeply scriptable, so that users can customize Glue for their particular data needs. I'll demonstrate these features and discuss Glue's design philosophy, to suggest how future tools might better empower researchers. Speaker: Chris Beaumont is a Senior Software Engineer at the Harvard-Smithsonian Center for Astrophysics, where he build tools to visualize and analyze multidimensional datasets. His main focus is currently Glue, which is being supported by NASA and the Space Telescope Science Institute to analyze future data from the James Webb Space Telescope. Prior to this, Chris was a graduate student at the University of Hawaii's Institute for Astronomy, where he received a PhD in 2013.


3:00 pm: Radio and Geoastronomy Division Talk. "On the Compaction and Erosion of Rapidly Growing Icy Planetesimals," Sebastiaan Krijt, Leiden Observatory. Room M-340, 160 Concord Avenue.

Abstract: The direct formation of planetesimals through the coagulation of microscopic dust particles is a difficult process, with fragmentation and radial drift frustrating growth beyond a meter or so in size. Recently, it has been proposed that icy aggregates with a high porosity suffer less from these issues, and might form km-sized planetesimals just beyond the snow line. We combine a Monte Carlo approach with a detailed physical model for the dust porosity, and follow the evolution of micron-sized dust grains into planetesimals, confirming the important role of grain porosity. Since our method allows us to resolve the entire mass distribution, we then study the effect of erosive collisions on the largest bodies and the shape of the mass distribution in general.


11:00 am: Institute for Theory and Computation (ITC) Colloquium. "Gravitational Wave Astrophysics with LIGO," Dr. Daniel Holz, University of Chicago. Pratt Conference Room.

Abstract: Gravitational waves were first predicted by Einstein almost a century ago, and the Laser Interferometer Gravitational Wave Observatory (LIGO) should be finally on the verge of directly detecting these waves. The most likely source for these detectors is the inspiral and merger of a stellar mass binary system, such as a pair of neutron stars and/or black holes, which LIGO will be able to hear from hundreds of megaparsecs away. In addition to being extraordinarily loud in gravitational waves, these coalescences may be associated with short gamma-ray bursts, and thus hold out the promise of multi-messenger astronomy: combining gravitational wave and electromagnetic observations to elucidate the physics and astrophysics of the sources. We present estimates for the event rate of binary systems, showing that LIGO can expect the first detections within months of operation. We examine the sky localization of LIGO sources, and explore some of the results that can be expected from gravitational wave astronomy, including shedding light on the process of black hole formation and precision measurements of the Hubble constant. We also discuss the loudest gravitational wave sources, and the potential to use these for internal calibration as well as for science. The era of gravitational-wave astronomy is rapidly approaching; a revolutionary new probe of our Universe awaits.

4:00 pm: Colloquium. "Photographing the Solar Corona without an Eclipse: The Forgotten Efforts of William Huggins," Barbara Becker, University of California, Irvine. Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: Following the solar eclipse of May 1882, amateur astronomer William Huggins was encouraged by observers' reports to attempt a bold plan for photographing the solar corona without an eclipse. His initial perception of success in this project led him to pursue it for many years with great zeal and conviction. However, these efforts are notably absent from his own retrospective account of his life's work which appeared in 1897. Reliance on this account led his biographers and later historians to exclude his imaginative and influential solar corona work. Building on an examination of Huggins's observatory notebooks and unpublished correspondence, this paper brings to light these long forgotten efforts. His difficulties in achieving his goal, rather than stifling his research efforts, motivated him to improve his research methods and instrumentation. They forced him to hone his rhetorical and technical skills in order to persuade his colleagues of the validity of his observations. And, his struggle to convince others of the validity of his coronal photographs renders visible the ordinarily tacit discussion of how a scientific community achieves consensus on what counts as conclusive evidence.

7:30 pm: Monthly Observatory Night. "What is a Planet?" Prof. Owen Gingerich, Dr. Gareth Williams, and Prof. Dimitar Sasselov, CfA. The lecture will be followed by telescopic observing, weather permitting. No tickets or reservations are necessary; however, seating is to the capacity of the hall. Doors open at 7:00 pm. Phillips Auditorium.

Abstract: In 2006, when the International Astronomical Union voted on the definition of a "planet," confusion resulted. Almost eight years later, many astronomers and the public are still as uncertain about what a planet is as they were back then. Tonight, three different experts in planetary science will present each of their cases as to what a planet is or isn't. And then, the audience gets to vote... is Pluto in or out?


12:30 pm: Radio and Geoastronomy Division Lunch Talk. "Gaps, Warps, Rings and Collisions: How Planets Interact with Debris Disks," Erika Nesvold, UMBC/GSFC. Room M-340, 160 Concord Avenue.

Abstract: Observations of resolved debris disks show a spectacular variety of features and asymmetries, including inner cavities and gaps, inclined secondary disks or warps, and eccentric, sharp-edged rings. Embedded exoplanets could create many of these features via gravitational perturbations, which sculpt the disk directly and by generating planetesimal collisions. We present the Superparticle-Method Algorithm for Collisions in Kuiper belts and debris disks (SMACK), the first code to simultaneously model the dynamical and collisional evolution of planetesimals in three dimensions. We use SMACK to investigate the effects of collisions on the morphology of a disk of planetesimals perturbed by a planet and apply our model to a number of resolved debris disks including Fomalhaut, beta Pictoris, and HR 4796. Including collisions can yield estimates for planet masses 5x smaller than collisionless models.

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


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