Past Astronomy Colloquia

Mon, 2018-03-19 15:00 - 16:15
Henry Ngo (Herzberg Institute of Astrophysics)
Discoveries of exoplanetary systems in the last two decades have revealed the diversity of planetary systems in our Galaxy. Due to their large masses and radii, giant planets are often the first planets discovered with each new planet-finding technique. Two giant planet classes on extreme orbits have raised new challenges for planet formation and migration models: the hot Jupiters found on close-in orbits and the directly imaged giant planets detected on wide orbits.
Mon, 2018-03-12 15:00 - 16:15
Tessa Vernstrom (Dunlap Institute, University of Toronto)
This exciting time of big data from new telescopes and surveys provides unprecedented opportunities for discovery. Cosmic magnetism is a vigorous and rapidly developing area. This surge of interest has been driven in large part by the prospect of dramatic new views of polarization and Faraday rotation offered by new wide-field technological developments. The combination of new deep extragalactic radio surveys, statistical methods, and data-mining techniques allow us to probe to new depths and examine questions such as: was there a primordial magnetic field and what was its strength?
Mon, 2018-03-05 15:00 - 16:15
Evan Scannapieco (Arizona State University)
The golden age of galaxies has come and gone. From an initial distribution of weak density perturbations, gravity acted bring forth ever-larger structures, overcoming a range of feedback processes to efficiently form stars and galaxies at an exponentially increasing rate. Then just as quickly as it arose, the epoch of efficient galaxy formation faded away, the cosmic star formation rate declining by 90% to its current day value. I will discuss our efforts to understand the processes that shaped this dramatic evolution.
Mon, 2018-02-26 15:30 - 16:45
Kelsi Singer (SouthWest Research Institute)
In July of 2015 the New Horizons spacecraft flew through the Pluto system, completing humanity's reconnaissance of the classical planets. Pluto turned out to be a world of remarkable geologic diversity, and its terrains display a range of ages, suggesting geologic activity of various forms has persisted for much of Pluto's history. Pluto's atmosphere was found to be more compact, and with lower escape rates, than previously predicted. Hi-phase images looking back at Pluto's atmosphere led to the discovery of numerous haze layers.
Mon, 2018-02-19 15:30 - 16:45
Mon, 2018-02-12 15:30 - 16:45
Mon, 2018-02-05 15:00 - 16:15
Jocelyn Read (California State University Fullerton)
Recent observations of merging neutron stars using gravitational waves, and a coincident gamma-ray burst, recently triggered astronomical observations across the electromagnetic spectrum. These observations are shedding new light on the dynamics of dense matter in neutron-star mergers. The dynamics of the compact binary, and thus its gravitational-wave signature, is primarily determined by the mass and spin of the components. Gravitational-wave observations of compact binaries can therefore measure mass and spin parameters.
Mon, 2018-01-29 15:00 - 16:15
Adrian Price-Whelan (Princeton University)
Conatal and coeval stars are important tracers of kinematics, stellar models, dark matter physics, and star and planet formation processes in the Galaxy: The disruption of these systems is sensitive to the Galactic gravitational field, their spectra can be used to calibrate stellar models at fixed age and chemical abundances, and changes or differences in their surface abundances likely relates to the stability and mass in planetary systems. A strong indicator that a given pair of stars are coeval is that they are co-moving in three dimensions. I'll discuss our group's effort to iden
Mon, 2018-01-22 15:00 - 16:15
Alex Hill (Dominion Radio Astrophysical Observatory, UBC Physics & Astronomy)
The ionization of the warm ionized medium has been a puzzle since its discovery in the 1970s. Observations suggest a power requirement that can only be explained with photoionization by O stars in the Galactic disk. I will discuss the success of models invoking supernova-driven turbulence to allow ionizing photons to travel from massive stars in the Galactic midplane to more than a kpc above the disk as part of the multi-phase interstellar medium. I will present Global Magnetoionic Medium Survey (GMIMS) observations obtained with the John A.
Mon, 2018-01-15 15:00 - 16:15
Rebecca Jensen-Clem (Berkeley)
Our understanding of exoplanet compositions and their implications for planet formation are closely linked to our understanding of the physical processes that govern exoplanet atmospheres. However, the atmospheric models that best fit the observed spectra tend to imply implausibly small radii Such discrepancies may be due to a lack of detail in the models of exoplanet clouds, which generally lack well-motivated cloud grain size distributions, depth variations, and horizontal structures.
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