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|Thu, Apr 02|
University of Washington/NASA Astrobiology institute
"The Virtual Planetary Laboratory and the Search for Life Beyond the Solar System"
In the coming decades, the search for life outside our Solar System will be undertaken using astronomical observations of extrasolar terrestrial planets. The NASA Astrobiology Institute's Virtual Planetary Laboratory teamuses an interdisciplinary suite of computer models, coupled with input from observations, field data and laboratory work, to explore the factors that affect planetary habitability and to identify key signs of habitability and life to be sought in exoplanet observations. This talk will highlight VPL results to date, including methods to detect oceans on distant worlds, aspects of planetary habitability for stars orbiting M dwarfs, potential signs of life from alternative biospheres, the generation of false positives for life in planetary atmospheres, and future prospects for the characterization of potentially habitable exoplanets.
|Thu, Apr 09|
University of Washington
"Fifty Years of UW Astronomy: 1965-2015"
In 1965 George Wallerstein and Paul Hodge joined Theodor Jacobson to formthe University of Washington Department of Astronomy. Since that time thedepartment has developed vibrant graduate and undergraduate programs, participated in many collaborations to build facilities and tocarry out multi-wavelength and multi-disciplinary astronomical research programs, gained considerable national and international recognition and developed strong outreach programs. Needless to say, there has been a lot of fun (and a few mishaps) to be had along the way. This presentation will review some highlights of UW Astronomy's past and present.
|Thu, Apr 16|
"Let's Figure Out What Dark Matter Is"
I will discuss efforts to use astronomical observations to understand the nature of dark matter. First I will summarize recent results, and present new ones, regarding the structure of dark matter halos on the smallest galactic scales. Then I will explain why cosmological+hydrodynamical simulations can help to resolve long-standing controversies in this field (disclaimer: I do not know how to run cosmological+hydrodynamical simulations). Finally, I will show how observations of the nearest dwarf galaxies convey information about dark matter's particle interactions -- and perhaps even a detection.
|Thu, Apr 23|
The discovery of an inhabited exoplanet is a primary goal of modern astronomy. Identifying habitable planets begins with locating the planet's orbit relative to its star's "habitable zone." However, thehabitable zone is only a zeroeth order approximation for planetary habitability, i.e rocky worlds with liquid water. Many phenomena impact the stability and longevity of surface water, including processes that are negligible on Earth. Planets in the habitable zones of M dwarfs are subjected to tidal forces, which in some cases can produce tidal heating strong enough to preclude life. Planets in mean motion resonances, in which two orbital periods are close to a ratio of small integers, can lead to wild eccentricity and inclination swings that can sterilize a planet. Or, for more modest orbital evolution, can induce obliquity fluctuations that suppress ice sheet growth and permit habitability at larger star-planet separations thanfor planets with static obliquities like Earth. Results such as these reveal the need for a broader definition of planetary habitability that includes all relevant factors. I will describe new tools thatenable the fast modeling of habitability in any planetary system, prioritization of exoplanets for biosignature detection, and the engagement of students at all levels.
|Thu, Apr 30|
University of Victoria
"Fomalhaut b as a Dust Cloud: Frequent Collisions within the Fomalhaut Debris Disk"
Fomalhaut hosts a beautiful debris disk ring and a directly imaged planet candidate, Fomalhaut b, which seems to continually defy expectations. Originally thought to be a Jovian-mass planet constraining the ring, its unexpected spectral properties and highly eccentric, possibly ring-crossing orbit have completely ruled out that possibility. In this talk I will discusssome of the many theories to explain the weird properties of Fomalhaut b, including a large circumplanetary ring, a system of irregular satellites, and a recent small body collision. I will expand on the last theory, discussing my recent collisional probability simulations of the Fomalhaut debris disk, based on the structure of our Kuiper belt, which show the catastrophic disruption rate of d~100 km bodies in the high-eccentricity scattering component is several per decade. This model paints a picture of the Fomalhaut system as having recently (with ~10-100 Myr) experienced a dynamical instability within its planetary system, which scattered a massive number of planetesimals onto large, high eccentricity orbits similar to that of Fom b. If Fomalhaut b is indeed a dust cloud produced by such a collision, we should soon see another appear, while Fomalhaut b will expand until it is either resolved or becomes too faint to be seen.
|Thu, May 07|
|Thu, May 14|
|Thu, May 28|
|Thu, Jun 04|