Past Astronomy Colloquia

Thu, 2017-08-10 12:30 - 13:45
Professor Donald Kurtz (Jeremiah Horrocks Institute, University of Central Lancashire)
In 1926 in the opening paragraph of his now-classic book, The Internal Constitution of the Stars, Sir Arthur Eddington lamented, “What appliance can pierce through the outer layers of a star and test the conditions within?” While he considered theory to be the proper answer to that question, there is now an observational answer: asteroseismology. We are in a time of a significant advance in our understanding of stellar astrophysics with data from the Kepler Mission. From its rich 4-year data set nearly 5000 exoplanet candidates have been discovered - the majority of all known.
Mon, 2017-04-24 15:30 - 16:45
Renu Malhotra (Lunar and Planetary Lab, University of Arizona)
Several recent studies have appealed to the clustering of the angular orbital elements of very distant, extreme Kuiper Belt Objects (eKBOs) to argue for the existence of a large planet in the distant Solar System. I will review these arguments, and also describe other properties of eKBOs that may support the existence of such an unseen planet. We observe that several eKBOs have orbital periods close to integer ratios with each other. These are not dynamically significant unless the eKBOs are in mean motion resonances (MMRs) with a massive planet.
Mon, 2017-04-03 15:30 - 16:45
Matthew Payne (Harvard-Smithsonian Center for Astrophysics)
I will discuss recent discoveries arising from our detailed search of the Pan-STARRS Outer Solar System survey data. These include the discovery of several hundred Kuiper-Belt and Scattered-Disk Objects, as well as Neptune Trojans and a possible population of Centaurs that appear to occupy a common plane. In addition I will discuss the heliocentric linking methodology that has facilitated these discoveries. I will go on to discuss issues related to the putative "Planet-9", a ~10 Earth-Mass planet hypothesized to lurk unseen in a distant orbit at the edge of the Solar System.
Mon, 2017-03-27 15:30 - 16:45
James Davenport (Western Washington University)
The MOST and Kepler space telescopes have pioneered the detection of extrasolar planets using high precision brightness monitoring of stars. With data spanning months to years for each star, these light curves also provide the best census of stellar phenomena including cool starspots and explosive flares. I will present results from studies of flares on active stars observed with Kepler and MOST, including the recently discovered exoplanet host stars TRAPPIST-1 and Proxima Centauri.
Thu, 2017-03-23 12:30 - 13:45
John Kormendy (University of Texas at Austin)
Dark matter (DM) halos of Sc-Im and dwarf spheroidal (dSph) galaxies satisfy scaling laws: halos in lower-luminosity galaxies have smaller core radii, higher central densities, and smaller velocity dispersions. These results are based on maximum-disk rotation curve decompositions for giant galaxies and Jeans equation analysis for dwarfs. (1) We show that spiral, Im, and Sph galaxies with absolute magnitudes M_V > -18 form a sequence of decreasing baryon-to-DM surface density with decreasing luminosity.
Mon, 2017-03-20 15:30 - 16:45
Jessica Werk (University of Washington)
Mon, 2017-03-13 15:30 - 16:45
Catherine Espaillat (Boston University)
We know that most stars were once surrounded by protoplanetary disks. How these young disks evolve into planetary systems is a fundamental question in astronomy. Observations of T Tauri stars (TTS) may provide insights, particularly a subset of TTS with “transitional disks” that contain holes or gaps in their dust disk. Many researchers have posited that these holes and gaps are the “footprints” of planets given that theoretical simulations predict that a young, forming planet will clear the material around itself, leaving behind a cavity in the disk.
Mon, 2017-03-06 15:30 - 16:45
Sean Couch (Michigan State University)
Core-collapse supernovae are the luminous explosions that herald the death of massive stars. While core-collapse supernovae are observed on a daily basis in nature, the details of the mechanism that reverses stellar collapse and drives these explosions remain unclear. While the most recent high-fidelity simulations show promise at explaining the explosion mechanism, there remains tension between theory and observation. I will discuss the recent developments in the study of the supernova mechanism that could lead to a predictive theory of massive stellar death.
Mon, 2017-02-27 15:30 - 16:45
Scott Chapman (Dalhousie University)
Recent facilities such as the South Pole Telescope (SPT), the Herschel Space Observatory, and the Atacama Large Millimeter Array (ALMA) have opened a window to the millimeter (mm) sky and revealed a unique and unprecedented view of the Universe. In a 2500-square-degree cosmological survey, SPT has systematically identified a large number (200) of high-redshift strongly gravitationally lensed starburst galaxies.
Mon, 2017-02-20 15:30 - 16:45
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