CIPS Seminar
Wed, March 14, 2018
Time: 12:30 - 1:30pm
Location: 131 Campbell Hall.
Speaker: Eric Nielsen (Stanford)
Title: The Gemini Planet Imager Exoplanet Survey: a Trend in Wide Separation Giant Planets Occurrence Rate with Stellar Mass
Abstract:
GPIES (The Gemini Planet Imager Exoplanet Survey) is an 600-star survey to detect and characterize giant planets between 5 and 100 AU orbiting young, nearby stars. GPI combines a high order adaptive optics systems, an apodized Lyot coronagraph, and an integral field spectrograph to reach contrasts of 15 magnitudes within 0.5" of the central star. I present an overview of the highlights from the survey, including the recovery of known planets and brown dwarfs around our target stars, and the discovery of 51 Eridani b, a 2 Jupiter mass planet orbiting 13 AU from its star, and characterization of its atmosphere and orbit since the discovery. I also present the cautionary tale of the putative giant planet HD 131399 Ab, where GPI observations found this object to in fact be a background star, and the lessons for planet imaging going forward. One of the key goals of GPIES is to directly measure the occurrence rate of wide-separation giant planets, and I present early results on this front based on an analysis of the first half of the survey. For the first time we are seeing a trend in occurrence rate with stellar mass, which has profound implications for how these planets form and evolve.
CIPS Seminar
Wed, March 07, 2018
Time: 12:30 - 1:30pm
Location: 131 Campbell Hall.
Speaker: Robert Citron (UC Berkeley/EPS)
Title: Oceans on Mars
Abstract:
Putative paleo-shorelines in the northern plains of Mars have been used as evidence of an early Martian ocean. However, the shorelines deviate in elevation from an equipotential (by up to several kilometers), which has been used to challenge the notion that they formed via (and the existence of) an early ocean. We show that long-wavelength variations in shoreline topography can be explained by deformation due to the emplacement of Tharsis, a volcanic province that dominates the gravity and topography of Mars. Our results imply that oceans on Mars formed early, and point to a close relationship between the evolution of oceans on Mars and Tharsis volcanism, with broad implications for the geology, hydrological cycle, and climate of early Mars.
Cosmology Seminar
Tue, March 06, 2018
1:10 pm (Cosmology/ BCCP)
Campbell 131
Viraj Sanghai, Dalhousie
Using the post-Newtonian formalism to understand theories of gravity in cosmology
I am going to split up my talk into two parts. In the first part I am going to show how we can use an extended version of the parameterized post-Newtonian formalism to parameterize theories of gravity in the cosmological background, as well as in the perturbations on non-linear and horizon-scales. This covers a range of scales that we don't think has been consistently parameterized before. In the second part of my talk I will discuss how we perform numerical ray-tracing simulations in a post-Newtonian cosmology (within general relativity) to understand the effect of inhomogeneities on the Hubble diagram.
CIPS Seminar
Wed, February 28, 2018
Time: 12:30 - 1:30pm
Place: Room 131 Campbell Hall.
Speaker: Megan Ansdell (UC Berkeley)
Title: Protoplanetary Disk Demographics with ALMA: Overview and Updates
Abstract: The recent successes of large-scale exoplanet surveys have opened the field of exoplanet statistics, revolutionizing our view of the universe. We now know that planets are common around other stars, but also that exoplanets come in a variety of sizes, compositions, and orbital architectures that that often differ in striking ways from our own solar system. But how and why do such diverse exoplanet systems form? To answer these fundamental questions, we must understand the structure and evolution of the "protoplanetary disks" of gas and dust around young stars where planets form. To this end, we are conducting large-scale surveys of nearby star-forming regions with the Atacama Large Millimeter/sub-millimeter Array (ALMA), which is now offering orders of magnitude higher sensitivity and resolution over previous (sub-)mm facilities. I will give an overview of the recent ALMA protoplanetary disk surveys and their implications for disk evolution and planet formation as well as present the latest results from our survey of gas disk sizes in the Lupus star-forming region.