MSI and Astro seminars are held on Tuesdays at 3:30 pm on alternating weeks during the fall and winter semesters.
Astro Seminars: feature speakers who discuss topics in astronomy, astrophysics and cosmology. Seminars will be held in the R.E. Bell Conference Room (room 103) in the Rutherford Physics Building.
MSI Seminars: feature speakers who discuss topics in astrophysics, planetary science, atmospheric science and astrobiology. Most seminars are held in the MSI conference room at 3550 University. Some seminars are held in the R.E. Bell Conference Room (room 103) in the Rutherford Physics Building (to accommodate larger audiences).
Europa is one of the most enticing targets in the search for life beyond Earth. With an icy outer shell hiding a global ocean, Europa exists in a dynamic environment where immense tides from Jupiter potentially power an active deeper interior and intense radiation and impacts bathe the top of the ice, providing sources of energy that could sustain a biosphere. Europa’s icy plate tectonics, and evidence for shallow water within the ice, implies that rapid ice shell recycling could create a conveyor belt between the ice and ocean, allowing ocean material to one day be detected by spacecraft. Beneath ice shelves on Earth, processes such as accretion, melt and circulation mediate the ice as an important element of the climate system. Here, ice-ocean exchange may be similar to that on Europa, but is difficult to observe given the harsh environment and thickness of the ice. Thus exploring the cryosphere can form the foundation of our understanding of other ocean worlds and a test bed for their exploration. In this presentation, we will explore environments on Europa and their analogs here on Earth. NASA will launch the Europa Clipper Mission in 2021, but while we wait to get there, we are looking to our own cosmic backyard to help us to better understand this enigmatic moon. I will describe our work on the McMurdo and Ross Ice Shelves under our 2017-2020 field program, RISE UP, using the Georgia Tech built under ice AUV/ROV Icefin. Using this new robotic capability, we are working to gather unique new data relevant to climate and planetary science, and develop techniques for exploring Europa, an ice covered world not so unlike our own.
McGill Space Institute
Neutron stars unite many extremes of physics and can serve as astrophysical laboratories that allow us to probe states of matter at densities which cannot be reached on Earth. One exciting example is the presence of superfluid and superconducting components in mature neutron stars. When developing mathematical models to describe these large-scale quantum condensates, physicists tend to focus on the interface between astrophysics and nuclear physics. Connections with low-temperature experiments are generally ignored, although there has been significant progress in understanding laboratory condensates. In this talk, I will highlight the connection between laboratory superfluids and neutron stars, suggesting several novel ways that we could make progress in understanding astrophysics using low-temperature laboratory experiments. I will specifically focus on the concept of mutual friction and present new results on how it influences the neutron star dynamics, in particular the initial response following a glitch.
UC Santa Cruz
Hazes and clouds are ubiquitous in all substantial atmospheres in the outer solar system. Abundant condensed particles are also inferred from the transmission observations in the warm and hot (500-2200 K) atmospheres of exoplanets which are hundreds to thousands of degrees warmer than the solar system planets. These exotic clouds could result from condensation of salts, silicates and metals, and/or hydrocarbons produced by atmospheric chemistry upon UV radiation. In this presentation, I will first talk about the thin, cold and hazy atmospheres in the outer solar system such as on Saturn’s moon Titan, Neptune’s moon Triton, and Pluto. I will present how these atmospheres regulate themselves such that the chemical-produced hydrocarbon haze particles significantly dominate the radiative energy balance over the gas volatiles. In particular, the haze particles could explain the colder-than-expected temperature on Pluto observed by the New Horizons mission. Then I will talk about the thick, hot and cloudy atmospheres of hot Jupiters and brown dwarfs. I will show how to form clouds of salts, silicates and metals in this regime, highlighting the important physical processes such as seed formation, nucleation, condensation, gravitational settling as well as atmospheric particle transport. I will also emphasize the importance of particle size distribution on interpreting the transmission spectra of exoplanets and how to predict it from first principles in a self-consistent microphysical cloud formation model.
Thousands of extrasolar planets and candidates have now been detected, but almost all through indirect methods, such as transit photometry or radial velocity. Though statistically powerful, these techniques provide in most cases just a basic measurement of an object’s size and orbital parameters, and are biased towards small separations. Direct imaging, by contrast, is most sensitive to planets in wide orbits (>5 AU); and if a planet’s light can be seen, it can be characterized spectroscopically. Currently this is only practical for young (below a few hundred million years) self-luminous massive (>1 Jupiter mass) planets. Although this has been done for only a dozen systems, each provides insights into the atmospheric structure and evolutionary history of such systems. This sample is expanding with new facilities such as the Gemini Planet Imager (GPI), a dedicated high-contrast adaptive optics instrument on the Gemini South telescope. Reaching contrast levels of 10-6 , GPI has reported its first planet discovery, 51 Eridani b, in 2015. This planet is sufficiently young, low-mass, and cool that it displays strong atmospheric methane features, and its luminosity likely retains the memory of its formation. I will discuss GPI, the discovery of 51 Eri b, its properties, and the emerging statistical picture of the frequency of wide-orbit planets. I will also briefly discuss future prospects for facilities such as WFIRST, HABEX, LUVOIR, and TMT, and the ultimate path to direct imaging of Earthlike planets.
University of Colorado Boulder
First recognized by Laplace over two centuries ago, the Moon’s present tidal-rotational bulges are significantly larger than hydrostatic predictions. They are likely relics of a former hydrostatic state when the Moon was closer to the Earth and had larger bulges, and they were established when stresses in a thickening lunar lithosphere could maintain the bulges against hydrostatic adjustment. We formulate the first dynamically self-consistent model of this process and show that bulge formation is controlled by the relative timing of lithosphere thickening and lunar orbit recession. Viable solutions indicate that lunar bulge formation was a geologically slow process lasting several hundred million years, that the process was complete about 4 Ga when the Moon-Earth distance was less than ~32 Earth radii, and that the Earth in Hadean was significantly less dissipative to lunar tides than during the last 4 Gyr, possibly implying a frozen hydrosphere due to the fainter young Sun.