Forum Schedule Spring 2021

All talks are conducted online

Fridays 3:45pm - 4:45pm BPB-217

Date Speaker Topic (click down-arrow to see abstract)
Jan 22 Jason Barnes
University of Idaho, Moscow
host: David Jeffery

Meeting link: https://unlv.webex.com/unlv/j.php?MTID=ma94ba6b10c8f8361c2302f4fc9335539
Meeting number: 120 184 5016
Password: 3kAfTBT3c$3
Dragonfly: NASA's Titan Rotorcraft Lander

Dragonfly is NASA's most recently selected planetary mission. Its science is prebiotic chemistry, habitability, and a search for chemical biosignatures on Saturn's huge moon Titan. Titan's draw derives from its status as an Ocean World. Like Europa, Enceladus, and potentially other icy outer solar system objects, Titan sports a liquid water ocean beneath its icy outer crust. But unlike those sister Ocean Worlds, Titan's surface and atmosphere contain a large quantity and complexity of carbon compounds. When liquid water develops transiently on Titan's surface -- either from cryovolcanism or impact melt -- water mixes with that surface organic material. Dragonfly will explore the chemistry of the resulting mixture at 80-km-diameter Selk Crater where that water, though now frozen, shows pathways for prebiotic chemistry that may resemble the process through which life formed on Earth 4 billion years ago. In my colloquium, I will discuss the specific scientific experiments that the Dragonfly lander will enable, as well as the instrumentation and exploration strategies that the science team will use to answer our science questions once we land in the mid-2030s.

Jan 29

Feb 5

Feb 12 Akimasa Kataoka
National Observatory of Japan (NAOJ)
host: Chao-Chin Yang
Measuring the grain size in protoplanetary disks by ALMA polarization observations

Dust coagulation is the first stage of planet formation, and observational constraints on the grain size in protoplanetary disks are essential for unveiling planet formation. We are tackling this task by using ALMA polarimetric observations. While polarization has been used for finding the direction of magnetic fields, we have shown that this is not the case in protoplanetary disks; the major process of the polarization is due to self-scattering of thermal dust emission. This new mechanism reveals that dust grains have a size of ~100 micron in protoplanetary disks. This contradicts a common assumption of millimeter to centimeter grains inferred from spectral index measurements. In this talk, I would like to discuss the basic mechanisms of the self-scattering polarization and implications to planet formation through the grain size measurements.

Webx meeting link:
https://unlv.webex.com/unlv/j.php?MTID=mc0ff6eca31b52ba7d231d1f17bd38640
meeting number:
120 458 5210
meeting password:
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Feb 19

Feb 26

Mar 5

Mar 12

Mar 19 Spring Break

Mar 26

Apr 2 Beibei Liu
Zhejiang University, China
host: Chao-Chin Yang
From pebbles to planets

Four major stages of planet formation are introduced through the talk. Dust grains first coagulate by perfect sticking but they cannot further grow much beyond cm size. Streaming instability is a key mechanism that clusters pebbles (~mm–cm size particles) into planetesimals with the help of self-gravity. After planetesimals form, they can grow into protoplanets by feeding from other planetesimals as well as by accreting inwardly drifting pebbles from the outer disk. The transition from planetesimal-dominated accretion to pebble-dominated accretion is around 1E-2 Earth mass. The subsequent planet growth is driven by pebble accretion and their core masses are regulated by the pebble isolation mass. I will present a pebble-driven core accretion model to study the formation of planets around low-mass stars and brow dwarfs. The forming planets are compared with the observed exoplanets in terms of mass, metallicity and water content. The results succeed in quantitatively reproducing several observed properties of exoplanets and correlations with their stellar hosts.

Webx meeting link:
https://unlv.webex.com/unlv/j.php?MTID=m41c00969da0d0c0e2902b3165339206d
meeting number:
120 195 5208
meeting password:
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Apr 9

Apr 16 Patrick Mullen
University of Illinois Urbana-Champaign
host:Daniel Proga
Magnetized Models for the Formation of the Moon

The leading theory for the origin of the Moon suggests that a planetary impactor struck the proto-Earth in an oblique collision shortly after the formation of the solar system. The giant impact produces liquid and vapor debris, drawn from the proto-Earth and impactor. The debris either escapes the system, falls back to the Earth, or enters circumterrestrial orbits forming a "protolunar disk". In this talk, I will highlight a suite of numerical models, using the Athena++ astrophysical magnetohydrodynamics framework, that investigates the dynamical role of magnetic fields in a Moon-forming giant impact scenario. Our models demonstrate that magnetic fields speed the evolution of the vapor component of the protolunar disk, while making Moon formation less efficient.

Webx meeting link:
https://unlv.webex.com/unlv/j.php?MTID=m6bb53309ff23a17c68ed6942fb8695f9
meeting number:
120 572 4763
meeting password:
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Apr 23

Apr 30 Woojin Kwon
Seoul National University, Korea
host: Chao-Chin Yang
TBA

May 7 Study Week

May 14 Finals Week

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