Oct. 3, 2019

noon - 1 p.m.
Slichter 3853

Presented By: Bryce Bolin,
Caltech

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Identifying ancient asteroid families: revealing the original planetesimal population

Asteroid families are the remnant fragments of asteroids broken apart by collisions, and only a few are known to be older than 2 Ga. We use a novel family identification technique sensitive to >2 Ga-old families to discover a 4 Ga-old family linking most dark asteroids in the inner Main Belt. The 4 Ga-old family reveals asteroids with D > 35 km that do not belong to any asteroid family implying that they originally accreted from the protoplanetary disk.

Oct. 10, 2019

noon - 1 p.m.
3853 Slichter

Presented By: Yasuhiro Hasegawa,
JPL

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Formation of Giant planets and the origin of their heavy elements

The origin of Jovian planets in both the solar and extrasolar systems is still elusive. The recent significant progress of astronomical observations and NASA's Juno mission has opened up invaluable opportunities of answering to this long-standing problem. In this talk, I will explore the origin of the total heavy-element content of Jovian planets. Making use of the existing semi-analytical formulae of accretion rates of pebbles and planetesimals, I will show that the total heavy elements inferred both for Jupiter and giant exoplanets would originate from solid accretion at the final stage of giant planet formation. In the stage, proto-jovian planets accrete solids from gapped planetesimal disks, and gas accretion is limited by disk evolution. I will also apply this finding to identifying the main formation site of these planets, and show that the plausible region may locate at r > 0.6 au, implying the importance of planetary migration. The combination of these efforts may enable us to move towards a comprehensive understanding of giant planet formation.

Oct. 17, 2019

noon - 1 p.m.
Slichter 3853

Presented By: David Ardilla,
JPL

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SmallSats for Exoplanet Science

The small satellite industry is experiencing a boom, with over 7,000 satellites predicted to be launched by 2027. Small satellites (SmallSats) have performed missions in planetary science, heliophysics, and Earth science. Within astrophysics, the use SmallSats remains limited and I explore the reasons behind the lack of astrophysics SmallSats. I discuss SPARCS, the Star-Planet Activity Research CubeSats, a SmallSat that will study variability in M-dwarfs in order to understand planet habitability. I address opportunities available for using SmallSats for Exoplanet Science, as well as technology gaps that need to be closed in order to fully exploit the new opportunities.

Oct. 24, 2019

noon - 1 p.m.
Slichter 3853

Presented By: Smadar Naoz,
UCLA

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TBD

Seminar Description coming soon.

Oct. 31, 2019

noon - 1 p.m.
Slichter 3853

Presented By: Renata Frelikh,
UCSC

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TBD

Seminar Description coming soon.

Nov. 7, 2019

noon - 1 p.m.
Slichter 3853

Presented By: Paul Rimmer,
University of Cambridge

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Impacts and Habitability on Exoplanets

Recent geological evidence suggests that the early Earth suffered a single impact from a moon-sized object about 4.3 billion years ago. This impact would have transformed the early atmosphere into a transient Miller-Urey atmosphere, dominated by H2, CO, CH4 and N2/NH3, an ideal environment for prebiotic chemistry. It is likely that Mars also experienced a single large impact early on, transforming its early atmosphere as well. Some exoplanets may be following a similar path to Earth and Mars, suffering one large impact and then several smaller impacts, leaving behind molecular signatures of these events. I take results from impact simulation experiments, and apply them to atmospheric chemistry and radiative transfer models to predict the molecular signatures of these events. I show that acetylene (C2H2) is produced effectively by impacts, and not by photochemistry, in potentially detectable quantities on impact-transformed planets.

Nov. 14, 2019

noon - 1 p.m.
Slichter 3853

Presented By: Akash Gupta and Allie Doyle,
UCLA

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TBD

Seminar Description coming soon.

Nov. 21, 2019

noon - 1 p.m.
Slichter 3853

Presented By: Lior Rubanenko,
UCLA

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TBD

Seminar Description coming soon.

Dec. 5, 2019

noon - 1 p.m.
Slichter 3853

Presented By: Emily Hawkins,
UCLA

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TBD

Seminar Description coming soon.