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Astronomy  /  Talks & Events  /  Astronomy Colloquium 2021

Astronomy Colloquium

Astronomy Colloquia at Caltech for 2021-22

Colloquia are held every Wednesday during the academic year at 4pm in the Cahill Hameetman auditorium. Wine and cheese will be served in the Cahill Foyer from 5:00-5:30pm (pending COVID restrictions).


Astronomy Colloquium Youtube channel

May 29, 2024 4:00 pm


Time-Domain Astrophysics in the Era of Big Data
Ashley Villar, Assistant Professor of Astronomy, Harvard University,

The eruptions, collisions and explosions of stars drive the universe's chemical and dynamical evolution. The upcoming Legacy Survey of Space and Time will drastically increase the discovery rate of these transient phenomena, bringing time-domain astrophysics into the realm of "big data." With this transition comes the important question: how do we classify transient events and separate the interesting "needles" from the "haystack" of objects? In this talk, I will discuss efforts to discover and classify unexpected phenomena using semi-supervised machine learning techniques. I will highlight the interplay between data-informed physics and physics-informed machine learning required to best understand the future LSST dataset of extragalactic transients.

June 5, 2024 4:00 pm


HERA and Beyond: Instrument Design in the Era of AI
Aaron Parsons, Associate Professor of Astronomy, Astronomy Department, UC Berkeley,

As the Hydrogen Epoch of Reionization Array (HERA) prepares for its final few years of observing in South Africa, its capabilities and limitations are becoming clear. HERA's large dishes and compact array configuration have supported sustained progress in sensitivity and foreground removal, enabling upper limits on the 21-cm power spectrum from cosmic reionization that constrain astrophysics in the early universe. However, these same characteristics limit the reconstruction of 3D intensity maps supporting cross-correlation studies. In this talk, I describe HERA's current limits and exciting forthcoming results, along our recent innovations in calibration and filtering that have the potential to free 21-cm interferometers from the dreaded wedge of chromatic foreground responses. I also describe the new tools that we are working on to design next generation experiments for 21-cm cosmology, and how the landscape of instrument design is changing with the availability of AI technologies.

June 12, 2024 4:00 pm


Characterizing Atmospheres of Transiting Exoplanets with JWST
Thomas Greene, Astrophysicist, Space Science and Astrobiology Division, NASA Ames Research Center,

JWST observations are revealing the chemical compositions and inner workings of exoplanet atmospheres. I will show some initial results, highlighting JWST MANATEE guaranteed time observations of transiting planets ranging from Earth-to-Saturn masses with equilibrium temperatures of 400 - 1000 K. These include the discovery that the Earth-sized planet TRAPPIST-1 b has no substantial atmosphere, a high-confidence detection of CH4 (methane) in a transiting planet, using molecular features and clouds to constrain the core and internal heat of a Neptune-mass planet, the compositions of mini-Neptune planets (unlike any in our Solar System), spatial inhomogeneities on planets' day and night sides, and constraining planet formation pathways. I will also present some lessons learned from analysis and modeling of panchromatic visible-to-mid-infrared exoplanet spectra.