Stars, Planets, and ISM Seminar
Nov
12
2025
Nov
12
2025
Description
Harriet Dinerstein, The University of Texas at Austin
An Organic Harvest: Carbon Macromolecules from Planetary Nebulae
Asymptotic Giant (AGB) stars are known to be major suppliers of dust to the ISM. We are now learning that, through the planetary nebulae (PNe) they expel, they are also sources of large C-bearing molecules such as Polycyclic Aromatic Hydrocarbons (“PAHs”), fullerenes (pure-carbon “soccer balls”), and similar structures. It is unclear whether these molecules form early on the AGB, or are created later in the PN, when UV radiation from the central star impinges upon the stellar ejecta, driving ISM-like chemistry. I will report on the efforts of the “ESSENcE” team, an informal international collaboration, to elucidate the formation processes of PAHs, fullerenes, etc., by observing spatially-resolved PNe with JWST. Our recent targets included the Ring Nebula, the Butterfly Nebula (NGC 6302), and Tc 1, the first astronomical source in which fullerenes were detected. We find that PAHs can form in O-rich material despite a widespread assumption that they require C > O, and that PNe can serve as useful testbeds for probing the origin and evolution of PAHs under nebular conditions in general including those in high-redshift galaxies.
Jesse Han, Harvard University
A Supermassive Black Hole in the LMC and How Roman Can Find It
Supermassive black holes can produce hypervelocity stars via the Hills mechanism. We directly trace a population of hypervelocity stars to the LMC, indicating the presence of an SMBH. We model the Hills mechanism to estimate its mass to be ~1e6 Msun; this mass lies precisely on the M-sigma relation expected for the LMC. We further discuss how an all-sky Roman survey can constrain the proper motion of faint stars such as hypervelocity stars, which can pinpoint where the SMBH resides.
Other Events in This Series
Apr
2
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar: Astrophysics in the Lab - Measuring Opacity at Solar Interior Conditions at the National Ignition Facility
Stars, Planets, and ISM Seminar
12:00 pm – 1:00 pm • In Person
Speaker(s): Bryce Hobbs - The University of Texas at Austin
Apr
9
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
12:00 pm – 1:00 pm • In Person
Speaker(s): Marvin Morgan - The University of Texas at Austin and Zoe Hackshaw - The University of Texas at Austin
Apr
16
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
Second Year Research Talk
12:00 pm – 1:00 pm • In Person
Speaker(s): Claire Finley - The University of Texas at Austin
Apr
23
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
12:00 pm – 1:00 pm • In Person
Speaker(s): Lillian Jiang - The Univeristy of Texas at Austin and Jaume Orell Miquel - The University of Texas at Austin
Apr
30
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
12:00 pm – 1:00 pm • In Person
Speaker(s): Ueejeong Jeong - The University of Texas at Austin and Harshil Kothari - University of Toledo
Aug
27
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
Organizational meeting
12:00 pm – 1:00 pm • In Person
Sep
3
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
The Demographics of Planets in Binary Star Systems
12:00 pm – 1:00 pm • In Person
Speaker(s): Kendall Sullivan - UC Santa Cruz
Sep
10
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
Ice and Metal in the Galactic Center
12:00 pm – 1:00 pm • In Person
Speaker(s): Adam Ginsburg - University of Florida
Sep
17
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
The Chemical Record: Elements of Galactic Memories
12:00 pm – 1:00 pm • In Person
Speaker(s): Jennifer Mead - Columbia University
Sep
24
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
Learning From Simulations Using ML/AI Tools
12:00 pm – 1:00 pm • In Person
Speaker(s): Viviana Acquaviva - City University of New York