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
Jan
15
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
No meeting
12:00 pm – 1:00 pm • In Person
Jan
22
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
No talk scheduled
12:00 pm – 1:00 pm • In Person
Jan
29
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
Two talks by Astronomy Department graduate students
12:00 pm – 1:00 pm • In Person
Speaker(s): Nathanael Burns-Watson - The University of Texas at Austin and Carlos Jurado - The University of Texas at Austin
Feb
5
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
No talk scheduled
12:00 pm – 1:00 pm • In Person
Feb
12
2025
Stars, Planets, and ISM Seminar
Special Seminar: galactic.ai — The New Frontier in Cosmology and Astrophysics
Special Seminar by ChangHoon Hahn of Princeton University
12:00 pm – 1:00 pm • In Person
Speaker(s): ChangHoon Hahn - Princeton University
Feb
19
2025
Stars, Planets, and ISM Seminar
Special Seminar: Beyond the Observable - A Machine Learning perspective on modern Cosmology
Special Seminar by Carolina Cuesta of MIT and Harvard University
12:00 pm – 1:00 pm • In Person
Speaker(s): Carolina Cuesta - MIT and Harvard University
Feb
26
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
No talk scheduled
12:00 pm – 1:00 pm • In Person
Mar
5
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
No talk scheduled
12:00 pm – 1:00 pm • In Person
Mar
12
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
Two talks by Astronomy Department graduate students
12:00 pm – 1:00 pm • In Person
Speaker(s): Erica Sawczynec - The University of Texas at Austin and James Mang - The University of Texas at Austin
Mar
26
2025
Stars, Planets, and ISM Seminar
Stars, Planets, and ISM Seminar
Two talks by UT Astronomy graduate students
12:00 pm – 1:00 pm • In Person
Speaker(s): Malia Kao - The University of Texas at Austin and Shelby Courreges - The University of Texas at Austin