JOINT SEMINAR 2026

Avoided Crossings in Asteroseismology

SpeakerDr J. M. Joel Ong, University of Sydney, Australia
Date/TimeMonday, 27 Apr, 3pm
LocationS11-02-07 Conference Room 
Host/Co-HostAsst/Prof Marc Hon

Abstract

Avoided crossings are an ubiquitous physical phenomenon in the dynamics of few-body systems. I illustrate how they emerge in asteroseismology — the analysis and interpretation of normal modes in stars — and specifically in variable stars possessing stochastically-excited oscillations. I describe a one-to-one correspondence between these standing waves and hybridised molecular orbitals. Operational predictions for the frequencies, lifetimes, and visibilities of normal modes emerge from this correspondence, and are now increasingly exploited to yield observational discoveries of stellar rotation, magnetism, and star-planet interactions. In particular I report recent uses of it to discover a new class of variable stars: those with insides and outsides that rotate around different axes. I will conclude with some outlines of ongoing investigations into azimuthally asymmetric magnetic configurations.

Biography

Joel Ong is an incoming ARC DECRA Fellow at the University of Sydney. Prior to this, he was a NASA Hubble Fellow at the University of Hawaiʻi — the first Singaporean to have been awarded a Hubble Fellowship. Dr. Ong received his PhD from Yale University, and his undergraduate education at the National University of Singapore (class of 2016).