Description:

The last decade has provided exceptional data on black holes and neutron stars: imaging of black hole shadows with the Event Horizon Telescope, precise measurements of neutron star radii with NICER, discovery of wide-separation binaries containing compact objects with Gaia, and hundreds of compact object binary mergers from LIGO-Virgo-KAGRA. These observations have re-invigorated the study of the densest objects in the Universe. Remarkably, decades-old theory has been exceptionally successful at describing these observations, with no major violations of general relativity, stellar evolution, nuclear structure, or supernova theory. It is surprising that we haven't been surprised. In every other case of such a data deluge in astrophysics—the cosmic microwave background, gamma-ray bursts, pulsars, dark matter, inflation, dark energy—paradigm shifts followed. I will present two potentially paradigm-challenging results. First, I will show evidence that LIGO neutron star mergers may not all originate from canonical field binaries. Second, I will present observations suggesting a new class of gamma-ray bursts with a Galactic origin. While preliminary, these results challenge our standard formation scenarios and may herald the surprises this field has been missing.

Ryan Foley, Associate Professor, University of California, Santa Cruz

Host: Wen-fai Fong