Astrophysics

Neutron stars born with magnetic fields greater than 1014 G (“magnetars”) are common in the Galaxy. Approximately 10 - 50% of the young neutron star population possesses such field strengths. These objects exhibit very slow rotation, spectacular...

The JWST, with its 6.5 m hexagonal mirror and its 4 infrared instruments, has yielded remarkable surprises. The first galaxies are brighter and hotter than expected, and they aren’t round, but are elongated into bananas and cigars. Galaxies and even...

Abstract: Massive neutrinos suppress the growth of cosmic structure on small, non-linear, scales. There is thus much interest in using statistics beyond the power spectrum to tighten constraints on the neutrino mass by extracting additional...

Abstract: Black hole horizons have been a mystery for more than a hundred years. What if they do not exist? Black shells are horizonless black hole mimickers inspired by string theory. The lecture introduces the physics of black shells as well as...

Collisionless shocks in space plasma are frequently observed in settings where the plasma is compressed against a magnetosphere (e.g., Earth’s bow shock) or in the neighborhood of energetic events such as supernovae or gamma ray bursts. This raises...

The Bahcall Lunch follow the astrophysics colloquium lecture. Registration is required by noon the previous Thursday so a meal can be provided.

Machine learning methods are having a huge impact in astrophysics. However, ML has a strong ontology — in which only the data exist — and a strong epistemology — in which a model is considered good if and only if it performs well on held-out...

The mid-2020s herald an exciting new chapter for cosmology, especially in the study of weak gravitational lensing. Stage-IV surveys—spearheaded by the Vera Rubin Observatory’s Legacy Survey of Space and Time (LSST), the Roman Space Telescope, and...