91×ÔÅÄÂÛ̳

91×ÔÅÄÂÛ̳ physics and astronomy graduate student awarded national prize

Ketevan (Keti) Kotorashvili, a graduate student in the ’s and a Horton Fellow of the (LLE), recently received the 2023 in Natural Sciences for her research on the evolution of stars.

The award is a national prize from Kotorashvili’s home country of Georgia that honors the achievements of “young, talented and promising Georgian creators in art and science.” It is given annually to a recipient between the ages of 18-30 in each of eight disciplines: Theatrical Art, Cinema Art, Literary Prose, Poetry, Music, Visual Arts, Humanities, and Natural Sciences. The 2023 Tsinandali Awards were presented at a ceremony in Tbilisi, Georgia, on December 8.

Kotorashvili was recognized for her research in theoretical astrophysics on the evolution of the rotation of stars and specifically for her paper “.” The paper is co-authored by her PhD advisor, , a professor of physics and astronomy at 91×ÔÅÄÂÛ̳ and an LLE distinguished scientist, and collaborator , a senior lecturer in exoplanet physics at Imperial College London. The paper addresses an ongoing mystery of stellar astrophysics: why do stars older than the sun appear to nearly stop spinning down as they age?

Spin down refers to the gradual reduction in the rotational speed of a star over time. By combining a detailed theoretical model of stellar spin down with a comprehensive comparison to observational data, Kotorashvili and her collaborators offered a novel possible answer to this question: maybe the stars do not actually halt their spin down. Stars have magnetized winds that carry away angular momentum, so scientists expect that a star would have a steady spin down. Previous studies that indicate stars halt their spin down, however, were based on comparisons of data to the spin evolution of theoretical “average” stars, which doesn’t accurately represent individual stars. When the variation of individual stars is incorporated, the evidence for halted spin down is dramatically reduced.   

This work will become part of Kotorashvili’s PhD thesis, as she continues to study new aspects of the spin evolution of magnetized stars.