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  • Writer's pictureErik Petigura

Congrats, Luke!

Very happy to celebrate Luke Handley's graduation from UCLA with a B.S. in astrophysics! Luke joined the group in 2021 as a third-year UCLA undergraduate. Over the past two years, Luke worked primarily on algorithms for the automated and equitable scheduling of Doppler time series to search for planets around other stars.

The Doppler technique, which senses planets by the tiny Doppler shifts they impart in stellar spectra, is a key tool for exoplanet discovery and characterization. Many of the cutting-edge science questions in Doppler studies of exoplanets require observations on many nights to sample planetary orbits and to model out variability due to stellar phenomena. Taken together, planetary and stellar signals have timescales that range from minutes to decades. Optimizing the science return on any Doppler instrument requires careful attention to the observational ‘cadence’ defined as the timing of and spacing between observations in a Doppler timeseries.

Luke developed algorithms to schedule Doppler observations with a particular eye toward facilities our group uses at Keck Observatory including the venerable High Resolution Echelle Spectrometer (HIRES, first light: 1993) and the newly commissioned Keck Planet Finder (KPF, first light: 2022). These are hard problems. Over a typical semester, Doppler planet searches at Keck Observatory collect up to ~3000 exposures, and there are N! ~ 10^3500 possible orderings of these exposures. This problem is closely related to several well-known problems in computer science such as the ‘set packing problem’ and ‘traveling salesman problem.’

This project opened the door to a rich literature in operations research (think Amazon logistics, FedEx truck routing, etc) which Luke was able to adapt and transfer to our astronomical context. Along the way, we have had a wonderful time collaborating with Prof. Velibor Mišić who studies optimization at UCLA’s Anderson School of Business. Luke and I have presented this work at AAS2023 and EPRV5 and papers are in preparation. Luke will be joining the Astronomy PhD program at Caltech in the Fall.

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