A Strongly Magnified Individual Star and Parsec-Scale Clusters Observed in the First Billion Years at z = 6

JWST was designed to study the first stars. Until recently, we assumed that meant populations of stars within the first galaxies. But in the past 3 years, 3 individual strongly lensed stars have been discovered at z~1. This offers a new hope of directly observing individual stars at cosmological distances with JWST. Here we propose JWST observations of a candidate strongly lensed star at z~6, dubbed LSz6. For the past 3 years, LSz6 has been steadily magnified by a factor of ~9000 on the lensing critical curve directly between multiple images of a bright star forming clump. The clump is also remarkable as the most distant known bound massive star cluster, with a radius < 6 pc, the size of local star clusters. This unprecedented spatial resolution is afforded us by the most highly magnified z=6 galaxy known, dubbed the "Sunrise Arc".

We propose 3 hours of NIRCam imaging in 2 epochs and 3 hours of NIRSpec MOS PRISM spectroscopy of 12 positions along the arc. These observations will:

1) Confirm LSz6 is an individual star at z=6 and place it on the H-R diagram with measurements of luminosity and temperature

2) Confirm the lensed clumps are bound massive star clusters, constrain their histories and fates, and measure their individual ionizing strengths

3) Confirm the existence of a galaxy core and measure outward gradients of mass, metallicity, and age for the first time in detail at z=6

Observations from this program will inform future JWST proposals to study the Sunrise Arc in even greater detail and provide time monitoring for years to come. We waive exclusive access to all data obtained from this program to benefit the community.