We present James Webb Space Telescope (JWST) Prime Extragalactic Areas and Reionization and Lensing Science (PEARLS) observations in the fields of massive galaxy clusters. One cluster, PLCK G165.7+67.0 (G165), was selected by its far infrared colors using Planck telescope, and not by the Sunyaev-Zeldovitch effect. A bright point-source was discovered that appeared in three locations as a result of strong gravitational lensing. Follow-up observations confirmed this source to be a normal Type Ia supernova (SN) at z=1.783 that we call "SN H0pe." SN H0pe is anchored to a host galaxy that is relatively massive and is surrounded by star-forming satellites. A delay in the arrival times of the SN light into each image arises from their different geometric light paths. This time delay, together with a lens model, returns a value for the Hubble-Lemaitre constant "H0."  Under double-blinded protocols, the two time delays were measured by photometric and rare spectroscopic approaches, and seven lens models were constructed. The time delays were augmented by measurements of absolute magnifications to obtain a set of five observables. On the day of the unblinding, the lens model-predicted observables were scaled to the measured set to infer a value of H0 = 75.7(+8.1)(-5.5) km/s/Mpc. This is the second time H0 has been measured by this method, and the first time using a standard candle. Regular monitoring of G165 and fields with similar properties may be well-rewarded by the detection of additional strongly-lensed SNe. 

Speaker: Brenda Frye (The University of Arizona)

The 2025 Spring Colloquium talks are held on Wednesdays at 3:00 PM. This colloquium is hosted by STScI and will be held as an in-person and virtual event.

You may join in person at STScI’s John N. Bahcall Auditorium or virtually on STScI's Live Science Events Facebook page.

Please direct questions or comments to contact above. The 2025 Spring Colloquium Committee members are: Nestor Espinoza (STScI), Joel Green (STScI), Nick Indriolo (STScI), Elena Manjavacas (STScI), Namrata Roy (JHU), Kevin Schlaufman (JHU), Ethan Vishniac (JHU).