Back to Listing

Astronomy Colloquium - "Engineering a Modern Distance Ladder for Modern Challenges"

Event Type
Astronomy Department
Astronomy 134
Sep 26, 2019   3:45 pm  
Rachael Beaton, Princeton University
Rebecca Bare
Originating Calendar
Astronomy Colloquium Speaker Calendar

Measurements in the early 21st century brought cosmology into its an age of concordance, but this was not to last. Today we face a ~4-sigma tension between the two modern measurement techniques: the traditional Cepheid-based distance ladder and model-fitting of the Cosmic Microwave Background. The resolution of this tension is either (i) uncovering heretofore unaccounted for systematics or (ii)  “new physics” that is currently absent from the standard, 6-parameter, Lambda-cold dark matter model. I will use backward design to motivate the fundamental limitations of the traditional distance-ladder based on Cepheids and explain how the unparalleled trigonometric datasets from Gaia give us the first real opportunity to build an alternate path to calibrate Type Ia Supernova -- our workhorse tool to constrain the expansion history of the Universe. I will walk through how the Carnegie-Chicago Hubble Program has realized a competitive calibration of the Type Ia Supernova using the tip of the red giant branch as a standard candle. I will further demonstrate how the TRGB employed in the near-infrared with future instrumentation could be used to transform fundamentally how we measure the Hubble Constant. I will describe the current challenges for the realization of this goal and my on-going plan for tackling these, and other limitations of the current distance scale.

link for robots only