Series: Astronomy Colloquium
Date: Wednesday 09-Nov-2022
Time: 16:05-17:00 (4:05-5:00 pm)
Location: Zoom
Speaker: Dr. Wendy Freedman (University of Chicago)
Title: "The Hubble Tension: Is There a Crisis in Cosmology?"
An important and unresolved question in cosmology today is whether there is new physics that is missing from our current standard Lambda Cold Dark Matter (LCDM) model. Recent measurements of the Hubble constant (Ho), which are based on Cepheids and Type Ia supernovae (SNe), appear to be discrepant at the 5-sigma level with values of Ho inferred from measurements of fluctuations in the cosmic microwave background (CMB). If real, the current discrepancy could be signaling a new physical property of the universe. I will present results based on Hubble Space Telescope Advanced Camera for Surveys data resulting in an independent calibration of SNe Ho based on measurements of the Tip of the Red Giant Branch (TRGB). The TRGB marks the luminosity at which the core helium flash in low-mass stars occurs, and provides a high-precision and accuracy standard candle. Moreover, the TRGB method is less susceptible to extinction by dust, to metallicity effects, and to crowding/blending effects than Cepheid variable stars. I will address the current uncertainties in both the TRGB and Cepheid distance scales, as well as discuss the current tension in Ho and the evidence for additional physics beyond the standard LCDM model.
In-person colloquia are usually preceded by espresso and ice cream at 1:45 pm outside room PSC 1150 and are followed by an informal reception at 5:15 pm in that room. Anyone interested in talking with the speaker, or being added to the colloquium announcement email list, should contact the colloquium organizer Dr. Leslie Sage. Lunch will normally be reserved for the speaker to talk to graduate students. Anyone asking a question during a talk is asked to raise their hand and be acknowledged before speaking. Contact Dr. Leslie Sage for details.
Colloquium Organizer:
Dr. Leslie Sage
Special accommodations for individuals with disabilities can be made by calling (301) 405-3001. It would be appreciated if we are notified at least one week in advance.
