Sizing up the Cosmos with the Help of Pulsating Stars
| Date/Time: | Monday, 16 Oct 2017 from 4:10 pm to 5:00 pm |
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| Location: | Phys 0003 |
| Phone: | 515-294-5441 |
| Channel: | College of Liberal Arts and Sciences |
| Actions: | Download iCal/vCal | Email Reminder |
Abstract
Just over a century ago, Henrietta Leavitt noticed that the brightness of some pulsating stars depends in a predictable way from their variability period. This groundbreaking insight enabled Edwin Hubble to discover his eponymous law, paving the way for an era of quantitative cosmology. A hundred years later pulsating stars remain the cornerstone of the extragalactic distance scale. Cepheids, the same kind of variables used by Leavitt and Hubble, are still astronomers' favorite stellar standard candles.
Relying on a single stellar distance indicator is however problematic. It carries the liability of uncertain physics and environmental conditions that may bias the results. The recent discovery of a tight period-luminosity relation for the more common RR Lyrae pulsating stars offers an alternative. In this Colloquium, I will discuss my NSF-funded program to establish a new high precision avenue to cosmological distances based on RR Lyrae. These stars will allow us setting the stage for constraining cosmological parameters with better than 2% accuracy. Our technique will provide an independent test for the presence of missing physics in cosmological models. This is a possibility raised by >3 sigma "tension" currently existing between competing measurements of the Hubble constant, based on Cepheids and the analysis of the Cosmic Microwave Background Radiation.