Women in American Cosmology


Jack C. Straton © 2000

University Studies

Portland State University.

straton [at}pdx.edu

Women in American Cosmology. 1) An exploration of the significant role women played in American astronomy over the last 150 years, despite pervasive discrimination in their work-roles, pay, and career choices. 2) Henrietta Levitt's 1908 discovery of the period-luminosity relationship for Chepheid variable stars, a key rung on the Cosmic distance ladder. 3) Wendy Freedman's 1994 observation of Cepheids in a distant galaxy, cutting the age of Universe in half. 4) Finding the age of Universe from its curvature and the galactic distance-velocity relation. 5) Accounting for Large-scale structure.

Day 1 - Women & Astronomy

Discuss "Gender and Science: Women in American Astronomy, 1859-1940," by John Lankford and Rickey L. Savings, Physics Today 43, 58 (March 1990).

Mitchell, sitting, surrounded by several unidentified women, probably at Vassar

Day 2 - Cepheids

Henrietta Levitt and her 1908 discovery of the relationship between the period of the variation and the absolute luminosity of Chepheid variable stars. Cosmic distance ladder.

Annie Jump Cannon, Henrietta Swan Leavitt

Cepheid Observed by Wendy L. Freedman using Hubble Space Telescope in the Virgo Cluster placing it at 50 million ly from Earth, half the previous value. Age of universe then half of previous value or 7-11 Billion years.


Day 3 - Hubble Expansion (optional)

Edwin Hubble's relationship between galactic recessional velocity and distance. Get the Hubble Constant Ho from the recessional velocity and distance of Virgo Cluster.

Since 1/Ho is a rough upper limit on the age of the universe, the new Hubble constant measurements are implying an universe age of only 12-13 billion years (expanding Supernova photosphere method vs. Cepheid method). This is in conflict with the ages derived for the oldest stars (found in globular clusters) of about 15-16 billion years.


Day 4 - Big Bang (optional)

The Big Bang: universe is open, flat or closed depending on how much mass there is in it. 1/Ho is intercept to tangent to where these three curves (hyperbola, parabola, ellipse) meet at present day.


Day 5 - Large-scale structure (optional)

How do we account for the Large-scale structure seen in the universe, voids of the order of 100 million light years wide?

Margaret Geller & structure

Sources - Women & Cosmology