- Grace Cathedral is an American cathedral of the Episcopal Church in San Francisco, California. On top of Nob Hill, Grace is the cathedral church of the Episcopal Diocese of California, led by Bishop Marc Andrus since 2006, while the cathedral’s local parish has been led by Dean Malcolm Clemens Young since 2015.
- Hertzsprung–Russell diagram (Wikipedia)
The Hertzsprung–Russell diagram (abbreviated as H–R diagram, HR diagram or HRD) is a scatter plot of stars showing the relationship between the stars’ absolute magnitudes or luminosities and their stellar classifications or effective temperatures. The diagram was created independently in 1911 by Ejnar Hertzsprung and by Henry Norris Russell in 1913, and represented a major step towards an understanding of stellar evolution.
