March 12, March 26, April 16, and April 30 2012.
Each year the Observatories organizes a series of public lectures on current astronomical topics.  These lectures are given by astronomers from the Carnegie Observatories as well as other research institutions.  The lectures are geared to the general public and are free.  More information can be found here.

The second of seven mirrors for the Giant Magellan Telescope has been cast at the Stewart Observatory Mirror Lab.  NPR's Joe Palka reported on the mirror casting and the challenges faced by engineers in shaping these "aspherical" mirrors.  You can listen to the news piece by visiting this link.