The Harvard-Smithsonian Center for Astrophysics (60 Garden Street in Cambridge) will host its monthly Observatory Night on May 19 at 7:30PM on the topic of The New Cosmos:  Answering Astronomy’s Big Questions.  Topics include dark energy, dark matter, water on Mars, the planethood of Pluto, the barred-spiral structure of the Milky Way, and the ubiquitous nature of black holes.  The lecture is intended for high-school and older audiences but children are welcome.  Admission is free, no reservations are necessary, and seating is limited.  For more information, call 617-495-7461 or email pubaffairs@cfa.harvard.edu.