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.

Founders Share Exchange (fShareX), a non-profit supporting Boston-area startups, will host a half-day event, Games and Contemporary Artificial Intelligence, on May 22 to teach students aged 13-16.  The cost is $53.74, which includes a student plus parent if purchased by May 17 or for the student only after that date.

The Clay Center Observatory, on the campus of Dexter Southfield School (20 Newton Street in Brookline; 5th floor), holds Public Telescope Nights on most Tuesdays in the spring and fall, from 8PM to 9PM.  This spring, they continue through May.  Register in advance (and sign up for the Center’s email list).  These events are canceled if weather is rainy or overcast:  Call 617-454-2795 one hour before the event for a recorded message.  The Clay Center offers a range of Outreach Programs for community groups.  Check the Center’s calendar for future events.

The observatory contains a 25-inch telescope with optically perfect mirrors — similar in optical design to the Hubble Space Telescope.  It’s protected by two airlocks, a dome powered by solar cells and wind turbine, and its own foundation that is completely isolated from the foundation of the surrounding building.  The telescope and dome are computerized and can be operated through the Internet by researchers anywhere in the world.