San Diego Astronomy Association (SDAA) sponsors speakers on a wide range of astronomy topics on the third Wednesday of every month at the Mission Trails Regional Park Visitors Center. The Program meeting begins at 7:00 PM. Each attendee receives one free door prize ticket. After announcements and a small amount of business, the audience is treated to the featured presentation. At the close of the meeting the door prizes are presented.  The event is open to the public. The Mission Trails Regional Park Visitors Center is at One Fr. Junipero Serra Trail, San Diego CA 92119.  Call the park at 619-668-3281 for more information or visit

Please contact Dave Wood if you have an questions, comments, or ideas for the Program Meetings.

October 16, 2019

Speaker: William Welsh

Topic: Circumbinary Planets at the K/T (Kepler-TESS) Boundary 

SDAA Speaker

NASA's Kepler Mission was spectacularly successful - it has discovered over 2300 exoplanets and revolutionized our understanding of the sizes and architectures of planetary systems. Among of the most interesting of these systems are the "circumbinary planets": planets that orbit around two stars. Like the fictional planet "Tatooine" from Star Wars, these planets have two suns in their skies. Currently we know of a dozen transiting circumbinary planets, and each has revealed an important new facet - and a new puzzle (headache) to solve. While still few in number, the sample is now large enough that some intriguing trends have emerged. I will briefly discuss what the ensemble of Kepler transiting circumbinary planets has to offer exoplanet science: the most accurately known masses and radii, challenges to understanding planet formation and migration, revising the definition of the habitable zone, and why circumbinary planets are often more suitable for life than single-star planets. Then I will discuss how NASA's TESS Mission is expected to reveal hundreds of new circumbinary planets via the "one-two punch" discovery technique, and how we are on the cusp of transitioning from detailed characterization of a handful of planets to being able to carry out statistical studies of the circumbinary planet population.

William Welsh is Professor of Astronomy at San Diego State University. He earned his PhD from the Ohio State University, followed by postdoctoral work at Keele University in England and at the University of Texas, Austin. Since joining the faculty at SDSU in 2000 his work has been focused on transiting exoplanets, and in 2008 he was selected to join NASA's Kepler Mission. Dr. Welsh has been a pioneer in the field of "circumbinary planets", a new class of planet that he helped establish. In 2015, he was honored with SDSU's College of Sciences "Monty" Award for Outstanding Faculty Contributions. 

Upcoming SDAA Program Meetings
January No general meeting - annual banquet
February 20 Dr. Richard Quimby (SDSU) - the Everyscope at Mt. Laguna Observatory
March 20 Donal O’Sullivan (Caltech) - Cosmic Web Imager at Palomar Observatory
April 17 Joint IDA / SDAA meeting
May 15 Kin Searcy and Dorothy Wood - Palomar Observatory Night
June 19 Steve Murray - Event Horizon Telescope
July 17 Jack Lightholder: Roving the Red Planet-20 years of Mars Exploration
August 21 Steve Hallman - Discovering The Darkness ... Dark Matter & Dark Energy
September 18 Dave Wood - TARO
October 16 William Welsh - Circumbinary transiting exoplanets
November 20 Rob Zellem - Exoplanets - TES & WFIRST