Presidio Lectures

About SFAA Presidio Lectures

Once monthly, the SFAA hosts distinguished guest speakers who are leaders in the fields of astronomy, physics and related disciplines. The speakers present to the public and SFAA members the latest developments from cutting-edge scientific programs.  The lectures are free.

Join us for informal coffee and light snacks at 7:30 PM followed by the General Meeting and announcements at 7:45 PM and lecture kick off at 8:00 PM.

Featured Speaker

19 December 2017, Tuesday, 7:45 PM, Presidio Officers' Club

"ExoComets: Now You See Them, Now You Don't"


Barry Welsh, PhD, UC Berkeley, Space Sciences Laboratory

Minor bodies such as Kuiper Belt Objects, comets and asteroids constitute the rocky, icy debris left over from the planet building phase of our solar system. The existence of reservoirs of small rocky bodies (i.e. asteroids/planetesimals) in orbit around young stellar systems is now well established. The initial proto- planetary disks that contain the reservoir of dust and gas required to to form exoplanets are short lived (<<1Myr). The circumstellar debris disk observed around young stars of ages 10-50 Myr are continually replenished by collision and evaporation amongst planetesimals. The gravitational field can potentially enable large numbers of kilometer-sized icy bodies into trajectories directed toward the young central star.

Artistic depiction of dust and comets around the young star Beta Pictoris as seen from the outer edge of its disk. NASA image by Lynette Cook.

Using high resolution spectrographs mounted on large aperture ground based telescopes, we have discovered 15 young stars that harbor swarms of exocomets. This lecture will describe attributes of comets in our solar system, and observing techniques to detect evaporating exocomets around young stars. The relevance of Kepler's discovery of "Tabby's Star" will also be discussed.

Brief Bio

Dr. Barry Welsh received his PhD from University College of London, and studied Far IR Astronomy. Researched UV Astronomy and Instrumentation at London and Oxford University. He researched physics and early mapping of the Interstellar Medium at the Space Sciences Laboratory, UC Berkeley. Dr. Welsh was project manager on UV detector systems for NASA SOHO, FUSE, GALEX and HST-COS mission and is now discovering exocomet systems and carrying out a search for optical laser pulses from exoplanet systems.


Directions to the Presidio Officers’ Club

Presidio Officers’ Club
50 Moraga Avenue
San Francisco, CA 94129 (intersection of Moraga Avenue and Graham Street on the Main Post)

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