Measuring very small things with very big buckets: sub-milliarcsecond angular resolution optical astronomy with the VERITAS observatory

Thursday, April 2, 2020 - 4:00pm
Phillips Auditorium
Center for Astrophysics | Harvard & Smithsonian
Abstract: 

Stars even visible to the naked eye typically have angular diameters on the order of one milliarcsecond (mas) or less. Therefore directly measuring their size, let alone revealing details across stellar surfaces such as starspots or transiting exoplanets, requires imaging with an angular resolution measured down to tens of microarcseconds. The Rayleigh criterion implies the need for kilometer-scale telescopes to achieve this level of angular resolution in the visible waveband, but there are ways around this limitation through the techniques of interferometry and high speed photometry. Imaging Atmospheric Cherenkov Telescopes (IACTs) are instruments for the indirect detection of very high energy cosmic and gamma rays, consisting of arrays of very large "light buckets" to gather the optical Cherenkov photons generated within extensive air showers. Whilst the optical imaging quality of IACT reflective surfaces may be modest it should not be forgotten that they are in actuality amongst the largest optical telescopes -- with sensitive camera equipment ideal for application to high time resolution optical astronomical photometry for timescales of seconds down to nanoseconds. In this talk I will discuss the recent advances that resulted in the VERITAS IACTs making sub-milliarcsecond resolution observations through the revived technique of intensity interferometry and obtaining the smallest optical angular resolution measurements to date in direct measurements of stellar diameters at the <=100 micro-arcsecond scale from observations of asteroid occultations of stars.

Special Note: 
Cancelled
Event Status: 
Cancelled