A novel technique using pairs of small telescopes to measure the sizes of nearby stars

Arizona State University, Scottsdale AZ

Investigators

Abstract

Astronomers at Arizona State University (ASU) have developed a novel new instrument that can be used to measure the size of bright stars and to separate stars that exist as a close pair and orbit each other. Known as an "interferometer", the instrument comprises two small telescopes which, when used together, act like a much larger telescope. Each telescope is only 50 centimeters in diameter. The telescopes are mounted on the roof of the School of Earth and Space Exploration at ASU. New cameras, developed by the project's principal investigator (PI) and his students, are being used on the two telescopes to take many thousands of images very quickly. By studying these sequences of images carefully the team can check for the dimming of the star as a planet passes in front of it. The equipment can also be used to study the "blinking" of very rapidly rotating stars known as "pulsars". Engagement with amateur astronomy communities is planned through monthly public demonstrations of the rooftop interferometer. The equipment will also be used to teach graduate and undergraduate students about the technique and the specialized cameras being used. The PI also hopes to eventually take the equipment to the Kitt Peak Observatory so that it can be tested on larger telescopes. The PI, along with a graduate student, aims to obtain high angular resolution observations of nearby bright stars using intensity interferometry with two or possibly more 8 to 18 inch telescopes. The telescopes will be coupled to single-photon detectors, which the PI and his students have been characterizing in their lab. The main science goal is to measure the angular size of each star by observing single photons from the same star with multiple telescopes and time-tagging them. In this way angular resolutions corresponding to the size of the telescope separations can be achieved. The measured stellar radii will be compared to other stellar properties, such as temperature, to improve our understanding of convection in main sequence stars and ultimately the equation of state. Secondary science goals include resolving close binaries, high-speed photometry of known exoplanet transits, and long-term high-speed monitoring of pulsars. The detectors that comprise the interferometer each fit within a module that can be moved to other telescopes; stage 2 of the project involves coupling these single photon counting detector modules to larger (1 and 4 meter) telescopes at Kitt Peak via fiber-optic cable. Stage 1 - commissioning of the interferometer using the smaller telescopes at Arizona State University - has already begun.