Fortnightly Talks: "The sixty-four-trillion-mile tape measure"

Presented by: Dr Jane Clark (CAS) & David Bennett (Bristol AS)



- Talk Description

Sixty four trillion miles - that's how far away nearby stars are. Nobody came up with a credible measurement until Friedrich Bessell managed this feat in 1838. Jane and Dave are trying to detect the parallax to enable them to calculate the distances to nearby stars. They have had to overcome many difficulties. Tiny effects like annual aberration and the precession of the equinoxes, not to mention the shimmer caused by the Earth's atmosphere, can completely swamp the effect they are looking for. The time the light takes to travel to our telescopes is also significant. So, can we overcome these challenges? They are still gathering observational data, and will give an account of the state of play at the time of the talk.



- Speaker Biography

Jane Clark has been an amateur astronomer for nearly 20 years now. Her activities are inspired by her background as a retired professional physicist. She has written on how to measure orbits of planets, and on astrophotography. Her latest book is Photographing Galaxies from Light Polluted Skies, published in 2025 by Springer. Looking for a new challenge, she joined David Bennet to try to measure the distance to a nearby star or two. She is minuting Secretary and Vice Chair of Cardiff Astronomical Society.

David Bennett is the Observatory Manager of Bristol Astronomical Society. He is heavily involved in measuring transits of exoplanets in front of their parent stars, and is a skilled astrophotographer. He has joined Jane Clark to try to measure the distance to a nearby star or two.

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