Physics & Astronomy News

A team of WKU faculty, staff, and students recently traveled to Odessa, TX, to view the annular eclipse there (it was only a partial eclipse in Bowling Green). But their trip had a more important purpose: to test the SunSketcher app being developed at WKU.

SunSketcher is a smartphone app being designed under a NASA grant on which Physics & Astronomy Professor Gordon Emslie is the lead investigator. Several other WKU faculty, from the School of Engineering & Applied Sciences and the Department of Art & Design are also involved.

Many WKU students have been involved with various aspects of the project, including writing app code, managing data transfer and storage, image processing, website development, and even public relations. If you're interested, you can also follow the project's TikTok page for updates: https://www.tiktok.com/@sunsketchers.

The SunSketcher app uses the GPS coordinates of a phone and an eclipse “ephemeris” (basically a lookup table) that can be interpolated to give, for a given location, the exact times when the edges of the Moon and the Sun coincide during a solar eclipse. At those times, the mountains on the lunar limb block the Sun’s light, but the valleys in between allow the light to pass through. This creates the phenomenon known as Baily’s Beads, bright spots of light visible near the limb of the Sun, for only a few seconds.

The app automatically takes sequences of pictures at these critical times and then (with the user’s permission) uploads the images to a WKU server for later analysis.

Analysis of the data uses the exact timing of the Baily’s Beads combined with accurate maps of the Moon’s limb (using data from the NASA Lunar Reconnaissance Orbiter satellite). This will allow the precise shape of the Sun to the determined, to an accuracy that is much better than ever previously achieved. Knowing the exact shape of the Sun allows scientists to probe flows of gas within the interior of the Sun and to determine the gravitational field of the Sun very accurately, thus allowing tests of post-Newtonian theories of gravity such as Einstein’s theory of General Relativity.

The measurements that are needed require continuous views of an eclipse along its entire path. No one observer can make such a measurement; a chain of observers is needed. Leading up to the April 8, 2024 total solar eclipse, the WKU team will use the results from the annular eclipse to refine the app and then release it through the App store. It is hoped that millions of people will download the app and use it during the April eclipse. Each of their uploaded image sets will make a unique contribution to an important science project. Follow this link for more photos!