By: Alexei V. Filippenko and Hugh Hudson
On August 21, 2017, a total solar eclipse will trace a shadow over a narrow band of the United States from Oregon to South Carolina. And if you own a digital single-lens reflex (DSLR) camera*, you can become a part of scientific history by joining hundreds of other photographers to make the first crowdsourced image archive of a total solar eclipse from coast to coast.
The “Eclipse Megamovie” project aims to capture many types of solar phenomena with images taken along the path of totality of the August 21 eclipse by over 1,000 trained volunteers, as well as photos from many more members of the general public through the use of smartphones and simple cameras. This first-of-its-kind citizen science project is a partnership between Google, UC Berkeley, and many others. Our primary goal is to collect as much imagery as possible and to hold it in a vast public-domain archive for future study.
A total solar eclipse is visible somewhere on Earth roughly every sixteen months (averaging about 74 per century), so what makes the eclipse of August 21 so very important? It’s the first total solar eclipse to cross a very long stretch of a highly populated and well-connected landmass in the modern era of digital communication. Total solar eclipses may occur fairly frequently, but rarely do they cross the entire country from coast to coast. The last total solar eclipse to cross the continental U.S. was in 1918, and the last one to have visited any part of the continental U.S. was in 1979, well before we had digital cameras and other instrumentation available to the general public that make it possible to not just observe but also to analyze solar phenomena over a long, continuous time interval.
A total solar eclipse happens when the Moon lines up perfectly with the Sun, blocking its bright disk and casting a shadow on some parts of Earth. These events offer us a chance to see the entire atmosphere of the Sun (that is, the chromosphere and corona) right down to the visible “surface” of the Sun (the disk or photosphere, below which the gases are opaque), something that specialized “coronagraph” telescopes (which artificially block the bright photosphere) cannot do for technical reasons. This lets us see very different physical processes than we can see when observing the Sun directly (without an eclipse) or with a coronagraph.
The Sun generates complex and very active magnetic fields, which contribute to “space weather,” a combination of factors that interact with and affect Earth’s magnetic field and outer atmosphere. We would like to more fully understand and even predict some of this solar magnetic activity because magnetic activity on the Sun can cause power outages and other problems for the electric grid, as well as navigation, satellites, and other systems on Earth. The magnetized structures of the inner corona, at multiple scales, made visible during a total eclipse at multiple scales, will hold clues to the origins of these effects. And photographs documenting this eclipse as it crosses the continental U.S. will reveal how these structures change with time, thereby potentially providing us with a greater understanding of them.
The team will create an “Eclipse Megamovie” by stitching together a subset of the crowdsourced images, showing the progression of the eclipse during the roughly 90 minutes it takes to cross the U.S. We urge you to contribute data and learn more about the project! Even if none of your images end up being selected for the Megamovie itself, they will be included in the image archive and you will have been part of the process.
The image archive will provide fertile ground from which researchers and citizen scientists alike can make discoveries; people are still superior to computer programs when it comes to both pattern recognition and spotting some types of anomalies. The huge advantage of the archive will be in its high degree of oversampling; from a good single site, such as Salem, Oregon, we might have ten asynchronous samples from a hundred cameras with ten megapixels each, thus providing some three terabytes of data. We would thus like to think that nothing the corona does (and it varies ceaselessly!) can escape scrutiny from such a fine-toothed comb. Moreover, with such a rich dataset, citizen scientists from all over the world should have many aspects to explore for years to come.
One of the more interesting of these possible future citizen science projects focuses on English astronomer Arthur Stanley Eddington’s celebrated (but not very convincing, by modern standards) detection, during a total solar eclipse in 1919, of the gravitational bending of light near the Sun, which was predicted by Einstein’s general theory of relativity. Although Lick Observatory astronomers made a more compelling detection of the bending during a 1922 eclipse expedition in Australia, it turns out that nobody has repeated the Eddington experiment during a total solar eclipse with modern solid-state detectors. Wouldn’t it be cool for citizen scientists to measure the positions of stars in the massive public archive of the Megamovie and detect this amazing effect of Einstein’s general theory of relativity?
Our number-one message to the American public is to try to experience the upcoming total solar eclipse firsthand. The best experience by far is to be within the path of totality. To help you plan on getting there, we have posted a number of eclipse resources on our website at https://eclipsemega.movie/resources. Find out more about the Eclipse Megamovie project and Sign In to become part of the team!
*Basic equipment and skills necessary for participating in the Eclipse Megamovie Project:
- Camera: interchangeable lens digital camera (DSLR or mirrorless)
- Telephoto or zoom lens: minimum focal length of 300 mm
- A stable and level tripod
- The ability to identify the GPS coordinates and time of your photographs to the nearest second
Alexei V. Filippenko is a Professor of Astronomy at the University of California, Berkeley, and Hugh Hudson is a Research Physicist in the UC Berkeley Space Sciences Laboratory.
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