NASA needs you to map the shape of the sun during the April eclipse

NASA needs you! Or more precisely: they need your phone to study the sun during the upcoming solar eclipse on April 8, 2024.

Now we’re sure conspiracy nuts are at their keyboards claiming this is a big takeover, or whatever, but there’s actually a good reason for this initiative. NASA encourages people interested in the celestial event to participate in their SunSketcher program. By installing NASA’s upcoming app, you can use your phone to collect data on the so-called Great American Eclipse 2024, allowing you to map the star’s shape.

As Professor Gordon Emslie, the lead researcher, explained: “The 2024 solar eclipse provides an unprecedented opportunity to measure the shape of the Sun and thus infer its inner structure. The SunSketcher project will use smartphone observations from Citizen Scientists along the two-thousand-mile eclipse path from Texas to Maine to reveal the precise shape of the sun’s disk.”

You may wonder why we need to determine the shape of the sun. I mean, it’s clearly a sphere, right? Well, that’s not really true. One of the most important factors is that the sun consists of plasma and is therefore not a solid. So when it spins, it bulges in the center, just like any other rotating spheroid.

This property is called oblateness, but is also called polar flattening. To be fair, the sun is not the only celestial body that experiences this. Within our solar system, Earth, Jupiter and Saturn all exhibit varying degrees of oblateness.

But the oblateness of the Sun is affected by several peculiarities related to the internal distribution of its rotation, which is not uniform. For example, the movement of sunspots tells us that the surface rotation is “differential,” meaning the spots move at different speeds depending on where they are – spots at the equator move 10 percent faster than those at higher latitudes. Scientists also expect that the gas flow that accompanies convection and magnetic activity also leads to transient distortions at a smaller level.

This is where SunSketcher’s data comes in and why NASA needs your help. As they explain, the data “will allow scientists to explore details of the Sun’s interior. An accurate measurement of the Sun’s oblateness will also allow very accurate calculations of the effects of the Sun’s gravity on the motions of the inner planets (e.g. Mercury), and comparison with observations of planetary motion will thus provide a test for various theories of gravity.”

So how does this all work? Well, in addition to the help of citizen scientists using the app, scientists also have to recruit the moon for help. When the moon makes its final pass across the sun during a total or annular solar eclipse, there is a spectacular moment when small flashes of light can be seen. This phenomenon is known as Baily’s beads and occurs when the sun’s light moves across the moon’s uneven surface (its craters, hills and valleys).

“This phenomenon has very precise parameters,” NASA explains. “[T]The geometry of the coincidence between observer and moon and its exact time on sub-second timing scales. The parameters differ systematically for observers located at different places and times within the path of totality.”

This is where the SunSketcher app comes into the picture. This is programmed to take a series of photos of the Baily’s Beads as they occur during second and third contact. Depending on where you are within the path of totality, the flashes will occur at different times. NASA can use this data to better map the oblateness of the sun.

“With your help, we hope to create a massive database of hours-long observations, more than we could ever do ourselves,” NASA explains.

You can already download the SunSketcher app for iPhone and the Android version will be available soon.

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