How solar eclipses have been revealing cosmic secrets for centuries

A total solar eclipse occurs somewhere on Earth approximately every 18 months, and that has been the case throughout human history. Not surprisingly, people have been studying these dramatic events for just as long, with the first records of solar eclipses dating back more than 3,000 years. During that time, we learned an amazing amount about the Sun, Earth, and even the basic laws of physics from total solar eclipses.

For most of history, humans could only see the faint outermost layer of the sun during total days (periods when the moon covers the entire sun’s disk). This faint blanket of plasma, called the corona, has been central to the scientific advances resulting from the study of solar eclipses.

The corona is home to many of the sun’s most fascinating phenomena, including coronal mass ejections (CMEs), which occur when the sun’s swirling magnetic fields blast bundles or clumps of matter into space. If a CME were to hit Earth, it could damage satellites and power grids, and could be extremely dangerous to astronauts in space, beyond the protection of Earth’s atmosphere.

“The Sun’s magnetic activity changes over time and changes across the star’s surface.” meredith mcgregor at Johns Hopkins University in Maryland. Currently, there is no good way to predict this activity. But by studying the coronavirus, we may be able to start doing just that.

A total solar eclipse isn’t the only way to see the outermost layer of the sun. There is also a device called a coronagraph, which uses a shade to block out the sun’s disk in a type of artificial solar eclipse. These instruments are used not only to study our own star, but also to study other stars that are more distant and look for planets around them that would otherwise be hidden in the glare of starlight. It is also important. “The idea of ​​using coronagraphs to block out the light of other stars and look for extrasolar planets comes from natural solar eclipses,” MacGregor says.

The same dimness that makes the corona difficult to observe in totality also makes it an excellent target for spectroscopy. Spectroscopy works by splitting light into its constituent wavelengths. This allows researchers to determine which elements are present in a material by the unique pattern of wavelengths each element emits or absorbs. Helium was discovered using spectroscopy during a solar eclipse in 1868. This was the first time an element had been discovered by studying the sky.

Shortly thereafter, astronomers discovered what appeared to be another new element in the corona, which they named corona, but it turned out that it was simply iron heated to extraordinary temperatures of several million degrees. found. Even though it was not a new element, it was a puzzling discovery. The surface of the sun is only about 5,600 degrees Celsius, so why is the outermost layer so hot?

I said, “Imagine you’re at a campfire and you start walking away from the campfire. It’s supposed to be cold, but it’s much hotter.” Frederick Bartley at the Ohio State Science and Industry Center. “That’s what’s happening with coronavirus, but no one knows why.”

The eclipse also provided some of the first proofs of Albert Einstein’s theory of general relativity, which governs the behavior of large-scale gravity. One of the key predictions of general relativity is that massive objects should bend the trajectory of light as they pass by. Einstein first published the theory in his 1915, and evidence of its truth came in his 1919 when astronomer Arthur Eddington observed starlight bending around the sun during a solar eclipse.

As a total solar eclipse passes over Central and North America this month, astronomers will continue a long-standing tradition of using it to observe the sun and precisely how it affects the space around it. It turns out. The sun still has many secrets to unravel, and eclipses are one of the best times to study them.