When a rare total solar eclipse passes over North America, scientists will be able to gather invaluable data on everything from the Sun's atmosphere to strange animal behavior - and even the possible effects on humans.
The eclipse will occur at a time when the Sun is near the peak of its 11-year solar cycle, setting the stage for a breathtaking show: The corona will shine spectacularly from the Moon's silhouette along the path of totality, a corridor stretching from Mexico to Canada and across the United States.
Total solar eclipses offer "incredible scientific opportunities," NASA Deputy Administrator Pam Melroy said at a news conference this week about the celestial event.
The US space agency is one of the institutions on standby for the eclipse, planning to launch so-called "sounding rockets" to study the effects on Earth's upper atmosphere.
Here's what researchers hope to learn from the upcoming eclipse:
The atmosphere of the Sun
When the Moon passes directly in front of the Sun and blocks it, the elusive outer edge of the Sun's atmosphere, or corona, will be visible in a very special way.
"There are things going on with the crown that we don't fully understand," Melroy said.
The heat in the corona intensifies with distance from the Sun's surface, a controversial phenomenon that scientists are trying to understand or fully explain.
Solar flares, a sudden explosion of energy that releases radiation into space, occur in the corona, as do solar bulges, huge plasma formations that spread out from the Sun's surface.
During an eclipse, the very bottom of the corona -- where much of this activity occurs -- is seen more clearly than when specialized instruments are used to block out the central part of the Sun, offering a golden opportunity for research, Shannon Schmoll pointed out. , director of the Abrams Planetarium at Michigan State University.
Researchers are particularly excited by the fact that the Sun is near the peak of its 11-year cycle.
"The chance of seeing something incredible is very high," Melroy emphasized.
Earth's atmosphere
The total eclipse will allow scientists to study changes in the upper part of Earth's atmosphere known as the ionosphere, which is important because it affects radio waves used for communication and navigation.
"Disturbances in this layer can cause problems with GPS and communications," explained Kelly Korek, eclipse program manager at NASA headquarters.
The ionosphere, which is where Earth's atmosphere meets outer space, is affected by the Sun, which charges particles in it with electricity during the day.
Three NASA sounding rockets will be launched from Virginia before, during and immediately after the eclipse to measure these changes.
The significant reduction in sunlight caused by the eclipse — faster and more localized than a typical sunset — should allow researchers to learn more about how light affects the ionosphere, so they can better predict potentially problematic disturbances.
Animal behavior
Surprising animal behavior has been observed during the eclipses: Giraffes have been seen galloping, and roosters and crickets may start crowing and "singing".
In addition to the reduction in sunlight, temperatures and wind—conditions to which animals are sensitive—can also decrease significantly during an eclipse.
Andrew Farnsworth, an ornithology researcher at Cornell University in New York state, studies how eclipses affect birds by using weather radar to detect birds in flight.
During the last total solar eclipse visible from the United States in August 2017, scientists saw "a drop in the number of animals flying around," Farnsworth explained.
The 2017 eclipse disrupted the daily activities of insects and birds, but did not trigger the animals' usual nocturnal behavior, such as bird migration or bat emergence.
This time, birds may be more likely to migrate during the eclipse, given that it is in April.
"These types of patterns are important for understanding the ways in which animals perceive their world," Farnsworth said.
The human miracle
"Eclipses have a special power. They make people feel awe at the beauty of our universe," said NASA Administrator Bill Nelson.
In 2017, researchers studied this feeling of admiration using data from nearly three million users of Twitter, now called X.
Those on the so-called "path of totality," in which the Moon will completely block the Sun, tend to use the pronoun "we" (as opposed to "I") and express concern for other people, according to Paul Piff, professor of psychology at the University of California, Irvine.
"What we're finding is that awe-inspiring experiences ... seem to tune people and connect us to each other, connect us to entities that are bigger than ourselves," says Piff.
This year, he plans to study whether the experience has any impact on political divisions in society.
Citizen scientists
About 40 citizen science projects are planned in connection with the eclipse, from using a phone app to record temperature and cloud cover to recording ambient noise during the event.
"We encourage you to help NASA monitor the sights and sounds around you," Nelson said. /BGNES
