For scientists focused on unraveling the secrets of the sun, it's not a new invention, but a periodic celestial event, a desire for world travel, and an unparalleled opportunity to observe the stars closest to us. provide an opportunity.
However, high-tech equipment can also be helpful.
A total solar eclipse, visible from a different location on Earth approximately every one to two years, occurs when the moon temporarily obscures the sun's disc (i.e., a large round circle) and radiates beyond the sun. The corona spreads out, exposing the outer atmosphere. Hello.
read more: How to observe the 2024 total solar eclipse
“A total solar eclipse allows us to study and see the corona in ways that are not possible at other times or in other ways,” said Amir Caspi, a solar astrophysicist at the Southwest Research Institute in Boulder, Colorado. Ta.
On April 8, the moon's shadow will fall across North America in a total path that begins in Mexico and ends in eastern Canada. Barring any technical glitches or bad weather, Caspi and other leading researchers are poised to receive a trove of new information about the coronavirus.
Animation: Megan McGrew/PBS NewsHour
The corona is a million times fainter than the sun's disk, making it impossible to see without assistance. To study the corona during normal times, researchers use cameras and telescopes equipped with occultation disks (essentially artificial moons) that block out the sun's ultra-bright side. These instruments, called coronagraphs, can be installed on the ground or in space.
French astronomer Bernard Riot invented the coronagraph in the early 20th century. “We were frustrated that solar eclipses happen so rarely, so we came up with this design that basically allows us to create an artificial solar eclipse at any time,” said astronomer Shadia Hubbar. Professor of Solar Physics at the University of Hawaii at Manoa Institute for Astronomy.
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However, these tools have some limitations. Ground-based coronagraphs have to compete with the brightness of the sky during the day, which can make it difficult to clearly see the dark parts of the corona. Cosmic coronagraphs typically use an occultation disk that is slightly larger than the Sun seen through a telescope, meaning it extends slightly beyond the Sun's surface and blocks the lower part of the corona from view, Caspi explained. .
“quality [of a coronagraph observation] It’s no different than what you get with a total solar eclipse,” Habal said. He is also the leader of Solar Wind Sherpa, an international team of scientists who travel around the world to record and observe the corona during total solar eclipses.
Animation: Megan McGrew/PBS NewsHour
Humans have been observing solar eclipses since ancient times. Astronomers have been predicting these events for thousands of years using the “clockwork of planetary movements,” Habal noted. Total solar eclipses were key for humans to realize that stars, including the Sun, have atmospheres that extend beyond their easily visible surfaces, she said.
The mystery of the scorching sun
Researchers are currently investigating the mystery of the temperature of the corona, which is surprisingly hotter than the sun's surface.
“That's a conundrum in some ways.” [view of] “It’s physics,” Hubbar says. “Typically, when a surface is hot, the temperature decreases as you move away from the surface.”
The surface temperature of the Sun is approximately 6,000 degrees Celsius, but the temperature in the upper atmosphere is between 1 and 2 million degrees Celsius. The cause of this difference is not yet clear. But far removed from ancient technological limitations, today's researchers can glean new insights by training modern observational tools on the Sun during an eclipse. These tools work by capturing a specific type of light that reveals all sorts of information about the celestial object from which it comes.
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Habal said temperature is not evenly distributed throughout the corona, a dynamic region containing several different structures. Some of that material will travel back towards the Sun's surface, forming a 2 million degree loop. On the other hand, the solar wind has a temperature close to 1 million degrees, and when it leaves the atmosphere, it enters interplanetary space.
During the 2017 total solar eclipse, Caspi and his colleagues used a special camera aboard a NASA high-altitude jet to collect images of the corona in the mid-wave infrared range. Its imager records vastly different temperature ranges, including some coronal structures that, while measuring tens of thousands of degrees, somehow glow in mid-wave infrared with about the same brightness as other structures at millions of degrees. Caspi said. In this year's experiment, his team plans to make new observations that help explain the physics behind this phenomenon.
Studying the coronavirus using solar eclipses
Caspi and Hubbar are each spearheading different eclipse research projects that use a combination of ground-based observations and instruments aboard two NASA jets.
These jets will reach an altitude of 50,000 feet, above 90 percent of the atmosphere, during the eclipse, Caspi said. This is important, he noted, because while our atmosphere absorbs or blocks different types of light, it also emits its own glow. At very high altitudes, jets can see the eclipse more clearly.
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The Caspi team's instrument captures light in several separate ranges across the infrared and visible regions of the spectrum, and can help explain what causes different parts of the corona to glow in the mid-wave infrared region and why it looks like it does. would allow more detailed imaging to help explain the Bright like them.
Habal's team selected two imagers and two spectrometers to fly during the eclipse. The imager records a kind of heat map of the corona, revealing which parts are at 1 million or 2 million degrees Celsius.
On the other hand, spectrometers are used to capture the chemical composition of the corona, or the various elements that can be detected in the corona. During the flight, one of the spectrometers captures near-ultraviolet light, a part of the light spectrum that cannot be seen from the ground, Habal said.
Caspi is also participating in Citizen CATE 2024, a program of 35 volunteer teams from Texas to Maine. Each group records a total solar eclipse in which the moon completely obscures the face of the sun. Recording time ranges from 3.5 to 4.5 minutes depending on location. These clips are later stitched together to create a single continuous observation.
The SwRI-led Citizen Continental America Telescope Solar Eclipse (CATE) 2024 project evaluated a special camera to measure the polarization of coronal light during a total solar eclipse in April 2023 in Exmouth, Western Australia. In this image, the colors indicate the polarization or direction of light. White features called prominences have no polarization. Image courtesy: SwRI/Citizen CATE 2024/Ritesh Patel/Dan Seaton
“Instead of being in totality for four minutes, we're going to be in totality for one hour,” Caspi said. This expanded view should help his team observe particularly dark crown structures and dynamic processes that take more than a few minutes to unfold, he added.
Meanwhile, Habal will be stationed in Arkansas, one of her team's ground observation sites, along with two other locations in Texas and Mexico. The locations are approximately 800 miles apart, and observations will span approximately 10 minutes of the total solar eclipse.One aspect of their ground-based research aims to discover whether temperatures within the corona reach 3 million degrees.
Chasing solar eclipses may sound appealing, but ultimately seeing these cosmic wonders with the naked eye is only part of the job. Caspi witnessed his first total solar eclipse in 2023, but said he could only see 10 to 15 seconds of the 58-second total eclipse because he was engrossed in live streaming the event.
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The 2024 eclipse will be Habal's 20th solar eclipse, but 40 percent of previous eclipses have been “clouded,” she said.
“I try to see it [corona] It is in perfect condition, but most of the time we are busy making sure everything is working,” she said.
Unlike other, more forgiving scientific research opportunities, total solar eclipses are a “hit-or-miss” situation, Caspi noted. Once a moment of totality is over, scientists must wait for the next moment to arrive.
“With solar eclipses, it's like, 'Well, if you miss it, you missed it,'” he says. “And if you miss even one minute, it’s over.”
