The total solar eclipse is a way for astronomers across the United States to study the sun and Earth using new technology, both on the ground and in space, that wasn't available during previous eclipses.
Observations from other eclipses through the centuries have provided important findings like the first descriptions of the sun's outer atmosphere, called the corona, measurements of the corona's intense heat, the discovery of helium and even verification of Einstein's General Theory of Relativity.
Because each eclipse is unique, it offers new opportunities that spur astronomers to build on the knowledge we've gained.
"Instead of being able to collect data from one spot or for just a few minutes, this eclipse is providing that window of opportunity to observe the corona over a long period of time," said Madhulika Guhathakurta, NASA's lead scientist for the eclipse. "This is also an opportunity to test out novel instruments and our models also to see how well are they working. And it's scientifically important because of this sun, moon and Earth connection."
Scientists are also looking forward to observing the impact of the sudden dimming of solar brightness on Earth's upper atmosphere, the ionosphere. They know it will have a different effect than the gradual change of nightfall.
The main obstacle to the experiments is weather. Cloud cover or a single rainstorm could disrupt years of careful coordination and calculation in planning for this event.
Last year, Guhathakurta was in Indonesia to carry out an experiment on behalf of Goddard Space Flight Center during the total solar eclipse there. Clouds and rain kept it from being successful. On Monday, researchers will attempt the same experiment -- pointing a new polarization camera at the corona to capture exposures at different wavelengths -- in Madras, Oregon.
Eclipses provide images of the corona in visible light, and observations taken at different wavelengths could reveal more about the corona's magnetic field and its structure.
"Space telescopes can't take us this close to the sun," Guhathakurta said. "The eclipse provides an opportunity for scientists to gather observations very close to the sun in white light, infrared, other wavelengths. This is the region that sets the boundary conditions for how the corona is heated, how is the solar wind accelerated -- conditions we call space weather. We are continuously still learning about this environment."
Observations of this eclipse could help scientists answer some of the persistent questions in solar physics: Why is the corona so much hotter than the surface of the sun, what makes it hot, and what keeps it that way?
Technology has come a long way from where it was during previous eclipses visible in the US, such as the 1979 event.
"Since 1979, an armada of solar telescopes (have been) deployed in orbit around the Earth and Sun to continuously monitor the Sun," Ed Guinan, a professor of astronomy and astrophysics at Villanova University, wrote in an email. "These solar missions -- more than (a) dozen of them -- keep a continuous watch on the Sun and solar activity, such a solar flares and coronal mass ejections."
Guinan will be in Grand Island, Nebraska, to fly cameras on drones and make high-speed videos of the shadow bands as the eclipse shadow moves rapidly along the ground.
"We have two solar telescopes also to capture images of Sun's corona to search for changes in its magnetically controlled structures when compared to other sites along the total eclipse path and also those images returned from solar space missions," Guinan wrote. "We are also carrying out meteorology-type experiments set up to measure changes in temperature and pressure, as well (as) measuring sky brightness changes over the eclipse."
Cameras have more sensitive detectors now, allowing them to capture more data and in greater detail. Even astronauts on the International Space Station are hoping to snap some images of the eclipse with their cameras.
"We are flying very sophisticated instruments on airplanes to look at the sun in multiple wavelengths we don't have access to from space," Guhathakurta said. NASA has funded 11 projects across the US to allow scientists a chance to observe the eclipse in different ways.
Amir Caspi of the Southwest Research Institute in Boulder, Colorado, and his team are using two of NASA's retrofitted WB-57F research jets to chase the eclipse over Missouri, Illinois and Tennessee. With telescopes mounted on the noses of the planes, they hope to capture the clearest images of the sun's corona to date, as well as the first thermal images of Mercury.
Flying in Earth's stratosphere will be less turbulent and the sky will be between 20 and 30 times darker than it is when seen on the ground.
Lower atmospheric layers of the sun can be a few thousand degrees, but the corona is millions of degrees. One known but unseen phenomenon called nanoflares creates micro explosions that could be causing some of the excess heat in the corona. These high-resolution images captured by the telescopes may be the first to glimpse nanoflares.
Meanwhile, the telescopes will focus on Mercury before and after totality of the eclipse, taking advantage of the darker sky to try to map the range of temperatures across the planet's surface and determine its soil composition. As Mercury rotates, the dayside of the planet can reach 800 degrees Fahrenheit, while the nightside cools to hundreds of degrees below zero.
Caspi's team will also search for vulcanoids, asteroids representing leftovers from the formation of the solar system that are hypothesized to orbit between the sun and Mercury. Between thermal imaging of Mercury and the possible discovery of vulcanoids, scientists could learn new things about planet formation.
The National Center for Atmospheric Research will use a Gulfstream V research aircraft to capture infrared measurements of the corona, in hopes of learning more about its magnetic field and thermal structure.
With the Eclipse Ballooning Project
, 54 teams of students in 31 states will fly high-altitude balloons fitted with cameras across the path, submitting video and images captured from near space in a continuous stream throughout the day.
This has never been done live, and views of the eclipse from the edge of the Earth are rare, project director Angela Des Jardins said at a NASA news conference.
NASA will also have a livestream of the eclipse, part of which will be provided with a bird's-eye view above the clouds from a NASA research plane with agency science director Thomas Zurbuchen and videographers aboard. Zurbuchen will use a spectrometer on the flight to analyze the corona.
There will be experiments to gauge a large variety of things happening on Earth, from a greater understanding of the planet's energy system to land and atmospheric responses to the eclipse.
You can also become a citizen scientist, if you're so inspired. Apps like GLOBE Observer
will allow you to share your observations, to be added to an interactive map to show how people across the country captured the eclipse. The Citizen Continental-America Telescopic Eclipse Experiment, known as Citizen CATE
, is also encouraging volunteers at schools, universities and labs across the country to use telescopes and cameras to take high-resolution images of the eclipse in a "relay race."
"Eclipses are great hooks for involving children and the public about astronomy and science," Guinan said.
"I am wishing for clear skies all across the path of totality and that everyone gets a view of this breathtaking moment of observing (the corona), a dimension of our star that most people don't know exists," Guhathakurta said. "It is an unbelievable sight and gives you that sense of profound connection with our star."