It’s been a busy week! If you’re making eclipse plans, much of the total eclipse path looks surprisingly good for weather. Extended forecasts in key places and regions like eastern Oregon, Casper, Wyo., western Nebraska, the Kansas City region, St. Louis, southern Illinois and Nashville all call for sunshine. The weather even looks good where I live in Duluth, Minn. with partly sunny skies and highs in the 70s in the outlook. Click here to get the forecast for your town.
While you and I will be watching and taking photos and video, astronomers will be busy leaning what they can about everything from how much heat Mercury’s soil holds to changes in the upper atmosphere caused by 161 seconds of darkness in the middle of the day. For ground-dwellers, total eclipse will last at most 2 minutes 41 seconds, but for one group of NASA-funded scientists, it will last over seven minutes as they chase the moon’s shadow in two retrofitted WB-57F jet planes.
By flying high in the stratosphere, observations taken with onboard telescopes will avoid looking through the majority of Earth’s atmosphere, greatly improving image quality. At the planes’ cruising altitude of 50,000 feet, the sky is 20-30 times darker than as seen from the ground, and there is much less atmospheric turbulence, allowing fine structures and motions in the Sun’s corona to be visible.
Taking observations from twin telescopes mounted on the noses of the planes, the team will capture the clearest images of the sun’s corona or outer atmosphere to date and the first-ever thermal images of Mercury, revealing how temperature varies across the planet’s surface. One of the biggest unsolved mysteries is how the corona can sizzle at millions of degrees, while the surface of the sun simmers at only 10,000° F. What heats the corona to such fantastic temperatures?
Astronomers have a couple of theories. Magnetic waves arising from the surface might steadily convey energy to the outer atmosphere where it then dissipates as heat. Then there’s nanoflares, micro-explosions too small and frequent to detect individually but taken as a whole might release enough heat to pump up the corona’s temperature. No one’s seen nanoflares, but high-resolution images taken at high speed from the jet just might do the trick.
Every day, the sun’s ultraviolet light strips electrons from the atoms in the upper atmosphere, creating a layer of electrically charged air called the ionosphere located 45-600 miles (75-10,000 km) over our heads. At night, with the sun gone, the electrons snap back to their atoms and cause the air to glow emerald and red, colors you can in any night photo taken from the space station. The light is called airglow.
During an eclipse, the light changes back and forth very quickly that could create a ripple or “echo” that travels along Earth’s magnetic field lines across the ionosphere that might be detected as far away from the eclipse path as the southern tip of South America. Jill Nelson of George Mason University in Fairfax, Va. started up a volunteer, citizen science project called Eclipse Mob. Each participant received a do-it-yourself radio receiver kit that plugs into a smartphone. On eclipse day, volunteers will receive signals from radio transmitters may vary in strength depending on their distance from the eclipse path. Nelson will gather the data in hopes of snaring the elusive ionospheric ripples.
These are just a few of the studies planned. Sometimes I find it amazing that there’s still so much to learn about the sun and Earth during a total eclipse even after a couple centuries of observations. I shouldn’t be. That’s the nature of science. There’s no end to new people with new hunches using new instruments seeking a deeper understanding of whatever phenomenon you choose. To learn more about other studies that will be underway during the eclipse, click here.
Wondering what the astronauts on the International Space Station will see? One their first pass, as the ISS flies over the western U.S., the partial eclipse will be in progress and they’ll see 37% of the sun covered. During their second pass through the moon’s outer shadow, 44% of the sun will be eclipsed and the crew will spot moon’s umbra moving from southwestern Kentucky to northern Tennessee 250 miles below.
During the third pass through the Moon’s penumbra, the ISS will experience a partial solar eclipse with 85% of the Sun covered up a few minutes before orbital sunset. The crew won’t see the umbra because it will have lifted off the surface of the Earth a few minutes prior, but they’ll catch the 27% setting sun and its “horns” behind them as it sets into the atmosphere at sunset. Pictures please!
** Eclipse filter update: I’m hearing that all the places on the AAS Reputable Vendors List are sold out. Check with your local Walmart, public library or university to see if you can still get one. If not you can always use indirect methods for viewing the sun described in my Be Safe, Get the Right Solar Filter blog. I had fun the other day punching a design in a paper plate with a darning needle to make a handy, indirect way of viewing the sun during the eclipse. No darning needle? Try a pencil point or a toothpick.