.png)
7 hours ago
8
After lunch on Wednesday, two Nasa aviators will climb into a research plane and take off from Keflavik airport on a western tip of Iceland. They will climb north towards Greenland and then bank to head south on a gently curving course 40 miles (64km) off the Icelandic coast.
Their mission can be described as chasing an eclipse, but in reality the eclipse is chasing them. As the plane cruises at 50,000ft (15,000 metres), the shadow of the moon will race up from behind, crossing the ocean below at more than 2,000mph (3,200km/h). The pilot will aim to reach the point of greatest eclipse, when the largest fraction of the sun is obscured by the moon, at the moment the shadow catches up with them.
For anyone standing directly beneath – or treading water, given the geography – the world will go dark for 2 minutes 18 seconds. But by flying at 460mph along the path of the eclipse, the pilot can extend totality to nearly 3 minutes. Which gives them more time to observe the blotted-out sun.
Cary Klemm, a sensor equipment operator at Nasa’s Johnson Space Center in Houston, who has flown eclipse missions in the past, described the experience at high altitude: “The big difference is that in the cockpit of an aircraft at 50,000 feet, it’s very bright in the sun. There are no clouds above you, and then all of a sudden, you’re hit with this slam of shadow.”
“You feel the temperature drop off; you’ll notice that you need more light from your instruments, and it’s kind of a weird, eerie shadow that you’re surrounded by. It wraps around the view in the cockpit,” he added.
Hidden in the nose cone of the WB-57 aircraft are four cameras. These will take dozens of pictures a second of the occluded sun in different wavelengths of light. The images should capture large, looping ribbons of plasma called prominences and magnetic explosions called nanoflares. Only with the glare of the sun’s disc blocked out are such observations possible.
“I’m super-excited,” said Dr Amir Caspi, the principal investigator on the mission at Southwest Research Institute in Boulder, Colorado. “Solar eclipses give us an opportunity to do science we couldn’t do at any other time.”
Despite the name, nanoflares pack a punch, each releasing thousands of atomic bombs’ worth of energy as they go off around the sun. The flares at least partly explain one of the sun’s greatest mysteries: why the corona or outer atmosphere is so hot, at more than 1,000,000C, while the surface is a mere 6,000C.
For these observations, aircraft are hard to beat. Ground-based cameras have clouds to contend with and atmospheric interference. Space-based cameras are above such concerns, but can send back only so much data. “As you can imagine, this is terabytes of information,” Caspi said.
The WB-57 is based on the English Electric Canberra bomber, the RAF’s cold war tactical nuclear strike aircraft, and flies above the clouds in the stratosphere. But other planes have been used for eclipse missions. In 1923, the US navy sent a fleet of biplanes to observe an eclipse, without much success. Fifty years later, scientists persuaded the French to cut holes in the roof of a Concorde prototype; hurtling over the Sahara at Mach 2, they kept up with an eclipse shadow for 74 minutes.
The more scientists learn about the sun, the better they should be able to grasp space weather, the barrage of energetic particles and radiation that are hazardous to astronauts, satellites and even power grids and communications on Earth. Caspi said: “Understanding space weather is critical for us as a technological species, and it starts with understanding the processes at the sun.”
Eclipses are not all about science though. “What percentage of humanity has ever witnessed a total solar eclipse? It’s a fraction of a fraction of a per cent,” Caspi said. “If you’re part of that rare group, you’re connected to the Earth and the sun and the solar system. It’s mind-blowing. It makes you feel very special, but also very small because you are this little mote in the universe.”
