Two spacecraft created an artificial total solar eclipse on May 23, one of their early attempts. One craft blocks the other’s view of the sun, resulting in images (one shown in visible light) of the corona, the outermost region of the sun’s atmosphere.
WOW algorithm/ASPIICS/Proba-3/ESA (CC BY-SA 3.0 IGO or ESA Standard License)
It takes two to tango. Or at least to imitate a total solar eclipse from space.
Two spacecraft orbiting Earth have begun to mimic the phenomenon, with images from one of the duo’s successful early attempts unveiled on June 16. These artificial eclipses — produced when one satellite blocks the other’s view of the sun — will help researchers better understand the solar system’s star, specifically its outermost atmosphere: the corona.
“It was so incredible,” says solar physicist Andrei Zhukov of the Royal Observatory of Belgium in Brussels, who works on the mission. “We could see the corona without any special image processing. It was just visible there, like during a natural total solar eclipse.”
The satellites have completed nine eclipses so far during a test phase of checking and optimizing systems, Zhukov says. The goal is to create two eclipses per week.
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Light emitted by iron atoms, artificially colored green, shows the hottest contents of the corona during a May 23 artificial eclipse. ESA/Proba-3/ASPIICS (CC BY-SA 3.0 IGO or ESA Standard License) -
The corona’s inner layer is visible in polarized white light, artificially colored purple, during a May 23 artificial eclipse. The imaging technique separates the structure’s polarized light from light scattered by space dust. ESA/Proba-3/ASPIICS (CC BY-SA 3.0 IGO or ESA Standard License) -
Light emitted by helium atoms appears yellow in this visible-light image. The grid shows the sun’s position behind the shadow-casting spacecraft, which is slightly off-center in this test image captured on March 25. ESA/Proba-3/ASPIICS (CC BY-SA 3.0 IGO or ESA Standard License)
The European Space Agency’s Proba-3 mission involves the spacecraft pair circling the Earth in an elliptical path, reaching a maximum distance of roughly 60,000 kilometers from the planet. That’s when the duo is closest to the sun. There, they create a total solar eclipse by lining up about 150 meters apart so that one craft casts a precise shadow on the other, which captures data on the corona.
At 1 million degrees Celsius, the corona is almost 200 times the temperature of the sun’s surface. The answers to why that temperature difference occurs and other burning questions may lie in the corona’s middle layer, which can be observed only during a total solar eclipse.
The sun’s light is completely blocked by the moon somewhere on Earth just once every 18 months, with an event lasting for a few minutes at most. The spacecraft duo, however, will replicate the phenomenon on demand. Every 20 hours, it can create an eclipse that may last up to six hours.
Proba-3 launched from India on December 5, and is expected to generate more than 1,000 hours of artificial eclipses over the next two years.
