Artificial solar eclipse: Why are satellites trying to block the sun?

European Space Agency launches Proba-3 to create an artificial solar eclipse and study the sun’s atmosphere, the corona.

When you see a solar eclipse, you often think of the moon passing between the Earth and the sun, then temporarily blocking the sun’s light from reaching Earth. This alignment is known as syzygy (sounds like siz-uh-jee).

However, last week, the European Space Agency (ESA) launched two spacecraft that will aim to mimic the behaviour of the moon by creating an artificial solar eclipse for the first time ever. The idea? To demonstrate the readiness of a technology called precise formation flying (PFF) and to study the sun’s atmosphere, known as the corona. The mission is called Proba-3 (Project for On-Board Autonomy).

“Right now this [the corona] is a region of the sun that has been poorly investigated, and scientists nowadays don’t really understand some of the phenomenon that’s happening there,” Ester Bastida, Proba-3 systems engineer, said in a recent ESA video. Among the key questions about the corona that scientists want to understand is why it’s significantly hotter than the sun itself.

While the surface of the sun is at roughly 5,500 degrees Celsius (9,932 degrees Fahrenheit), the corona — the wispy outer atmosphere of the sun — can reach temperatures of 1-3 million degrees Celsius (1.8-5.4 million degrees Fahrenheit).

Although the circumference of the sun is roughly 4,373,000 kilometres (2,717,000 miles), solar flares from the corona can reach Earth, almost 150 million kilometres (93 million miles) away.