The Nasa plane chasing the solar eclipse

As daytime skies turn dark and the Moon's giant shadow sweeps across northern parts of the Earth on Wednesday, a Nasa research plane will launch an extraordinary chase through the skies.

Flying high above Iceland at almost 460 miles per hour, the aircraft will follow the eclipse in an effort to help scientists investigate one of the Sun's biggest mysteries.

A solar eclipse happens when the Moon moves between the Earth and the Sun. As the Moon passes in front of the Sun, it blocks some or all of the sunlight reaching parts of our planet. A total solar eclipse happens somewhere on Earth roughly every 18 months.

The plane's mission is to examine the Sun's corona, its outer atmosphere. The corona stretches millions of miles into space but is usually hidden from view because the Sun's surface is so dazzlingly bright. During a total solar eclipse, the corona is revealed as a glowing halo around the darkened Sun.

For people in the UK, the eclipse on 12 August isn't total, but the Moon will cover around 90% of the Sun across most of the country. Some areas in the south-west will see even more.

IMPORTANT: If you are hoping to see the eclipse, remember this safety rule: Never look directly at the Sun.

Looking at the Sun without proper eclipse-viewing glasses can seriously damage your eyes, even when part of the Sun is covered by the Moon.

Ordinary sunglasses are not safe. Instead, use specially designed solar eclipse glasses or make a pinhole projector.

The aircraft, called the WB-57, is a specially adapted research jet that can fly at around 50,000 feet - that's roughly twice the height of many passenger airliners.

Flying so high allows it to get above most clouds and water vapour, meaning its cameras capture clearer images of the Sun's mysterious corona.

With the corona in view, scientists want to study enormous loops of superheated gas, called plasma, that can be viewed twisting and leaping from the outer edge of the Sun.

They also hope to learn more about a puzzling problem known as the heating paradox.

Strangely, the corona is millions of degrees hotter than the Sun's visible surface, even though it is farther away from the Sun's centre. Scientists are still trying to understand why.

Hidden inside the nose of the WB-57 are four powerful cameras that will photograph the corona in different wavelengths of visible and infrared light.

By chasing the Moon's shadow, the aircraft can keep the eclipse in view for nearly three minutes, longer than many people watching from the ground.

Kelly Korreck, Nasa's eclipse programme manager, said: "From our unique perspective on Earth during a total solar eclipse, scientists can study the Sun's corona in a way we can't from anywhere else in the solar system."

She added: "The Sun impacts our daily life, satellites and astronauts in space, and we can take advantage of this moment to advance our understanding of that influence."