A space observatory has witnessed a unique “eclipse of the Sun” of a type that can never be seen from Earth. Nasa’s Stereo B satellite watched from a million miles away as the Moon slowly drifted in front of the solar disk.

From Earth, the moon appears the same size as the sun in the sky. But Stereo’s view, using cameras built in the UK, showed it as a much smaller silhouette crossing the sun’s brilliant and active surface.

The jaw-dropping images, captured in the extreme ultraviolet part of the spectrum, amazed scientists who saw them. One said it was like being in the wrong solar system!

Stereo B is one of two space observatories launched last October to monitor activity on the sun. It sits a million miles behind the Earth while its twin craft flies a million miles ahead of us.

As scientists were putting the two probes into their final positions, they tweaked Stereo B’s flightpath in order to capture the unique transit of the moon across the sun. You can see a dramatic movie of the event using the links here.

Nasa scientist Lika Guhathakurta said: “The images have an alien quality.
“It’s not just the strange colors of the sun. Look at the size of the moon – it’s very odd. It’s like being in the wrong solar system.”

The two solar observatories will watch the biggest explosions in the solar system, getting a 3D view of violent flares. They will check for any that hurl billions of tons of hot gas directly towards us at a million miles an hour, threatening communications satellites, power grids and even astronauts’ lives.

Britain has contributed £1.9 million to the £280 million space weather mission, called Stereo. Biggest UK involvement has come from the Rutherford Appleton Laboratory, near Oxford, and Birmingham University. Explosions on the sun – called coronal mass ejections – are equal to setting off billions of nuclear bombs.

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