Rare solar eclipse to provide new insight into sun’s corona
The world will turn a little darker on Friday as the moon wanders across the face of the sun and casts a dark shadow over parts of Europe and the Arctic Ocean.
The rare solar eclipse will completely blot out the morning sun on the Faroe Isles, 200 miles (321km) north of Scotland, and in Svalbard, the Norwegian archipelago in the Arctic Ocean – the only two land masses to experience a total eclipse this time.
In Britain and much of the rest of Europe, the eclipse will be only partial. From around 8.25am in the UK, the moon will start to hide more than 90% of the sun in Scotland, and about 85% in London. The spectacle will be over by 10.41am.
The last total eclipse visible from Britain was in 1999 when thousands of people descended on Devon and Cornwall to experience the eery spell of daytime darkness. The UK will not see another total eclipse until 2090.
Clear skies permitting, the best place in the UK to watch the eclipse is the Isle of Lewis where the moon will cover about 98% of the sun. Hundreds of people, possibly more, are expected to arrive at the Callanish Stones on Friday morning, where the Stornoway Astronomical Society (SAS) is holding a public viewing.
“The interest is unbelievable. We’ve had inquiries from Southampton, Portsmouth, Dublin, Cork and even Munich,” said Donny Mackay, president of the SAS. He plans to get to the stones at 5.30am to set up two telescopes fitted with special filters to observe the eclipse.
“I’m really looking forward to it. If you’re not on the Faroe Isles or in Svalbard, this is best place to be. We’ve lived a quiet life for a while, but this is putting our name in front on people. Even people on the island didn’t know we existed,” he said. The society ordered 100 pairs of viewing glasses for people to wear at the event.
Scientists from all over the world are on their way to observe the total eclipse. Huw Morgan, from Aberystwyth University, is sending two PhD students to Svalbard’s main town, Longyearbyen, to assemble telescopes for a project run by Shadia Habbal, from the University of Hawaii. The moment the sun is totally blocked out, the scientists will study its corona, in the hope of learning why it is so much hotter than the rest of the sun. “It’s one of the big mysteries of astronomy,” said Morgan. “The corona is 1m to 2m degrees Kelvin, but the surface is only about 6,000 Kelvin. There’s this huge jump in temperature as you move away from the heat source.”
Morgan has witnessed eclipses in the Libyan Sahara, the Gobi desert and on Tahiti, but is staying home this time. “All the team have had to do safety training, including polar bear training. They will have a guard with a rifle. I hope they come back in one piece,” he said. “I didn’t fancy the cold.”
Inside the 100 mile-wide umbra where the sun’s light is totally blocked out, the sky will darken to twilight. But outside, even where 90% of the sun is obscured by the moon, the change in light level will barely be noticeable.
In Edinburgh, 93% of the sun will be hidden by the moon. “If it’s a clear day, it will feel a bit dull, a bit overcast, but you won’t get a sense that it’s getting much darker. The sun is so bright that even if you cover most of it up, it’s still millions of times brighter than anything else around,” said Tom Kerss, an astronomer at the Royal observatory, Greenwich.
It is still dangerous to look directly at the sun during a partial eclipse, Kerss warns. Special eclipse-viewing goggles block out the most harmful rays, but Kerss recommends a makeshift pinhole projector. Punch a tiny hole in a sheet of card and look at the shadow it casts. Where the hole is, there will be a projection of the eclipse that is perfectly safe to look at. Even better, Kerss said, use a colander. Each hole will cast its own projection, producing an eclipse montage.
Eclipses are so rare because the plane of the moon’s orbit is tilted relative to the Earth’s orbital plane. The tilt means that most of the time, the moon appears above or below the sun. For an eclipse to happen, the moon has to be at a “lunar node”, one of two places where the Earth’s and the moon’s orbits cross. It also has to be a full or new moon, and so in a direct line between the Earth and the sun.