Concurrence of eclipse, supermoon and spring equinox is extremely rare
Parts of Europe will be treated to three astronomical events at once on Friday: a supermoon, a total eclipse of the sun and the spring equinox. The concurrence of all three celestial events is rare and has excited both amateur and professional skywatchers. Gautam Naik reports.
Parts of Europe will be treated to three celestial events at once on Friday: a supermoon, a total eclipse of the sun, and the spring equinox, when night and day are of equal duration.
Solar eclipses are rare. The illusion of a supermoon can be witnessed several times a year, when the moon flies closest to the Earth and therefore appears larger than usual. The spring equinox occurs once a year, and marks the beginning of spring in the northern hemisphere.
But the concurrence of all three events is extremely unusual, and has excited skywatchers.
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| Astronomer Brendan Owens with a telescope at the Royal Observatory in Greenwich, England, on Thursday ahead of Friday’s solar eclipse. |
“These are rare events and therefore memorable,” said Radmila Topalovic, an astronomer at the Royal Observatory Greenwich, England, which will aim a dozen specially modified telescopes at the sky on Friday so people can view the two-hour eclipse. “Despite all the planning it’s going to be a humbling experience.”
A solar eclipse occurs when the moon completely blocks our view of the sun’s disk, turning day into night. Though total solar eclipses occur somewhere on earth every 18 months on average, they recur at any given place just once every 360 to 410 years. The moon is 400 times smaller than the sun but also 400 times closer, so it appears the same size in the sky and virtually covers all of the sun during a solar eclipse.
During a total eclipse, the cone-shaped shadow of the moon becomes narrower as it extends toward Earth. The path of “totality” is typically 10,000 miles long but only about 100 miles wide.
On Friday, people living in parts of the Arctic and the far north of Europe will witness the eclipse in its totality, while most of Europe and parts of northern Africa will see a partial eclipse. In parts of Britain, the moon will blot out 85% of the sun and cast an eerie light during the morning rush hour and school run.
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| A total eclipse of the sun as seen in Zimbabwe in 2001. Skywatchers in parts of Europe are preparing for a solar eclipse on Friday. |
Skywatchers in the U.S. will have to wait until Aug. 21, 2017 to see the next total solar eclipse.
A supermoon, by contrast, is an illusion. Because of the moon’s oval orbit, a full moon appears to vary in size when it is viewed from Earth. The moon follows an elliptical route around Earth such that one side, or perigee, is roughly 50,000 kilometers (31,000 miles) closer than the other. A supermoon occurs on the perigee side of the moon’s orbit.
Because it is so close, a supermoon can seem unusually big and bright. They are especially dramatic when they are just above the horizon. A supermoon seen in the U.S. in June 2013 was 14% bigger and 30% brighter than other full moons that year. And last year, the parts of the U.S. witnessed three supermoons—in July, August and September.
Friday’s supermoon could affect how some viewers witness the eclipse, such as those in the Faeroe Islands who are in the path of totality. Because the moon will be closest to Earth that day, Faroe Islanders will witness slightly more of the sun’s face covered up when compared with what they would see during a regular, total solar eclipse.
“They’re very lucky,” said Dr. Topalovic. “They’ll see full coverage.”
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