Rare hybrid solar eclipse sweeps the globe
Sen—Many thousands of people around the world witnessed a particularly unusual eclipse of the Sun yesterday and saw it in quite different ways.
Critically, the event was what is known as a hybrid eclipse because while most places on the shadow’s central track experienced totality, the starting point only experienced an annular event.
Furthermore, a large part of the global audience, notably along the eastern coast of the USA, witnessed the stunning sight of a partial eclipse rising from the sea horizon.
Most of the 13,600 km (8,450 miles) track of the eclipse crossed the Atlantic Ocean. Around 1,000 km east of Jacksonville, Florida, it would have been possible to get the first views of the Moon passing completely in front of the Sun’s disk at 11.05 UT.
By a wonderful coincidence, the Moon and the Sun appear approximately the same angular size in the sky because their differing sizes are made up for by the fact that the Moon is significantly closer to us.
But at this earliest stage of the eclipse, as seen from the ocean surface, the Moon was just too small to cover the Sun completely. A narrow ring of light remained around the Moon at maximum eclipse, hence the description annular.
The brief moment of totality captured through thin cloud from Uganda. Credit: Daniel Fischer
Within just 15 seconds, the geometry caused by the Earth’s uneven shape changed the event from an annular to a total eclipse. The Moon’s dark umbral shadow now reached the sea.
Circumstances continued to improve as the shadow’s track swept across the sea towards equatorial Africa. Greatest eclipse occurred while the shadow was still over the sea at 12h 47m 36s UT, 330km (205 miles) southwest of Liberia. Any seafarers in the vicinity would have enjoyed 1 minute 39 seconds of totality at this point with the Sun more than 70 degrees high in the sky.
Still heading eastwards, and with the Sun rapidly sinking in the sky, the eclipse shadow finally hit land on the coast of Gabon where totality was reduced to 1 minute 7 seconds. After crossing the Congo, the umbral shadow headed northeast to reach Uganda (23 seconds of totality), northern Kenya (14 seconds of totality) and finally Somalia which experienced just one second’s total eclipse at sunset.
Among European astronomers who travelled to Africa for the eclipse was Janne Pyykkö from Finland. He took a bus to Gulu where, sheltering from heavy rain, he met the young local woman, university student Irene, who features in our main image, carrying two plates of oranges.
Janne observed with a crowd of enthusiastic youngsters. As he only had a single pair of filtered “eclipse glasses”, they used smoked glass to view the eclipse, a method that is usually discouraged for safety reasons.
The blue line shows the central track of the eclipse from the Atlantic to Somalia. Credit: F.Espenak/NASA
Janne told Sen: “We got a permission to use the flat grass field of a orphanage home. The nurses and staff were watching the eclipse with us with a great joy.
“The eclipse was very short. But I saw two clear diamonds in the ring, when the totality started. I heard afterwards that Irene’s grandfather did not see the eclipse because he was inside watching TV.”
Noted space writer and commentator Daniel Fischer, from Germany, drove across Uganda to find good sky conditions and managed to take some lovely images of totality through thin cloud just east of Pakwach, including the one above. You can see the rest on his Twitter timeline.
Eclipses come in families, with related events space at intervals of about 18 years and 11 days, a term called a Saros. This group, labelled Saros 143, began delivering partial eclipses as far back as 1617 and the final eclipse in the series will occur in 2897 (on 23 April if you want to put it in your diary!).