Annular eclipse — solstice ring over Taiwan (2020)
On the solstice of 21 June 2020 a very thin annular eclipse ran from Africa over northern India, Tibet and southern China to Taiwan. The Moon covered 99.4% of the Sun's width, and in Chiayi, Taiwan, a thread-like ring lasted just under a minute.
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The story
21 June 2020 was the June solstice, the longest day of the year in the Northern Hemisphere. On that day a ring of fire as thin as a thread swept across Earth. The Moon covered 99.4% of the Sun's width, leaving only a narrow rim of light around the edge. Had the Moon looked just a little larger, it would have hidden the Sun completely in a total eclipse.
The Moon's shadow began in the Democratic Republic of the Congo, crossed South Sudan, Ethiopia and Eritrea, and moved on to Yemen and Oman. It then passed over Pakistan and northern India, climbed over the Himalayas and the Tibetan plateau, crossed southern China, and left over Taiwan into the Pacific. The stretch over the Himalayas and Tibet ran across high land where hardly anyone lives.
In Chiayi, Taiwan, the ring appeared at about 16:10 and lasted around 56 seconds. Northern Taiwan had been inside an annular path in May 2012; this time it was the south of the island that lay in the path. Although the Sun was almost completely covered, the thin rim was still bright, so the sky only dimmed a little, like a cloudy afternoon.
The eclipse happened while the COVID-19 pandemic made travel difficult. Instead of journeying far, many people watched from near home with a single pair of eclipse glasses, and many more followed live broadcasts online. The orbit view reproduces the Moon's shadow cutting diagonally across the globe from Africa to Asia.
Viewing guide — where, when, how
The ring could be seen starting in the Democratic Republic of the Congo, South Sudan and Ethiopia, then over Yemen and Oman, Pakistan and northern India, Tibet and southern China, and finally Taiwan. Near the point of greatest eclipse, in Uttarakhand in northern India, the ring lasted 38 seconds. A partial eclipse was visible across much of Africa, south-eastern Europe, most of Asia, and New Guinea and northern Australia.
The thinner the ring, the more the filter matters. Even a tiny sliver of Sun can hurt the eyes if viewed without protection. Because the ring lasted less than a minute, photographers did best by fixing their camera settings in advance and shooting continuously before and after the ring formed. Even after the brief ring ends, filters must stay on through the partial phases before and after.
The sky view follows the Sun over Chiayi and slows down to reproduce the moment the ring forms. Changing the viewing place to Hong Kong shows that afternoon's deep partial eclipse, with most of the Sun covered. This makes it easy to compare how much of the Sun was hidden from different places. Switching to northern India shows the view near the point of greatest eclipse as well.
See this for yourself — open that sky at that moment · replay the moment in the orbit view
Why this eclipse is special
This eclipse shows clearly how different an almost-total eclipse is from a true total one. In a total eclipse, the moment the last sliver of Sun disappears, the sky darkens and the corona and stars appear all at once. An annular eclipse never crosses that line. Even a tiny piece of remaining Sun keeps the sky bright, so the corona stays hidden.
The thinner the ring, the more the shape of the Moon's edge shows. That edge has mountains and valleys, so a very thin ring may not look smooth; it can break into separate beads of light, known as Baily's beads. Recording these beads from many places gives data for measuring the heights along the Moon's edge and the size of the Sun.
The eclipse falling on the solstice was pure chance, but it caught people's attention. On the day when the Sun stays up longest in the Northern Hemisphere, that same Sun briefly shrank to a thin ring. Coincidences like this are a good way to spark interest in how the Sun and Moon move. Also, around the June solstice Earth is near its farthest from the Sun, so the Sun looks slightly smaller, which helped the Moon cover almost all of it.
Background and earlier eclipses
This eclipse is the 36th member of Saros 137. The previous member was the annular eclipse of 10 June 2002 over the Pacific, and the next is the annular eclipse of 2 July 2038, which crosses the Atlantic and Africa. Similar eclipses repeat about every eighteen years over different parts of the world. Eclipses in the same series return at a similar time of year and in a similar form.
Six months earlier, on 26 December 2019, an annular eclipse had crossed southern India and South-East Asia. Six months later, on 14 December 2020, a total eclipse crossed Chile and Argentina. Even in 2020, a year when travel was hard because of the pandemic, the centre of the Moon's shadow crossed Earth twice.
The next annular eclipse, on 10 June 2021, took a very different path across the far north of Canada, Greenland and Siberia. For East Asia the next ring does not come until 1 June 2030, when the band crosses north-eastern China and northern Japan.
FAQ
Why did the sky not go dark?
The Sun was almost completely covered, but the thin rim that remained shone with the full brightness of the Sun's surface. The darkness of a total eclipse comes only when the Sun is completely hidden.
How long did the ring last?
Near the point of greatest eclipse in northern India it lasted 38 seconds. Toward the end of the path, in Chiayi, Taiwan, it was actually a little longer, at about 56 seconds.
Was the ring seen outside the band?
No. Outside the band only a partial eclipse was seen, and less of the Sun was covered the farther a place lay from the path.
Why was it not a total eclipse?
On that day the Moon looked very slightly smaller than the Sun. Its width was only 99.4% of the Sun's, so a thin rim of sunlight was left.
Related
- The 2019 annular over Singapore
- The 2020 total eclipse over Chile and Argentina
- The 2021 Arctic annular
- The Moon — object index
- The Sun — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.