First published May 24, 2020.
June 2020 brought two eclipses about two weeks apart. On June 5 the full Moon slipped into the faint outer part of Earth's shadow in a penumbral lunar eclipse, with the deepest point at about 19:25 UTC. On June 21, the day of the June solstice, the new Moon crossed in front of the Sun in an annular solar eclipse, a "ring of fire", with greatest eclipse at about 06:40 UTC. The ring was visible along a narrow strip from central Africa through Arabia, Pakistan, northern India and China to Taiwan; much of Asia, eastern Europe, Africa and northern Australia saw a partial eclipse.
Below is a clear guide to what happened, why these two events look so different, and how to watch any eclipse safely.
Lunar versus solar eclipses: who is blocking whom
The two kinds of eclipse are often confused, and early versions of many eclipse round-ups mixed them up. The simplest way to keep them apart is to ask which body is casting the shadow.
- Lunar eclipse: Earth sits between the Sun and the Moon, and Earth's shadow falls on the Moon. It can only happen at full Moon, and anyone on the night side of Earth can see it.
- Solar eclipse: the Moon sits between the Sun and Earth, and the Moon's shadow falls on part of Earth. It can only happen at new Moon, and only people inside that shadow see it.
Because the Moon's orbit is tilted by about five degrees to Earth's orbit, the three bodies line up closely enough only during "eclipse seasons", roughly every six months. That is why eclipses tend to come in pairs or trios a fortnight apart, exactly as they did in June 2020. Astronomers can calculate these alignments centuries ahead.
The penumbral lunar eclipse of June 5, 2020
Earth's shadow has two parts. The dark inner cone, the umbra, is where the Sun is completely hidden. Around it lies the penumbra, where the Sun is only partly blocked. On June 5 the Moon passed only through the penumbra, so it never turned the coppery red of a total lunar eclipse. Instead, one side of the Moon took on a subtle grey shading that many casual viewers did not notice at all.
The eclipse began at about 17:46 UTC, peaked at about 19:25 UTC and ended a little after 21:00 UTC. It was visible wherever the Moon was up: Europe, Africa, most of Asia and Australia, and the far east of South America at moonrise.
Penumbral eclipses are the least dramatic kind, but they are completely safe to look at with the naked eye, binoculars or a telescope, since you are looking at the Moon rather than the Sun.
The annular "ring of fire" eclipse of June 21, 2020
The Moon's orbit is an ellipse, so its distance from Earth changes. When a solar eclipse happens while the Moon is relatively far away, its disc looks slightly smaller than the Sun's and cannot cover it completely. The result is an annular eclipse, from the Latin annulus, meaning "little ring": a dark Moon surrounded by a bright circle of sunlight.
On June 21, 2020, the Moon was only just too small. The eclipse magnitude was about 0.994, so the ring was extremely thin, and at the point of greatest eclipse, over northern India near the Himalayas, annularity lasted only around 38 seconds. The path of the ring crossed parts of the Republic of the Congo, the Central African Republic, the Democratic Republic of the Congo, South Sudan, Ethiopia and Eritrea, then Yemen, Oman, Pakistan, northern India and southern China before ending over Taiwan and the Pacific.
Outside that strip, observers saw a partial eclipse, with the Moon taking a bite out of the Sun. Local times varied by several hours depending on location, so a single "global" time never tells an individual observer when to look. Because 2020 was the year of the pandemic, many people watched through livestreams from observatories in India, Taiwan and elsewhere.
All six eclipses of 2020
2020 had six eclipses in total, a fairly typical number. Some round-ups at the time wrongly promised total lunar eclipses in June and December; in fact there were none that year.
- January 10: penumbral lunar eclipse
- June 5: penumbral lunar eclipse
- June 21: annular solar eclipse
- July 5: penumbral lunar eclipse
- November 30: penumbral lunar eclipse
- December 14: total solar eclipse, visible from parts of Chile and Argentina
Earlier in 2020, skywatchers also enjoyed a run of bright "supermoons" in spring and the Eta Aquariid meteor shower in early May, which is made of debris from Halley's Comet.
How to watch a solar eclipse safely
An annular eclipse is one of the most dangerous to watch carelessly. Even when 99 percent of the Sun is covered, the remaining ring is bright enough to burn the retina, and the damage can be painless at first and permanent. A few simple rules apply to every solar eclipse:
- Use eclipse glasses or handheld solar viewers that meet the international standard ISO 12312-2, from a reputable supplier. Ordinary sunglasses, however dark, are not safe.
- Never look through binoculars, a camera or a telescope unless a proper solar filter is fitted to the front of the instrument. Do not combine eclipse glasses with an unfiltered optical device.
- Pinhole projection is an easy alternative: a small hole in a card, or the gaps between leaves, will project tiny crescents or rings onto the ground.
- Supervise children closely.
If your eyes hurt or your vision changes after watching the Sun, talk to a doctor or eye specialist promptly.
Common eclipse myths
"Eclipses are harmful to pregnant women or food." There is no scientific evidence for this. An eclipse is only a shadow; it does not change sunlight in any harmful way. The one real danger is looking at the Sun without protection.
"The ring of fire is the Sun's atmosphere." In an annular eclipse the ring is the Sun's ordinary bright surface. The faint pearly corona can only be seen during a total eclipse.
"Penumbral eclipses turn the Moon red." The red "blood Moon" colour comes from sunlight bent through Earth's atmosphere into the umbra, so it appears only during total lunar eclipses, and sometimes faintly during deep partial ones.
For people in ancient times, a darkening Sun or Moon could be terrifying, and many cultures told stories of a creature swallowing the sky. Today the same event can be predicted to the second, which makes it no less beautiful to watch.
Sources: NASA Eclipse Website: Eclipses during 2020; NASA: path of the June 21, 2020 annular eclipse; Wikipedia: Solar eclipse of June 21, 2020; NASA: Eclipse safety; EarthSky: Annular solar eclipse on June 21, 2020.
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