Solar eclipse: between chance and totality

By a sublime and unimaginable coincidence, the moon and sun are exactly the right size, and the distances between earth, sun and moon are such that the latter neatly covers the solar disc during that fleeting but dazzling moment of a total solar eclipse. In a path of about 120 miles wide, one of the most splendid sights of our immediate cosmic neighborhood reveals itself, transcending both science and mind.

By Kathelijne Bonne.

A total solar eclipse sweeps over North America from west to east on 8 April 2024. In the central part of the totality path, the unsettling darkness lasts for about four minutes. Each solar eclipse leads to new discoveries and more beautiful images, and is described by everyone who has already experienced it as particularly moving, for some even literally as a 'total eclipse of the heart'. This latest of several great American eclipses will be as unforgettable as past ones, for those lucky enough to witness it, preferably under a cloudless sky.

Eclipses are amongst those rare events in which crowds of people of all walks of life gather, dissolving all walls between science and wonder. Ordinary spectators buy eclipse glasses, astronomy amateurs and photographers set up their expensive gear within the totality path. Space agency professionals also plan their meetings conveniently in the umbra of the moon.

The moon, usually such a faint and changeable object in the night sky, yet indispensable to life on earth, will briefly obscure the sun, our ultimate source of life to put on a grandiose show. From the moment the moon fully covers the solar disc, the sun, in its fiery response, will expand its bright flames. The corona, a million degrees hot, becomes visible, veiled in iridescent, unearthly colors. Only during a total solar eclipse can the corona be seen with the naked eye. The hot plasma streams into the universe in long strands, distorted by the sun's immense magnetic fields.

The total solar eclipse of 8 April 2024 will be extra special. The temporary darkness will be deeper than usual because the moon is closer to Earth, making it appear larger and covering more sunlight. The sun is also in the most active phase of its 11-year cycle, which increases the chances of seeing coronal mass ejections, i.e., large solar eruptions that blast masses of ionized particles into space. The planets bend this particle flow in their own magnetic field, leading to auroras, that other cosmic show visible from Earth. Large mass ejections can cause geomagnetic storms and disturbances and power outages in radio networks, a reason why the sun is intensely studied, e.g. by the Solar Orbiter, which will monitor the sun's activity during the upcoming eclipse, delivering a lot of exciting new data.

Totality

An eclipse begins with the moon taking a small bite out of the sun. The coverage increases, and can last for more than an hour. Just before totality, a diamond ring can be seen; the sun's rays still break through on one side.

Then the long-awaited totality arrives. The sun goes black, the corona expands like a scintillating bloom. Colors of the day fade to dark shadows to make way for colors never seen before. The sky becomes a deep indigo, the landscape may get a silvery tinge. A chilly wind starts blowing. All the usual familiar colors are gone.

When totality begins, the moon's massive shadow suddenly flashes across the landscape at a cosmic speed, only to pull away again a few minutes later, after totality. During the American eclipse of 8 April, the shadow will accelerate from 1,500 to 5,000 miles per hour and its shape will deform from round to elongated until it falls off the planet and the eclipse is completely over.

People who experience a total solar eclipse call the phenomenon surreal and indescribable, spine-chilling and splendid at the same time. They feel a sense of nullity in the face of the monumental and inescapable dance of our closest celestial bodies. In the past, humans must have thought that the end of time was imminent. Even now, with all our technical foreknowledge, the magic of totality goes beyond human comprehension. Such pivotal events in which the cosmos connects more closely than ever with our deepest emotions, are best reflected through the prose and verse of writers, poets and thinkers, such as Maria Mitchell (1818-1889), Emily Dickinson (1830-1886) or Mabel Loomis Todd (1856-1930) (see links in bibliography).

Corona

Corona means crown in Spanish, so named by the Basque José Joaquín de Ferrer (1763-1818) in 1809, who witnessed two total solar eclipses. He discovered that the corona belonged to the sun, although it had already been suggested earlier, namely in 1724 by astronomer Giacomo Maraldi (nephew of the more famous Cassini).

Speaking of the solar corona may inadvertently bring to mind the coronavirus, which a few years ago brought our human world to a standstill in a whole different kind of totality. The link between the names of this solar phenomenon and a virus is not coincidental. The infamous virus consists of a nucleus with genetic material and around it a ring of protein protrusions. That reminded virologist June Almeida (1930-2007) of the halo of prominences and rays visible around the eclipsed sun. She identified the coronaviruses and gave them their name.

My first and only eclipse

The only solar eclipse, a partial one, that I ever witnessed was in 1999 in Marbella in southern Spain (in my native Belgium the eclipse was total, but it seems we didn't want to sacrifice our summer holiday, and preferred a blazing Spanish sun over an eclipsed sun under a possibly cloudy or rainy sky). In Marbella, we sat on the roof terrace under an ultramarine sky, waiting and watching the sun through a tiny hole in a piece of cardboard. It got noticeably darker and chillier. There was a big bite in the sun. The birds ceased their singing, dogs stopped barking, and it became strangely quiet in our typically Spanish housing compound in the middle of nature (probably also a product of predatory speculation). Or was the eerie quietness due to the siesta? 

Totality of course, never came, and I have yet to witness it. 

Transits

A transit is a similar, subjective phenomenon, which as in a solar eclipse, also depends on the vantage point of the viewer. A planet or moon slides in front of the sun or another star, or a moon in front of a sunlit planet. Transits cannot be seen with the unassisted eye, only through telescopes. 

A Mercury transit took place in November 2019, described in one of my first posts on GondwanaTalks, 'a pale black dot'.

The photo below shows a Venus transit (find Venus).

Thanks to these seemingly unimportant and subjective events, so far thousands of exoplanets orbiting other stars have been discovered outside our solar system. During a transit, starlight filters through the exoplanet's atmosphere, giving clues about whether there is water or oxygen, and about the possibility of whether the planet may host life. The planets of the Trappist system, Gliese, Proxima Centauri, and others, are potentially "habitable" planets. Some are ocean planets, just like Earth.

But until hard evidence of life is found beyond Earth, we are unique and alone in the universe.

Events like total solar eclipses give us a chance to pause and marvel at how extraordinary life is. We could also do that every day.

Here is a quote on the end of totality, by Fred Espenak, astronomer and eclipse specialist:

"Totality is over. The memory of this fleeting event will be replayed many times in the years to come. But for some people it will not be enough. They will travel to the far corners of the globe at the appointed time and place to witness the grand spectacle again. And again. And again. They are the eclipse chasers." (*)

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Read my post on exoplanets and what habitability really means. And to observe space you don't have to be an astronomer, many amateurs make beautiful images. Or read how the Moon was formed due to a massive impact, and why it is necessary for life on Earth. 

The Moon used to be closer to Earth and appeared much bigger, which must have led to particularly grand and terrific solar eclipses.

Kathelijne: I am intrigued by how earth, life, air, ocean and societies interact on geological and human timescales.

Why I started GondwanaTalks.

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