Solar eclipse April 20, 2023

The upcoming eclipse will be unusual. Like many astronomers, solar eclipses are total, annular and partial. Partial phases (I’ll clarify right away – this is exactly what the eclipse phases are called in astronomy, in which the Moon does not completely cover the entire sun, but only part of it) always accompany a total and annular eclipse, but if an eclipse is called partial, then this means that nowhere on There is no total or annular solar eclipse on the planet. Total and annular phases of solar eclipses are still sometimes combined with the term “central phases” and not every eclipse reaches them. But our eclipse will be exactly central.

What is its unusualness?

And that, having begun ring-shaped, it suddenly becomes full. This type of solar eclipse is called “Hybrid”. Hybrid eclipses are quite rare. there are only a few in a century. In the 21st century there are 7 of them, and 2 have already passed.

What causes hybrid eclipses?

Because of the same thing that causes all the other eclipses – because of the moon. But there are nuances.

The Moon’s orbit has an inclination to the plane of the Earth’s orbit, which is why most often for an Earth observer during new moons, the Moon passes above or below the Sun. The visible paths of the Sun (the ecliptic) and the moon in the sky have two intersection points – these are the so-called lunar nodes. If a new moon occurs near the lunar node, an eclipse may occur.

The lunar orbit is not circular. It looks more like a slightly elongated ellipse. At different times, the Moon is a little closer or a little further from the Earth. Because of this, the Moon appears to the earthly observer of a different angular (apparent) size. The angular size of the moon is greater than the angular size of the Sun, or less. When the Moon is near the perigee of its orbit (perigee is the closest point to the Earth in the orbit of a celestial body circling the Earth), the Moon looks much larger than the Sun. And if the eclipse happens near the perigee of the lunar orbit, the eclipse can be total (if the cone of the lunar shadow does not miss the Earth). If, during the eclipse, the Moon is near the opposite point of the orbit – near the apogee, where it is farthest from the Earth, its apparent size will not be enough to cover the entire Sun, and a bright rim will remain around the sun. This is an annular eclipse.

And what will happen if the eclipse occurs near that point of the lunar orbit, being in which the Moon has an angular size equal to the solar one – somewhere between perigee and apogee?

This is where a hybrid eclipse can occur. If by the beginning of the eclipse the Earth and the Moon are separated by a distance close to 375 thousand kilometers, the lunar shadow cone does not reach the Earth’s surface. But the Earth is round – convex towards the Moon, and in the process of orbital movement the top of this cone still bumps into the Earth – from a certain moment the eclipse turns from annular to total, but not very long. Further, the band of the full phase becomes wider, and the duration of the full phase is longer, but it is unlikely that it will be more than one and a half minutes in the Earth location closest to the Moon, having passed through which the shadow of the Moon will again cover an ever smaller zone, until it again breaks away from the Earth. Although, the latter is not necessary. And if, moving along the orbit, the Moon approaches the perigee of the orbit (and, therefore, to the Earth), then, having begun as an annular, the eclipse may end in a total eclipse without returning to the annular phases.

And maybe vice versa – having begun full, by its end the eclipse will turn into annular.

On April 20, 2023, a solar eclipse will begin in the Indian Ocean, somewhere between Africa and Antarctica. The central phases at the beginning of the eclipse will be exactly annular, but as the cone of the lunar shadow moves over the water surface of the ocean, the top of this cone will touch the water a little northeast of the Kerguelen Archipelago (FSA – French Southern and Antarctic Territories). From this meta (46 degrees south latitude, 71 degrees east longitude) the eclipse will become total, and the total phase band will rush towards Australia.

The total eclipse will affect Australia only in passing – the town of Exmouth with a population of 2,400 inhabitants and a number of small villages near it on the west coast of Australia will fall into the zone of the total phase. The width of the full phase band here will be only 30 kilometers, and the duration of the full phase will be less than a minute. The moon shadow will immediately “dive” into the ocean, rushing to the island of Timor, where it will visit its eastern part – a state called East Timor.

In East Timor, the eclipse will reach its largest phase (1.013), duration 1 minute 16 seconds, and the width of the total phase of the eclipse will be 49 kilometers.

Further, the total phase band will reach the island state of Maluku, followed by West Papua, and break out into the expanses of the Pacific Ocean, where the width of the band will begin to narrow rapidly, the duration of the total phase of the eclipse will decrease, and at the point with coordinates 5 degrees south latitude and 171 east longitude, the cone of the lunar shadow breaks away from the water surface – the eclipse will again become an annular. But very soon the lunar shadow will finally leave the Earth, and the eclipse – including its partial phases – will cease on the entire planet.

As you might guess, this eclipse will not be visible in Russia and most of its neighboring states.

Minor partial phases (1-2%) can be observed on the southeast coast of China. In Cambodia and Vietnam, the partial eclipse phase can reach 10-15%.

The best conditions for observations will be in Australia – this entire continent will be affected by the lunar penumbra, and the phase value will vary from 20 to 101% (in the same Exmouth), but it is the full phase that will affect the tiny North West Cape peninsula.

And of course, all the islands and countries of Oceania, located between Australia and Southeast Asia, will also become the region of visibility of the eclipse – mostly private, but in some places (mentioned above) it will be possible to see, albeit a fleeting, but complete phase.

Of the bright luminaries that can be observed in the sky at the time of the onset of the full phase, I note first of all Jupiter, which is now practically behind the Sun, and in the sky is distant from it at an angular distance of about 5 degrees. Mercury and Venus will also be in the sky and will be visible during the full phase, but much further east.

April 20 is the first day of the Sun’s stay within the constellation of Aries, which does not have such bright stars that could be visible during a shallow total eclipse. There are no bright stars in neighboring Pisces either. But not far from Venus, you can see the orange-red Aldebaran, heading the constellation Taurus, and even – with luck – Orion filled with bright stars and even Sirius and Canopus.

But if you happen to be somewhere in the Indian or Pacific Oceans, where the eclipse will be annular, there, of course, no stars will be visible in the sky during the deepest phase. The only luminary that can be seen during the annular phase of a solar eclipse is Venus. But to an observer in the Indian Ocean, Venus would be below the horizon. For an observer in the Pacific Ocean, caught in the band of visibility of the annular phase, Venus will be visible.

A bit of timing

Start 01:34:16 UTC

Complete phases 02:36:56 — 05:56:35 UTC (Universal Time)

Ending 06:59:14 UTC

Duration 3 hours 20 minutes

PS: Elon Musk intends to launch his Starship (second attempt) exactly at the eclipse. Let’s see what it turns out to be.

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