Like any other opaque objects illuminated by a light source, the Moon and the Earth cast shadows into space as they block the sunlight that hits them. Each shadow has 3 different areas: the umbra, the penumbra, and the antumbra.

Umbra Definition

The umbra is a shadow's dark core. Imagine a light source and an object casting a shadow. If you are standing within theumbra, you will not be able to see any part of the light source as the object blocks all direct light rays.

The other 2 areas are:

• Penumbra – the lighter outer part of the shadow.
• Antumbra – the lighter part of the shadow that begins where the umbra tapers to a point.

Why are there 3 shadows?

When the Earth enters the Moon's shadow, we see asolar eclipse; when the Moon travels through the Earth's shadow, alunar eclipse occurs. Thetype of eclipse depends on the type of shadow that is involved.

Moon's Umbra Causes Total Solar Eclipses

If you are within the Moon's umbra and look into the direction of the Sun, you will see a total solar eclipse as the Moonblocks the all of the Sun. On its journey through space, the Moonalways casts an umbra. This means that somewhere in space, on the dark side of the Moon, a total solar eclipse ishappeningright now.

The reason why solar eclipses are so rare is that the Moon's umbrararely hits the Earth's surface. Even during atotal solar eclipse, the umbra only covers a small area on Earth.

As both the Moon and the Earth are in constant motion, the umbra moves across the face of the Earth during the eclipse, sothe total phase can usually only be seen along a slim eclipse path. For example, thetotal solar eclipse on April 8, 2024 was only visible along a narrow belt stretching across the United States, Mexico, and Canada.

What is a hybrid solar eclipse?

How Large Is the Moon's Umbra?

The size of the area on the Earth's surface covered by the Moon's umbra during a total solar eclipse depends, amongst otherthings, on theMoon's current distance from Earth. The smaller the distance, the larger the umbra.

If the Moon is at its closest to Earth (itsperigee) during the eclipse, the Moon appears larger in the sky. In that case, the umbra's path across the Earth'ssurface typically has a width of roughly 150 km (90 mi) at the Earth'sequator. At higher latitudes, the Sun's rays hit the Earth's surface at a shallower angle, so the umbra's size growsaccordingly. During some total solar eclipses, the umbra's path width reaches over 1000 km (600 mi) at the poles.

If the eclipse occurs when the Moon's distance is greater, the tip of the Moon's cone-shaped umbra (see illustration) may onlyjust reach the Earth's surface during parts of the eclipse, meaning that its diameter is close to zero. The total phaseof the solar eclipse then lasts only a short moment. For example, thetotal solar eclipse on December 6, 2067 will last only 8 seconds at its maximum point, with partial phases before and after totality. This eclipse will be ahybrid solar eclipse.

If the Moon is close to its apogee, its farthest from Earth, during the eclipse, the umbra does not reach the Earth's surfaceat all, and it is replaced by theantumbra, producing anannular solar eclipse.

Earth's Umbra Causes Lunar Eclipses

Like the Moon, Earth always casts an umbra. In fact, we travel through it quite regularly. It is called: night. Every timethe Sun goes down, we delve into the darkness created by Earth's umbra. However, as with total solar eclipses, lunareclipses only occurevery so often because they require the Moon to enter the Earth's umbra.

The Earth's umbra is involved in both total and partial lunar eclipses. During atotal lunar eclipse, the entire Moon enters the umbra. Apartial lunar eclipse occurs when the umbra covers only part of the Moon's surface.

Apenumbral lunar eclipse occurs when the Moon enters the Earth'spenumbra.

No Umbra During Planet Transits

During aplanet transit of the Sun,Mercury orVenus pass in front of the Sun, as seen from Earth. Because of their large distance from the Earth, their umbrasend a long way before they reach the Earth's surface.

This means that we travel through a planet's antumbra during a transit. As the antumbra's diameter increases with growingdistance, it is very wide when it reaches Earth, so most planet transits take several hours.

Never look directly at the Sun!

Topics:Eclipses,Sun,Astronomy,Moon,Earth

Total Solar Eclipse

2026年8月12日 (水)15時34分UTC …See more

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