Solar eclipses on the Moon

Painting by Lucien Rudaux, showing what a lunar eclipse might look like when viewed from the surface of the moon.^[1]

A simulation of the start and end of the August 28, 2007 lunar eclipse, seen from the center of the moon.^[2]

Solar eclipses on the Moon are caused when the Earth passes in front of the Sun, blocking its light. Viewers on Earth will see a lunar eclipse.

The solar eclipses are only seen in the Nearside portion and smaller parts of the Farside where the Earth is seen during librations, making up the visible portion of the Moon and eclipses there are seen during the lunar sunrise and sunset as well as furthermost areas of the Nearside but mainly not in the polar areas of the Moon. As the Moon revolves around the Earth, the Earth rotates nearly 24 hours, but its position at the sky is only in one position as it never changes as it does with some other moons (or satellites) in other planets or dwarf planets and a few asteroids even inside the solar system but are very rare in the outer part of the solar system.

The last solar eclipse on the Moon was a total eclipse on July 27, 2018, with the whole Nearside and the tiny surroundings of the Farside seeing totality.

Length

Unlike the Earth which sees its eclipse for up to 2 1/2 hours the longest in one area as the Moon's shadow touches for over 5 1/2 hours the longest. Some of the eclipses on the Moon lasts for about 5 hours in one area the longest as the Earth's shadow touches for over 6 hours the longest.

Some eclipses are longer when the Earth is slightly closer (on Earth, the Moon is seen with its apparent diameter is larger than the sun's), some eclipses are shorter when the Earth is slightly further (on Earth, the Moon is seen with its apparent diameter is smaller than the sun's).

Unlike the Earth where its eclipses starts and ends at a different place. All of its solar eclipses begins in the westernmost parts of the Nearside and ends in the easternmost parts of the Nearside.

Solar eclipses starting near and within the polar areas has only partial eclipses while solar eclipses starting at or within the equator has only total eclipses.

Penumbral shadow

In its eclipses, the penumbral shadow does not appear until it is around 25–30% obscuration, it gets slightly darker when the Earth blocks the sunlight until it reaches totality in some eclipses.

In some eclipses, its penumbral shadow covers the whole surface whereas the center of the Earth's shadow missed a portion of the moon while every part of the Nearside sees a partial eclipse, they are very rare. The last century that not all parts of the Nearside and the surrounding parts of the Farside saw only as partial was the 18th century. On Earth, they are seen as a Total penumbral eclipse.

It is a narrow path for the moon to pass within the penumbra and outside the umbra. It can happen on the Earth's northern or southern penumbral edges.

These eclipses can last up to about over 4 1/2 hours without having any part of the moon (notably especially at its poles) having totality.

Center of the Earth's shadow

Unlike the Earth which receives the smallest portion being inside the center of the moon's shadow during total solar eclipses. During its total eclipses on the Moon, the center of the Earth's shadow covers the whole Nearside part of the Moon and lasts much longer than on Earth with up to around 1.8 hours.^[3] Some total-partial eclipses have a most, half or a part of the Moon being in the center of the Earth's shadow.

Unlike the Earth which it umbral shadow shows black, as the Moon has no atmosphere, the surface appears not just black but red and brown (according to the Danjon scale) because the only sunlight available is refracted through the Earth's atmosphere on the edges of the earth forming an atmospheric ring as it is shown in the sky in a painting by Lucien Rudaux.^[1]

Temperatures during long totality

The mid-infrared image of the Moon was taken during a September 1996 lunar eclipse by the SPIRIT-III instrument aboard the orbiting Midcourse Space Experiment (MSX) satellite. On the Moon, they are seen as solar eclipses. At these wavelengths, MSX was able to characterize the thermal (heat) distribution of the lunar surface during the eclipse. The brightest regions are the warmest, and the darkest areas are the coolest. The well-known crater Tycho is the bright object to the south of center. Numerous other craters are also seen as bright spots, indicating that their temperature is higher than in the surrounding dark mare.

During eclipses with long totality, temperatures plunges but not in many parts of its mares especially Oceanus Procellarum and Mare Tranquillitatis, and mid to large craters (especially with basalt floor) mostly in the middle portion of the Moon, some young craters and a few distant large craters, notably Tycho (being located at 43.31°S) where the temperatures remains high.^[4] Some craters are slightly cooler but as warm as the surface and warmer than areas outside the mares (basins) such as Copernicus and Langrenus.

Partial eclipses

On the Moon, when there is a partial eclipse, one example is when half of the Sun is blocked (north or south), a part of the moon has a partial eclipse (north or south). In some partial eclipses when the center of the Earth's shadow misses the moon, one example is one hemisphere has a partial eclipse and the other does not. In some eclipses when the center of the Earth's shadow covers a part or most, one part has a total eclipse and one part has a partial eclipse. Partial/total eclipses together with simiply partial last for up to about 6 hours without having totality in all parts of the Nearside and a very small part of the Farside next to the Nearside. Partial/total eclipses alone in between partial lasts for up to about 3 1/2 hours.^[3]

At its edges of the Nearside and its small surroundings

At the edges of the Nearside and a small surrounding part in the Farside where the Earth is mostly, half or partly seen, in the west, some solar eclipses begins at sunrise and the sun is seen after sunrise, in some eclipses the sun is half seen, in some eclipses, it is partly eclipsed, in the east some solar eclipses ends at sunset and the sun is seen before sunset, in some eclipses, the sun is half seen. It also occur in several polar areas. In that part of the Moon, the Earth is seen in the upper parts of the crater, its hills and its mountains and a few areas such as lunar seas (plains), in some parts, it can be seen through a deep crater hollow while most or much of the lower parts around ground level and in some parts, the middle parts, the Earth is never visible and its eclipses are never seen as the crater and its mountains including crater ones blocks the view. In areas around 7–8 degrees near the Farside, a part of the Earth's view is blocked, in some eclipses, it begins not long after sunrise in the west and beings not long before sunset in the east. At that location, they are seen in higher parts and most of the middle portions.

At the furthermost areas of the Farside within the Nearside, a part of the Earth is seen but only in the highest portions.

Exception on one part of the Moon

Much of the Farside portion (about 91%) are free of solar eclipses as the Earth is never seen there, as the limit of the view of the planet during librations is about 8 degrees within the Nearside.

Also it is not seen in the fringes of the Nearside, within the Farside, it is not seen in the lower and most of the middle parts, around it, it is not seen in the lower parts. Also in that location and around it, the eclipses are never seen in most crater hollows, some of it the lowest part of some crater hollows. Also eclipses are never seen in crater hollows in the polar regions where the sun never shines, between the 75th and the 80th parallel north or south, the eclipses are never seen in most crater hollows such as the middle and notably the lowest portions.

History

In early lunar history after around 4.3 billion years ago when the Moon was formed, the Moon was closer to its current orbit. The totality of its eclipses lasted longer the current eclipses, millions of years later, totality shrank and the partial portion of the eclipse was rising. Eclipses were more frequent, tens of millions of years later, eclipses became less numerous as the lunar orbit slowly moved away from the Earth. The view of the sun, even its chromosphere was blocked by the Earth. Around some hundreds of millions of years ago, the Earth blocked all of the sun's chromosphere, totality was slightly longer than the partial portion. At the same time there were more partial eclipses on the Moon. As the moon recedes about 3 cm each year, eclipse totality length slowly shrinks and the partial portion slowly lengthens.

Saros series

The Solar Saros series of the Moon is the equivalent to the Lunar Saros series of the Earth.

List of solar eclipses on the Moon

In popular culture

In a package of Wills's Cigarettes, one of the tobacco cards first issued in 1928 for a few years displays the solar eclipse on the Moon showing the atmospheric ring.^[5] This is considered the first depiction of a solar eclipse as seen on the Moon.

See also

• Planetary eclipse (not common to be called as an Earthly eclipse) – the opposite of the solar eclipses on the Moon where the shadows of the Moon block the view of the Sun on Earth making it a planetary eclipse, on Earth, they are Solar eclipses
• Lunar eclipse – What the Earth sees when there is a solar eclipse on the Moon
• Danjon scale – varying the different colors of the umbra during certain eclipses.

References

External links

• KAGUYA (SELENE) Successfully Captures Moving Images of the Earth at the Time of a Penumbral Lunar Eclipse using HDTV SELENE