What is A Lunar Eclipse?

(Image Credit: Time and Date)

July 12, 2023

Letîcia Alves da Silva

12th Grade

Colégio Militar do Rio de Janeiro



A lunar eclipse occurs when the Earth is positioned between the moon and the sun, causing a precise alignment of the shadow of Earth with the lunar surface, darkening it. Depending on the type of eclipse, it can occur twice a year or every two or three years. It is noteworthy that such a phenomenon only happens during the full moon phase. In general, there are three types of lunar eclipses.

A total lunar eclipse happens when, despite the moon settling entirely in the shadow of the Earth, the sun’s rays can still reach it. Thus, as the wavelengths of red and orange are long, they cross the Earth’s atmosphere causing the moon to appear an orange or red color.

In a partial lunar eclipse, coming from an imperfect alignment, the Earth’s shadow covers only part of the lunar surface.

Lastly are penumbral eclipses. This is more difficult to see because the moon becomes slightly darker from passing through the penumbra of the Earth, that is, the weak external part of its shadow.

Researchers recorded a temperature drop in two locations where Apollo 12 - the second US spacecraft to land on the moon - had landed. In a period between ten and thirty minutes, the temperature varied from 75.7 C to -102.1 C. The same occurs during lunar eclipses. The satellite's temperature drops dramatically when the Earth’s shadow sweeps the moon—even causing some lunar rocks to disintegrate and gasses to escape from inside the Moon. 

It is important to note that the reason eclipses do not occur every month is that the moon’s orbit is inclined at approximately 5º relative to Earth’s orbit (ecliptic). Thus, an eclipse happens only when the sun and the moon are in the line of intersection of the moon’s orbit with the ecliptic.

Reference Sources

Dobrijevic, Daisy. “Lunar Eclipses 2023: When, Where & How to See Them.” Space.Com, 9 Nov. 2022, 

https://www.space.com/33786-lunar-eclipse-guide.html.

“Eclipses | Phases, Eclipses & Supermoons – Moon: NASA Science.” Moon: NASA Science, 

https://moon.nasa.gov/moon-in-motion/phases-eclipses-supermoons/eclipses/.