Eclipses are phenomena that occur when one large celestial body moves between two other large celestial bodies, with at least one of the latter two emitting or reflecting light. Eclipses are unique, in that they can be classified as both space and optical phenomena.
There are two main types of eclipses that most people are familiar with: solar and lunar eclipses. There is at least one other type that people are less familiar with, called a planetary eclipse, which we will also be discussing in this article.
The Sun is several hundred times larger than the Moon. In fact it is just a hair over 400 times larger. From our perspective though, the Moon and the Sun are just about the same size in the sky, because the Moon is much closer to Earth than the Sun.
Solar eclipses occur when the Moon moves between Earth and the Sun. As the Moon moves in front of the Sun, it begins to block out light from the Sun, and the sky here on Earth begins to darken.
During these eclipses, the Moon isn’t always the same distance between the Earth and the Sun. The Moon’s orbit around Earth is elliptical, and the Earth’s orbit around the Sun is elliptical too. As this distance varies, the amount of Sun that is “hidden” by the Moon during a given eclipse varies too.
A total eclipse occurs when the Moon lines up precisely with the Sun, and is close enough to the Earth to entirely block out the Sun. Total Eclipses are extremely rare, and can only be seen from a small section of the Earth where the alignment is perfect. This small section is known as the path of totality.
During a total eclipse the sky becomes dark and stars become visible. The corona of the sun can be seen as well. A diamond ring effect occurs at the beginning and end of the total eclipse, when a faint coronal ring appears around the Moon and the Sun shines brightly just to the edge on one side or the other.
An annular eclipse occurs when the Moon lines up precisely with the Sun but the Moon is too far from the Earth to cover the Sun up entirely.
Many observers outside of the path of totality will see a partial eclipse. A partial eclipse occurs when the Moon does not line up precisely with the Sun, but a portion of the Moon still moves in front of the Sun. During a partial eclipse, the sky may still darken considerably, but only to a fraction of the darkness witnessed in a total eclipse.
Viewing Solar Eclipses
Many people travel hundreds and even thousands of miles to view a solar eclipse from the path of totality. There are even watch parties at prime viewing locations, where people congregate in groups to see these incredible phenomena.
Safety must be taken into consideration while viewing these events! You should never look at them directly without proper eye protection. Special glasses can be worn to look directly at them, but precautions need to be taken when buying or selecting the right ones to wear.
Always buy them from a reputable source, and ensure that they are ISO Certified. An ISO label must be present on the glasses, but even that doesn’t necessarily mean they are safe as some vendors simply steal the label. The American Astronomical Society, or AAS, has put together a list of Responsible Vendors through which these glasses can be purchased.
Lunar eclipses occur when Earth moves between the Sun and the Moon, and Earth’s shadow is cast on the Moon. Like Solar eclipses, lunar eclipses can be either partial or total.
The Moon’s orbit around the Earth is tilted about 5 degrees from Earth’s orbit around the Sun. As with solar eclipses, the Sun, Earth and Moon need to be in alignment for a lunar eclipse to occur. These alignments are somewhat rare, but still occur several times a year.
During a partial lunar eclipse, only a portion of the Moon is covered by Earth’s shadow. During a total lunar eclipse, the entire Moon is covered. During these events, the moon turn a hazy red shade