Skywatchers Treated To 'Blood Moon', Close Encounter With Mars

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MIAMI (CNN) - Attention skywatchers and anyone who likes cool celestial stuff.

There are two events happening, but you will only be able to see one of them if you live in the US.

First, the longest total lunar eclipse of the century happens Friday, showcasing a blood moon for most of the Eastern Hemisphere.

The lunar eclipse happens during daylight hours for those in the Western Hemisphere, so people in North America will miss it. The entire US won't be able to see a full lunar eclipse again until January.

Lunar eclipses can occur only during a full moon and this one is extra special because of the blood moon.

A blood moon happens when it is in perfect alignment with the sun and Earth, with the moon on the opposite side of the Earth from the sun.

When the full moon moves into Earth's shadow, it will darken, but it won't disappear. Sunlight passing through Earth's atmosphere will light the moon in a dramatic fashion, turning it rusty, brick-colored or blood-red. That's why it's referred to as a 'blood moon'.

This happens because blue light undergoes stronger atmospheric scattering, so red light will be the most dominant color highlighted as sunlight passes through our atmosphere and strikes the moon.

This full moon in July is also known as the Full Buck Moon and the Thunder Moon, occurring when a male deer's antlers are in full growth and at a time of frequent thunderstorms, according to the Old Farmer's Almanac. It's also a "mini-moon" because the moon is the farthest from Earth and appears small. The fact that the moon appears so small and takes longer to pass through Earth's shadow is also why the eclipse lasts longer.

Mars in the sky

Our red moon will have some company. Mars is at its closest distance to Earth in more than a dozen years.

Mars is reaching its opposition, when it's in alignment on the opposite side of the Earth and the sun. This occurs at the same time that it will reach one of its closest points to the Earth, about 35.9 million miles away. That is what makes it appear so bright in our sky.

While Mars will be overhead for people in central Chile, South Africa, and Australia, it will be low in the southern sky for those watching in the US and Europe.

"Despite its glorious girth, northern observers will pay a price during this juicy Mars apparition," Sky & Telescope contributing editor Bob King said. "At most perihelic oppositions, including this one, the planet retreats to the belly of the ecliptic low in the southern sky."

Mars will actually be at its closest approach since 2003 on Monday and Tuesday when it is 35.78 million miles away. So if bad weather disrupts your opportunity on Friday, there will be more chances. Experts estimate that Mars' brightness will persist for several weeks.

Mars' closest approach will be at 4 a.m. EST Tuesday, according to EarthSky.org.

Although it won't look nearly as large as the blood moon, Mars will be its largest if you're looking through a telescope and close to its maximum brightness in our sky. Mars is also safe to view with the naked eye.

(©2018 CBS Broadcasting Inc. All Rights Reserved. CNN contributed to this report.)