A total lunar eclipse is sometimes known as the Blood Moon due to the reddish tint that the Moon takes on. Blood moons are a fairly rare event, appearing slightly more frequently than twice every three years. Between now and 2025, for example, astronomers expect only five blood moons to appear.
What is the cause of a blood moon eclipse?
Although the term Blood Moon is unscientific, it is associated with an atmospheric effect that occurs during a total lunar eclipse.
During a total lunar eclipse, the lunar orb completely enters the planet’s umbra, the direct shadow cast by sunlight.
Although the whole may briefly make the Moon disappear, sunlight still indirectly reaches the Moon’s surface.
Sunlight scattered around the edges of the planet’s dusty atmosphere filters in, leaving ruddy light waves to reach the Moon.
The effect, known as Rayleigh scattering, is equally responsible for the color of sunsets and sunrises.
READ MORE: Jupiter’s moon Europa could sustain life in the ocean, according to NASA
According to the US space agency NASA, if you saw Earth from the Moon’s surface during a Blood Moon eclipse, the planet would be bathed in a red halo.
NASA said: “Air molecules in Earth’s atmosphere scatter most of the blue light.
“The remaining light is reflected off the Moon’s surface with a red glow, making the Moon appear red in the night sky.
“The name ‘Blood Moon’ is also sometimes used for a Moon that appears reddish due to dust, smoke, or mist in the sky.
“And it may be one of the full moons of fall when the leaves turn red.”
But the eclipse will also be penumbral, which means that the Moon will pass through the two weakest shadows on Earth.
Sunlight casts two shadows behind Earth: the umbra and the twilight.
The umbra is the darkest, direct shadow that narrows as it extends into space.
The penumbra is much weaker and more diffuse, extending into space on either side of the umbra.
Unfortunately, penumbral eclipses can be difficult to detect if ignored.
As a result, next month’s lunar eclipse will not be a Blood Moon.
It will have to wait almost a year before the next total eclipse.
The following five eclipses of Blood Moon fall on:
May 26, 2021
May 15, 2022
November 8, 2022
March 13, 2025
September 7, 2025
