A rare ‘supermoon’ lunar eclipse is expected to be visible in the night sky on Sunday. But, you may be wondering what exactly this astronomical event is.

Here are the five things to know about the supermoon lunar eclipse.

What is a supermoon lunar eclipse?

The supermoon lunar eclipse is a combination of two things. 

First off, there will be lunar eclipse. 

A lunar eclipse occurs when the Earth passes between the sun and moon, and the Earth's shadow covers the surface of the moon.

Many refer to total eclipses as "blood moons," or "hunters moons" due to the reddish-orange tint cast over the moon. The glow is caused by the light from sunsets and sunrises glinting off the surface of the Earth.

In a celestial combination that that hasn't been seen since 1982, the eclipse will be coupled with a "supermoon.” 

A supermoon occurs when a full moon makes its closest approach to Earth, approximately 385,000 kilometres away. Supermoons appear up to 14 per cent larger than usual due to proximity.

When will it be visible and how long will it last?

According to NASA, Sunday's supermoon lunar eclipse is expected to last 71 minutes. 

“The supermoon will be visible after nightfall, and the eclipse will case into shadow beginning at 8:11 p.m. EDT,” NASA said. “The total eclipse starts at 10:11 p.m. and will peak at 10:47 p.m. EDT.” 

Where will the supermoon be visible?

The supermoon lunar eclipse will be visible in North and South America, Europe, Africa, part of West Asia and the eastern pacific, NASA says.

Light pollution and weather will be factors in the supermoon eclipse’s visibility. 

When will the next supermoon eclipse occur?

Another supermoon lunar eclipse won’t occur until 2033, NASA says. However, the next lunar eclipse will be in January 2018. 

When was the last supermoon eclipse?

The last supermoon lunar eclipse occurred in 1982.