(CNN) This year started off with a meteor shower and the first month of 2020 continues with a penumbral lunar eclipse during the full moon, on Friday.

Lunar eclipses can only occur during a full moon. But a penumbral lunar eclipse is different from a total lunar eclipse.

The eclipse on Friday will occur when the moon moves into Earth's penumbra, or outer shadow. This causes the moon to look darker than normal.

During a total lunar eclipse, the change is more dramatic because the entire moon appears to be a deep red color.

The eclipse will last for about four hours.

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