LOS ANGELES (CBSLA.com) — A so-called “Blue Moon” is expected to grace the skies at sunset Friday, according to the National Aeronautics and Space Administration.

Despite its name, NASA says most Blue Moons look pale gray and white and are similar in appearance to other full moons.

On “rare occasions,” however, the moon can in fact turn blue, explained NASA, adding that this usually requires a volcanic eruption.

The astronomical event marks the second full moon in the month of July this year as the first was recorded July 2.

CBS San Francisco, citing the National Oceanic and Atmospheric Administration, reports that two full moons in one month happen every three years.

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