On Friday night, a full moon – the second of the month – will light up the night sky.

Jackie Faherty, an astronomer at the American Museum of Natural History, said this so-called blue moon, however, won’t actually look blue. In fact, she explained that the name is believed to have originated from a derivation of an Old English word that sounds like the word blue, but actually had nothing to do with the color.

Now, a blue moon refers to a second full moon in the same month, which is a phenomenon Faherty said occurs every two to three years.

“The phrase ‘Once in a blue moon,’ meaning that this happens rarely, is also a misnomer,” she explained, “because the blue moon happens quite often.”

The last blue moon was in December 2009, and the next will occur in July 2015, she added.

Despite the lack of a blue hue, Faherty said the visual will still be exciting to see when the moon rises around 7:13 p.m., and until it sets at 6:25 a.m. Saturday

“I think it invokes a strange amount of mystique among people, especially since full moons really light up the evening,” she said. “You can see when you probably shouldn’t be able to see so much.”