The Stargazers of Bay Area may have noticed something unusual on Saturday night: a different halo around the moon.
Twitter was vague. One user wrote, “Moon is haunted. Another wrote, “The moon is looking crazy tonight.
What is the reason?
A local meteorologist, Jan Null, Said on Twitter That, “to create a well-defined 22-degree lunar halo, light from almost the full moon is interrupted by ice crystals this evening in thin circus clouds over an area deeper.”
Null shared a photo of the event on Twitter, showing a bright halo around the moon in the dark sky.
According to National Weather Service officials, a halo is “a ring or light that forms around the sun or moon because the light from the sun or moon removes ice crystals present in a thin layer of circus clouds.”
It is an official effect that occurs when the weather conditions are “right,” the weather service said.
Yes, it is a lunar ring or lunar halo. This effect occurs when light is withdrawn by ice crystals in high, thin clouds called cirrostratus.
– NWS Bay Area (WSNWSBayArea) December 27, 2020
Explaining haloes and other types of optical effects on its webpage, meteorologists said that in the atmosphere, under certain conditions water droplets and ice crystals can act as a prism, allowing us to see different colors that become visible light. “It is because of these properties that we get various atmospheric optical effects.”
The halo was clear on Saturday night, while the bay area was mostly clear and dry, but rain is expected in the area on Sunday and Monday.
Light from almost the full moon is being interrupted this evening by ice crystals in high thin circus clouds over an area deeper to form a well-defined 22 degree lunar halo. pic.twitter.com/QHwuHymA8O
– Jan Null (2G Weather) December 27, 2020
Lure Ren Hernandez is the author of the San Francisco Chronicle Staff. Email: [email protected] Twitter: YByLHernandez
