Wildfires in California turn Sun lavender

William Atkins
Monday, 30 June 2008 17:47

Science - Climate

Several photographers have taken pictures of the Sun through the haze of the smoke produced by these fires.

One especially visual photograph appears on the SpaceWeather.com website. Christopher Calubaquib took the image over El Sobrante, California, on June 26, 2008.

Calubaquib states, "Because of the smoke, the sun was not very bright, and I didn't need to use a filter to take the picture.” [Photo: SpaceWeather.com]

Photographer Mike Kelly took another picture of the Sun over the sky in Arcata, California on June 27th. Kelly states, “This photo was not processed or retouched; it's how the sun really looked.” [SpaceWeather.com: “SpaceWeather photo: "Sun Through Smoke”]

The so-called effect called the “lavender Sun” is produced when the Earth’s atmosphere becomes filled with particles measuring about one micron (one millionth of a meter) across.

Such a size for the particles is just a bit larger than the wavelength of red light. Thus, these micron-sized smoke particles scatter red light coming to the Earth from the Sun, but let the Sun’s blue light (whose wavelength is smaller) to pass through the atmosphere.

Consequently, we see the Sun as a lavender, or purplish, color. The Sun hasn't changed colored, only our perception of it has changed.

An additional picture named “Smokey Sunset” is available from Ray Rochelle of Chico, California, on the SpaceWeather.com website.