THE SOUTHWORTH PLANETARIUM

207-780-4249       www.usm.maine.edu/planet
70 Falmouth Street  Portland, Maine 04103
43.6667° N,                    70.2667° W
Founded January 1970

              "Life has turned us all into tightrope walkers.    Yesterday is a fading memory, tomorrow is wholly imaginary. and now never sticks around for long."



THE DAILY ASTRONOMER
Wednesday, April 6, 2016
Zodiacal Light

Today's schedule allowed us just enough time to address one of Pandora's many questions.    If you have submitted one and haven't heard a response, please accept our sincerest apologies.  We are not ignoring your question.  Instead, we haven't withdrawn in from Pandora's jar, yet.     We assure you that though Pandora will never be empty, each question it contains will find an answer.

This next Pandora inquiry pertains to a sky phenomenon that is rarely ever discussed: the mysterious "zodiacal light."

"I’ve been reading about zodiacal light being visible this time of year in the northern hemisphere, toward the Taurus constellation. Have you ever seen it? Are there too many lights in the Portland area for it to be seen here?"
-L.B,   Portland, ME

Zodiacal light is the diffuse glow that one can rarely observe at night along the ecliptic, defined as the Sun's annual path through the sky.   Zodiacal light appears because the Sun's light illuminates dust particles gathered around the ecliptic, producing a "light cloud" that is best seen just after sunset or just before sunrise around either the spring or fall.     The reason we see this light best in the spring and fall is because around these times the angle of the ecliptic relative to the horizon is steep, so the sunlight originating from below the horizon is aligned with the dust cloud.  In the summer or winter, the sun's angle not as steep and the sunlight is not as closely aligned with the dust band.

Zodiacal light is often mistaken for the Milky Way and sometimes for the aurora.*   I believe I have seen it about three times.     It is one of those sky sights that vanishes in moonlight and with any light pollution at all.  So, it would be exceedingly difficult to see this light when you have any light pollution at all. 

If you do have a dark sky, you might be able to observe the zodical light around the constellation Taurus, a zodiacal constellation close to the setting Sun.        Go to the Daily Astronomer web-site to see images of Zodiacal Light:  usm.maine.edu/planet/da-7-december-2015 [Note: the light in these images is slightly brighter than the real zodiacal light as the images were time exposure photographs.]


*Although the aurora is a northern event, unless it is one of those dramatic aurora that pervades the sky.      Zodiacal light is eastern or western.  Rarely it will extend along the entire visible section of the ecliptic.