Over the years I’ve enjoyed hearing from readers who excitedly describe seeing something they never knew about or had never been able to see before.
I find this quite rewarding since some of the sights about which I write can be pretty challenging.
The past two weeks I wrote about Venus, one of the easiest celestial sights available, but now’s your chance to seek out something even more elusive.
Once the brilliant moon leaves our early evening sky late this week, you may want to head out to the dark, pristine skies of the wilderness to glimpse the wintertime sky in all its splendor.
In addition to the stars, constellations, planets and the occasional meteor zipping across the heavens, you might catch a glimpse of a unique sight — one the average stargazer seldom sees (or even knows about).
It’s called the zodiacal light.
As evening twilight fades from view — around 60-90 minutes after sunset — begin looking toward the western sky for a huge, softly glowing pyramid of light.
In its brightest parts, the zodiacal light exceeds the brilliance of the Milky Way, which now appears rather faint as it streams north to south high overhead.
Stargazers often confuse the zodiacal light with the lingering rays of twilight or with the Milky Way itself. They also tend to expect a much smaller or brighter glow.
The zodiacal light ascends around 20-40 degrees into the western sky along the constellations of the zodiac and, right now, can be seen flowing from brilliant Venus low in the west toward the Pleiades (Seven Sisters) star cluster and bright Jupiter high in the west.
Its base near the western horizon typically appears around 15 degrees wide, and the cone tapers to about 5 degrees wide at the top.
Keep in mind that the phenomenon is extremely faint, so any light pollution, haze or moonlight is sure to obliterate it from view. Binoculars or telescopes have much too small a field of view to see this phenomenon.
The zodiacal light is caused by sunlight scattered from dust particles spread out along the plane of our solar system.
Most of these particles — continually generated by passing comets or by collisions among asteroids — are only about four-hundredths of an inch in diameter and are separated by an average distance of five miles.
The plane defined by this dusty glow passes through the constellations of the zodiac — hence its name — and roughly defines the plane of our solar system called the ecliptic.
Since only during late winter and early springtime does the ecliptic form a steep angle with the horizon in the early evening hours, now is a great time to begin searching for this elusive glow.
If you miss it this week, check again next week. In fact, throughout the entire spring, you’ll have the best opportunity to see it in the early evening, as long as you’re observing from a dark, nonlight-polluted site and the moon is nowhere to be found.
Good luck with this one. It’s quite a challenge, and I hope you’ll let me know of your success!
