Zodiacal Light, A Stellar Eclipse And A Moon-Saturn Tryst Tonight

Two big glows show in the picture taken last February: the dome of Duluth light pollution at left and the slanted cone of zodiacal light standing up from the western horizon.The cone is created by sunlight reflected off comet and asteroid dust in the plane of the solar system. Photo: Bob KIng

The temperature is struggling to clear zero degrees this morning despite blue sky and sunshine. Tonight looks clear without a moon. If you’ve got some extra time on your hands early this evening and good weather’s in the forecast, consider a drive to the country to see the zodiacal light.

Beginning in February and continuing through early spring, the “thumbprint” of the zodiacal (Zoh-DYE-uh-cull) light makes its appearance in the western sky during late twilight and early night for observers at mid-northern latitudes.

The combined glow of dust particles in the plane of the solar system reaching from the sun's vicinity to beyond Mars is responsible for the zodiacal light. Planets are shown as colored disks. Illustration: Bob King

This large, oval or cone-shaped glow, which is composed of minute dust particles shed by passing comets,  spreads through plane of the solar system. In mid-winter, we see that plane tilted steeply upwards in the west during evening hours, “lifting” the dim, diffuse zodiacal light high enough to clear the lower, hazy air and improve its visibility.

Anytime over the next week and a half is ideal to look for the Z-light, since the moon won’t disturb the darkness required to see this curious cometary remnant. That’s why I recommend a trip to a rural area where light pollution is at a minimum. The cone is widest near the western horizon and narrows as you direct your gaze upward and to the left. The best way I’ve found to spot it is to turn your head left and right while facing west and look for a large, soft haze similar in brightness to the Milky Way.

If you have any doubt as to which direction to look, consider that Venus lies in the plane of the solar system just like the comet dust that creates the zodiacal light. The planet is smack dab in the middle of the cone with Jupiter, the other bright evening planet, just beyond its tip.

The best time to see it is starting about 90 minutes after sunset (roughly around 7 p.m. for Duluth) when twilight is ending and night beginning. To tell it apart from the miasmic glare of light pollution, look for a large, tapering glow with a distinct tilt to the left.

The waning gibbous moon visits Saturn and Spica the next two mornings. Created with Stellarium

Since this is a Saturday and you might be visiting a local pub for a brew, there’s a special sky treat if you leave around closing time. Take a look toward the waning moon in the southeast. Not far away you’ll see Virgo’s brightest star Spica and the planet Saturn.

Not planning on being up at 1 or 2? You can see them instead at dawn around 6 in the southwest.

The gibbous moon just after sunrise over Kearsarge Peak in the Sierra Nevada mountains. Credit: Andrew Kirk

Andrew Kirk of Independence, Calif. sent me this beautiful photo of the waning gibbous moon setting over Kearsarge Peak in the Sierra Nevadas yesterday morning. The picture reminds us that we can now see the moon again in the morning sky after sunrise for the next week. Look well to the right or west of the sun.

Algol B, larger and fainter than Algol A, partially eclipses it every 2.9 days causing the system to fade. Illustration: Bob King

Two last observing notes. For those of you with telescopes, Jupiter’s Great Red Spot, which looks pale pink right now, will be facing directly at us tonight around 8 p.m. CST. You can go out an hour earlier or later and the view will almost as good. Use 100x and wait for the air to settle to see it best. And if you don’t have a telescope, you’ll only need your naked eyes to watch the binary star Algol in Perseus undergo an eclipse for about two hours centered on 9:50 p.m. CST. Normally the star is magnitude 2.1 – as bright as a Big Dipper star – but when its companion star eclipses it, Algol fades to 3.4. For the Midwest, if you look as soon as it gets dark, you’ll see the star fade over the next couple hours to minimum. Click HERE for more information and a map to find it.