This Week’s Twilight Specials

The sun rises over Lake Superior this morning. The "second" sun below the real one is an inferior mirage created when sunlight is refracted (bent) by warmer air near the water's surface. Details: 400mm lens at f/8. Photo: Bob King

I’m more of a night man and don’t usually get up for sunrises, but I’m glad I did today. Inspired by the spectacle of piled and broken ice along the shore of Lake Superior and this morning’s moon-Venus pairing, I pulled the covers back at 5:30, got in the car and drove down to the lake.

Another fellow named Brett showed up not long after I arrived. He smiled broadly when we greeted one another and then walked with purpose to a big hole along the shore filled with sloshing ice. There he set up camera and tripod and began to photograph. Like me, Brett had also been inspired by lake ice to make the dawn trek.

The first peep of sun at the horizon this morning. Broken plates of ice from Lake Superior lie heaped in the foreground. Photo: Bob King

I wasn’t prepared for how sudden the sunrise was. It exploded across the water like an orange supernova. Once the solar disk had pulled itself up over the horizon, differences in the density of air along the line of sight distorted its shape into something resembling a nuclear explosion. Perfectly appropriate given that the fusion of hydrogen into helium is what powers the sun in the first place.

Seeing the crescent moon and Venus at dawn was a great way to begin the day. Thin cirrus clouds created halos around both. Details: 135mm lens, f/3.5, 1/2 second at ISO 400

Earlier, during the drive down to Lake Superior, the moon and Venus were worthy of stopping right in the middle of the road to admire and photograph. You can still see the moon tomorrow at dawn, when it will be even thinner and very low in the southeastern sky about 45 minutes before sunrise.

I’m tempted to go out again for another solar supernova and one more morning crescent before this Friday’s new moon.

With the evening sky still moonless or nearly so through the end of the week, it’s an ideal time to look for the eerie zodiacal light in the western sky during late twilight. This cone-shaped glow looks something like city light pollution but it’s steep angle to the horizon and tapering form hint at something beyond the bounds of Earth.

The zodiacal light cone reaches nearly to the Pleiades (at top) on the night of Feb. 26. Jupiter is the bright "star" near the bottom. The pink light at left is city light pollution. Details: 16mm lens at f/2.8, ISO 1600, 30-second exposure. Photo: Bob King

The zodiacal (zoh-DIE-uh-cul) light is really sunlight reflected off billions of tiny dust motes shed by comets as they swing through the inner solar system. It’s centered on the ecliptic, an imaginary circle in the sky that defines the path of the sun, moon and planets as they travel around the celestial sphere. During March and April, the ecliptic is tipped at a high angle to the horizon, pitching the cone of light up for easier visibility.

I went out a few nights ago about 10 miles north of the city and was struck by how far up in the sky I could trace its form. Broader near the horizon and nearly centered on Jupiter, the softly-glowing wedge of light reached all the way up to the Pleiades star cluster more than four “fists” high in the west.

The best time to see this curious cone is about 1 1/2 hours after sunset near the end of twilight. Find an extra-dark location with a wide open view to the west-northwest and sweep your gaze back and forth across the sky. You’ll be looking for a large, leftward-leaning, glow. Jupiter and the Pleiades can help you gauge the cone’s extent.

Enemies of the zodiacal light include the moon, haze and light pollution. You’ve got through Sunday before the moon interferes, but don’t worry if plans or bad weather get in the way. The light will return to view later this month and in the latter half of in April too.

In this illustration, you can see how the zodiacal light is centered on the ecliptic or centerline of the zodiac, where the sun, planets and moon travel. The cone is broadest and brightest near the bottom, because the dust is thicker and closer to the sun and therefore reflects more brightly. Created with Stellarium

Oh, I nearly forgot. The word ‘zodiacal’ comes from ‘zodiac’, which is the belt of constellations centered on the ecliptic. Learn more about the zodiacal light in this earlier blog.

UPDATE: According to the space weather forecast, there’s a possibility for aurora tonight, at least in the far north. If you live in the northern U.S. it might be worth keeping an eye out for it. Auroras were seen earlier today near Anchorage, Alaska.

2 Responses

  1. Again, thanks for your astronomy blog. Today’s, with the account of your 5:30 AM trek to Lester River, with its sun/venus photos was terrific. As I said in our phone conversation, I greatly regret that this is not a regular feature in the print version of the DNT. The public would really appreciate it.

    Thanks, John S

  2. John Ebeling

    There is a possibility of a geomagnetic storm either Feb. 1 or 2 which may produce some Aurora.

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