See A Beauty Morning Conjunction / Zodiacal Light Returns

This will be the scene tomorrow morning Oct. 17, when two planets and a very thin crescent moon, resplendent with earthshine, gather in the eastern sky. Created with Stellarium

We’ve hit a run of clear skies, so it feels like a shopping spree up there. Anything a skywatcher might want to see — sunsets, meteors, a last look at Saturn, the Milky Way, the latest comets — is easy pickings. It’s no wonder the hobby of astronomy can drive some people crazy with its boom and bust cycles in the everlasting battle with the clouds.

If you’ve got good weather, take advantage of the late sunrise to step outside and gawk at a great gathering of a splinter-thin crescent moon just 1° (two moon diameters) from the planet Mars tomorrow morning (Oct. 17). Only 6° below the pair, you’ll see the beacon of Venus like a spotlight directing your eyes to the action. Start looking about an hour-and-a-half before sunrise in the eastern sky or around 6 a.m. low in the eastern sky. All three rise higher in a brightening sky as the sun works its way to the horizon.

The tapering glow of the zodiacal light appears over Lake Superior north of Duluth earlier this month about 1 hour 20 minutes before sunrise. The bright object near its base is the planet Venus. The view faces east. The name “zodiacal” refers to location: the glow lies along the zodiac, appearing in the zodiac constellations familiar from astrology. Credit: Bob King

From mid-October through November is the best time to catch sight of another dawn phenomenon, the zodiacal light. It’s a big cone of diffuse light, broader at its base and tapering along its length, that tilts up from the eastern horizon shortly before the start of dawn. The soft, glowing nature of the light resembles the smoky look of the Milky Way. But while the Milky Way’s misty appearance comes from the combined light of billions of distant suns, the zodiacal light originates from the sunlight scattered off quadrillions (at least!) of tiny, dust-mote sized comet grains and bits of asteroid debris.

The dust nearest the sun gets lit up brightest, hence the bright and broad base of the cone. The farther you look up and away from the sun’s direction, the less intense the scattered light, the reason the cone tapers and fades. It’s an eerie thing to see and worth getting up a little earlier. The zodiacal light is easily visible from a dark, eastern sky starting about two hours before sunrise, but most impressive at the very start of twilight about 90 minutes before sunrise, when the eastern sky begins to brighten.

Because of technical problems I wasn’t able to post any images of this past Friday night’s aurora (Oct. 13). We had a brief but fantastic display from late twilight until around 8 p.m. with three different colors showing — at least in the camera. The next potential for auroras will happen on Oct. 24-25. The streak at top is an Iridium satellite flare. Credit: Bob King

The crescent moon is thin and faint enough that the zodiacal light should return to view — at least faintly — tomorrow morning. After that through about Nov. 2nd, when the moon returns to the morning sky, it’s open season on comet dust watching!

12 Responses

  1. Edward M. Boll

    I do not know what it is increased surface lights. I have not seen Northern Lights in several years. I used to enjoy them frequently. My favorite was on Oct. 22, 1989.

    1. astrobob

      Hi Edward,
      I remember that great display in ’89. The lights are still out there for sure, and there have been many nice shows in recent years though I’ve not seen as much red as I remember seeing in the ’89 storm.

  2. Edward O'Reilly

    Hi Bob. Is Ed from New Brunswick,Canada. I haven’t checked
    in for a while. Have you tried for C/2017 O1 lately? From mildly
    light polluted skies, I tried using 50×80 binos last Thursday. Saw
    a couple of areas that looked like possible faint smudges but can’t
    confirm either was the comet. It should be at peak mag now but
    doesn’t seem to be setting the night sky on fire! lol Will likely try with
    my 8 inch Dob next couple of nights.

    1. astrobob

      Hi Edward,

      The comet might be just a little below your binocular range only because of low surface brightness. It’s fairly large — giving it a bright total magnitude — but not very condensed, so it looks on the faint side even in my 15-inch. You should be able to spot it in your Dob. Let us know if you do. I’d be interested in its appearance in that size telescope.

  3. Edward O'Reilly

    Thanks for the info,Bob. Thought the size and low surface brightness
    might be a problem. Will try my scope on it the next few nights,depending
    on the weather. Will let you know how I do

    1. astrobob

      Hi UK,

      The comet is C/2017 O1 (ASASSN1) currently moving north through Perseus into Camelopardalis. About mag. 9.5.

  4. Mary

    6.45am I am looking at the Moon and Mars to my left but can you tell me the very bright star high on the right. Is it the morning stat? thank you

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