Green Comet, Green Aurora – Astronomy’s Going Green!

Delicate rays and a bright green arc cut through the Bowl of the Big Dipper early this morning around 12:30. The green color is given off by excited oxygen atoms. The pink, invisible to the eye, is likely also oxygen, which can emit both red and green light when bombarded by subatomic particles from the solar wind. Photo: Bob King

I love it when a forecast proves true. That was the case last night when northern lights were predicted for high latitudes. While Duluth may seem like the Arctic, at 46.7 degrees north, we’re fewer than five degrees of latitude north of Chicago.  Not exactly high latitude but enough to make a difference.

A double auroral ray reaches upward from the arc. Photo: Bob King

I noticed the aurora around 10 o’clock as a glowing presence in the northern sky below the Bowl of the Big Dipper. Nothing obvious … at first. About the time I was ready to go to bed, I made the mistake of checking one more time to see if anything new had developed. Uh-oh, that subtle glow had strengthened into a bright green arc. Bye-bye sleep. I dug out camera and tripod and scouted the neighborhood for a spot with a good view to the north.

After midnight things took a new twist.  Faint spears of light materialized out of nowhere and weird, glowing patches probed the sky above the bright arc. It was fascinating to watch how the arc would intensify in one section and fade in another. All of this happened in the bottom 10 degrees of sky (one outstretched fist). Sky watchers at those higher latitudes – where the aurora was high above the horizon – must have seen a truly great show. Check out this photo taken the same night from Norway by photographer Ole Christian Salomonsen.

The space weather forecast calls for more activity tonight, so it might be worth your while to check the north before you turn in.

The green puff of Comet Hartley 2 wasn't far from Perseus' brightest star Mirfak (above right of center) in this photo taken last night. Details: 135mm lens at f/2.8, ISO 800 and 2-minute exposure on a tracking mount. Photo: Bob King

The moon is now returning to the evening sky, which means Comet Hartley 2 will soon become more difficult to see in the lunar glow especially in binoculars. The coming few nights you’ll still have good opportunities, but once the moon is 3/4 full, you’d do better to go out and view the comet in the morning sky after moonset. Reports indicate that sky watchers living near bright cities aren’t having much luck finding Hartley 2. Part of the reason for this is because the comet is very diffuse and susceptible to light pollution. The outer suburbs and the countryside are another matter. While you wouldn’t call it bright, Hartley 2 is easy to see in binoculars night after night as it wends its way across northern Perseus. Use the map below to help you find it. Click HERE for a more detailed sky chart.

The W or "zigzag" of Cassiopeia will still your guide to Comet Hartley 2 this coming week. Mirfak in Perseus is about two horizontally-held outstretched fists below the lower end of the W. Use binoculars to see the comet best. Illustration created with Chris Mariott's SkyMap software

4 Responses

  1. Robert

    I really appreciate your site. I have been out numerous times over the past 6 days to view the comet Hartley 2, but though I have a pretty powerful binocular, I still haven’t been able to detect which heavenly body is the comet. I have used your maps and believe I am in the right area. The Double Cluster was new for me and now Mirfak. I do see a blur that seems to be in the area shown on the map. Could the comet appear blurred? If you can help me further, please let me know. The binoculars are 10 x 50 power.
    Thank you.

    1. astrobob

      Robert, that blur is the comet! In the photos I’ve posted, you’ve noticed it’s a round glow with no tail. Through both binoculars and telescope, it looks exactly like a blurry spot or smudge of light. Very diffuse and soft-looking with edges that just melt away into the sky. Your description fits that. Sure sounds to me like you found it. Now that you know what to look for, you should be able to watch your “blur” move night to night.

  2. Skip Fischer

    Howdy, Bob. Greatly enjoyed your class during October. Thanks for a great series of presentations.

    1. astrobob

      Thank you Skip. It was great to have you there – your enthusiasm made it fun to teach. I appreciated your phone too!

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