Three Planets And A Smile At Dawn

Venus right next to the moon just a minute or two before it was covered yesterday afternoon. The difference in brightness is striking. Venus was still visible with the naked eye at the time. Photo: Bob King

I hope some of you got to see Venus alongside the crescent moon yesterday afternoon. The view through binoculars was simply amazing.  Venus was brilliant compared to the dull moon. Though the moon was officially brighter — magnitude -9 vs. -4.5 for Venus — the planet’s surface brightness was far higher because it’s wrapped in clouds that reflect sunlight well. The moon in contrast is covered in charcoal-toned dust and rocks.

The difference between the two could not have been more profound. By the way, the moon was only brighter overall. What it lacked in surface brightness, it made up in surface area.

Perseid meteor shower activity is winding down, but I managed to catch a busy spell when I stepped out at 3:15 this morning. Four meteors including a sputtering fireball shot out of Perseus in just five minutes of looking up. Amateur astronomer John Chumack uses a low-light video camera to record meteors from his home in Dayton, Ohio. He compiled all the meteor images he captured over August 11-12 into a single video. Hit play to see 220 Perseids fly by in just 2 minutes!

Venus is far to the right of the sun and high in the dawn sky in August. On the 15th it reaches a maximum separation of 46 degrees from the sun as seen by an observer on Earth. Planets and sun not to scale. Illustration: Bob King

Venus reaches greatest elongation tomorrow (Aug. 15) when it’s as far off to one side of the sun as it can get. That means it rises well ahead of the sun and stands high in the eastern sky at dawn. For Duluth, Minn. the planet comes up at 2:30 a.m., fully 3 1/2 hours before sunrise. As seen from Earth, Venus is almost exactly 50 percent illuminated by the sun and looks like a little half moon in a telescope. When the planet is west of the sun and visible in the morning hours, astronomers say it’s at greatest western elongation. At greatest eastern elongation, Venus shines in the evening sky and its other half is lit. At “full” and “new moon” phases the planet is either nearly in front of or behind the sun and lost in the solar glare.

Mercury joins Venus and Jupiter to form a long arc of naked eye planets visible in the morning sky at mid-month. The map shows the sky tomorrow morning about 45 minutes before sunrise. Created with Stellarium

While you’re out admiring Venus, look much lower in the northeastern sky about 45 minutes before sunrise for yet another planet at greatest western elongation – Mercury. Mercury is farthest west of the sun (18 degrees) on the 16th and easy to see if you have a wide open view to the east. The moon helps point the way tomorrow morning.

4 Responses

  1. Stephan

    Great Picture! You must have very clear skies, very clean air over there in Duluth. And congratulations! You caught the two just before that cloud came up. I’ve never been able to see Venus in broad daylight with unaided eyes down here…to much haze all the time.


    1. astrobob

      Thank you Stephan. We were lucky that day to have very clean skies though our summer has been hazier than usual. I decided to look for the moon much earlier in the day when it was higher – that way I could memorize the sun-moon angle which made it easier to locate later that afternoon.

  2. Gene Crady

    Approx. around Aug 15th or 16th, I was up to see the 3 planet alignment and the moon. What I witnessed was totally unexpected and I can’t find a term to fit it. Apparently, the moon was obscured from the sun at 15 degrees above the horizon, but at the moment I happened to look for the reflection off earth to the back side of the moon, the sun began to illuminate the quarter crescent. It took only 2 or 3 seconds and I’ve never even heard of this type of event. Can you define what I saw, or pass it on to someone who might.
    Many thanks,
    Gene Crady
    Louisville, Ky

    1. astrobob

      Hi Gene,
      So you were looking at the dimmer, Earth-lit part of the moon and all of a sudden, the bright sunlit crescent became visible? I wonder if a cloud or other obstruction was blocking the crescent part and then moved off. The crescent part should have been lit by the sun the whole time, since the moon doesn’t move fast enough to pop into view in just 2-3 seconds. The crescent was there the entire evening. Or am I misunderstanding something?

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