Venus and Jupiter make one star

The year’s closest conjunction of planets comes this Saturday – and they are the two brightest.

Venus-Jupiter close conjunction

Venus will pass north of Jupiter by only 0.07° (2.3 times Jupiter’s apparent width), so they will be like a single star.  Their magnitudes of -3.9 and -1.7 add up, in the logarithmic way of magnitudes, to -4, not quite as brilliant as Venus can  be by itself when farther out from the Sun.  The “appulse,” or closest moment, is August 27 about 22 Universal Time, which is 6 PM by clocks in eastern North America, 3 PM on the Pacific coast – a couple of hours before the time of this twilight picture.

The planets are 22° out east from the Sun, but unfortunately for us in the northern hemisphere they are out along the southward-sloping late-summer reach of the ecliptic, therefore at a low angle to our horizon.  At the time pictured, they are only about 2 degrees above the horizon, and soon to set.  Possibly you can spot them sooner, or even by daylight.  At only 10 minutes after sunset, they will be more like 8° high.

Mercury is nearby, and will at Aug. 28, 4 UT, form a tightest grouping with the other two, a “trio,” the three fitting in a circle of minimum diameter barely over 5°.  But Mercury, unlike the other two, happens to be well south of the ecliptic, thus hopelessly out of view for northern observers.

For those living on the southern hemisphere of our rounded planet, the scene is tilted much more favorably.

Venus-Jupiter conjunction as seen from Australia

The season here is late winter and the ecliptic slopes steeply upward from Sun to planets.  At this place and time, Venus and Jupiter are 12° above the horizon, Mercury 15°.

This is how the planets are moving in space.

Planets in space, 2016 August 28

Their courses are shown for the month of August, with sightlines from Earth at Aug. 28.0.  The dashed line is the vernal equinox direction, the origin or “Greenwich” for our mapping of space.


9 thoughts on “Venus and Jupiter make one star”

  1. We were lucky here in central Virginia to have clear skies, so I had a nice view of the pairing in bright twilight, around 8:15 p.m. local time. Unfortunately, I am in the midst of moving, so I didn’t have access to my camera equipment, nor the time to go to the trouble of trying to get a picture.

  2. I still haven’t seen Venus since its latest superior conjunction. It’s always exciting to see if for the first time in the evening sky.

    I like your new blog design. I think it’s sharper, more organized.

    Maybe it will accept a picture now above my name. I’ll give it another try when I get some time.

  3. VERY COOL!… I’ll take a look tonite as the skies seem to be clear enough.Who knows what tomorrow might bring. Thanks.

  4. Guy, again we appreciate the your post! Great job. For my information, and if you do not mind sharing, how do you generate the graphic representations of the solar system?

    1. I’m afraid the answer to that would be too long. I started programming in Fortran, long ago, and have built up such a huge system that way that I could not transfer to any of the more modern programming languages. I make my programs (the ones that plot pictures) write files in the language that Adobe Illustrator uses.

  5. Guy’s weblog has become more universal! I hope everything will work out. I like the new layout, although like any other new thing it will take me a little while to get used to it.

    I’m very much hoping to see Venus and Jupiter tomorrow evening. Because of unrelenting clouds and fog I missed Mars’ transit through the Saturn-Antares line earlier this week. Tomorrow afternoon I’ll be on the east side of San Francisco Bay and I’ll head up into the hills, hopefully above the fog, to see Venus giving her dad a peck on the cheek.

    1. Success! I drove to the Oakland Mormon Temple, which has a sweeping view over the bay (the Temple, with its five tall and distinctive spires, serves as an important landmark) and set up my 15×70 binoculars on a tripod in the parking lot. The young security guard was curious, and welcoming when I explained what I was doing. There were a lot of people coming and going for different activities: wholesome-looking young white couples, big Pacific-Islander and Latino families, presumably all united by their Mormon faith.

      The sky was partly cloudy, but I found Venus in a big hole in the clouds 15 minutes before sunset, and Jupiter as a faint ghost just before sunset. Ten minutes after sunset Venus was faintly visible to the naked eye, and Jupiter resolved to a dusky disk in binoculars. Half an hour after sunset both were visible to the naked eye and distinctly separate, 11 arcminutes apart according to my planetarium software. They disappeared and reappeared behind passing clouds. I looked for Mercury and the Galilean moons, but didn’t see them. By 45 minutes after sunset Jupiter and then Venus descended into the final cloud bank.

      I shared the view with a few people, including a young woman who had studied astronomy in college, and a boy of perhaps five who was enthralled to see Jupiter, which he knew was the biggest planet.

      1. That is good data on the visibility of the planets when low. You even mention “cloud” low to the horizon, not just haze. I have no hope of seeing a low clear horizon from anywhere near me now.

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