Venus on January 12 reaches 47 degrees of elongation, that is, distance from the Sun, on the left side (as seen from our northern hemisphere) – the evening side.
It happens because Venus is coming around to overtake Earth on the inside.
The planets’ paths are shown for December, January, and February. The planet globes are 300 times exaggerated in size. The sightline from Earth to Venus, at Jan. 12, is tangent to Venus’s orbit. (The dashed line and stylized ram’s-head symbol mark the vernal equinox direction, traditionally called “the First Point of Aries.”)
To see more ways of illustrating the situation, click on the “Astronomical Calendar 2017” tab above, then on “Mercury and Venus.” Scrolling down, you can find (and enlarge, by some rubbing with your mouse or finger) the chart of Venus’s path among the constellations; the graph of “Mercury and Venus apparitions compared”; and the large horizon-based picture for “Venus, SUNSET sky, latitude 40° NORTH.”
As the last two of those show, Venus at the moment of maximum elongation is, for latitude 40° north, not quite at its highest above the sunset horizon; that situation will come a bit later, around Feb. 3.
Indeed, some say that the real climax of the planet’s apparition is when it shows its greatest illuminated extent (that is, the crescent of sunlit surface visible in the telescope has the greatest angular area). This will come on Feb. 17. It is brought about by the balance between the planet’s increasing width, and the increasing narrowness of its crescent, as it wheels toward us.
Almost at the maximum-elongation moment (actually 8 hours later) Venus passes only 0.36° north of distant Neptune. But this angular gap is 54 times wider than Venus itself; and Neptune is about 12 magnitudes dimmer, which means it is sending us about 80,000 times less light.
Comet 45P Honda-Mrkos-Pajdusaková may now be at about the same magnitude as Neptune, or a shade brighter, but it is even more difficult to find, not only because deeper in the Sun’s glare but because comets’ light is spread into a little cloud.
Nice blog entry. Was wondering when you were going to mention this. Ive already been telling folks to be lookin for Venus in daylight since before the last moon’s passing of it. As for Neptune and that comet you mentioed, guess I’d better get a newer more powerful telescope; although I may have mentioned in the past I have once viewed Neptune through a backyard scope in the heyday of my telescoping days. Thanks, and still wishing folks a Happy New Year.
Thanks Guy. I needed to be reminded of this. The San Francisco Bay Area has been deluged with rain for the past few days, and the US news media have been deluged with bad news. It’s good to know the planets are still keeping their appointed rounds.