Venus hovers near Spica

Watch out for a new product, to be called the “Zodiacal Wavy Chart.”  This is a snippet of it:

I’ll let you know when it becomes available, after we’ve solved the means of production.

And there will be a parallel product, “Astronomical Calendars Any-Year,” a bottomless barrel of information of which this is a snippet:

Together, the Wavy Chart and the Any-Year Calendar will go far to replace my former large and laborious printed books, the Astronomical Calendars.

Charts and lists have their complementary advantages.  It was while working on the Wavy Chart for the present year that I noticed the wriggly movement of Venus near to Spica in November.  Such motions stand out more readily in a picture than in a table of numbers.  The table mentions that Venus becomes “stationary in right ascension”, and then “in longitude”, but it’s the chart that enlivens these dry statements.

Venus, tomorrow, comes to an apparent halt; that is, it ceases to move westward in right ascension, relatively to the background constellations.  The movement is curved, because Venus is in the part of its orbit that slopes northward (to cross the ecliptic on Nov. 22), so the moment of halting in longitude – that is, relative to the ecliptic – comes 56 hours later, on Nov. 16.

If the timing had been slightly different, Venus appearing for us a little to the right, if would reach the same direction as Spica, might even occult the great star.  What will actually happen is an appulse (a moment of nearest approach) without a conjunction of either kind, right ascension or longitude.

The 1.5° minimum of this Venus-Spica appulse comes at Nov. 15 0h by Universal Time, which is back in Nov. 14 by American clocks – 7 p.m. for the Eastern time zone, 4 p.m. for California.

What happens in planetary space is this:

You are looking from a viewpoint outward from Earth and 15° north of the ecliptic plane.  Shown are the paths of the planets in November, and sight-lines from Earth at the beginning of Nov. 14.  Our sightline to Venus is 26° west of our sightline to the Sun.  This is the elongation at which Venus reaches its stationary moment.  The elongation from the Sun continues to increase, because the Sun is moving eastward for us more rapidly than Venus yet is.  Not till 2019 Jan. 6 will Venus be at maximum morning elongation, 47° from the Sun, our sightline to it tangent to its orbit.

The nearest we can get to seeing Venus and Spica closest together is the morning of Wednesday Nov. 14.  Here is what the pre-dawn sky will look like:

The arrows through the moving bodies represent, this time, their movements (relative to the starry background) over a span of 30 days, so that you can see here, too, Venus’s sweep toward Spica.  The straight arrow for the Sun is over the same 30 days, so you can see why it is that, though Venus begins its chase eastward, it is as yet still becoming more separated from the Sun.

Venus appears 5.5 magnitudes brighter than Spica (the 15th brightest star), a factor of 160 in light.  Whereas Venus is about 0.31 astronomical units or 47,000,000 kilometers from us at this time (increasing that distance as it goes on around its orbit), Spica’s distance may be 260 light-years, or about 2,500,000,000,000,000 kilometers.  More than 50,000,000 times farther.

How can a star be small, a cloud immense?