Venus is about to position herself less than a quarter of a degree – less than a quarter of the width of your little finger held at arm’s length – above Jupiter. This is the closest conjunction of two planets in 2014, and they are the two brightest planets by far.
This will happen on Monday, August 18, at 4 hours Universal Time, which is 3 a.m. by Daylight-Shifting Time in Britain; in the eastern U.S. it is 11 p.m. by Daylight-Shifting Time on the previous date, Sunday Aug. 17; 8 p.m. on the Pacific coast. But the exact time of the conjunction doesn’t matter vitally. Over three days or more the brilliant “double star” makes a striking sight, fainter Jupiter at first to the left and then to the right of Venus. Around the central time they will, at a hasty glance, look like one super-brilliant star. What matters more is that they are 18 degrees west of the Sun. That is, they stand in the pre-dawn sky, rising only a little more than an hour before the Sun. I think I glimpsed Venus this morning, in the daylight sky when the Sun, which had risen moments before, was behind a low cloud.
Venus is at magnitude minus 3.9, Jupiter minus 1.8; the brightest star, Sirius, is of magnitude minus 1.4. This means (“magnitudes” are a peculiar system) that Venus is at present about seven times brighter than Jupiter, and Jupiter about one and a half times brighter than Sirius.
If you can manage to see all this in a darker sky – that is, soon after the planets have risen around 4 Universal Time – you just might be able to see that they are against an interesting background: just southwest of the beautiful star-cluster in the middle of the constellation Cancer, called the Beehive or, anciently, Praesepe (the “manger”). Venus will slide closer past the southern stars of the cluster a few hours later, Jupiter will do the same in the middle of the next day. Up to the right (northwest) from this group are Castor and Pollux, the Twin stars of the constellation Gemini.
What is happening in space is that Venus is wheeling around toward the far side of the Sun from us, and will pass behind the Sun on October 25. So it is relatively far and, for Venus, dim – it can be nearly one and a half times brighter. It is about 1.6 Sun-Earth distances away from us, Jupiter about 6.2. (The Sun-Earth distance, or astronomical unit, is about 150 million kilometers or 93 million miles.) Jupiter is appearing to move in the opposite direction, because we are overtaking it on an inside track; it emerged from behind the Sun on July 24. The stars are immensely farther away – Pollux about 34 light years, Castor about 52, the Praesepe cluster about 590. (A light year is about 9.5 ,million million kilometers or 6 million million miles.)
All this of course figures in my Astronomical Calendar 2014, in the pages about August, the charts for Venus and Jupiter, the rising-and-setting graph, and elsewhere.
Jupiter was a sky god whose weapons were the thunderbolts; Homer’s stock description of him was nephelêgeretâ Zeus, “cloud-herding Zeus”; he corresponds to Thor in Norse mythology (his day is Thursday or Donnerstag in Germanic languages, Jeudi or Giovedi in Romance ones). Venus, “mater amorum” as Galileo called her, Mother of Loves, was Jupiter’s daughter.