¡SkyCaramba! Weekly astronomy blog for the week ending June 20, 2015
Venus and Jupiter are about to meet up just a little west of the sickle in Leo. They’ll be barely 0.3° apart. You could think of this rendezvous as a reprise of another meeting these two planets have had there. Two millennia ago, they were less than 0.1° apart. They were so close, they would have looked like they merged into one object!
Venus has been in our evening sky since December. Since then it has passed close to Mercury and Mars while passing through Capricorn, Aquarius, Pisces, Taurus, and Gemini. It is now in Cancer and heading toward Leo. Jupiter moves much more slowly. Since December, it has gone westward and then eastward in the space between Leo and Cancer. That is the region where the two planets will meet up right at the end of June.
Jupiter and Venus 1/3° apart will be a beautiful sight with and without a telescope. That’s less than the apparent width of the full moon. But try to imagine them with only about 1/5 the separation. That’s what you would have seen 2,017 years ago! If we extend our current calendar backward, that super close conjunction occurred on August 12, 3 BC (or the year -2 if you include a zero year while counting backward).
That conjunction of two millennia ago was so close, many observers would have thought the two planets merged into one. A telescope would have easily resolved them into two again, but people didn’t have telescopes then. It happened in almost exactly the same place in the stars as the coming conjunction of June 30, 2015. However, the event of 3 BC was visible in the morning, so it would have appeared above the rising lion instead of below the lion as it set.
Some scholars believe the 3 BC conjunction prompted a famous journey by some wise men who were watching for signs in the heavens that a new king was born. They think such a close meeting of the two brightest planets near the star Regulus (whose name means king) was the Star of Bethlehem. No one knows for sure, and there are other astronomical events various scholars have proposed other astronomical events as the signal to the wise men that one era was giving way to another so long ago.
That matter may never be settled. But you can ponder it as you see Venus and Jupiter reunite briefly as one month yields to another this year.