The central event of the seasons

The summer solstice looms – Sunday, June 21 – but on that day I shall be embarking for an adventure in northwestern Spain, so I must post this in advance.

First, there are interesting sights before the solstice, and the evening of Friday June 19 is the time to start looking.

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The Moon comes climbing from the sunset, and on Saturday June 20 it will pass south of Venus and, a bit more than 12 hours later, Jupiter. These events are closer together in time than those of May 21 and 24, the planets having moved closer to each other; they are also closer approaches, especially the Moon-Venus one. However, Jupiter is now only 51 degrees from the Sun, as against 73 in May, so the Moon when passing it is slimmer. The appulse (closest approach) to Venus is at about 8 Universal Time, so the nearest American sunset to it is the one of Friday June 19. The passage by Jupiter, about a degree closer, is at about 21 UT.

Jack Gambino may again tell us about his success in using the Moon as guidepost to spotting Venus and Jupiter in the daytime sky.

(Asteroid Juno is, at magnitude 10.7, far below naked-eye brightness, fainter than it was at its opposition in January and fainter than thousands of stars not shown; I decided to let it stay in the picture only because it happens to be not far from the goddess Juno’s husband Jupiter.)

Now, the solstice. It comes this year on June 21 at about 17 hours UT, which by clocks on summer Daylight Shifting Time is 6 PM in Britain, 1 PM in eastern and 10 AM in western Usamerica.

What the solstice means is that the Earth’s north pole is most tipped toward the Sun.

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As seen from Earth, the Sun reaches its northernmost point in its yearly journey around the sky.

SunChJunPart of the chart for the Sun in Astronomical Calendar 2015. This is the part of the starry sky now obscured for us by the glare of the Sun. The plot is in the ecliptic framework, so that the Sun’s course appears straight, whereas if plotted in equatorial coordinates it would be humped to the north. The smaller circles for the Sun are at true scale, the month-beginning ones are at twice size.

The solstice point is at longitude or right ascension (they coincide here) 90 degrees. And so, according to the old astrological system, the Sun passes at this moment from the third “sign,” Gemini, into the fourth, Cancer.

But in reality, because of the precessional twist of the Earth’s attitude over about two thousand years, the Sun appears a whole constellation further back: it is passing from Taurus into Gemini. The moment when it does this is June 22, 2 UT.

Roughly the same happens at the other places around the sky where the Sun progresses from constellation to constellation – the “roughly” being because the astronomical constellations have irregular shapes, not constant 30-degree widths like the astrological signs. But this is the most interesting of these pairs of events. It is the first at which the difference has begun to be slightly more than one constellation. Briefly, from June 21 17 UT (solstice) to June 22 2 UT (constellation boundary), the Sun is still in Taurus when astrology says it should be in Cancer.

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This began to be so in 1990, when the Taurus-Gemin boundary crossing moment overtook the solstice.

I shan’t be back till July 4 (my birthday), so shall probably be late with the news I would then like to bring you about July 5.

6 thoughts on “The central event of the seasons”

  1. This just in today…
    Space Weather News for June 29, 2015
    http://spaceweather.com

    SUNSET SKY SHOW: The two brightest planets in the night sky are converging for a spectacular close encounter. On June 30th, Jupiter and Venus will be just a fraction of a degree apart, forming a pair so bright that you can see them even before nightfall. Check http://spaceweather.com for observing tips and more.

    You are subscribed to the Space Weather mailing list, a free service of Spaceweather.com: http://spaceweather.com/services/ .

  2. Hey folks, As Guy’s gone til 4th of July, I thought I might pick up the torch so to speak, and with a heads up from http://www.spaceweather.com, thought I might impart this conjunction/appulse, whatever term Guy might use for Venus and Jupiter. Skies in NY were finally clear enough last nite to show some cousins the moon and planets and instructed them how to see them today, I think Jupiter’s already lost some brilliancy to be seen easily in daylight, but Venus is still sparkling away.
    “As the new week unfolds, the Moon is moving away from the planets–but the show is far from over. In the evenings ahead, Venus and Jupiter will draw closer and closer to one another. On June 30th, they will be a whisper-thin 1/3rd of a degree apart. You’ll be able to hide the pair behind your little pinky finger outstretched at arm’s length. Such a close pairing of bright planets is truly mesmerizing. Mark your calendar and enjoy the show!”,,, credit to spaceweather .com.
    Guy, I hope you don’t mind….

  3. Guy, you KNEW it! I think that this is one of the most exciting times to show those unfamiliar with the skies and think you can see these things, even the moon, only at night. But with the moon in its position now, you can easily spot Venus and Jupiter almost anytime you can see the moon, remembering their relative positions from the previous evening and extrapolating them the following day, maybe even as early as midday. A joke I like to play on some folks is to get the to see Venus, then tell them I was only joking and let them then convince me that it’s really there. Try it for a laugh or two.
    Have a great trip in Spain, Guy, and great viewing to all others.

  4. Yesterday afternoon, June 18, about 1800 PDT, so about two and a half hours before sunset, I found a place in my neighborhood where I could put the Sun behind a building, and looked for the Moon and Venus. I found Venus first, and she helped me find the Moon. The sky was rather hazy, and Venus was higher, and a bright point of light, rather than a ghostly crescent.

    I was surprised by how far south the Moon was from the line between Venus and the Sun. I knew intellectually that the Moon can be up to 5 degrees north or south of the ecliptic, but now I have a clearer sense of what that looks like. Venus is 1.75 degrees north of the ecliptic, so that exaggerated the effect.

    An hour or so later I set up mounted binoculars on the sidewalk in front of my home and showed passersby (de)crescent Venus. Among the visitors were an older Scotsman in a kilt and his wife, and a Latino man who knew a lot about ancient meso-American calendars, many of which used Venus’ evening and morning apparitions as a fundamental cycle, but he had never seen Venus at magnification before. We had a good talk.

    By the way, is Usamerican your own neologism?

    1. And the southward angular distance from Venus to Moon was also increased by your own latitude north of Earth’s equatorial plane.

      I don’t know how unusual it is to use Venus to find the Moon, as opposed to the other way around!

      Yes, I rather object to using “America” for just one of its countries. I’ve been quixotically propagating my suggestion of “Usamerica” for, I don’t know, a couple of decades. Let me know if you ever notice anyone else using it.

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