MAINE SKIES

Gravitational disturbances, ‘wobble’ of Earth’s axis can cause the sun to be in two places at once

Posted May 29, 2013, at 11:33 a.m.

How can the sun be in two places at the same time? On the solstice the sun enters the astrological sign of Cancer but less than half a day later enters the astronomical sign of Gemini.

What does this mean? The answer lies with precession, a circular motion or “wobble” of the Earth’s axis of spin due to gravitational disturbances caused by the sun and moon. The north celestial pole traces out a complete circle roughly every 26,000 years causing the celestial north pole to point to different parts of the sky over long periods of time. This has two effects with one being the pole star changes over time. Today we know it is Polaris but about 3000 B.C., it was Thuban in Draco and in 14,000 A.D., it will be Vega in Lyra. The other effect is to have the axis of spin point to different houses of the zodiac at any given time of the year.

It takes 2,150 years for the point to change 30 degrees or one “house” of the zodiac. When astrologers started to fix the signs of the zodiac about 22 centuries ago, the axis of spin pointed to Cancer but has since precessed to Gemini at the solstice. Astrologers do not factor in the precessional change, hence the sun can be in two different places depending if you ask an astrologer or an astronomer.

Focus on the planets

Mercury, Venus and Jupiter line up in the early evening twilight with Mercury to the upper left, Jupiter to the lower right and Venus in the middle as June opens. View the trio quickly as Jupiter disappears during the first week of the month.

Mercury is well up in the northwest shortly after sunset and remains in view nearly all month. Look for a thin crescent moon passing to the lower left of Mercury on June 10.

Venus starts June low in the northwest to the lower left of Mercury and continues in that position throughout the month. On June 25, Venus forms a nearly straight line with Castor and Pollux of Gemini.

Mars rises in the northeast about an hour before the Sun and will be just visible with binoculars if the sky is clear.

Jupiter starts very low in the northwest on June 1 and is gone a few days later. Although we cannot see it, the sun occults Jupiter during its conjunction on June 19, an event that occurs only twice during the planet’s 12-year orbit.

Saturn is about half-way up on the southern horizon at dusk. Saturn is diminishing in both size and brightness but the rings still offer a breathtaking view tilted at 17 degrees to our line of sight. Its major moon Titan, one of more than 60 moons, continues its dance around the planet.

Uranus and Neptune rise after midnight with the former’s blue-green disk and the latter’s blue-gray disk visible by telescope. The website skypub.com/urnep maintained by Sky & Telescope magazine offer finder charts for these elusive and far distant planets.

June events

1 Sunrise, 4:53 a.m.; sunset, 8:14 p.m.

3 Uranus may be visible through binoculars just to the lower right of the moon just before dawn.

8 New moon, 11:58 a.m.

9 Moon at apogee or farthest distance from Earth today.

10 Look to the northwest about an hour after sunset for Venus with Mercury to its upper left and the thin crescent moon passing by the two innermost planets to the left.

11 This would be a favorable night for the Gamma Delphinid meteor shower but they are unlikely to occur. Only one reported sighting has been made since 1930 however it might be worth checking out as this could be the lucky year.

15 Venus and Mercury continue together on the western horizon after sunset with the Twins, Castor and Pollux, directly above.

16 Moon in first quarter, 1:24 p.m.

18 Saturn is well up on the southern horizon around 10:00 p.m. with the moon just to its lower right.

21 Summer solstice, 1:04 a.m. The Sun has reached its most northern point above the celestial equator giving the longest day of the year for the northern hemisphere. The Sun enters the astrological sign of Cancer at the solstice however, only nine hours later, enters the astronomical sign of Gemini.

23 Full moon, 7:33 a.m. The full moon of June is known as the Strawberry Moon, Rose Moon or Flower Moon. The moon is at perigee or nearest approach to Earth. The coinciding of full moon with perigee could result in very high tides.

30 Moon in last quarter, 12:54 a.m.; Sunrise, 4:52 a.m.; sunset, 8:25 p.m.

Send astronomical queries to Clair Wood at cgmewood@aol.com or care of the Bangor Daily News, Style Desk, P.O. Box 1329, Bangor 04402.

 

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