Monday, December 9, 2013
By BERNIE REIM
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Instead of three planets dancing in our evening sky, only two will grace our western sky this month. We will lose the king of the planets, Jupiter, leaving our two innermost planets on display all month long.
This month our first planet, Mercury, will start about 5 degrees above our neighboring planet, Venus. Then they will drift closer and closer until they will be less than 2 degrees apart two days before the start of summer. Then keep watching as they switch places and Mercury ends up below Venus low on the west-northwestern horizon 45 minutes after sunset. This will be Mercury's best evening apparition for this whole year. Through a telescope, notice that Mercury starts about half lit and decreases to a thin waning crescent, while Venus only decreases to 92 percent illuminated by the end of June.
You may want to consider starting your solstice marking exercise on the evening of June 10, when a wonderful slender waxing crescent moon joins the pair of planets in Gemini the twins, about 10 degrees below Castor and Pollux, the mortal and immortal twin, respectively. The next evening the moon will be 7 percent larger and 12 degrees farther east along the ecliptic at the same time of the evening. That will add the moon into the equation as you track the precise relationship of the earth and the sun around the summer solstice to help increase your awareness of all the wonderful motions we are always involved in without our sensing any of it.
On an even larger scale, Earth is always traveling around the sun at 67,000 mph, or 18.6 miles per second, which translates to getting from New York to Los Angeles in just under three minutes. Then go even farther and realize that the sun and our whole solar system, of which we can only see a tiny part from our narrow window confined to the surface of Earth, is constantly being flung around our giant Milky Way galaxy at about seven times that speed. That means if it takes you about 10 minutes to read this column, we will have traveled about 75,000 miles through galactic space in that time, which translates to three times around the world.
Saturn rises in the east just before sunset. The ringed planet is still in retrograde or westward motion this month in Virgo, but the rate of that motion is slowing. Look halfway up in the southern sky from June 17 through June 19 to catch the waxing gibbous moon passing just below Spica and then Saturn.
Mars finally makes reappearance into the eastern morning sky late this month along with Jupiter, but you will probably need binoculars to see them.
• June 3. On this day in 1948 the 200-inch Hale telescope was dedicated on Mt. Palomar.
• June 4. On this day in 2000 the Compton gamma ray telescope was allowed to reenter our atmosphere.
• June 8. The new moon is at 11:56 a.m. On this day in 1625, Giovanni Cassini was born. The most obvious gap in Saturn's rings is named after him, the Cassini Division.
• June 10. The Mars rover, Spirit, was launched on this day in 2003.
• June 13. Pioneer 10 leaves the solar system on this day in 1983.
• June 16. First-quarter moon is at 1:24 p.m. On this day in 1963, Valentina Tereshkova became the first woman in space and still holds the only solo spaceflight by a woman.
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