Clouds foil stargazing plans

Thursday, June 18, 2009

Well, so much for that idea. For most of the last week, including the occultation of Antares by the moon on June 7, the skies have been clouded over.

Of the 13 times the moon will occult, or cover up, Antares during the current year this was the best one for us here in the United States. Although there will be one viewable from Alaska on Nov. 17, if you want to go that far.

One event that won't be covered by any kind of clouds is the summer solstice on Saturday, June 20. Now, most of your calendars will show the solstice on Sunday, June 21. The solstice occurs at 1:46 a.m. eastern daylight time which, counting back two hours for the time zone changes, puts it at 11:46 a.m. Mountain Daylight Time on Saturday June 20, here in Southwest Nebraska and northwest Kansas.

The solstice, Latin for "sun stands still," is when the sun reaches the point farthest north of the equator. At that time it will be over the Tropic of Cancer, one of the three imaginary lines drawn around the Earth depicting the travels of the sun. The other two are the equator indicating the middle and the Tropic of Capricorn which marks the point farthest south.

Each of the tropic lines are either 23.5 degrees north of south of the equator corresponding the 23.5 degree tilt of the Earth's axis. When the sun reaches the Tropic of Cancer, the Earth's northern hemisphere is leaning 23.5 degrees toward the sun, and consequently the southern hemisphere is leaning 23.5 degrees away from the sun. Hence, summer starts for us and winter starts for the good folks south of the equator.

When asked why the summer is so hot, some folks have said that is when the sun is closest to the Earth. But, alas for them, that is not the case. In fact, during the northern summer the Earth will be at the farthest point in its orbit from the sun, on July 3 actually. Conversely, during the northern winter the sun is at its closest orbital point.

So dig out the swim suits and beach gear and lets get ready to head for the lake. And to our good friends south of the equator, better start finding the coats and long johns.

SKY WATCH: The summer constellations are becoming more prominent each evening, especially the Summer Triangle of Deneb, the tail star in Cygnus, the Swan; Vega, in Lyra, the Harp; and Altair, in Aquila, the Eagle. All three are above the eastern horizon by 10:30 p.m. The other "Dynamic Duo" of summer, Sagittarius, the Archer and Scorpius, the Scorpion are high in the south just after midnight. For the early risers of the bunch, be out about an hour before sunrise starting today, June 17, and look for very bright Jupiter high in the south. Use your binoculars to find much dimmer Neptune above and right of Jupiter. The pair will be together for most of the rest of the month. Just above the eastern horizon another planetary pair can be seen. Very bright Venus with dimmer Mars above and to its left. Binoculars will be needed to find Mars. If you are out again on June 19, look for a very slender crescent moon above the Mars/Venus pair. Follow the moon on Saturday, June 20, as it moves in to join the Pleiades star cluster. This pairing will be very close the horizon. If you have a good, clear, horizon to the northeast on Sunday, June 21, and lots of patience, you might be able to find very dim and tiny Mercury about six degrees (a little more than the width of your binocular field of view) below and right of the lunar crescent. The pair will be very close to the horizon. A good time to look will be about a half hour to 45 minutes before sunrise, but be warned, the sky will be getting bright and may wash out any view of the tiny planet.


More astronomical blathering.

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