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Touring the Skies By: Jim Bonser (jbonser@usa.net)

December 6, 2013
Northern-Sun Print
Ps. 19:1 The heavens declare the glory of God; the skies proclaim the work of his hands. Okay, last month I mentioned that cooler temperatures had arrived. Well, as I write this a few days before Thanksgiving, the thermometer outside reads 20 degrees, but the wind chill according to Accuweather says it feels like 8 degrees! Looking out my backyard door I can see bright Jupiter about 30 degrees off the horizon shining steady and bright but guess what? I am not even tempted in the least to go out and open the observatory. I would really like to get some fresh pictures of Jupiter, but I draw the line at anything below 20 degrees unless it is really special. I guess I better get the snowmobile suit and gloves ready though since something special just might happen this month: comet C/2012 S1 aka: ISON. In one article I read about comets the author quoted a friend as saying “Comets are like cats: they have tails and do whatever they want!” That is exactly right! Predicting how a comet will behave is like guessing the weather forecast 2 years from now. Although many had hoped that ISON would be much brighter by mid-November than it turned out to be, in recent days it has actually brightened quite a bit and so many have their fingers crossed, hoping the comet will hold together and not break apart as it swings around the Sun. To give you an idea what this comet is enduring and help explain some of the uncertainty about its future, consider that when it was observed back in January, it was approaching the Sun at a relatively leisurely 40,000 miles per hour. On Thursday, November 21 it had accelerated to 150,000 mph and it is not done yet. When ISON swings around the Sun before heading back our way, it will get very close to the surface of the Sun, only about 730,000 miles. The average distance to the Moon is 238,857 miles – so ISON will pass by the sun only about 3 times the distance from Earth to the moon – the heat and force of gravity will be incredible! On top of that, by the time it gets as close as it can it will be traveling at an incredible 828,000 mph. Wow! Being that close, it may be bright enough to see in the daytime – wouldn’t that be impressive? So, if it survives the gravity and the heat and radiation it may provide a truly spectacular sight in the middle weeks of December and in fact, will be closest to Earth traveling almost over our north pole on the day after Christmas – kind of a Christmas Star for us this year. Don’t worry about any collisions though because even at its closest approach ISON will not get within 40 million miles of us and it probably will never be seen again as it heads out toward deep space. Let’s hope for a wonderful Christmas Comet this year, Amen? As for other things to watch in the clear, cold December skies, Jupiter will be big and bright this month rising in the east a little after 7:30 pm on December 1st. Jupiter reaches opposition early in January so it will get steadily brighter as the month goes by and rise earlier and earlier. In a telescope, Jupiter will appear 47” (that’s 47 arc seconds) wide. If you are familiar with telescopes what that means in technical terms is that Jupiter will look really big! Jupiter is always fun to view in a telescope and that is doubly true when it gets close to opposition (when Jupiter is on the opposite side of the Earth from the Sun). The colored bands of clouds and polar caps and the Great Red Spot are always a pleasure to study and enjoy. On the other side of the evening sky, in the west, Venus also continues to get brighter as she races toward inferior conjunction on January 11th. Inferior conjunction means a planet that is closer to the Sun than the Earth such as Mercury or Venus will be directly between us and the Sun. Sometimes this means that we can see the silhouette of the planet against the face of the Sun like the Venus transit in 2010. But because of the tilt of the planet’s orbits that will not happen this time. Nevertheless, Venus will be getting closer and closer and therefore bigger and brighter even though its phase will be getting smaller and smaller. I know, your head is probably spinning, but if you have access to a telescope, take the time to point it at Venus in the twilight every few days this month. Without a telescope you will clearly notice how bright it is getting. Through the telescope you will see Venus’s disk grow from 37” to 59” by the end of December. Remember, we said Jupiter would look great at its maximum of 47”. Venus will not show cloud belts like Jupiter but it will go from 30% lit which would be like a couple of days before a 1st quarter moon, down to only about 5% lit – an extremely thin crescent – by the end of the month. The Geminid meteors on December 13-14 are usually a good shower to watch but the moon will be very bright and make the sky too light to see any but the very brightest of them. Mars rises about 1 AM on December 1st and is getting brighter but is still a long way away and very small so for now we won’t be able to see any details on its surface, but it will make a pretty addition to Virgo’s head this month. Perhaps a few excited young people might even spy red Mars as they watch for Santa’s sleigh on Christmas Eve.? By then Mars will have moved from being a jewel in Virgo’s crown to a gem in her necklace that rises around 12:30 in the morning. Clear Skies and Merry Christmas!
 
 

 

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