Visualizing astronomical concepts can make astronomy a real challenge for the beginner. That's why nice people create simulations to help us understand how objects like comets move and evolve as they fly headlong into the inner solar system.
Let's take a look at C/2012 S1 ISON, the comet currently in the astronomical spotlight. INOVE Space Models has come up with a beautiful, interactive portrayal of ISON as it sweeps in from deep space, swings rapidly around the sun during its closest approach on Nov. 28 and then returns from whence it came.
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With a click and drag of your mouse you can zoom in, change perspective and see basic information on the planets and comet. I guarantee you'll get a great feel for ISON's orbital path in three dimensions and how the comet changes speed as it approaches the sun. When you it loop-de-loops around the sun at perihelion, the comet's true speed will be around 840,000 mph (1.35 million km/hr). That's some roller coaster ride.
German astronomer Uwe Pilz has made a series of simulations of Comet ISON's tail around the time of perihelion based on how dust particles spew from a comet's nucleus under the influence of sunlight. The images, which I've compiled here into a mosaic, show its tail quickly lengthening to 40 degrees or longer in early December.
The latest brightness predictions for Comet ISON according to NASA's JPL Horizons site puts it at 10th magnitude - small telescope visibility - by mid-October. The naked eye limit won't be crossed until a month later on Nov. 13-14. Not until a week and a half after that will the comet reach 2nd magnitude, but twilight will greatly interfere with the view. At perihelion the ISON could rival Venus at -4 magnitude, but it will be too close to the sun then to see with the naked eye.
Best views will come in early December when the comet will shine around 2nd magnitude during evening and morning twilight. While the head might be relatively faint, a long tail is expected.
