By David Ward
A special guest is coming for a visit during the holidays – Comet ISON. Will it be the most amazing celestial spectacle any of us have ever seen in our lifetimes, or a complete dud? That question is being hotly debated in astronomical circles right now and nobody has a clue. Here is the scoop.
Comet ISON is a newcomer to the inner solar system. It began its long fall towards the sun from the Oort Cloud, that almost mystical realm of comets far, far out beyond the orbit of Pluto, hundreds of thousands or perhaps even millions of years ago. It was discovered a little over a year ago out near the orbit of Jupiter by a couple of Russians. It got everyone’s attention right off the bat because it was a lot brighter than anyone expected. Speculation went wild, with some predicting it would appear brighter than the full moon when it came closer to us.
Comets are often referred to as “dirty snowballs,” being composed of bits of dust, rocks and ices, particularly carbon dioxide, carbon monoxide and water. As a comet approaches the sun, heat from the sun evaporates those ices, causing it to glow. Dust blown out from the comet by the solar wind creates a long tail.
As it has fallen closer to us, Comet ISON has not brightened as much as hoped, causing most astronomers to downgrade their expectations of a truly spectacular comet. It recently passed Mars and is now picking up speed as it approaches the sun. It should reach naked eye visibility around mid-November, although do not expect to have to wear your sunglasses to look at it. At this point you will probably have to use binoculars to find it.
Nov. 28, Thanksgiving Day, is the day of reckoning for Comet ISON. That is the day it makes a spectacularly close pass around the sun, less than one solar diameter away. It will reach its top speed of 234 miles per second and the comet will be heated to a temperature of near 4,000 degrees Fahrenheit. What comes out the other side is anybody’s guess. The huge gravitational forces of the sun could disintegrate the comet completely or something truly amazing could emerge into view.
With any luck, Comet ISON could be a beautiful addition to our skies for the month of December. Its closest approach to Earth will occur at the end of December, but because it will be further from the sun it will not be at its brightest. If you miss it this time around, you may not get a second chance. Some astronomers think it will get such a gravitational kick from its close pass to the sun that it will be thrown out of the solar system altogether, never to come our way again.
If you want to see Comet ISON you will not only have to go out into the cold and the dark, but, I hate to tell you this, you will have to go out at the coldest and darkest time of the night, just before dawn. You will need to be somewhere you can see low into the east, and be sure to dress warmly. Around mid-November, look for it near the bright star Spica in the east. On Nov. 22 through 24, the comet will be near Mercury and Saturn even lower in the east.
As it gets closer to the sun the comet will brighten but it has to compete with the brightening dawn in the east. If it survives its fiery ride around the sun it will probably be at its brightest in early December, again in the eastern sky just before dawn, when we may see a striking tail jutting up from the horizon.
What will we actually see? No one knows for sure until later this month. As the famous comet hunter David Levy once remarked, “Comets are like cats. They both have tails and they both do exactly as they please.”
For updates on Comet ISON check out this website www.Astronomy.com/ISON or email me at email@example.com.