As it approaches the sun, Comet ISON will pass just 6.5 million miles (10.5 million km) from Mars on Oct. 1, perhaps providing a worthy target for imaging by the NASA’s Mars rover Curiosity.
ISON will take exactly one month to cross from the orbit of Mars to the orbit of Earth, reaching us on Nov. 1. The comet will be steadily brightening during this time from magnitude +10 to +6. It will be in the morning sky, and during the first half of the month will be keeping pace just to the north of Mars as the pair slides eastward in the sky through the stars of Leo (The Lion).
On Oct. 14 and 15, Mars and ISON will line up closely with Leo’s brightest star, the blue first-magnitude Regulus. By the end of October, the comet should be easily visible in binoculars and quite possibly even with the unaided eye.
During November, as the comet races toward its rendezvous with the sun, it should brighten dramatically as it drops lower in the dawn twilight. A tail may begin to appear at this time, perhaps becoming noticeably longer with each passing morning.
On the morning of Nov. 18, ISON — now possibly as bright as 3rd magnitude — will stand less than 1 degree from the first-magnitude star Spica in the constellation Virgo. (Your outstretched fist held at arm’s length measures about 10 degrees.)
Five days later, the comet will shine perhaps as brightly as zero magnitude as it zips past the similarly bright planets Mercury and Saturn.
Finally, the comet will arrive at the sun on the Nov. 28. ISON will pass through the inner corona of the sun, experiencing temperatures of up to 2 million degrees Fahrenheit (1.1 million degrees Celsius)
Having been in a cosmic deep freeze for countless thousands of years, ISON will suddenly be subjected to unbelievable heat. Perhaps the comet’s nucleus will shatter, as sometimes happens when you pour hot tea into a cold cup.
But this is not a certainty; some sungrazers like the Great Comet of 1882 and Comet Ikeya Seki in 1965 indeed broke into several fragments and headed back out into deep space literally in shambles. Others like Comet Lovejoy in 2011 somehow emerged from out of the solar furnace still pretty much in one piece.
Courtesy and Source : Space.com Click this link to read the complete article.