Comet C/2012 S1 ISON was first observed by CCD images recorded in observatories of Mount Lemmon and Panstarrs in the U.S. between December 28 2011 and January 28, 2012, but only had its orbit calculated from the remarks made by Russian astronomer Artyom Novichonok and his colleague Nevski Vitali, from Belarus, who used images taken by the robotic telescope of 400 mm belonging to the network ISON (International Scientific Optical Network), near the city of Kislovodsk, Russia.
The orbit of C/2012 S1 ISON is kind of hyperbolic, so is not considered as part of the Solar System. Apparently, the comet originated in called the Oort cloud, a hypothetical region of space located trihões to 7.5 kilometers (50,000 AU – astronomical units), where supposedly comets and asteroids formed.
According to some mathematical models, the Oort cloud could accommodate between one and a hundred billion comets, and its mass estimated at approximately five times that of Earth.
The first calculations made after the discovery showed that the comet C/2012 S1 ISON reach perihelion (closest distance from the Sun) on November 28, 2013, when arrive at a distance of only 1.8 million miles from the center of the star, or 1.1 million km from its surface.
The calculations also showed that on October 1, 2013 the comet will pass just 10 million miles from the planet Mars on Dec. 26 and will reach its lowest point of approach to the Earth, 60 million miles away.
Size and Brightness
Even without any chance of collision with the Earth, which draws the attention of this comet is undoubtedly its proximity to the Sun, scheduled for November 2013.
Currently, C/2012 S1 ISON is only a dim light that can be seen only with large telescopes, but this situation will change as the sun begin to warm the comet nucleus and vaporize the ice that makes up most its structure, turning it into a big mane and a long tail blown by wind solar.
When was imaged by Remanazacco observatory, Italy, September 22, 2012, C/2012 S1 ISON was about 6547 AU, ie, 975 million miles from Earth. On occasion, the records showed that the coma of comet occupied about 5 arcseconds on sky, equivalent to 23,000 kilometers in diameter. However, with the approach and the consequent action of the Sun, this often eat to grow and become increasingly brighter.
According to some models of magnitude, the brightness of C/2012 S1 ISON could reach up to 19 negative magnitudes. This is about 4000 times the brightness that the comet C/1965 S1 Ikeya-Seki in 1965 and then presented 40 times the brightness of the full Moon.
However, in a projection made by Apolo11 using the SSD model (Solar System Dynamics), NASA, the smaller magnitude (brightest) achieved was -11.64 magnitudes, to be observed on December 29, 2013. Despite being a very big difference to other models, yet the brightness of C/2012 S1 ISON is almost three times that of Comet Ikeya-Seki or 25 times more intense than that of comet C/2006 P1 McNaught, who called much attention in 2007 and can be seen even during the day.
To date, the brightest comet ever seen and had its magnitude was estimated C/1965 S1 Ikeya-Seki, which in 1965 was seen in daylight to shine with 10 negative magnitudes. Then it was the turn of C/2006 P1 McNaught, the second brightest comet ever recorded. McNaught reached a magnitude of -5.5 and negative became a show in the sky around the world, including Brazil, where it can also be seen in daylight.