cording to NASA blogs,
“..ISON was discovered on Sept. 21, 2012, by two Russian astronomers using the International Scientific Optical Network’s 16-inch (40-centimeter) telescope near Kislovodsk. NASA’s Near-Earth Object Program Office, based at JPL, has plotted its orbit and determined that the comet is more than likely making it first-ever sweep through the inner solar system. Having not come this way before means the comet’s pristine surface has a higher probability of being laden with volatile material just spoiling for some of the sun’s energy to heat it up and help it escape. With the exodus of these clean ices could come a boatload of dust, held in check since the beginnings of our solar system. This released gas and dust is what is seen on Earth as comprising a comet’s atmosphere (coma) and tail. ISON will not be a threat to Earth – getting no closer to Earth than about 40 million miles on Dec. 26, 2013. But stargazers will have an opportunity to view the comet’s head and tail before and after its closest approach to the sun — if the comet doesn’t fade early or break up before reaching the sun..”.
Orbit Graphics for Comet ISON (C/2012 S1)
Below are some graphics I have generated using the Java applet provided by NASA for working out Comet positions and view angles. (I used the 3 dates (today, 26th Nov & 26th Dec) for this graphics.
The light-blue parabolic arc in these diagrams shows the path of the Comet. It is an `anti-clockwise’ path .. that is above the ecliptic plane of the Earth’s orbit. However the path of the Comet `dips’ below the orbital plane, sling-shots past the Sun and up again..and leaves the inner Solar system (top light blue line).
[Note from NASA: Additional Notes: the orbits shown in the applet are color coded. The planets are white lines, and the asteroid/comet is a blue line. The bright white line indicates the portion of the orbit that is above the ecliptic plane, and the darker portion is below the ecliptic plane. Likewise for the asteroid/comet orbit, the light blue indicates the portion above the ecliptic plane, and the dark blue the portion below the ecliptic plane. Orbit Viewer applet originally written and kindly provided by Osamu Ajiki (AstroArts), and further modified by Ron Baalke (JPL).]
..On 1st October, 2013 (figure 2 below) , this Comet will be closest to Mars. (graphics below shows this. )
On 28th November 2013, the Comet C/2012 S1 will graze past the Sun (fig 3b below).
On 26th Dec’13, comet ISON (C/2012 S1) moving further away from the Sun will be at its closest to Earth at some 40 millions miles!
Well, that’s all the basics. I’ll be dong more research and exploration on this one.. as the date of closest approach to Sun is quite an important one for me personally.. Even the date of closest approach to Mars is of interest to me…so much so..I think I may have to give this Comet a special magical name of my own. Thor’s Hammer? Centaur’s Arrow? Hern’s Spear? :-)
More on those aspects in another blog :-)
(blog updated on 18Feb13 with Fig 3b above, and previous fig 3 removed. Explanation for name Comet ISON added).