On the 28th of November the long awaited comet ISON (C/2012 S1) will reach perihelion (closest approach to the Sun). And we shall finally know if it is going to survive intact and give us a show to remember
The comet was first discovered by Vitali Nevski and Artyom Novichonok, 2 Russian astronomers working with the International Scientific Optical Network (ISON) which is where the Comet takes its common name. At the time that it was discovered the comet was 6.29 AU from the Sun (1 AU = the average distance between the Earth and the sun which is around 150,000,000km or 93.2 million miles).
The comet is on what’s known as a hyperbolic trajectory meaning it is in a tight elliptical shape around our Sun. This suggests that it is a fresh comet from the Oort cloud, a hypothesized spherical cloud of icy debris left over from the formation of the solar system and lies around 1 light year from the Sun. Nearly quarter of the distance to the next nearest star. If the comet does survive its spin around the Sun it will be travelling fast enough to escape our Solar system never to return.
The Comet was initially dubbed as the comet of the century as it was predicted at first to become very bright perhaps even bright enough to be seen during the day but as the comet has been getting closer and its brightness monitored it now looks as though it is going to fall below its initial predictions. This graph compiled by Seiichi Yoshida from Japan shows the comets initial brightness prediction as a blue line, the black dots show the measured brightness at different intervals and the red line is the current prediction which still is pretty good. Seiichi’s website has more information here and is well worth a browse!
On October 1st comet ISON passed close to Mars at a speed of around 35 Km/s (80,000mph) and a distance of 10.5 million Km which is closer than it will get to Earth. The Mars Reconnaissance Orbiter took these images as it flew past.
We have to keep in mind that both the orbiter and the camera were not designed to do this kind of work so it took a fair amount of effort to get these.
Ernesto Guido, Nick Howes, and Martino Nicolini captured this image of the comet as it was passing Mars using the 2 meter Liverpool telescope. It shows an already impressive tail and coma. Which the team state, was at 3 arc minutes in length.
The comet is currently visible in small telescopes but you will need to be up early and have a good clear Eastern horizon to see it just before sunrise. This image shows the rough location on Nov 3rd at 3am UT by this time it will be just about inside the orbit of Earth continuing to accelerate towards the sun. At this point it is estimated to be around magnitude 7 but its by no means a certainty.
As we head on through November the comet will be getting closer and closer to the sun becoming a daytime object and unobservable and then, on the 28th of November at 18:32:38UT (JPL prediction at time of writing) it will come within 1.2 million miles of the sun’s surface. If it survives this very close encounter it will be flung around travelling at a staggering 845,000mph back out of the solar system and then hopefully the comet will become considerably brighter possibly visible with the naked eye and by mid to late December we will start seeing it at a more sociable evening time. The comet (if it survives) will make its closest approach to Earth on December 26th at a distance of 40 million miles. Let’s all hope that it does make it around the sun and give us something beautiful to observe and image but as for it being the comet of century? I guess we’ll have to wait and see. For more info about comet ISON visit www.cometison2013.co.uk Below I have added finder charts for early November. The comet will get lower each day.