Organizer: The Japan Astronomy Council Comet ISON Campaign Committee
Supporting Organizations: Japan Telescope Manufacturers Association
AstroArts Inc.

Comet ISON is a new comet that was discovered by Belarusian Vitali Nevski and Russian Artyom Novichonok. It was named Comet ISON (C/2012 S1) after the initials of the International Scientific Optical Network to which the two discoverers belong. Due to the proximity at which the comet will pass the Sun, it is hoped that Comet ISON will become a rarely seen Great Comet. At its closest point to the Sun, Comet ISON will be approximately 1,200,000 km from the Sun’s surface. While this may seem very far when compared with our day to day sense of distance, when you consider that the diameter of the Sun is 1,400,000 km, you might say it’s close enough to “graze” the Sun.

Comets are astronomical objects which, from the shape of the long tail trailing behind, are sometimes referred to in Japanese as “Broom Stars.” Mainly composed of ice mixed together with dust and sand, a comet can be compared to “a dirty snowman.” As it nears the Sun, the comet is heated up which causes the release of gas and dust which can be seen as a faint glow. The tail is the comet’s main feature, and comes in two varieties. The first is made of gas and called the “ion tail.” Blown by solar winds, this thin blue tail extends from the comet in the opposite direction to the Sun. The other tail, the “dust tail,” is made of dust and also extends away from the Sun; however, the way the tail spreads out varies according to the size of dust particles released by the comet which causes the dust tail to take on a different appearance to that of the ion tail.

Comet ISON is thought to have originated in the Oort cloud, a cloud of icy planetesimals on the outer edge of the Solar System. For one reason or another, a planetesimal in the Oort cloud will change its orbit and head into the inner Solar System. As it gradually moves closer to the Sun, it changes into a comet with a tail. Because Comet ISON is on a parabolic orbit, which will not return to the Solar System, this is the first and last time we will be able to see it. Let’s make sure we get a good look at Comet ISON for this one-time meeting in our vast Universe.