All eyes on ISON

It is being touted as the comet of the year, if not the comet of the century. Comet ISON is set to make an appearance towards the end of the year. Astronomers say the comet’s trip may end up being its first and last one to the solar system. They are excited about its appearance because it could give them a rare opportunity to study comet composition.

Have you seen a comet which is brighter than the moon? Astronomers have discovered a comet which is 15 times brighter than the moon. Comet ISON, discovered by Russian scientists, will be visible in India towards the end of the year. Experts say the comet, which will be seen above the western horizon after sunset, is likely to be visible to the naked eye.

The comet called C/2012 S1 (ISON) was discovered by Russian astronomers, Vitali Nevski and Artyom Novichonok, with the aid of International Scientific Optical Network telescope. It will pass within two million miles of the sun’s surface. The Russian astronomers have said that the comet may be brighter than any comet spotted in the last century, visible even in broad daylight, and this may end up being its one and only trip to the solar system, as its trajectory may see it plunge into the sun, ending in a fiery death.

The most exciting aspect of this new comet concerns its preliminary orbit, which bears a striking resemblance to that of the ‘Great Comet of 1680’. When the comet was still a long way from the earth, in February, NASA’s Deep Impact spacecraft took a series of images of the comet. NASA’s twin Solar Terrestrial Relations Observatory (STEREO) spacecraft currently does continuous observations of the sun from orbit. This should afford the observatories a good view when the comet swings by the sun in November. Even as recently as April 10, the Hubble Space Telescope managed to capture images of the comet.

Astronomers are excited about the comet’s appearance, for ISON’s flyby could give them a rare window into comet composition. It is currently moving inwards from beyond Jupiter, and as it approaches the earth, the ‘dirty snowball’ could produce a dazzling display, burning brighter than the moon and potentially being visible in broad daylight. The comet will pass within two million miles of the sun’s surface — making it a sun-grazing comet. It is on a parabolic orbit, which means it probably originated from the outer skirts of the solar system, perhaps from the Oort cloud — a mass of icy debris which lies 50,000 times further from the sun than the earth does. ISON is expected to get as close as 8,00,000 miles (1.2 million km) from the sun’s surface, providing it survives the gravitational forces or the sun’s radiation. That closest approach will take place on November 28, 2013.

With a perihelion passage of less than two million kilometers from the sun on November 28, 2013, current predictions are of an object that will dazzle the eye at up to magnitude 16 (lesser the magnitude, brighter the object). If predictions hold true then, C/2012 S1 will certainly be one of the greatest comets in human history, far outshining the unforgettable ‘Comet Hale-Bopp of 1997’.

C/2012 S1 is currently in the northwestern corner of Cancer. At magnitude +18, it is too dim to be seen visually but, it will be within the reach of amateur astronomers with CCD equipment in the coming months as it brightens. It is expected to reach binocular visibility by late summer and will be a naked eye object in early November. The comet will be easier to watch for northern hemisphere observers.

Following its peak brightness in late November, it will remain visible without optical aid until mid January next year. Comet brightness predictions sometimes exceed their performance. Amateur astronomers may remember the ‘Comet Kohoutek hype of 1973’ — not quite the ‘damp squib’ it was portrayed as, because it actually reached naked eye visibility. Even if C/2012 S1 takes on the same light curve as Kohoutek it is certain to be spectacular, quite possibly a once-in-a-lifetime event.