Comet ISON photographed on Nov. 15th by amateur astronomer Mike Hankey of Auberry, California. The comet’s recent brilliance is a result of an outburst on Nov. 13-14 that boosted it’s brightness ten-fold. Image courtesy NASA
Keep your eyes open for comet ISON, now inside the Earth’s orbit and screaming toward the sun, en route to a momentous encounter later this month.
Named after the Russian institute International Scientific Optical Network that discovered it in September 2012, ISON is being tipped as ‘comet of the century.’
Star gazers are keeping their fingers crossed for an extraordinary display. A spurt in brightness in mid-November has rekindled the subdued excitement, after a lacklustre show over the past few weeks. Now, observatories are capturing clear photos of the comet’s green atmosphere and blazing tail.
Astronomers will keenly observe the comet’s ‘perihelion’ (closest approach to the sun) on November 28. If ISON disintegrates, as comets often do, due to extreme gravitational pull of the sun, then it might as well be a ‘no show.’
But what if it stays intact? It will outshine Hale-Bopp, one of the brightest comets in recent times, and may even match the full moon, according to some estimates.
“We are being cautiously optimistic,” says Jay Anderson of the Royal Astronomical Society of Canada (RASC), Winnipeg Centre. “Personally, I would be happy if it reaches an apparent magnitude of -5.”
The apparent magnitude of celestial objects is a measure of their brightness, with their position on the scale being inversely related to the brightness. For instance, the sun has an apparent magnitude of -26.74. Venus, the brightest planet is at -4.89, the brightest star Sirius at -1.46, while the much dimmer Pole Star is at +1.97. An object with magnitude higher than +6 is not visible to the naked eye. To match the full moon, ISON has to strike -12.74.
But will it survive the close encounter, grazing the solar surface at just about 1,165,000 km? The chances are high, with size and speed being on ISON’s side. An estimated diameter of about 2 kilometres means it has enough matter to escape relatively unharmed, even if it loses dust and gas by vaporization. The high speed will ensure it escapes the inferno zone quickly. But even if it breaks up, there might be something to gaze at in the night sky. A disintegrated comet will leave a fascinating tail of dust.
ISON can be best viewed after November 28, when it appears in the evening sky. It will be in a favorable position in early December, and will be visible for most of the month. Winnipeggers will have to wait a while longer to know if there will be a RASC public viewing event. “We will see how it fares during the perihelion on the 28th (November),” says Jay Anderson. “A star party, if it happens, will be announced at short notice. So keep an eye on the RASC website, or tune in to the radio. Assiniboine Park or Bird’s Hill Park are the venues on our mind.”
As ISON braces for its climax, astronomers the world over are sitting with a prayer on their lips.
