Published in The Patriot Ledger> November 9, 2013
We may have a spectacular show in the sky coming very soon – comet ISON. Since its discovery in September 2012, NASA and astronomers around the world have been studying its detailed progress from the outer solar system towards its flyby of the Sun later this month and debating its potential to become one of the brightest comets in many years. It even has its own website, cometisonnews.com, and its own Facebook and Twitter pages, surely a first for a comet.
Comets are mixtures of ices and rocks that travel in elongated orbits from the outer solar system to near the sun - and back again. As they approach the sun, increasing temperature transforms the ices into gas, producing long tails of gas and dust. Although most comet nuclei are only a few miles wide, their tails can extend for millions of miles.
Amateur astronomers with good telescopes have been getting nice photographs of ISON for some time now – many posted on cometisonnews.com. And it is now visible with binoculars – if you are willing to get up before dawn. It’s currently moving from constellation Leo into Virgo and later Libra. It rounds the sun on the 28th, and if it survives that close encounter, should be at its brightest in mid-December, easily visible to the naked eye.
As ISON passed Mars on October 1, NASA’s Mars Reconnaissance Orbiter got a picture as it flew by. The Hubble telescope has already had several good looks, and will, along with ten other NASA spacecraft at various locations in outer space, gather more data on ISON as it nears and then whips around the sun. This will be a well-studied comet.
ISON was discovered last year by two Russian astronomers working for the International Scientific Optical Network. Usually comets are named after their discoverers, but ISON was named for their organization rather than for themselves, probably because ISON is a catchier name than Nevski-Novichonok.
ISON was spotted early because there are now many telescopes around the world serving as parts of an early-warning system, searching for asteroids and comets that may threaten to impact Earth. The ISON nucleus is estimated to be about 3 miles wide, and would do considerable damage if it hit us - but calculations of its orbit make it clear that it will miss us by many millions of miles. Phew.
Halley’s is the most famous comet, recognized centuries ago as a periodic comet that reappears every 75 years. Several spacecraft were sent out to study Halley’s during its latest approach in 1986, gathering data on its chemical composition, and one captured the first photo of a comet nucleus. Even more impressive was NASA’s Stardust mission, which flew by Comet Wild-2 in 2004 to collect dust from its tail, its Sample Return Capsule landing successfully in Utah two years later.
Two comets that made major news in recent years were Shoemaker-Levy, which dramatically crashed into Jupiter in 1994, making it very clear that comets can be dangerous as well as beautiful, and Hale-Bopp, whose appearance in 1997 led to the mass suicide of 39 members of the Heaven’s Gate cult.
How many headlines ISON will generate will depend on how it survives its close flyby of the sun late this month. Some predict that, in our December skies, it will be brighter than Venus and become the “comet of the century.” Others think that it may break up in the sun’s gravity during the flyby, which will be of great interest to scientists, but a disappointment for naked-eye viewing.
Will ISON sizzle or fizzle? As comet hunter David Levy once said, “Comets are like cats – they have tails and do what they like.”