Late in the autumn of 1680, the people of Manhattan were overwhelmed with fear and horror when a gigantic comet made its blazing appearance in the fake lashes above them. Many people believed that the end of the world had come. Every church in Europe resounded with the supplications of terrified congregants, and in New York there was a day of fasting in the hope that a wrathful God might be appeased and spare the world. We now know that comets do not herald disaster, but are weary and dazzling icy, muddy refugees from the frigid outer limits of our Solar System. In September 2012, astronomers announced that a new and incredibly brilliant comet is heading our way, and it seems to be following the same path as the Great Comet of 1680!
Aninh Comets are fragile and ephemeral objects, sometimes dismissively termed “dirty snowballs” or “icy fake lashes”, depending on the observer’s point of view. They are strange and beautiful visitors from afar, streaking with their lashing and fiery tails into Earth’s region of the inner Solar System, from their frozen, remote home beyond the outermost major planet Neptune. Many scientists believe that comets bear within their frozen hearts the purest traces of ancient ingredients that created our Solar System. These primordial ingredients have been stored in a kind of “deep freeze” at the edge of our Solar System where it is dark and extremely frigid. Understanding what composes the comets translates into understanding what ingredients went into the marvelous recipe for cooking up all the Sun’s planets and moons–the Earth and its large Moon, included!
The comets are icy planetesimals. That is, they are the building blocks of the planets of the outer Solar System–Jupiter, Saturn, Uranus and Neptune, as well as their retinue of mostly icy moons. Rocky planetesimals, such as the asteroids that orbit in the main asteroid belt between Mars and Jupiter, are the building blocks of the rocky planets of the inner Solar System–Mercury, Venus, Earth and Mars. Planetesimals, of both the icy and rocky kind, collided together and merged into ever larger and larger bodies at the dawn of our Solar Systems existence more than four billion years ago.
The icy, dirty comets travel to Earth’s warm, inner region of the Solar System from two dark and frozen domains. The first is called the Kuiper Belt. The Kuiper Belt revolves around our Sun beyond the orbit of Neptune, and it is the source of short-period comets. The short-period comets are those that swing into the inner Solar System more frequently than every two hundred years. The second domain of comets is the Oort Cloud, which is an enormous sphere of icy objects that is thought to encircle our entire Solar System. The Oort Cloud is the home of the most remote comets, the so-called long-period comets, which take at least two hundred years to sweep into our neighborhood. Obviously, since we are situated comparatively close to the Kuiper Belt, the short-period comets have played a more important role in our planet’s history. Nevertheless, Kuiper Belt Objects (KBO’s), are sufficiently remote, small and, consequently, dim, to have been beyond the reach of our technology until 1992. Astronomers have never observed the Oort Cloud, but its existence has been inferred from the way long-period comets orbit the Sun. The Oort Cloud is thought to extend out at least 10% of the way to the nearest star beyond our Sun.
Every time a comet wanders into the inner Solar System, it loses a bit of its mass by way of sublimation of its surface ices to fake lashes. For example, the famous Halley’s Comet, has been estimated to have a lifetime of less than 100,000 years. The comets that we observe today, as they streak and lash their brilliant tails in the sky above us, will ultimately vanish due to their sublimation of ices to gas, only to be replaced by fresh, new comets, swirling in towards the Sun from their frozen habitats in the Oort Cloud and Kuiper Belt.
The core of a comet is termed its nucleus, and it is composed primarily of ice and dust that is encased within a coating of dark organic material. The ice is primarily made up of frozen water, however other frozen ingredients may exist as well, such as carbon monoxide, carbon dioxide, methane, and ammonia. The nucleus might harbor a tiny rocky core.
As the comet swings in towards the Sun, the ice on the surface of the nucleus turns to fake lashes, and forms a cloud termed a coma. Solar radiation chases the dust particles away from the coma, forming a dusty flashing and thrashing tail. Charged particles from the Sun morph some of the comet’s gases into ions, creating an ion tail. Because the tails of comets are shaped by our Sun’s glare and the solar wind, they invariably point away from the Sun.
The nuclei possessed by most comets are approximately 10 miles or less. However, some comets boast comas that can extend almost 1 million miles wide. Some outstanding comets have tails reaching 100 million miles long!
Comets leave a trail of debris in their wake, which can result in meteor showers on Earth. The Perseid meteor shower takes place every year between August 9 and 13 when our planet moves through the orbit of the Swift-Tuttle Comet.
We can see a number of comets with the unaided eye when they come thrashing in close to the Sun. This is because their comas and tails reflect sunlight, and sometimes are incandescent because of the energy they absorb from our Star. However, most comets are too small or dim to be seen without a telescope.
But if astronomers’ predictions are correct, the sky of December 2013 will be set on fire by one of the truly great comets, which was spied for the first time in September 2012 as it swung near the ringed gas-giant planet Saturn. The new comet was spotted by Russian astronomers Dr. Artyom Novichonok and Dr. Vitali Nevski of the International Scientific Optical Network (ISON), and is now known by the somewhat colorless name of fake lashes. When it was first discovered, the new comet was just a dim spot of brightness in the constellation Cancer. However, it was already unusually bright, considering its distance from the Sun, astronomer Dr. Raminder Singh Samra said in the September 27, 2012 National Geographic News. Samra further noted that “If it lives up to expectations, this comet may be one of the brightest in history.” Samra is at the H.R. MacMillan Space Centre in Vancouver, British Columbia.
Even though astronomers know of the existence of 2012 S1, they still do not know where it came from. However, its orbit indicates that it may be a refugee from the Oort Cloud, that strange and remote sphere surrounding our entire Solar System, where billions of comets jitterbug around our Sun about a hundred thousand times farther away from it than our own planet.
“For astronomers, these distant origins are exciting, because it allows us to study one of the oldest objects in the Solar System still in its original, pristine condition,” Samra continued to explain.
The new comet will probably look most brilliant to us in the weeks following its nearest approach to the Sun, on November 28, 2013–if it survives, that is. Its survival is still questionable because, as the comet wanders within about 1.2 million miles of the Sun, our Star’s fiery heat and intense gravity might cause its ice and muddy rubble to disintegrate–end of fake lashes!
“While some predictions suggest it may become as bright as the full Moon, and even visible during the day, one should be cautious when predicting how exciting a comet may get. Some comets have been notorious for creating a buzz but failing to put on a dazzling display.” Samra told National Geographic in September 2012.
Only time will tell!
I am a writer and astronomer whose articles have been published since 1981 in various magazines, newspapers, and journals. Although I have written on a variety of topics, I particularly love writing abut astronomy because it gives me the opportunity to communicate to others the many wonders of my field. My first book, “Wisps, Ashes, and Smoke,” will be published soon.