Virgin Material - A Series of Articles about Comet ISON
by Pecier DecierdoÂ
Comet ISON was discovered in November 2012 by astronomers Artyom Novichonok and Vitali Nevski using a 16-inch telescope that is part of the International Scientific Optical Network (ISON), from which the comet got its name. (A 16-inch telescope is a telescope with a main diameter, or aperture, of 16 inches. The larger the diameter of a telescope, the more light it gathers, the more powerful it is. As such, larger telescope can spot dimmer objects. The Mind Museum has two telescopes, one is a 6-inch telescope while the other is 4 inches in diameter.)
Many things suggest that this is Comet ISON’s first visit to the inner Solar System. Scientists therefore describe it as being dynamically new. This is also probably the comet’s last visit to the Solar System. If this last part is true, this means that Comet ISON is a single-apparition comet.
Many comets, like the famous Halley’s Comet and Comet Swift-Tuttle from which the Perseid meteors originate, are called periodic comets because they periodically return to the inner Solar System every few hundred years. Periodic comets have very eccentric orbits, which means their paths around the Sun are very elongated. They spend most of their time very far away from the Sun, usually in a region beyond the orbit of Neptune called the Kuiper Belt, where they move very slowly and are relatively inactive, basically just chunks of dirty ice. Their orbit periodically takes them very close to the Sun. During this time of proximity with the Sun, they move very quickly and shine brightly, producing a tail of gas and dust as they zip their way around the Sun. After this brief show, the periodic comet then returns to the cold and dark of the Kuiper Belt.
Other comets return to inner Solar System, but only after a very, very long time (tens of thousands of years). These comets are called long-period comets. One example is Comet Hyakutake, sometimes called the “great comet of 1996”. Assuming the gas giant planets don’t change its path too much, it will comes close to the Sun once every 70 thousand years! The orbits of long-period comets are even more eccentric than those of periodic comets. The current scientific consensus is that long-period comets are visitors from the part of the Solar System known as the Oort Cloud, which is even farther out than the Kuiper Belt. The Oort Cloud is a collection of dirty snowballs that extends up to up to 100,000 astronomical units from the Sun. (An astronomical unit or AU is the mean distance between the Earth and the Sun. 1 AU is roughly equal to 150 million kilometers.) Astronomers also think that objects in the Oort Cloud are remnants from the formation of the Solar System, spare parts that didn’t form into planets or their satellites.
Based on studies of Comet ISON’s path, its orbit around the Sun is not an elongated ellipse but is probably a hyperbola. This implies that Comet ISON is on a one-way trip to the inner part of our Solar System. Being dynamically new, the stuff that make up Comet ISON are therefore remnants from the early stages of the Solar System’s formation. Unlike periodic comets that get baked by the Sun’s radiance at regular intervals, the dust and ice of Comet ISON will be coming in contact with the Sun’s heat and radiation for the first time since the Solar System began some 4.5 billion years ago. By studying the materials that are ejected by the comet as it whizzes through the inner Solar System, scientists will get clues on how our Solar System formed and what kinds of stuff were there in the beginning. This is one of the biggest reasons why scientists are geeking out over Comet ISON.
