(Written for the Buenos Aires Herald in May, 1997.
During the course of this month, the comet Hale-Bopp will become visible to people in Argentina as its orbit carries it away from the sun. For some months now, those living in the northern hemisphere have been treated to the beautiful sight of this comet when it was closest to the sun. One of the brightest objects currently in the sky, it can even be seen from within the smog and glare of a major city.
Comets have been a feature of life on Earth for thousands of years, the most famous being Halleyâ€™s Comet. It is shown in the Bayeux Tapestry, a commemoration of the Norman Conquest of England in 1066, and even appears in Chinese writings from 240 BC. Unfortunately, when it reappeared in 1986, it was of more interest to scientists than the general public, as it was practically invisible without a telescope. Other recent comets of note for the general public have been Schoemaker-Levy 9, parts of which impacted with the planet Jupiter, and the comet Hyakutake, which was visible early in 1996 as a faint smudge in the sky.
Comets are believed to be the remains from the formation of the solar system and are generally a mixture of ice and dust. As they approach the sun, the increasing heat turns the ice into gas, allowing it to escape the comet, along with the previously trapped dust. This creates a tail, millions of kilometres long, which points away from the sun and is the most prominent part of the comet for the general public. Additionally, a second tail may be seen which is formed by interactions between the cometâ€™s materials and the â€œsolar wind,â€ a stream of charged particles coming from the sun. This second tail is much fainter and generally has a blue colour.
Comets often have a strange effect on the people who see them, aside from the excitement that is generally found in scientists and amateur astronomers. In the past, comets were believed to be the messengers of doom, appearing in the skies as a symbol to warn of a impending disaster. Earlier this year, a group of people determined that there was a space vessel hidden in the tail of the comet, waiting to take them to a better life. Their method of transiting to this UFO was rather drastic, however, as it involved suicide. It may not come as a surprise for some that there are so many comets arriving as the end of the millennia approaches. Currently there are over 30 comets that can be seen via telescopes, but few of them are likely to reach the brightness of Hale-Bopp.
Hale-Bopp was first discovered in July of 1995 by Alan Hale and Thomas Bopp in the USA. They were working separately and announced their discovery to the Central Bureau for Astronomical Telegrams within minutes of each other. After analysing the orbit, it was determined that the last visit from this comet was some 4,210 years ago and that it will not be back for another 2,380 years. Following observations from many sources, including the Hubble Space Telescope, astronomers have been able to gather large amounts of information that is changing their concepts about comet formation and life cycles.
If you have the chance, it is highly recommended that you try to view this comet, as it is certainly one of the most spectacular, it even has its own page on the World Wide Web. Starting during May, people in Argentina can look towards the north west horizon in the early evening, a few hours after sunset. Those away from city lights and pollution should get the first and best views, as it will be quite low in the sky. Having tried to view the comet during the first week of May, both here in Buenos Aires and near General Pico, La Pampa, I must admit to not having much success. Hopefully this was due to pollution in Buenos Aires and dust near the horizon in La Pampa, rather than general reluctance on the part of the comet.
Over time, the comet will be found higher and higher in the sky each night, its light gradually fading as it moves away from the sun. It is expected that it should be quite visible to the general public for a number of months. Those people with telescopes should be able to follow it for the next couple of years as it slowly moves out in its orbit, never to return until about 4377 AD.