![]() Of course, they didn't appear precisely at 6.25-year intervals. There are eight on the list, making an average of one about every 6.25 years. Now back to the original question: When might we see another bright comet? In the table below, I have listed the brightest comets that have appeared over the past 50 years. Related: Amazing Comet Photos by Stargazers Cast of comets ![]() So, it appears that the tail is what determines how impressive a comet will look to the average person. To the unaided eye, it appeared more like a nova, a moderately bright yellow star, in the constellation Perseus. Then, there was Comet Holmes in October 2007, which unexpectedly flared in less than two days from magnitude +17 to +2.5. In May 1983, Comet IRAS-Araki-Alcock passed within 2.9 million miles (4.7 million km) of Earth and, within a week, sped across the sky, resembling nothing more than a fuzzy ball of light about the size of the moon. Indeed, a comet can get bright yet lack a tail. The line of people patiently waiting for a look was incredibly long, but after peering through the eyepiece and seeing only a small, nebulous patch with a starlike center, virtually every person asked the same question: "Where's the tail?" One nonplussed woman seemed to speak for everyone when she exclaimed (a bit like Lucy from the Peanuts comic strip), "What good is a comet if it doesn't have a tail?" I brought my 10-inch Dobsonian telescope and used low power to provide a nice wide-field view. Local astronomy clubs set up telescopes for the general public. At Jones Beach on Long Island, about 40,000 people gathered to catch a glimpse of Halley. In all five boroughs, Koch had arranged for designated locations to temporarily extinguish their normally bright lights to give his constituents the opportunity to get a better view of this famous comet, which was low in the western evening sky. I still remember a cold Saturday evening in January 1986, dubbed "Halley's Comet Night" by then-New York Mayor Ed Koch. Speaking of tails, that particular appendage might be the most important factor in determining whether a comet can be branded as a truly prominent object. But if Hyakutake had approached no closer than Comet Hale-Bopp (122 million miles, or 196 million km), it would have appeared no brighter than magnitude +6, which would have placed it right on the verge of naked-eye visibility in a non-light-polluted sky.Ĭonversely, if Hale-Bopp - which was at its best in March 1997 - had passed as closely as Hyakutake, it would have blazed at magnitude -6, three times brighter than Venus, with a tail stretching across the entire sky! The tail wags the comet ![]() It reached zero magnitude and was accompanied by a 100-degree tail (stretching across more than half the sky). An excellent case in point is Comet Hyakutake, which made a close approach to our planet in March 1996, coming to within 9.5 million miles (15.3 million kilometers) of Earth. An average-size comet can appear stupendously large and bright if it passes very close to Earth. Perhaps just as important, if not more important, than a comet's approach to the sun is the comet's distance from Earth. The physical appearances and behaviors of comets are as varied as the appearances and behaviors of people no two are alike. Put another way, as a comet's distance from the sun is halved, its brightness increases by a factor of 16, or three magnitudes.īut comets can be capricious and, like people, have their individual quirks. Usually, a comet's activity increases rapidly as it draws closer to the sun the brightness typically varies (roughly) as the inverse fourth power of its solar distance. To predict comets' activity, astronomers have developed general formulas and models for comet brightness based on the observed behavior of many comets going back to the late 19th century. But such emissions from the nucleus are often nonuniform. This part of a comet, usually only a few miles across, is gradually warmed by the sun's heat, and expels gas and dust into space, often in distinct jets. The nucleus's dusty, rocky material and frozen gases are similar to the composition of Saturn's rings. What we see depends on many variables - the comet's orbit the relative locations of the comet, Earth and the sun and the size and composition of that icy clumping of solar system rubble that forms the comet's nucleus. The unpredictability of a passing comet's appearance and brightness is no surprise to those who study these enigmatic objects. So what are our chances of seeing such a celestial showpiece? More on that in a moment, but first, let's talk about what needs to happen to produce a bright comet. But whether it will appear three weeks, three months or three years from now is unknown.
0 Comments
Leave a Reply. |