NAME ________________________________ COMETS - HALLEY, SWIFT-TUTTLE, AND BEYOND 1. Set up Dance of the Planets by pressing the following underlined keys. Bring up the Menu, choose More Options, Resumes, and type in 1910 for the filename, followed by the [enter] key. We can visualize the plane of the ecliptic because Dance is drawing those parts of orbital paths which lie below the ecliptic in a darker shade of grey (a whiter shade of pale?). You may adjust the shading by using the SHIFT and S keys. Experiment with this to get the best view on your video screen. The scene is a view from space, just outside the orbit of Pluto. You see the orbits of the planets. Use Label to identify them. Halley's comet in 1910 is also shown. Notice the date at the lower left of the screen. Increase the Zoom to 32X, and increase the Pace to about 2000 and watch the simulation. Notice that as the comet moves through space in its elliptical orbit around the Sun, rising up out of the plane of the ecliptic, it will catch up to the Earth just as the comet moves below the ecliptic plane. Estimate the date of closest approach of the comet with Earth. You may wish to adjust the Pace to a negative value to run the simulation in reverse to get the best estimate. Date of closest approach ____________________ 2. Use the Access key, then choose Object status, and indicate below how close the comet came to Earth. Closest approach ____________________ AU Comment on the position and alignment of the tail of the comet with respect to the Earth in 1910. 3. Now set up the simulation as in part 1 above, except choose a resume filename of 1985. You will see a similar space view of the inner solar system for Halley's latest apparition. Again set the Pace up to 2000, and watch the simulation. Comment below why this latest apparition of the comet was less than favorable. 4. Comet Halley has been seen many times in the past, with its earliest certain recorded apparition of 240 BC. Some have hypothesized that an apparition of Halley's comet occurred in 1066 AD. This date should be familiar to you. It maked the defeat of England's King Harold, and the Norman conquest of England by William, Duke of Normany. These events are celebrated on the famous Bayeux Tapestry - a 70 meter long embroidered picture history. The tapestry resides in the French city of Bayeux, in Normandy. It is one of the few cities spared the ravages of war just after D-Day, June 1944. Using Menu, More Options, Resumes, type in the date 1066, followed by an [enter]. The scene is a view from space, showing the inner planets and Halley's Comet. Use Label to identify these objects in space. Change the Pace up to 1000, and observe the motion of Earth and the comet. Comment on the visibility of Halley's Comet as seen from Earth in the spring of 1066 AD. 5. Some have speculated that Halley's Comet was the Star of Bethlehem, as recorded artistically in 1304 AD by Giotto di Bondone in his Adoration of the Magi. With a period of 76 years, the third apparition following 240 BC would have been 12 BC, or -11 for Dance. Set up the simulation as you did before, except choose a resume filename of 11BC. The simulation will now show the southeast horizon as seen from the Earth. Use Label to find the comet, denoted by -11. Notice that Halley's comet would have been clearly noticed just West of the Sun in the morning sky before sunrise in the constellation Libra, just above the "face" of Scorpio the scorpion. 6. Biblical and historical records of that time suggest that Jesus Christ was born closer to 6 BC, late in the year (remember that the Roman year began in March and ended in February). Set up Dance as you did in part 1, except choose a resume filename of 6BC. The date will indicate -5. Use Label to indicate the positions of the planets. Set the Pace up to 10k, and notice whether or not any bright planets group in a small area of the sky (about the size of a quarter on your screen). Record any such groupings below. It has been hypothesized that a conjunction (grouping) of two or more bright planets, itself a rare astronomical event, may have been the 'Star' of Bethlehem. These dates therefore may help fix the date of the birth of Christ. Date_______________ Planets___________________________________________ Date_______________ Planets___________________________________________ Date_______________ Planets___________________________________________ 7. By rare and happy coincidence, a comet named Swift-Tuttle (after its discoverers) was recently recovered after being lost for over a century. Set up Dance again as you did in part 1, except choose a resume filename of 1992. The simulation shows the inner part of the solar system as seen from a point just outside and above the orbit of Mars. Use the pace control to speed up the simulation, and notice that the comet's path very very nearly intersects Earth's path! Determine the date when the Earth arrives at that point of intersection. Date of intersection ____________________ 8. Every year near this date, a meteor shower, known as the Perseids, is observed. A meteor shower consists of many streaks of light crossing the sky, sometimes as many as several each second, lasting for many hours. With the knowledge that comet Swift-Tuttle intersects the orbit of the Earth, with the Earth arriving at that point at the height of the yearly meteor shower, comment below on the association. 9. There is a chance, albeit rare, that a comet could also arrive at the point of intersection at the same time as a planet. A collision between a large comet and the Earth would be catastrophic. It would probably mark the end of civilization, just as a collision with a comet or asteroid 65 million years ago marked the end of the reign of the dinosaurs. Another comet, named Shoemaker-Levy after the discoverers, has had a most unusual past, and is scheduled for a most unusual future. Set up Dance to run a script by pressing the home key, then page-down until the script for "A Most Peculiar Comet" appears. Then press the [enter] key and follow the directions. 29 December 1995