MATERIALS
big telescope, at least five strong people, good eyes, decent artisit, misc. photography supplies, data sheets
BACKGROUND INFORMATION
The Progression of Universal Theory/The Cosmological Model
A starting point for understanding any part of the universe is a basic understanding of the universe as a whole. The lack of this knowledge plagued astronomers for years, and still plagues us today as a result of our incomplete perception of astronomical truths. However, this deficiency in knowledge can be seen, in retrospect, to have been far more crippling to the science of astronomy in ancient history. The ancient Babylonians, for example, realized that certain stars were visible in the night sky at the same time every year. This understanding, however momentous, was only used by the Babylonians to create accurate calendars because they did not have an accurate understanding of what was “out there”. At this point, the earth was thought to be a flat disc around which everything else in the universe rotated once a day. It was not until 4 BC in ancient Greece that the earth was proved and accepted to be spherical. Even this was not much of an improvement, however, for although it was quietly suggested at the time that the universe was heliocentric, the earth remained the center of a divinely created universe. In fact, even as far a 2 AD, the time of the Greek philosopher Ptolemy, the earth remained in this position in the “grand scheme of things”. Ptolemy’s cosmological model of the universe, known as the “Ptolemaic System”, put the earth at the center of eight concentric spheres. On these spheres were placed the moon, Mercury, Venus, the sun, Mars, Jupiter, Saturn, and the stars. Of these eight spheres, the eighth sphere of the stars was the only sphere that had been revealed to man by god. Over the next several centuries there were still more murmurings of a heliocentric system from such far off places as the middle east, but since the Christian church had adopted the Ptolemaic model (which it thought fit the idea of divine creation) and no one wanted to speak up on such an issue and risk excommunication, none of it really had any widespread influence. Even Copernicus, himself a priest in the sixteenth century, did not make a fuss when he determined that the earth did indeed orbit around the sun. He published his observations in a work entitled Concerning the Revolutions of the Celestial Bodies before his death, but they were not widely known or accepted. This was due in part to the huge influence of the most widely accepted observer of the day, Tycho Brahe. Brahe’s meticulously accurate observations of the heavens were interpreted by him so as to support the current status of the earth at the center of the universe. He saw flaws in these existing theories, but unfortunately was able to provide enough theoretical models to support a rejection of heliocentrism and the Copernican system. Ironically, however, it was Brahe’s observations of the heavens that provided the foundation for a move towards the acceptance of heliocentrism. Brahe died in 1601 and left his notes in the hands of his assistant, Johannes Kepler. Kepler used these same notes to further develop his three laws of planetary motion, and thereby disprove Brahe’s own theories and laws. The acceptance of Kepler’s laws, due in a large part to their support from the observations of Galileo on the craters of the moon, phases of Venus, and moons of Jupiter, was a giant step forward in universal theory. These three laws put the sun at the center of the universe, the planets in elliptical orbits around it, and predicted these planetary orbital periods. Although the support for Kepler’s third law would not be evident until the seventeenth century, with the work of Newton and the proof of his gravitational theories, our modern school of Astronomy now had its basis.
Johannes Kepler
Since it was Kepler’s extraordinary work that founded modern astrology, and it is this same work that is the basis of our experiment, we thought it would be fitting to include a section in this proposal that detailed the life of the man himself. Johannes Kepler was born on the twenty-seventh of December, 1571 in the town of Weil der Stadt, Germany. Kepler first studied the arts, and then theology at the University of Tubingen with the intention of becoming a priest in the Lutheran church. However, in 1594 Georg Stadius, the mathematics professor at the Protestant School in Graz died, and the theological faculty at Tubingen recommended Kepler for the post. Kepler had been introduced to Copernican theory at Tubingen by his teacher Michael Maestlin, and now that he was away from the Lutheran theological school in which he had begun to hold such doubt, he began to compile a list of superiorities of the Copernican system over the Ptolemaic system. In Kepler’s view, the Copernican system was the only system closest to astrological truth, because this system provided answers to questions that only provoked astonishment in other schools of thought. However, although Kepler used observations to prove his theories as Copernicus did, Kepler still believed that the motions and arrangements of the planets could be explained in part by religion and divine influence. Kepler used a combination of science, philosophy, and religion to discover and develop his theories of planetary motion. But it was his basis of theory on observational data that provided Kepler with the tools to further the entire school of astrology. Throughout most of astrological thought prior to the time of Kepler, the idea of divine creation, and thereby such concepts of perfect spherical orbital motion had formed astrology’s basis instead. This concept and others that were seen to fit most conveniently into a divinely inspired plan for the universe limited the interpretations that astronomers could make on observed phenomena. Therefore, observed data was explained in ways that made it support current theories, rather used generate new hypotheses. Kepler’s use of religion as a tertiary means of support and explanation provided the magical combination of religion and empirical science that allowed his laws to be accepted by a religion-dominated society, and the forward movement of the astrological field.
Kepler’s Laws
Kepler’s three laws describe the motion and relationships of planetary orbit. With these three laws it should be a simple process to predict the orbital motion of a body--however, this prediction is skewed somewhat by the effects of gravitiation between the planets on each other’s orbital motion.
Kepler’s first law states that the orbital rotation of the planets and other celestial bodies around the sun are elliptical in nature. The definition of an ellipse states that it is a figure drawn around two points called the foci such that the distance from one focus to any point on the figure back to the figure is defined as a constant. This constant is the measure of the long diameter of the elipse, the major axis. Half of this segment is called the semimajor axis. The short diameter, the minor axis, is the perpandicular bisector of the major axis. Similarly, half of the minor axis is called the semiminor axis. Kepler put the sun at one focus, and nothing at the other.
Kepler’s second law states that a line from the planet to the Sun sweeps over equal areas in equal amounts of time. These areas in the ellipse are called sectors. In the following diagram, as the planet moves from point A to point B along its orbit, a long, skinny sector is created.
C
B
A
D
If we wanted to create a sector of equal area at points closer to the Sun (points C and D), the result is a short, fat sector. According to Kepler, the time it takes for the planet to get from A to B is equal to the time it takes the planet to get from C to D. This means that a planet orbits slower as it moves further from the Sun.
Kepler’s third law deals with the lenght of time a planet takes to orbit the sun, called the period of revolution. The law states that the square of the period of revolution is proportional to the cube of the planet’s average distance to the sun:
P = a
Because of the way a planet moves along its orbit, its average distance from the Sun is half of the long diameter of the elliptical orbit (the semimajor axis). The period, P, is measured in years and the semimajor axis, a, is measured in astronomical units (AU), the average distance form the earth to the sun.
Our Solar System
In our solar system, there are five major regions in its structure. The first region, which our planet is a part of, is known as the terrestrial region and the four planets in it are the terrestrial planets. These four planets--Mercury, Venus, Earth, and Mars--are small planets made of mostly rock. The next region is known as the asteroid belt, and is composed of hundreds of thousands of pieces of rock that range in size from a few yards across to more than 620 miles. This region is thought to have been created when the universe was forming and the immense gravitational pull of Jupiter did not allow for the possible formation of another planet in this region. The next region contains the four “gas giants”--Jupiter, Saturn, Uranus, and Neptune--also known as the Jovian planets. These planets are called the “gas giants” because they are thought to be planets with massive gaseous atmospheres and liquid or rocky cores. The fourth region is contains only the planet Pluto, which is the smallest planet and because of the close proportional size of its moon in relation to it, it is thought of as almost a double planet. Its unusual orbit, which is on an inclined plane to the orbits of the other panets of our solar system, has prompted some speculation as to whether or not Pluto was once a satellite of Neptune that was somehow thrown out of orbit. The fifth and final region is largely unexplored, but it is thought to stretch almost halfway to the nearest star and contain an enormous shell of icy bodies that is the source of our comets.
Jupiter
Jupiter, the largest of all the planets, orbits the sun at a distance of 483 million miles with an orbital period of 11.9 years. It is 318 times the size of the Earth with a diameter size of 89,000 miles, and has 2.64 times the gravity of earth. While its temperature is -150 celcius, it is composed of mainly hydrogen and helium and was almost a second sun in our solar system. In fact, today Jupiter is referred to as a brown dwarf because although it is not hot enough to be a star (its core temperature probably never exceeded 50,000 degrees and is even now thought to be only 25,000 degrees at its iron core) it does produce more energy than it recieves from our sun. Jupiter has many unusual visual features as well. One of these features is the light and dark bands on its surface that are indicators of a layered, dense atmosphere. The light bands of Jupiter are a result of rising gas that is primarily composed of gaseous ammonia. The dark bands are probably lower layers of compounds of sulfur. Another famous set of visual features that mark the surface of Jupiter are its many oval features--and more specifically the Great Red Spot. These oval features are massive columns of rotating gas, a.k.a. storms, in Jupiter’s atmosphere. The Great Red spot is a storm on the surface of Jupiter that is estimated to be over 300 years old. A feature only relatively recently discovered in the course of the Voyager mission is the presence of dark rings that are centered around Jupiter and extend from right above its clouds to 87,000 miles above its surface.
The Galilean Satelites
Scientists have found Io to be one of the biggest surprises as well as a moon that occupies a “special place” in the history of space science. Before its discovery by Galileo and S. Marius in 1610, space science was exploring the system of satelites around Jupiter to get the information expected, but when scientists started discovering surprises on Io, they opened their eyes. Io, the closest of Jupiter’s four large moons, was named after a woman loved by the king Zeus whom his wife, Hara, turned into a cow out of pure jealousy. A moon of many bright colors, Io (pronounced “eye-o” or “ee-o”, either one) is known as the “pizza moon” for having all the colors found on a pizza. Io is going through a lot of pressure from Jupiter that causes it to stretch and sometimes squish. Due to its intensely strong attraction to Jupiter, Io is full of active volcanoes. The atmosphere on Io is made almost entirely of sulfur. However, it changes according to how active the volcanoes are. When Voyager flew by Io, it discovered a great deal of unusual chemistry and a strange magnetic field around Jupiter and Io. A new theory is that while Jupiter is affecting Io, another moon, Europa, is also forcing it to be active by what is known as the “Io-Europa Resonance Heat Pump”. Either way, Io’s energy is greatly built up so that it is released through these volcanoes at speeds up to 2000 mph. Io is so active that the outer surface can only be as old as 1000 years. It is also the source of a huge dust storm in space with the biggest cloud of dust in the solar system. Io is slightly bigger than the Earth’s moon and takes about 42 hours to rotate around Jupiter. What we found most interesting is that Io’s orbit is a perfect circle.
Europa is 3,138 kilometers in diameter, slightly smaller than the Earth’s moon. It is the sixth largest satellite in the solar system, but is the smallest of the Galilean moons. Europa has an icy surface, which makes it the smoothest object in the entire solar system. The surface of Europa has five times the illumination of the Earth’s moon. Europa is a very flat satellite, with nothing exceeding one meter in height. Scientists believe there is a liquid ocean under the surface of Europa. The ocean on Europa is because of the warming from the tidal pulling with Jupiter. With this ocean of warm ice, many scientists believe that life could exist within these oceans. The ice on Europa is cracked. It can sometimes have geysers along the fault line. These geysers are sometimes referred to as “dirty” because they release dark silicate fragments and mixtures of ice. Sometimes this is followed by a clean flow of water that gives Europa a white, shiny appearance. Some cracks can extend for thousands of miles. The geysers along the fault lines lead scientists to believe that the crust is only about 150 kilometers thick. Scientists have thought about the possibility of life on Europa. They say there are three things necessary for life: an energy source, liquid water, and organic molecules. Europa has water and energy sources. It is the only one of the four Galilean satellites on which life could possibly exist because of the abundance of water below its surface.
Named after one of the god Jupiter's many lovers from Greek/Roman mythology, Ganymede was first discovered by Galileo in 1610, and named as one of the Galilean Satellites. Of the 16 moons, it is the 7th closest to Jupiter, at a distance of 670,900 km. It is the largest moon in the solar system, much larger than the earth's moon, with a diameter that is about the distance across the United States (5262 km). Ganymede is one of the icy satellites and its main characteristic is the grooved terrain on its cratered surface. There has been no icy volcanism on Ganymede, but it does seem that there has been a kind of tectonism, or surface motion. Examination of the surface of Ganymede reveals many kinds of faulting and fracture. These provide evidence of stress (pushing and shoving) which the crust of Ganymede has undergone through time. There is evidence of both graben style faulting (another name for continental rifting) and imbricate faulting. Instead of icy-volcanism, the surface of Ganymede reveals a gradual surface deformation reminiscent of the crustal deformation of the Earth. In this case, crustal extension of the surface of Ganymede resulted in big blocks of the crust being pulled apart. The pulling apart of blocks of crust is similar to the terrestrial process of rifting. The lack of icy-volcanism, such as that found on Europa, probably stems from a lack of the kind of heating undergone by Europa. The existence of surface extension and deformation suggests that there has been some heating of Ganymede, nonetheless. When the Galileo spacecraft flew by Ganyemde it indicated that Ganymede was fully differentiated into two or maybe three distinct interior layers. The innermost layer is thought to be a small metal core, the second rocky material, and the third ice of various phases. Moreover a very strong magnetic field was measured. This may provide further evidence that Ganymede has an iron core and is not completely frozen.
Paragraph on Callisto here--a mix-up occurred as to who was to write a paragraph on which moon, and we will include this paragraph in our final proposal.
Proposal
In order to test our hypothesis, we plan to observer Jupiter and its four moons every other night for a month, and then for the remainder of the experiment, we will observe only once a week. When observing, we will measure and note the distances between Jupiter and its moons. We also plan to map Jupiter’s position in the sky with drawings in relationship to our nightly observation of the moon. If possible, we will also be photographing our nightly observations of the Galilean satellites by focusing through the telescope with special-exposure film. Hopefully, in doing so, we will find support for Kepler’s third law.
By doing this experiment, we also hope to learn more about the telescope. In our seminar class, we will try to teach the other lab groups what we have learned about the telescope as well so that they can help us in gathering data on a succession of nights of viewing Jupiter.
Members present: _________________________________________________________
Date: _____________
Time: _____________
Distance Between:
Io & Jupiter _________ Callisto & Jupiter _________
Europa & Jupiter _________ Spread of System _________
Ganymede & Jupiter _________
Special Notes from observations:
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