Individual ActivityWith your counselor's approval and guidance, do ONE of the following: Personally take a series of photographs or digital images of the movement of the Moon, a planet, an asteroid or meteoroid, or a comet. In your visual display, label each image and include the date and time it was taken. Show all positions on a star chart or map. Show your display at school or at a troop meeting. Explain the changes you observed.
List at least three different career opportunities in astronomy. Pick the one you in which are most interested and explain how to prepare for such a career. Discuss with your counselor what courses might be useful for such a career
*This exercise is meant to illustrate that planets does usually not follow the motion of distant stars, and that they sometimes can have a retrograde motion (e.g. Venus in this example). Note that the prograde or retrograde motion depends on the relative position between the earth and the planet, and therefore depends on the date (thease do not repeat into an annual pattern).*Kepler postulated that the orbits of the planets were ellipses (previously these were thought of being circular) and that the orbital period squared was proportional to the cube of the semi major axis of the ellips. Keplers laws were based on experimental observations (obtained from Tycho Brahe), specifically the orbit of mars.
Copernicus was the first to suggest a heliocentric solar system a century earlier. This was, however, still widely disputed at the time of Kepler (e.g. Tycho Brahe was a firm believer of a geocentric solar system).
Galileo, a contemporary to Kepler, is the first to use a telescope for astronomical observations. It was observations of Venus that further supported a heliocentric model of the solar system. The only way the planet could have phases similar to the moon, required that Venus would be placed between the sun and the earth. Furthermore, he observed that size of the disc was larger when a crescent phase was observer as opposed to a gibbous phase, which is consistent with the planet being between the sun and earth at the crescent phase and on the far side of the sun in the gibbous phase.
Isaac Newton, born a half century later, was able to explain Kepplers laws in terms of the laws of gravity and classical mechanics (and by inventing calculus).*The seas are actually not seas, the were called seas by early astronomers who believed that the darker areas of the moon were bodies of water. They are instead believed to be the result of an event called the late heavy bombardment, where orbital debris slammed into the lunar surface. Some impacts were so monumental that they gouged impact basins that eventually filled up with dark basaltic lava (perhaps a direct result of the impact). The flooded basins formed a pristine smooth surface that we see today.*Sunspots are areas of the Sun's photosphere that are cooler than the surrounding regions. Cooler being relative in this case, with the sunspot having a temperature of about 3,700 degrees Kelvin, about 2,000 degrees cooler than the rest of the solar surface. Sunspots are only appear dark in contrast to the rest of the brilliant surface.
Manifesting intense magnetic activity, sunspots host secondary phenomena such as coronal loops (prominences) and reconnection events. Most solar flares and coronal mass ejections originate in magnetically active regions around visible sunspot groupings. Similar phenomena indirectly observed on stars are commonly called starspots and both light and dark spots have been measured.
*Stars appear to be exclusively white at first glance. But if we look carefully, we can notice a range of colors: blue, white, red, and even gold. In the winter constellation of Orion, a beautiful contrast is seen between the red Betelgeuse at Orion's "armpit" and the blue Bellatrix at the shoulder. What causes stars to exhibit different colors remained a mystery until two centuries ago, when Physicists gained enough understanding of the nature of light and the properties of matter at immensely high temperatures. Examples are Betelgeuse, Cappella and Rigel.
*In the early 1900's, Ejnar Herstzprung and Henry Norris Russell independently made the discovery that the luminosity of a star is related to its surface temperature. The resulting plot is amazing. A schematic Hertzsprung-Russell diagram is shown to the right. A Hertzsprung-Russell diagram for the old cluster M55 (Mochejska & Kaluzny, see APOD, 2001 Feb 23) is the top panel on this page. The Hertzsprung-Russell (HR) diagram was one of the most important astronomical discoveries of the twentieth century.