Unit II: What is a Solar System????

Read Seeds: Section 5.1

Figure 1: Credit: JPL/NASA Figure 2: Text Credit: C. Burrows and J. Krist (STSCI), WFPC2 IDT Team, NASA, ESA Figure 3: Text Credit: Mt. Wilson Obs.

Lecture: Most of us think of a solar system as a gravitationally bound group of bodies, including planets, which orbit a central star. That would be an appropriate description of our solar system. However, not all solar systems are like ours. Today, one very active are of research is to identify planetary systems similar to our own. The obvious problem of detecting planetary systems similar to ours is the obvious difficulty of identify planets orbiting distant stars. Recently, however, several candidates have been identified. One such candidate is Beta Pectoris (figure 2). A 200-billion mile diameter dust disk encircling the star reveal an unexpected warp that can be best explained as caused by the gravitational pull of an unseen planet. Other newly discovered planets have been detected around the stars 51 Pegasi, 70 Virginis and 47 Ursae Majoris. Still, planetary systems are thought to be relatively uncommon. More common are multiple star systems. Such systems consist of two or more stars orbiting each other. An example of such a binary system is Lambda Ophiucus (figure 3). Of what types of bodies is our solar system composed? A central Sun. nine planets, moons, asteroids, meteoroids and comets. Complete these Self-check Questions: What is the difference between a star and a planet? (ans.) What is the difference between a planet and a moon? (ans.) Homework Questions: (To submit your answers to the homework questions, first copy the questions from this page and paste them into the homework form. Insert your answers below the questions. Fill in the remaining form elements and submit. Your homework will be e-mailed to me. I will return your graded homework to you in the private e-mail of the comm center). Planetary systems are difficult to discover because of the great distance of stars and the small size of planets. Use the optional related websites below and summarize how astronomers locate potential planets. (2 points) Write a description of one of the newly "discovered" planets and describe how it was discovered. (2 points) Do a search of the Web and identify by name a binary system other than those listed in this unit. (1 point) View These Optional Related Web Sites: Visiting these sites are optional, not required. Astronomy Picture of the Day: Planets Around Normal Stars Astronomy Picture of the Day: Lalande 21185: The Nearest Planetary System? Discovery of a Planetary Orbit Around the Nearby Star 51Pegasi Searching for Extrasolar Planets Possible planet orbiting Beta Pictoris A Parade of New Planets The Nine Planets: An Overview of the Solar System