PART 2 TUTORIAL Formation of the Solar System
The Sun formed when material at the center of a giant rotating cloud of gas and dust, called the Solar nebula, gravitationally pulled together. When this protosun gathered enough material, it became massive enough to exert tremendous pressure on its core. This raised the temperature high enough for nuclear fusion to occur there. This produced the energy necessary for the Sun to begin to shine, or more simply, to give off light and heat to its surroundings. The leftovers of the original nebula or the Sun’s solar nebula provided the material from which the planets of our solar system would form.
Figure 4.5 shows the regions, around the protosun, in which diff erent materials condense.
- About how far from the sun would you expect temperatures to cool down as low as 150 K or less (see Table 4.4 and Graph 4.1)?
This distance from the Sun is called the frost line.
- What materials in Table 4.3 could then condense (become solid) on the already formed protoplanets beyond the frost line, creating a second layer of material on these objects?
What common name do we give to these materials when they condense on something (remember, they are beyond the frost-line)?
- So, where, relative to the Sun, are larger objects found? Where are smaller objects found? Where are no objects found at all?
- State whether or not you agree with each student and why or why not.
Student 1 The objects forming closer to the Sun will be more massive because they are made of heavier rock and metal, while the objects forming father will be less massive because they will be made partly of ice.
Student 2 No. Rock and metal condensed everywhere past the rock-metal line, and the objects forming beyond the frost line also got a coating of ice so they are more massive.
- Which materials in Table 4.3 do not condense (do not become solid) anywhere in the solar nebula? Why can’t they?
- Which planetary objects, the larger or smaller ones, are now likely to collect large amounts of the remaining uncondensed gases from the solar nebula? Give two reasons for your answer. Hint: Keep in mind that temperature is a measure of the energy of molecular motion, so molecules in warmer regions are moving much faster than those in cooler regions.
- Now describe the smaller objects that have formed. Of what materials are they mostly composed? Where did they form relative to the Sun and to the larger objects? In how many layers (or steps) did they form?
What type of planet that you are familiar with are these
- Describe the larger objects that have formed. Where did they form relative to the Sun and to the smaller objects? In how many layers (or steps) did they form? What type of planet that you are familiar with are these? 13. Which type of planet is more evolved (has gone through more steps in its formation)?
- Based on the investigation you have just undertaken, what is the single most important factor in deter-mining what kind of planet will form at a given location?
On what does this factor depend
- State whether or not you agree with each student and why or why not.
Student 1 The planets farther from the Sun got more massive by collecting a layer of gases because farther out where temperatures are lower, the gases don’t move as fast so they were easier to catch than they would be closer to the Sun.
Student 2 I think the planets farther from the Sun got more massive because the layer ice that formed on them made them massive enough to gravitationally collect gases, while the planets closer of the Sun were not massive enough to do this.
- What names have we given to smaller objects composed of various materials that condensed from the solar nebula that did not become part of a planet?
Of what would small objects that formed closer to the Sun be made? What do we call them?
Of what would small objects that formed farther from the Sun largely be made? What do we call them
Examination of the radii bar graph, Figure 4.1a, shows that there are diff erent-sized objects (the numbers on the bar graphs match the numbers in Table 4.1). Objects five and six, Jupiter and Saturn, are very large compared to objects seven and eight, Uranus and Neptune, which are medium in size. Earth and all the others are very small by comparison. The mass bar graph, Figure 4.1b, shows that Jupiter is by far the most massive, and then Saturn, with Uranus and Neptune the only others that even register on the graph. Per-haps at this point, Jupiter, Saturn, Uranus, and Neptune could be considered a group of large and massive planets, while Earth and all the others could be called small and less massive plane
Examine the data for the objects in Table 4.1 and the bar graphs in Figures 4.1a, 4.1b, and 4.1c of this chapter.
1. Examine the bar graph comparing the radius (or size) of the objects. Which objects are large?
Which are small?
2. Examine the bar graph comparing the mass of the objects. Which are high mass? Which are low mass?
3. Examine the bar graph comparing the density of the objects (how compact they are). Which are more dense?
Which objects are less dense? What can density tell you about an object?
4. Based on the comparisons you have made, have any objects been grouped together every time? How many groups are there? Which objects are in which groups?
5. State whether or not you agree with each student and why or why not. Student 1 Jupiter, Saturn, Uranus, and Neptune are larger, more massive, and more dense than Earth, Venus, Mars, and Mercury. Student 2 No, Jupiter, Saturn, Uranus, and Neptune are larger and more massive than Earth, Venus, Mars, and Mercury, but they are less dense, being made of mostly liquid and gas, while the smaller objects are made of mostly rock and metal.
6. Examine the data in Table 4.1 comparing the number of moons orbiting each object. Which group’s members have many moons?
Which group’s members have few (or no) moons? On what does the number of moons orbiting an object likely depend?
Examine the data in Table 4.1 comparing the orbital radius (distance from the Sun) of each object. Which group is closer to the Sun?
Which group is further from the Sun?
8. By now, you may have noticed that there are two major groups of planet classification. Label each group, and list the members of each of your groups.
List what properties from the data table and bar graphs that the objects in each of your groups have in common
9. Is (are) there an (any) object(s) that do(es) not seem to fit into a group? Which objects? Have you heard about a fairly recent decision made about one of these objects? Did this exercise help clarify the reason for the decision?
10. State whether or not you agree with each student and why or why not.
Student 1 Pluto and Eris should be in a group with Earth and the other objects like Earth (the terrestrial planets) because they are small, of low mass, do not have very many moons, and have longer rotation periods.
Student 2 No. Pluto and Eris should be in a group with Jupiter and the other objects like Jupiter (the Jovian planets) because they have lower density and are far from Sun.
Student 3 Maybe. Pluto and Eris do not fit into either category and should be considered a diff erent type of object than the terrestrial or Jovian planets. Small, low mass, lower density objects with few or no moons and longer rotation periods that are even farther from the Sun than the Jovian plane