Our Solar System

1. Our Solar System • Chapter 28

2. Formation of the Solar System • 28.1

3. A collapsing interstellar cloud • Stars and planets form from interstellar clouds • They appear dark because of dust blocking out the light • The light can cause it to glow, or even become heated • Starts and solar systems are “born” this way • Collapse accelerates • The collapse of this cloud is slow, but it accelerates and becomes denser at the center

4. This collapse and spin results in a flattening at the equatorial plane • Matter condenses • Our solar system may hav eformed this way when temperature and pressure cause hydrogen to fuse into helium • The temperature differential allowed for different elements to concentrate in different areas around the sun • This is why the inner planets are rocky and have a higher melting point • Outer ones are less dense and made of ice and gas

5. Planetesimals • Much like coalescence, the planetesimals combined to get larger in many cases to become the known planets. • Gas giants form • Jupiter was the first to form • Icy planetesimals combined to form it • Its mass (gravity) caused it to collect much of the debris • The others formed the same way, but Jupiter took most of the extraneous material

6. Terrestrial planets form • the merging of planetesimals in the inner portion of the disk • Made of materials that resist vaporization • Most of the gaseous material and “smaller stuff” consumed by the sun, hence fewer satellites. • Debris • All of the “junk” left over • Some became comets • Some ejected from solar system or destroyed in collisions • The asteroid belt between mars and Jupiter is the rest

7. Modeling the Solar system • Initially the geocentric theory stated that everything moved around the earth. • Retrograde motion led astronomers to find a different explanation • The heliocentric model (Copernicus) put the sun at the center and planets in orbit around it. • Proximity to the sun caused planets to move at different speeds • This explained retrograde

8. Kepler’s Laws • 1st law is that planets move in elliptical orbits • The sun was at 1 focus • The semi-major axis (half the length of the major axis) is where we get the AU (astronomical unit) distance many distances are measured in • This is more math that I want to get into! • The eccentricity of the orbit is how “squashed” the orbit is • 2nd law is an equal area is swept out in equal amounts of time (although the orbital distance may be different) • 3rd law he defined the size of the ellipse and the orbital period (year)

9. Gravity • Gravity is the attractive force between 2 objects • It is affected by mass and distance • Gravity is what determines the orbit planets follow • Newton’s explanation of gravity supported Kepler’s laws of planetary motion.

10. The Inner Planets • 28.2

11. Terrestrial Planets • these are the 4 inner planets • similar densities to Earth • solid rocky surfaces

12. Mercury • closest to the sun • 1/3 Earth’s size • no moons • 2 Mercury Years is 3 Mercury days • Atmosphere • O2 and Sodium • replenished daily by the sun

13. Surface • covered with craters and plains • the plains formed much like the maria on the moon • the craters are smaller with less ejecta • Interior • the density suggests a dense core similar to the Earth • the magnetic field suggests its partially molten

14. Venus • Has no moons • the brightest planet because of proximity and albedo 75% • Thick atmosphere doesn’t allow for direct observation • probes and satellites have provided radar images of 98% of the surface

15. The Outer Planets 28.3

16. The Gas Giants • These planets include: Jupiter, Saturn, Uranus and Neptune • All larger than Earth by 15-300 times

17. Jupiter • The largest planet 1/10 of the sun and 11X Earth’s • Better than 70% of the planetary mass of the solar system • 52% albedo • Has a banded appearance • “the great spot” is a storm that has lasted for better than 300 years

18. Density is relatively low for its size • The is because of it composition (H and He in gas or liquid form. • Rotation • Shortest day in the solar system about 10hrs • This fast spin distorts the shape • This also contributes to its banded appearance • Belts are low lying dark-colored clouds • Zones are high light-colored clouds • Moons • More than 60, but some are very small

19. Mostly composed of ice and rock • Gravity assist

20. Saturn • Second largest planet in the solar system • Atmosphere and interior • Slightly smaller than Jupiter • Density less than water… it would float! • Rings • Much broader and brighter than other planets’ • 7 major rings made up of ringlets • Gravity keeps the rings in place

21. Moons • 55 moons • Titan, the largest is bigger than Mercury • Odd among moons because of content with dense atmosphere and methane’s existence in 3 states

22. Uranus • 4x larger and 15Xmass of the Earth • Atmosphere • Bluish appearance cause by methane gas • Clouds are similar in appearance to the surface • Liquid surface with a small solid core • Moons and Rings • At least 27 moons and faint rings

23. The rings are dark and almost not observed • Rotation • Almost a top to bottom rotation • Poles vacillate between 42 years of darkness and light

24. Neptune • Atmosphere • Smaller and denser than Uranus but 4XEarth • Similar in color to Uranus (twins??) but does have some color variation on surface • Belts and zones give it texture • Moons and Rings • 13 moons Triton being the largest • Triton has retrograde orbit • Also has nitrogen geysers when heated by the sun • Rings are invisible from Earth but exist