1. Space Science Formation of the Solar System and Other Planetary
Systems

2. Space Science Key Terms
Astronomy: study of the universe (do not confuse with astrology)
Galaxy: a large collection of stars, dust and gas bound together by________.
We measure distance in space using Astronomical units (AU)
1AU is the average distance from the Earth to the sun (about 150 million km)

3. Key terms cont.
Solar system: sun and all the planets and dwarf planets that revolve around the sun.
Planets: major bodies that revolve around the sun.
Solar nebula: the rotating cloud of dust and gas from which the sun and planets are formed.

4. You will discover… how the solar system formed
why the environment of the early solar system was much more violent than it is today
how the planets are grouped
how astronomers characterize each planet’s “personality”
how the moons throughout the solar system formed
what the debris of the solar system is made of
that planets have been observed around a growing number of stars
that newly forming star and planet systems are being observed

5. Video

6. Ejection of Matter from Stars
The lightest and simplest elements, hydrogen and helium, are abundant in the universe. Heavier elements, such as iron and silicon, are created by thermonuclear reactions in the interiors of stars, and then ejected into space by those stars.
Ejection of Matter from Stars
FORMATION OF PLANETARY NEBULA
SUPERNOVA EXPLOSIONS

7. Great clouds of gas and dust ejected from old stars are gathered into regions from which new stars can be made.
This region in the constellation of Orion shows new stars still surrounded by the nebula from which they were formed.

8. Solar System Formation

9. The Formation of a Solar System
A solar system begins as a gas cloud that collapses toward the center under the influence of gravity.
A condensation forms at the center, which is called a protostar. This forms the sun of the solar system from fusion (contains 99% of matter from the nebula)
A flattened disk of matter surrounds the protostar, which begins to shine.

10. The Formation of a Solar System
The rising temperature from the sun removes the gas from the inner regions, leaving dust and larger debris.
The planets establish dominance in their regions of the solar system.
After almost all of the remaining gas, dust, and small debris has been collected by the larger objects, the solar system takes on the form we recognize today.

11. PLANET FORMATION
Within the disk that surrounds the protosun, solid grains collide and clump together into planetesimals.
The terrestrial planets are built up by collisions and the accretion of planetesimals by gravitational attraction.
The jovian planets are formed by gas accretion.

13. COMPUTER SIMULATION OF THE FORMATION OF THE SOLAR SYSTEM

14. Planets and moons which have no appreciable atmosphere will show scars from impacts with planetary debris, called craters.
Our Moon still has numerous craters, providing evidence of many impacts in its history.

15. Debris in Our Solar System Today
Asteroids—rocky bodies several kilometers across which orbit the sun—are found mainly in the asteroid belt located between the orbits of Mars and Jupiter.
Even smaller rocky objects, called meteoroids, are scattered throughout the solar system.
Billions of chunks of rock and ice called comets are located beyond the orbit of Neptune. Occasionally, one of these will be pulled toward the inner solar system and form the familiar “tails” as it orbits close to the Sun.

16. Comparative Planetology
ORBITS
The planets nearest to the Sun (Mercury, Venus, Earth, and Mars) are relatively close together, while those farther away (Jupiter, Saturn, Uranus, Neptune, and Pluto) are more spread out.
Most of the planets are in nearly circular orbits.

17. SIZE=the physical volume of the planet
MASS=the amount of matter in an object
DENSITY=the amount of mass per unit volume Density depends on the composition of an object and not just the size. The objects shown here all have the same mass but different densities.

18. Two Basic Groups of Planets
TERRESTRIAL
Small size
Low Mass
Higher density
Mostly rock, heavy elements (iron, nickel)
Mercury, Venus, Earth, Mars
JOVIAN
Large size
Massive
Low density
Mostly gas (did not lose lighter elements); colder
Jupiter, Saturn, Uranus, Neptune

19. Pluto: The first Dwarf Planet
Best described as an ice ball made of frozen gases and rock.
Very tilted orbit, unlike the other planets.
2006 classified as a dwarf planet, not a “real” planet.

20. Formation of Solid Earth
Young Earth was very hot (high temp from becoming a new planet), which was hot enough to melt iron.
Iron sank to the middle of the earth (core) and less dense materials forced up to the surface.
This led to the differentiation of the distinct layers of the geosphere.
What are these layers?

21. Formation of Earth’s Atmosphere
During the differentiation process, lighter elements (hydrogen, helium) made their way to the surface of Earth.
The high concentrations of these elements did not stay in the atmosphere
Earth’s gravity was top weak to hold them in the atmosphere.
Blown away by solar wind

22. Formation of Earth’s Atmosphere
Outgassing: volcanic eruptions very frequent, leading to the release of new elements into the atmosphere (water vapor, carbon dioxide, nitrogen, sulfur dioxide, methane, ammonia)
The radiation from the sun caused the ammonia and water vapor to break down. Also, oxygen combined to form ozone.
Early life on Earth consisted of plants, which converted CO2 to O2 by photosynthesis
Oxygen levels in the atmosphere increased.

23. Formation of Earth’s Oceans
Some of Earths water may have come from space
Ice bodies (comets) collided with Earth, water became part of the atmosphere and cooled to form rain.
First ocean was probably first fresh water.
Over millions of years rainwater fell to Earth. Overtime, more dissolved materials were carried to the oceans. Some of these chemicals combined to form salts.

24. WHAT DO YOU THINK? How many stars are there in the solar system?
Was the solar system created as a direct result of the formation of the universe?
How long has the Earth existed?
Is Pluto always the farthest planet from the Sun?
What typical shapes do moons have?
Have any Earth-like planets been discovered orbiting Sun-like stars?

25. WHAT DID YOU KNOW? How many stars are there in the solar system?
Only one star, the Sun.
Was the solar system created as a direct result of the formation of the universe?
No. All matter and energy were created by the Big Bang, but the solar system formed billions of years after the Big Bang.
How long has the Earth existed?
4.6 billion years.

26. WHAT DID YOU KNOW? Is Pluto always the farthest planet from the Sun?
No. Pluto’s orbit is highly eccentric, bringing the planet inside Neptune’s orbit for about 20 years every 250 years.
What typical shapes do moons have?
Most look roughly like potatoes.
Have any Earth-like planets been discovered orbiting Sun-like stars?
No. Nearly all the planets orbiting Sun-like stars are Jupiter-like gas giants.