Our Solar SystemIntroduction and Key Terms

Learning Outcomes (Students will…)-Explain the theories for the origin of the solar system

-Distinguish between questions that can be answered by science and those that cannot, and between problems that can be solved by technology and those that cannot with regards to solar system formation.

-Estimate quantities of distances in parsec. Estimate the age of the solar system. -Describe and apply classification systems and nomenclature used in the sciences. Classify planets as terrestrial vs. Jovian, inner vs. outer, etc. Classify satellites. Classify meteoroid, asteroid, dwarf planet, planet. Classify comets as long period vs. short period. etc

-Formulate operational definitions of major variables. Given data such as diameter and density describe the properties that divide the planets and moons into groups.

-Tools and methods used to observe and measure the inner and the outer planets and the minor members of the solar system

Planetary Systems

• A planetary system consists of the various non-stellar objects orbiting a star such as planets, dwarf planets, moons, asteroids, meteoroids, comets, and cosmic dust.

Solar System

• A specific planetary system around our star• The region of space that falls within the gravitational

influence of our Sun• If you consider the edge of the Solar System to be

Pluto’s orbit, the Solar System has a diameter of 79 AU

• Consists of:– an ordinary yellow star – the Sun– Eight Planets– Their moons– Dwarf planets– Asteroids, Comets, Meteors and Meteorites– Cosmic dust

Star

• A star is a massive, luminous ball of plasma that is held together by gravity.

• Our star is the Sun

• The gravity on the Sun is 274 m/s2

Planets

• There are now 8 planets in our Solar System

• The Sun is one of the foci for each of these planets

What is a Planet?

• Former definition: NASA (2000):– Planet: A non-luminous celestial body larger

than an asteroid or comet, illuminated by light from a star, such as the sun, around which it revolves.

– What is wrong with this definition?– Why did the definition change?

New definition: NASA (2006):

A “planet” is a celestial body that

• (a) is in orbit around the Sun,

• (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and

• (c) has cleared the neighbourhood around its orbit.

Classifying Planets

• Planets can be classified by:– 1) Composition– 2) Size– 3) Proximity to the Sun– 4) Position relative to Earth– 5) History

1) Composition1) Composition

A)A) Rocky or Terrestrial Rocky or Terrestrial planets (4)planets (4)

B)B) Jovian planets (4)Jovian planets (4)

Terrestrial PlanetsTerrestrial Planets

- Composed primarily of rock Composed primarily of rock and metaland metal

- No ringsNo rings- Few satellites (moons)Few satellites (moons)- High densityHigh density- Slow rotationSlow rotation- Solid surfaceSolid surface

Jovian PlanetsJovian Planets

- Composed primarily of gas Composed primarily of gas (hydrogen and helium)(hydrogen and helium)

- RingsRings- Many satellites (moons)Many satellites (moons)- Low densityLow density- Rapid rotationRapid rotation- Deep atmospheresDeep atmospheres

2) Size2) Size

A)A) Small planets (4)Small planets (4)

B)B) Giant planets (4)Giant planets (4)

Small PlanetsSmall Planets

- Diameters less than - Diameters less than

13,000 km13,000 km

Giant PlanetsGiant Planets

- Diameters greater than - Diameters greater than

48,000 km48,000 km

- Also called gas giants- Also called gas giants

3) Proximity to Sun3) Proximity to Sun

A)A) Inner planets (4)Inner planets (4)

B)B) Outer planets (4)Outer planets (4)

The asteroid belt between Mars The asteroid belt between Mars and Jupiter forms the and Jupiter forms the boundary between the inner boundary between the inner solar system and the outer solar system and the outer solar system.solar system.

4) Position relative to 4) Position relative to EarthEarth

A)A) Inferior planets (2)Inferior planets (2)

B)B) EarthEarth

C)C) Superior planets (5)Superior planets (5)

Inferior PlanetsInferior Planets

- Closer to the Sun than Earth

- Show phases like the Moon’s when viewed from Earth

Superior PlanetsSuperior Planets

- Farther from the Sun than Earth

- Always appear full or nearly full

5) History5) History

A)A) Classical planetsClassical planets

B)B) Modern planetsModern planets

C) EarthC) Earth

Classical PlanetsClassical Planets

• Known since prehistoric times

• Visible to the unaided eye (no telescope needed)

• In ancient times this term also referred to the Sun and the Moon

Modern PlanetsModern Planets

• Discovered in modern times

• Visible only with optical aid or telescope

What is a Dwarf Planet?

• NASA (2006):

A “dwarf planet” is a celestial body that

(a) is in orbit around the Sun,

(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,

(c) has not cleared the neighbourhood around its orbit, and

(d) is not a satellite.

Ceres (dwarf planet) Photo: Hubble Space Telescope

SHAPE…

Dwarf Planets

• Pluto (direct observation)• Ceres (direct observation)

– Discovered in 1801!!!– Classified as a planet for 50 years– Demoted to asteroid– Promoted to dwarf planet

• Eris (larger than Pluto)– Discovered in 2005– Controversial decision regarding Pluto…

Dwarf Planets

• Makemake and Haumea are determined to be dwarf planets using mathematical calculations…

Other Celestial Bodies in Our Solar System

• All objects besides planets and dwarf planets, except satellites, orbiting the Sun shall be referred to collectively as “Small Solar-System Bodies”.

• Some “small Solar-System bodies” include:– Asteroids– Comets

Asteroids

– An asteroid (or minor planetor minor planet)

• (a) orbits the Sun inside the orbit of Jupiter • (b) does not have sufficient mass for its

self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium shape (it is not round shaped),

• (c) has not cleared the neighborhood around its orbit, and

• (d) is not a satellite.

SHAPE…

Vesta (asteroid or minor planet)

Clearing the Neighborhood

• There are very few other objects in the vicinity of Jupiter and the inner planets that orbit the Sun.

• Vesta and Ceres have many other asteroids in relatively nearby orbits.

Key Terms

• 1) Draw a diagram for each with labels to show the difference between a planet, dwarf planet and asteroid.

• 2) Create a metaphor or analogy for comparison.

3) Create a Venn Diagram for these three terms.

1) Decide…Planet, Dwarf Planet or Asteroid?

2) Decide…Planet, Dwarf Planet or Asteroid?

3) Decide…Planet, Dwarf Planet or Asteroid?

4) Decide…Planet, Dwarf Planet or Asteroid?

5) Decide…Planet, Dwarf Planet or Asteroid?

6) Decide…Planet, Dwarf Planet or Asteroid?

7) Decide…Planet, Dwarf Planet or Asteroid?

8) Decide…Planet, Dwarf Planet or Asteroid?

New English Words…

• Plutoed…

• Ceresed…