Today’s APODAPOD Read Chapter 7 – Survey of the SS Homework 6 – Impact Craters, due on Friday Kirkwood Obs. open Wednesday This week’s Quiz via.

Today’s APOD

Read Chapter 7 – Survey of the SSHomework 6 – Impact Craters, due on

FridayKirkwood Obs. open WednesdayThis week’s Quiz via Oncourse T&S

The Sun Today

A100 Survey of the Solar System

EARLY VOTING WHERE? Curry Building (7th & Morton, one block

west of College Ave) EVERY day until November 3rd

Monday – Saturday: 8:30am – 6:00pm Sunday: 1:00pm – 5:30pm November 3rd: 8:30am – 12:00

TRANSPORTATION: Students may take a free early vote shuttle any weekday between the hours of 11:00am – 5:30pm. The shuttle leaves every 15 minutes from the IMU circle drive and the 10th street side of the Wells library.

Voters MUST present their Indiana drivers license, student id, or passport when they go to vote.

Another possible activity:

Close Encounters at Ivy Tech Bloomington

An academic panel discussion will explore how different academic disciplines might aid in welcoming extraterrestrial visitors

Thursday, Oct. 30, 6 PM, Ivy Tech 4th floor Auditorium, Room 438

Use general activity worksheet

The Solar System

A diversity of objects – The Sun, planets, dwarf planets, asteroids, comets, dust, gas

An underlying order in the dynamics of their movements

Two main families of planets: solid rocky inner planetsgaseous/liquid outer planets

The Sun

The Sun is a starA ball of hot,

incandescent gas Energy comes from

nuclear reactions in its core

Composed mainly of hydrogen (71%)helium (27%)

Plus traces of nearly all the other chemical elements

The SunThe Sun is the

most massive object in the Solar System

700 times the mass of the rest of the Solar System combined

The Sun’s mass provides the gravitational force to hold all the Solar System bodies in their orbits around the Sun

The PlanetsOrbits are almost

circular and lie in nearly the same plane

Plutoids do not lie in the plane of the planets’ orbitsPluto’s orbit has an

inclination of 17°Rotational axes

are not lined up

Revolution

andRotationAll of the planets travel counterclockwise

around the Sun (as seen from high above the Earth’s north pole)

Six planets rotate counterclockwise; Venus rotates clockwise (retrograde rotation), and Uranus and Pluto appear to rotate on their sides

Small “rocky” bodies Differentiated crust, mantle, core

Mainly silicon and oxygen crust and mantle Iron/nickel cores

Relatively thin or no atmospheres Large differences in surface structures and processes

Inner (“Terrestrial”) Planets

Mercury Venus Earth Mars

Outer“Gas

Giant”“Jovian” Planets

Jovian planets are much larger than terrestrial planetsJupiter’s radius is 11 times larger than Earth’s

No well-defined surfaceGaseous, liquid, or “icy” (H2O, CO2, CH4, NH3)

What is a surface?

Terrestrial planets – the surface is the hard boundary between the crust and the atmosphere

Jovian planets (and the Sun!) – the “surface” is the top layer we can see

Jovian planets don’t have a real surface – we see the tops of the clouds

Dwarf Planets

& Plutoids

Pluto and similar objects don’t fit either planet family Astronomers have discovered more than 200 objects

like Pluto orbiting the Sun In 2006, a new family was introduced – the dwarf

planets Massive enough to pull themselves spherical Orbits have not been swept clear of debris

Lots of Moons!

More and more moons of the outer planets are still being discovered!

Jupiter > 62 Saturn > 31 Uranus > 27 Neptune > 13 Mars - 2 Earth - 1 Mercury, Venus have

no (known) moons Plutoids and asteroids

have moons

Comets and Asteroids Comets are icy bodies about 10 km or less

across Comets can grow very long tails of gas and dust as they

near the Sun and are vaporized by its heat

Asteroids are rocky or metallic bodies ranging in size from a few meters to 1000 km across (about 1/10 the Earth’s diameter)

Where are Asteroids

Found?

Asteroids may be the failed building-blocks of a planet

Some asteroids lead or trail Jupiter around its orbit known as “Trojan Asteroids”

Most asteroids orbit the Sun in a band between Mars and Jupiter

Where Are Comets Found?

Most comets orbit the Sun far beyond Pluto in the Oort cloud, a spherical shell extending from 40,000 to 100,000 AU from the Sun

Some comets may also come from a disk-like swarm of icy objects that lies beyond Neptune and extends to perhaps 1000 AU, a region called the Kuiper Belt

How Do We Determine

the Composition

of the Planets?

Since the inner and outer planets differ dramatically in composition, it is important to understand how composition is determined

A planet’s reflection spectrum can reveal a planet’s atmospheric contents and the nature of surface rocks

Seismic activity has only been measured on Earth for the purposes of determining interior composition

Density tells us about composition

A planet’s average density is determined by dividing a planet’s mass by its volumeMass determined from the planet’s moons

using Kepler’s modified third lawVolume derived from a planet’s measured

radius

Composition from

Density Once average density known, the following factors

are taken into account to determine a planet’s interior composition and structure: Densities of abundant, candidate materials Variation of these densities as a result of compression

due to gravity Surface composition determined from reflection spectra Material separation by density differentiation Mathematical analysis of equatorial bulges

Densities of Terrestrial Planets

Average densities ranging from 3.9 to 5.5 g/cm3

Largely rock and ironIron coresRelative element ratios similar to the Sun except for

deficiencies in lightweight gasses (hydrogen and helium)

Densities of Jovian PlanetsAverage densities from 0.71 to 1.67 g/cm3

Compositions similar to the Sun – with hydrogen and helium

Contain Earth-sized rocky cores

Atmospheres

Interiors

ASSIGNMENTSthis week

Chapter 7 Homework and quiz on

Friday Kirkwood Obs. open on

Weds.

Dates to Remember