Solar System and Earth Solar System and Earth 30 Sep: Solar System and Earth05 Oct: Earth-Moon07 Oct: Terrestrial Planets12 Oct: Mars Close-up14 Oct: Jovian Planets19 Oct: Asteroids, comets, etc21 Oct: Planet formation26 Oct: Extra-Solar Planets……….. …………….. ……

Solar SystemSolar System

9 planets going around Sun9 planets going around Sun

Other than that the solar system is Other than that the solar system is practically empty. Most of that is practically empty. Most of that is near perfect vacuum.near perfect vacuum.

Large: about 12 billion km acrossLarge: about 12 billion km across

This image shows the sun and 9 planets approximately to scale.

The order of these bodies are Sun, Mercury, Venus, Earth, Mars, Jupiter , Saturn, Uranus, Neptune, Pluto

Average Distance from Sun Average Distance from Sun (AU)(AU)

MercuryMercury 0.390.39

VenusVenus 0.720.72

EarthEarth 1.00= about 1.00= about

MarsMars 1.521.52

JupiterJupiter 5.205.20

SaturnSaturn 9.549.54

UranusUranus 19.1819.18

NeptuneNeptune 30.0630.06

PlutoPluto 39.539.5

m11105.1

Scientific NotationScientific Notation Express numbers in a general form,Express numbers in a general form,

A × 10A × 10nn,,

which is convenient for both large and which is convenient for both large and small numbers. small numbers.

m 000,000,000,150m105.1

...

m 000,15m105.1

m 500,1 m105.1

m 150m105.1

11

4

3

2

QuestionQuestion

If something happens at Sun (e.g. If something happens at Sun (e.g. Explosion), we know the eventExplosion), we know the event

(a) immediately(a) immediately

(b) about 3 sec after(b) about 3 sec after

(c) about 8 min after(c) about 8 min after

AnswerAnswer

(c) About 8 min after (c) About 8 min after

Note: in only one second, Note: in only one second, light can circumnavigate the Earth light can circumnavigate the Earth more than seven timesmore than seven times

Solar SystemSolar System

Orbits are almost in a plane (within a Orbits are almost in a plane (within a few degrees) and close to circular.few degrees) and close to circular.

Mercury and Pluto are most eccentric Mercury and Pluto are most eccentric and have highest inclination.and have highest inclination.

Masses of 9 Planets

Earth

?

Eart

h

Mercu

ry

Venu

s Mar

s

Jup

iter

Satu

rn

Ura

nu

s

Neptu

ne P

lut

oSun:332,946 (Earth Mass)Much heavier!!

The nine planets are often further classified as follows

Terrestrial Planets (inner 4 planets) Mercury, Venus, Earth and Mars small, high density, low mass, rocky little or no atmosphere

Jovian Planets (next 4) Jupiter, Saturn, Uranus and Neptune Massive, low density, gaseous probably no solid surface

Pluto: ball of ice and rock, not much the larger than the largest asteroids

Terrestrial Jovian

Rocky, no atmosphere Gaseous, no solid surface

Mars Neptune

TerrestrialSmall, high density

JovianMassive, low density

Pluto

CompositionComposition

Two ways to find out what the Two ways to find out what the planets are made ofplanets are made of

(1) Go There! (Mars and Venus)(1) Go There! (Mars and Venus)

(2) Spectroscopy – either from Earth(2) Spectroscopy – either from Earth or from a spacecraft passing by or from a spacecraft passing by or in the orbit around the planetor in the orbit around the planet

CompositionsCompositions

Terrestrial planets are rocky - Terrestrial planets are rocky - silicon, iron compounds silicon, iron compounds

Jovian planets are gaseous – Jovian planets are gaseous – hydrogen, helium, methane, hydrogen, helium, methane, ammonia, carbon monoxide, ammonia, carbon monoxide, carbon dioxide, water vapor etc. carbon dioxide, water vapor etc.

Water on Mars!Water on Mars!

greeting card from my hockey mate at Jerusalem

Other Solar StuffOther Solar Stuff

Moons: small bodies that orbit Moons: small bodies that orbit PlanetsPlanets

Asteroids: small bodies that orbit Asteroids: small bodies that orbit Sun. Sun.

Comets: dirty snowballs in highly Comets: dirty snowballs in highly elliptical orbits around Sunelliptical orbits around Sun

AsteroidsAsteroids

Most of them are between Mars and Most of them are between Mars and Jupiter: Asteroid BeltJupiter: Asteroid Belt

The composition is similar to that of The composition is similar to that of terrestrial planets (rocks and metals)terrestrial planets (rocks and metals)

Comets (Ices, rocks)Comets (Ices, rocks) Comets have ices covering them, and Comets have ices covering them, and

these vaporize and produce these vaporize and produce a gas haloa gas halo around the comet when it comes close to around the comet when it comes close to Sun.Sun.

Kuiper belt cometsKuiper belt comets : from extended wedge : from extended wedge of asteroids beyond the orbit of pluto, 30-of asteroids beyond the orbit of pluto, 30-100AU100AU

Oort cloud cometsOort cloud comets: from very extended : from very extended halo of comets, probably it extends to halo of comets, probably it extends to 100,000AU.100,000AU.

QuestionQuestion

What is the farthest Planet to the What is the farthest Planet to the sun?sun?

(a) Mars(a) Mars

(b) Mercury(b) Mercury

(c) Earth(c) Earth

(d) Moon(d) Moon

(e) Pluto(e) Pluto

AnswerAnswer

(e) Pluto.(e) Pluto.

Sometimes Neptune is further, but it Sometimes Neptune is further, but it is not a choice.is not a choice.

QuestionQuestion

Which of these is not a Planet?Which of these is not a Planet?

(a) Mars(a) Mars

(b) Mercury(b) Mercury

(c) Earth(c) Earth

(d) Moon(d) Moon

(e) Pluto(e) Pluto

AnswerAnswer

(d) Moon.(d) Moon.

Mars is either a planet or a candy Mars is either a planet or a candy bar, Mercury is either a planet or a bar, Mercury is either a planet or a metal, and Pluto is either a planet or metal, and Pluto is either a planet or a cartoon dog. Moon most definitely a cartoon dog. Moon most definitely is not a planet.is not a planet.

QuestionQuestion

What is the closest Planet to the What is the closest Planet to the Sun?Sun?

(a) Mars(a) Mars

(b) Mercury(b) Mercury

(c) Earth(c) Earth

(d) Moon(d) Moon

(e) Pluto(e) Pluto

AnswerAnswer

(b) Mercury.(b) Mercury.

QuestionQuestion

Which of these takes the least time Which of these takes the least time to travel around the Sun?to travel around the Sun?

(a) Mars(a) Mars

(b) Mercury(b) Mercury

(c) Earth(c) Earth

(d) Moon(d) Moon

(e) Pluto(e) Pluto

AnswerAnswer

(b) Mercury.(b) Mercury.

Kepler’s LawKepler’s Law