Astronomy C12, Earth & Planetary Science C12, Letters & Science C70 The Planets Saturn’s...

Astronomy C12, Earth & Planetary Science C12, Letters & Science C70

The PlanetsThe Planets

Saturn’s Moon, Dione

Saturn & RingQuickTime™ and a

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Prof. Geoff Marcy

Prof. Michael Manga

Tu, Th 11-12:30 amLeConte 4

ProfessorsMichael Manga 177 McCone Hall manga@seismo.berkeley.edu

(office hours MWF 11:15-12:00)

Geoff Marcy 417 Campbell Hall gmarcy@berkeley.edu (office hours T,Th, 1pm)Departments of Earth & Planetary Science and AstronomyDepartments of Earth & Planetary Science and Astronomy

GSIs:Gilead Wurman gwurman@seismo.berkeley.eduAlyssa Sarid alyssa@eps.berkeley.eduShuleen Martin smartin@astron.berkeley.eduJim Watkins jwatkins@berkeley.edu

8 Discussion Sections 1 hr each (Start Start NextNext Week) Week)

Review, Clarification, Homework Help Sign up for Section on Telebears

Text: The Cosmic Perspective

Bennett et al. (2008) 5th Edition(Also: Used 4th Edition)

Web Site on bspace: http://bspace.berkeley.edu

• Syllabus, Schedule & Lecture Figures• Assignments: Reading, Homework, Observing Project• Class Information

Homework: 50% of your grade

• 12 assignments during semester

• Most questions from your text

• The Astronomy Learning Center (TALC): • 264 Evans Time: Wed @ 6pm

• First homework set available Friday

• Due by Friday Feb 1

• Turn in HW every Friday at noon: • Box labeled Astro/EPS 12 in the basement of Campbell Hall.

Homework:

• You are encouraged to work together, but MUST turn in your own work, in your own words

• The graders can recognize copying, and answers found with Google

• Refer to the Berkeley Code of Student conduct if you are unclear about what constitutes cheating or plagiarism

AnnouncementsAnnouncements

• No discussion sections this week

• Read Ch 1 of the text this week; Ch 2 by next

• First Homework Assignment: posted Friday.

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The Solar SystemThe Solar System

Inner Solar System Outer Solar System

Our place in the Our place in the UniverseUniverse

Overview

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13 billionLight Years

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The Solar System:The Solar System:

Sun and 8 PlanetsSun and 8 Planets Moons, Asteroids, Comets, and DustMoons, Asteroids, Comets, and Dust

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Milky Way Galaxy

You Are Here

200 Billion StarsPhoto taken from Earth

Our Sun moves relative to the other stars in the local Solar neighborhood.

Our Sun and the stars orbit around the center of the Milky Way Galaxy every 230 million years.

Spiral Galaxies

Elliptical Galaxies

Irregular Galaxies

The Galactic The Galactic NeighborhoodNeighborhood

100,000 Light YearsThe ``Local Group”The ``Local Group”of Galaxiesof Galaxies

The ``Local Group’’The ``Local Group’’of Galaxiesof Galaxies

And outward…10 Million Light Years10 Million Light Years

The Universe:The Universe:All matter and All matter and

energyenergy

> 100 Billion Galaxies

Astronomical Numbers Astronomical Numbers

Best to use Exponential Notation

Exponential notation is handy:

10N x 10M = 10(N+M)

103 = 1000 Thousand106 = 1,000,000 Million109 = 1,000,000,000 Billion

Also:

10–3 = 1/1000

= 0.001

103 x 106 = 109 thousand million billion

Example:

How many stars in our visible Universe?

a) 106 (1 million)

b) 1012 (1 million million

c) 1018 (1 billion billion)

d) 1022

e) infinite

The National Debt is $7.6 Trillion

U.S. Population = 300 x 106

$7.6 x 1012 / 3 x 108 =$2.5 x 104

$25,000 per person

= $7.6 x 1012

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Calculate Your Debt:

Federal DebtT

rillio

ns o

f D

olla

rs

Debt Total

02 03 04 05

Distance, time and number :

Radius of our Galaxy:6,000,000,000,000,000,000 m =

Radius of a Hydrogen atom:0.00000000005 m =

Time for one vibration of an oxygen molecule, O2:

0.00000000000001 s =

Age of the Universe:470,000,000,000,000,000 s =

Scientific notation: 6 x 1018 m

1 x 10–14 s

4.7 x 1017 s = 14 billion years

0.5 x 10–10 m

SI (Systeme International) Units

Base units: 1 meter (m) length ~ 3.3 ft

1 kilogram (kg) mass ~ 2.2 lb

1 second (s) time

MKS System of units and measure

SI (Systeme International) Units

Base units: 1 meter (m) length

1 kilogram (kg) mass

1 second (s) time

MKS System of units and measure

Sometimes easier to derive other units from these:

km, g, ms, µs, … km = 103 m kilo

g = 10-3 kg kilo

ms = 10-3 s milli

µs = 10-6 s micro

UNITS ARE IMPORTANT!!!UNITS ARE IMPORTANT!!!

Mars Climate Orbiter: Launch: 11 Dec. 1998

Orbit insertion: 23 Sep. 1999

Followed by: Loss of Communication

WHY?

Failed to convert from English units (inches, feet, pounds) to Metric units (MKS) $$Billion errorBillion error

Light takes time to travel:Light takes time to travel:

3 x 108 m/sec

= 3 x 105 km/sec

= 0.3 m/ns (1 ns = 10-9 s)

Light Year = 9 trillion km = 6 trillion milesLight Year = 9 trillion km = 6 trillion milesLight HourLight HourLight Minutes are unit of Distance: Light Minutes are unit of Distance:

How far Light Travels in that interval of timeHow far Light Travels in that interval of time1 light second = 3 x 101 light second = 3 x 1055 km km1 light ns = 30 cm ≈ 1 foot1 light ns = 30 cm ≈ 1 foot

Driving the Mars Exploration Rovers (MER)

• How long does it take to communicate with the rovers?

NASA/JPL/Cornell

How long does it take for radio waves (light) to reach Mars?

a) Less than 1 second

b) 10 seconds

c) 5 minutes

d) 1 day

e) 1 year

Powers of TenPowers of Ten“Cosmic Voyage”“Cosmic Voyage”

The MovieThe Movie

How to deal with very large & small numbersHow to deal with very large & small numbers

•Develop a useful arithmeticExponential notation; convert between units

•Visualize using a sequence of images (movie)Use different sequences

•Visualize by way of a scale modelTry different models

A Scaled Model of the Solar SystemA Scaled Model of the Solar System

10 Billion x Smaller10 Billion x Smaller

Sun’s diameter: 14 x 1010 cm (~ 106 miles)

Scale 1010: 14 cm

Earth diameter: 1.3 x 104 km 0.13 cm

Jupiter’s diameter: 150,000 km 1.5 cm

Earth’s distance from Sun: 1 “Astronomical Unit” = 1 “AU”

= 1.5 x 108 km1 AU ?? cm

Ans: 1500 cm = 15 meters

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1010 Scaled Down

“Sun”

a) 0.15 cmb) 1.5 cmc) 15 cmd) 150 cme) 1500 cm

How large is the Solar System?• Let’s view it to scale

– say the Sun is the size of a large grapefruit, 15 cm (6 inches) - then:

Planet dist (AU) Scaled dist (m) Where?

Mercury 0.4 6 6 rows back

Venus 0.7 10 10 rows

Earth 1.0 15 15 rows

Mars 1.5 22 22 rows

Jupiter 5 75 3/4 football field away

Saturn 10 150 1.5 football field away

Uranus 20 300 Sproul Plaza

Neptune 30 450 Bancroft Ave

Pluto 50 750 Durant Ave

Oort Cloud 50,000 5 x 105 Oakland

.

100 m

SaturnSaturn

oo

UranusUranus oo

NeptuneNeptune oo

JupiterJupiter o

You Are Here:You Are Here:Earth’s OrbitEarth’s Orbit

How Far is the Nearest Star?

Grapefruit-sizedSun in Berkeley

Nearest Grapefruit:

In Washington D.C.

Alpha Centauri

d = 4 light years = 4 x 1016 m

Scales to:4 x 106 m(~ 3000 mi)

How old is the Universe?

• The Cosmic Calendar– if the entire age of

the Universe were one calendar year

– one month would be approximately 1 billion real years

• What does our solar system look like when viewed to scale?

• How far away are the stars?

• How do human time scales compare to the age of the Universe?

Key Issues So Far:

TODAY’S LECTURE

• Solar System Resides within our Milky Way Galaxy

• Ranges of distances and time are huge.

• Exponential notation and models are a real Help!

• Distance Units:

1 Astronomical Unit (AU) = Earth - Sun Distance

= 93 million miles

= 150 million km

What is the origin of the Universe?• The two simplest atoms (H and He) were created

during the Big Bang.• More complex atoms were created in stars.• When the star dies, chemical elements are expelled

into space…. to form new stars and planets!

Most of the atoms in our bodies were created in the core of a star!

The Universe in a DayThe Universe in a Day 

Look at the entire history of the Universe as though it took place in a single day. The present is at the stroke of midnight at the end of that day. Since it is about 13.5 billion years old, each hour will be ~0.5 billion years. A million years takes only a little over 7 seconds.

The Big Bang (a dense, hot explosion) and the formation of H and He all take place in the first nanosecond. The Universe becomes transparent in about 2 seconds. The first stars and galaxies appear after about 2am.

Our Galaxy forms at 4am. Generations of stars are born and die.

The Universe in a DayThe Universe in a Day 

The Solar System does not form until 3pm. The first life (bacterial) appears on the Earth by 4pm. Our atmosphere begins to have free oxygen at 7 or 8 pm, and this promotes the development of creatures which can move more aggressively and eat each other. Life does not begin to take on complex forms (multicellular) until 10:45pm. It moves onto land at 11:10. The dinosaurs appear at about 11:40, and become extinct at 11:52. Pre-human primates appear at around 14 seconds before midnight, and all of recorded history occurs in the last 70 milliseconds.

Looking to the future, we can expect the Universe of stars to go on for at least another millennium (using the same time compression factor). After that, there are other ages of the Universe (not dominated by stars), which grow colder and more bizarre, and take place on astronomical timescales…

The Earth orbits around the Sun once every year!

The Earth’s axis is tilted

by 23.5º!

What is the Earth’s velocity about the Sun?

Radius of Orbit (1 AU): 150 x 106 km

Circumference: 2 π x radius

Distance around the Sun that the Earth travels:

2 π x (1.5 x 108 km) = 9 x 1011 m

Earth orbits the Sun once a year:

1 yr = 3 x 107 s

Velocity = Distance/Time = 9 x 1011 m / 3 x 107 s

= 3 x 104 m/s = 30 km/s

110,000 km/hr or 75,000 miles/hr!110,000 km/hr or 75,000 miles/hr!

A Universe in motion• Contrary to our perception, we are not “sitting still.”

• We are moving with the Earth.– and not just in one direction

The Earth rotates around it’s axis once every day!

Looking back in time• Light, although fast, travels at a finite speed.• It takes:

– 8 minutes to reach us from the Sun– 8 years to reach us from Sirius (8 light-years away)– 1,500 years to reach us from the Orion Nebula

• The farther out we look into the Universe, the farther back in time we see!

The Milky Way moves with the expansion of

the Universe! • Mostly all galaxies

appear to be moving away from us.

• The farther away they are, the faster they are moving.– Just like raisins in a raisin

cake; they all move apart from each other as the dough (space itself) expands.

.

100 m

SaturnSaturn

ooUranusUranus oo

NeptuneNeptune oo

JupiterJupiter o

You Are Here:You Are Here:Earth’s OrbitEarth’s Orbit

How Far is the Nearest Star?

Grapefruit-sizedSun in Berkeley

Nearest Grapefruit:

In Washington D.C.

Alpha Centauri d = 4 light years = 4 x 1016 m

Scales to:4 x 106 m(~ 3000 mi)