Astronomy C12, Earth & Planetary Science C12, Letters & Science C70 The Planets Prof. Geoff Marcy Prof. Michael Manga Saturn’s Moon, Dione Saturn & Ring Tu, Th 11-12:30 am LeConte 4
Professors Michael Manga 177 McCone Hall firstname.lastname@example.org (office hours MWF 11:15-12:00) Geoff Marcy 417 Campbell Hall email@example.com (office hours T,Th, 1pm) Departments of Earth & Planetary Science and Astronomy GSIs: Gilead Wurman firstname.lastname@example.org Alyssa Sarid email@example.com Shuleen Martin firstname.lastname@example.org Jim Watkins email@example.com 8 Discussion Sections 1 hr each (Start Next 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
Announcements • No discussion sections this week • Read Ch 1 of the text this week; Ch 2 by next • First Homework Assignment: posted Friday.
Last Time :: The Solar System
The Solar System Inner Solar System Outer Solar System
Overview Our place in the Universe 13 billion Light Years
The Solar System:Sun and 8 PlanetsMoons, Asteroids, Comets, and Dust
Milky Way Galaxy 200 Billion Stars Photo taken from Earth You Are Here
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.
The ``Local Group” of Galaxies 100,000 Light Years The Galactic Neighborhood
And outward… 10 Million Light Years
The Universe: All matter and energy > 100 Billion Galaxies
Exponential notation is handy: 10N x 10M = 10(N+M) Astronomical Numbers Best to use Exponential Notation 103 = 1000 Thousand 106 = 1,000,000 Million 109 = 1,000,000,000 Billion Also: 10–3 = 1/1000 = 0.001 Example: 103 x 106 = 109 thousand million billion
How many stars in our visible Universe? 106 (1 million) 1012 (1 million million 1018 (1 billion billion) 1022 infinite
The National Debt is $7.6 Trillion Federal Debt = $7.6 x 1012 U.S. Population = 300 x 106 Calculate Your Debt: $7.6 x 1012 / 3 x 108 = $2.5 x 104 Trillions of Dollars $25,000 per person 02 03 04 05 Debt Total
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 0.5 x 10–10 m 1 x 10–14 s 4.7 x 1017 s = 14 billion years
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
$Billion error 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)
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 miles Light Hour Light Minutes are unit of Distance: How far Light Travels in that interval of time 1 light second = 3 x 105 km 1 light ns = 30 cm ≈ 1 foot
NASA/JPL/Cornell Driving the Mars Exploration Rovers (MER) • How long does it take to communicate with the rovers?
How long does it take for radio waves (light) to reach Mars? • Less than 1 second • 10 seconds • 5 minutes • 1 day • 1 year
How to deal with very large & small numbers • Develop a useful arithmetic • Exponential notation; convert between units • Visualize using a sequence of images (movie) • Use different sequences • Visualize by way of a scale model • Try different models
A Scaled Model of the Solar System 10 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 km 1010 Scaled Down “Sun” 14cm 1 AU ?? cm 0.15 cm 1.5 cm 15 cm 150 cm 1500 cm Ans: 1500 cm = 15 meters
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
You Are Here: Earth’s Orbit Uranus o Saturn o Jupiter o . 100 m Neptune o
How Far is the Nearest Star? Nearest Grapefruit: In Washington D.C. Alpha Centauri Grapefruit-sized Sun in Berkeley Scales to: 4 x 106 m (~ 3000 mi) d = 4 light years = 4 x1016 m
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
Key Issues So Far: • 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?
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 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 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!
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.
You Are Here: Earth’s Orbit Saturn o Uranus o Jupiter o . Neptune o 100 m
How Far is the Nearest Star? Alpha Centauri d = 4 light years = 4 x1016 m Scales to: 4 x 106 m (~ 3000 mi) Grapefruit-sized Sun in Berkeley Nearest Grapefruit: In Washington D.C.