ASTR 1120 ASTR 1120 General Astronomy: General Astronomy: Stars & Galaxies Stars & Galaxies Prof. Rosalba Perna TA:Thomas Rogers http://amalfi.colorado.edu/~rosalba/astro1120/astro1120.html MAKE SURE TO GO OVER THE SYLLABUS (if you haven’t already done so)
Goals of the day Goals of the day • This Course - basic info review • Order of Magnitude Astronomy – Reasonable estimates • Size Scales - getting used to astronomy • Light year – Measuring distances in astronomy
Who should take this course? Who should take this course? • No prerequisites, No prerequisites, • aimed at non-science non-science aimed at majors majors • No lab credit No lab credit • • Moderate amounts of Moderate amounts of • quantitative work quantitative work (algebra) (algebra) • More quantitative More quantitative • course – – ASTR 1040 ASTR 1040 course
MATH REVIEW SESSION : Will you attend it? A.YES B. NO In the process of coordinating with other classes
Course Information Course Information COURSE WEB PAGE: : COURSE WEB PAGE http://amalfi.colorado.edu/~rosalba/astro1120/astro1120.html You can find You can find announcements, announcements, assignments and assignments and handouts, lecture notes, handouts, lecture notes, and other useful things and other useful things there there Grades will be will be shown on shown on Grades CULearn CULearn
Required Text Required Text The Cosmic Perspective The Cosmic Perspective by Bennett et al., 2007, 5 by Bennett et al., 2007, 5 th ed th ed Includes: Includes: Access to textbook website Access to textbook website www.masteringastronomy.com .com , , www.masteringastronomy Ebook (animations, etc), and (animations, etc), and Ebook SkyGazer planetarium planetarium SkyGazer software. software. You will need your own own You will need your `masteringastronomy’ ’ account! account! `masteringastronomy it Course ID: ASTR11202009A Most homeworks homeworks require require it Most
How to succeed in this course How to succeed in this course • PUT IN THE TIME: 3 credits at CU = 6-9 hours outside of the classroom • Read the textbook • Read the textbook sections as assigned in sections as assigned in class, discuss with class, discuss with friends, do homeworks homeworks, , friends, do come to come to class class • Come see us during office hours!
Come talk with us Come talk with us • Prof. Rosalba Perna Rosalba Perna’ ’s s office hours: : • Prof. Tue: 1pm-2pm; Tue: 1pm-2pm; Th Th: 1pm-3pm in : 1pm-3pm in JILA Tower 506A (phone: 303-492- (phone: 303-492- JILA Tower 506A 0389) rosalba@colorado rosalba@colorado. .edu edu 0389) TA Thomas Rogers office hours: • • TA Thomas Rogers Wed, Fri: Wed, Fri: 2pm-3:30pm in Duane D1B31 2pm-3:30pm in Duane D1B31 (phone: 720-308-9382). (phone: 720-308-9382). Thomas.Rogers@colorado Rogers@colorado. .edu edu Thomas. • Or call or email (any of us) to make • Or call or email (any of us) to make an appointment! an appointment!
Observatory Nights Observatory Nights • Starting Wed Sept 2nd at 8:30pm, then about every 2 weeks • Sommers-Bausch Observatory (next to Fiske): 16” and 18” telescopes • Not mandatory, but you can get extra credit towards your grade (Fill out summary sheet available at observatory) • Signup required on CULearn website
Clickers Clickers GRADED clicker questions will start NEXT WEEK. Remember to bring your clicker to class always. Clicker questions TODAY UNGRADED .
Clicker Test Clicker Test • What class are you in? • A) Freshman • B) Sophomore • C) Junior • D) Senior • E) Other
Clicker Test Clicker Test • What is the nationality of your professor? • A) French • B) Spanish • C) Argentine • D) Italian • E) Greek
Reading Clicker Question Clicker Question Reading If the history of the entire universe was If the history of the entire universe was condensed into a single year single year, the earliest , the earliest condensed into a humans (hominids) would have appeared humans (hominids) would have appeared about: about: A. September 1 B. December 1 C. December 30 D. 9 p.m. December 31 (3 hours before year- end) E. 11:59:30 p.m. December 31 (30 seconds before year-end)
THE COSMIC CALENDAR THE COSMIC CALENDAR
Order of Magnitude Order of Magnitude Astronomy Astronomy • Astronomy frequently deals with very BIG numbers • When dealing with really big quantities, the small details become trivial – For example, when we say that the nearest galaxy is 2 million (2,000,000) light-years away, does it really matter if its actually 2,000,001? 2,000,100? – How far is it to drive from here to Los Angeles? (centimeters won’t matter…) What’s a factor of � between friends?
More on order of magnitude More on order of magnitude Astronomy Astronomy How many piano tuners are How many piano tuners are there in Boulder County? there in Boulder County? A. 2 B. 20 C. 200 D. 2000 E. Too many to count!
Start with known facts and known facts and Start with reasonable guesses guesses reasonable Population of Boulder County? – ~300,000 people • How many people have a piano? – 1 in 30? • Could be off but probably not by much! • How many pianos? – ~10,000 pianos in Boulder County • How often do you need to tune a piano? – Once a year?? 10,000 piano tunings/year
More reasonable estimates estimates More reasonable • How long does it take to tune a piano? – 3-4 hours? = 2 tunings per day 500 piano tunings 2 piano tunings x 5 days week x 50 weeks year = tuner day year 10,000 piano tunings year = 20 tuners piano tunings year 500 tuner
Scales in the Universe: Scales in the Universe: our Cosmic Address our Cosmic Address Earth Sun/Solar System Milky Way Galaxy Local Group Local Supercluster
Scale models of the Universe Scale models of the Universe • Scale Sun as a grapefruit (1:10,000,000,000)
What about distances from the Sun on the same scale? • Earth = tip of ball point pen, 15 meters (49 feet) – Moon = 4 cm away from earth • Mars = tip of ball point pen, 23 meters (75 feet) • Jupiter = marble, 78 meters (255 feet)
Moving out of the solar system Moving out of the solar system • On this scale, the nearest stars would be a system formed by a cantaloupe, a small apple and a kiwi fruit, located in the middle of Alaska Alaska (with solar system in Boulder) • There is essentially nothing in between!!
New Scale for the Galaxy: Scale for the Galaxy: New • Stars are microscopic - located a few mm apart • Milky Way galaxy is 100 meters in diameter, contains 100,000,000,000’s (100’s of billions) of stars 1 to 10^19 scale - MW=100 m 3000 yr to counts all the stars in the MW, one per second Solar system: dot ~20 meters away from center
Yet Another Scale for Everything Scale for Everything Yet Another Else Else • Galaxies are 10” paper plates • Milky Way and nearest neighbor Andromeda) are 5 meters apart • Galaxy groups and clusters contain 10’s to 1000’s of galaxies
• Superclusters 50 meters across (size of buildings in our scale model) are the largest structures we see • Observable universe is about In this image, each dot is an entire size of Boulder galaxy county on this scale
Which of these are the most Which of these are the most likely? likely? A. Two planets colliding B. Two stars colliding C. Two galaxies colliding D. None of the above… there’s too much space!
Measuring cosmic distances Measuring cosmic distances • Most useful measure is based on the speed of light = 300,000 km/sec – Light-year = the distance light travels in a year = ~ 10 trillion kilometers = 10 16 m • Like saying “I live 30 min from Boulder” • Constant speed for light traveling in space • Nothing travels faster through space
Clicker Question Light-year: which of the following Light-year: which of the following sentences makes sense? (the sentences makes sense? (the others are nonsense) others are nonsense) A. We’ll wait light-years before Mars is as close as it is tonight. B. The Galileo spacecraft has traveled 30 light- years since its launch in 1989. C. The globular cluster M13 is located 16,000 light- years away from Earth. D. The next generation of the Space Shuttle will be able to travel 1.3 times the speed of light.
Not A: light-years measure distance, not time. Not B: Light travels 1 light-year in 1 year. Nothing travels faster than light! C: correct! Not D: Same as B. Nothing can travel faster than the speed of light.
Measuring Distances with Light: Measuring Distances with Light: • Earth-Moon = 1.5 light-seconds • Earth-Sun (a.k.a. astronomical unit, or AU) = 8 light-minutes • Solar system = light-hours
• Nearest stars = several light-years • Milky Way= 100,000 light-years = 10 5 ly – Galactic Center is 28,000 light-years away • Local group = several million light-years =10 6 ly • Observable universe = 14 billion light-years = 1.4 x 10 10 ly
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