Download Topic E: Astrophysics E1 Introduction to the Universe.

Topic E: Astrophysics
E1 Introduction to the Universe.
E.1.1 - Outline the general structure of the solar system.
 Students should know that the planets orbit the Sun in ellipses and moons orbit planets.
(Details of Kepler’s laws are not required.) Students should also know the names of the
planets, their approximate comparative sizes and comparative distances from the Sun, the
nature of comets, and the nature and position of the asteroid belt.
http://solarsystem.nasa.gov/planets - Tons of interesting stuff about our solar system
Planets
 Aug. 2006 the International Astronomical Union declared the official definition of a
planet:
 A “planet” is a celestial body that:
a) is in orbit around the _____________________
b) has sufficient mass for its self-gravity to overcome rigid body forces so that is assumes a
hydrostatic equilibrium (__________________________________ )
c) has cleared the neighborhood around its orbit.
Our Solar System
 8 Planets – name them….
 Elliptical orbits – to have a circular orbit an object must have a very specific ________________. Any
variations create and elliptical or hyperbolic shape
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 Moons
 Period - 27.3 days
 Which planets have them???? _________________________
 Phases of the moon
 Asteroids
 belt between Mars and Jupiter
 size – ____________ to hundreds ___________________
 Comets
 Similar to asteroids but made up of ____________________ particles of ice and rock.
 ________________ is blown off by solar winds and melted by radiation.
 Some orbit, others only pass the sun once
 Planetoids???
 Pluto….
 Relative size video. - http://www.youtube.com/watch?v=Dv6OtEnIAQk
E.1.3 - Define the light year.
 Light year (ly) – the distance that a beam of light will travel in one year.
 How far is that? (3 x 108m/s = c)
_________________________
 Used to measure distances _____________________ of our solar system
Other important units.
 Astronomical unit (AU) – the average distance between the Sun and Earth
 1AU = 1.5 x 1011m
 Used to measure distances ____________________our solar system
 Parsec (pc) – 1parsec = __________________ ly
 Defined by making a triangle between the Earth, the Sun and a distant object. If the angle at the
distant object is 1 arcsec then it would be 1 parsec away. (more later)
E.1.2 - Distinguish between a stellar cluster and a constellation
E.1.4 - Compare the relative distances between stars within a galaxy and between galaxies, in
terms of order of magnitude.
Distribution of stars
 Stars are not evenly distributed.
 Stellar _____________________ – small groups of stars that gravitationally interact with one another.
 Physically close to each other
 Closest star, besides the sun is Proxima Centauri - ______________ly
 Galaxy – a very large number of stars bound together by gravity
 Trillions of stars
 ______________________ light years across
 Each star is approx. 1 ly apart
 ______________________ is about 2.5x106 ly away
 Galaxy cluster – small group of galaxies that gravitationally interact with one another
 There are about 20 other galaxies we are clustered with.
 Supercluster – bigger than a cluster
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How did galaxies get that way?
 The simplest explanation is that
 if all the gas is made into _____________________ before the gas has time to form a disk, then you get an
elliptical galaxy.
 if the gas has time to _________________ into a disk before it is all used up, then you get a spiral galaxy.
 Or perhaps some of the elliptical galaxies are made from merging of other types of galaxies.
 Observations of distant galaxies indicates that spiral galaxies were more common in the past than
they are today.
 So maybe yesterday's spirals are todays ____________________.
 This is an active research area. One problem is that if most of the mass in galaxies is unaccounted for,
we have a hard time understanding the dynamics of galaxy formation.
 ________________________ – groups of stars that are “linked” visually
 Ancient civilizations played “connect the dots”
 Located in the same general direction from Earth
 Not necessarily close to each other
 __________________
 Different ones are visible at different times during the year.
E.1.5 - Describe the apparent motion of the stars/constellations over a period of a night and over a
period of a year, and explain these observations in terms of the rotation and revolution of the
Earth.
This is the basic background for stellar parallax. Other observations, for example, seasons and the
motion of planets, are not expected
 Why do the stars move through the night sky?
 Because the rotation of the _______________
 It also matters where you are located on Earth
 Ex. North Pole
 http://www.yorku.ca/ns1745b/figs-ch1.html
 This rotation takes ________h and _______min every time.
 The effect is that it seams that the stars position at 12:00 changes each night.
 This means that the Earth rotates 360º in 23h and 56min.
 Which means 4min it will rotate _________º.
 Which means it only takes 360 DAYS for the constellations to make one compete rotation.
Sun rise
 The Sun doesn’t make the same path through sky every day.
 For us, the summers are ______________in the sky, winters are ___________ on the horizon.
 This is because the axis of rotation for the Earth and the axis in which we orbit around the sun aren’t
the same angle.
Precession
 The Earth is not a perfect _________.
 This means that depending on it’s location in it’s orbit, it will feel more or less pull from the Sun
 This pulls on the Earths axis of rotation and makes it wooble.
 This is technically called _______________.
 This means that the “North Star” won’t always be the north star.
 Period – _________________ years
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Other plant’s movement
 The word planet comes from the Greek word for ________________.
 Planets will shift back and forth in the night sky relative to the constellation background.
 Apparent ________________________ motion comes from the Earth’s orbit around the sun.
 See Diagram on board
 Apparent _____________________ motion come from the other planet’s orbital plane being at a different
angle from ours.
Name _______________________ Date __________ Block ___
Option E.1: Astrophysics
Introduction to the universe
E1 Intro to the Univers
General overview
Start off with a little perspective of how we fit in with the rest of the universe. Check out this
video. http://www.youtube.com/watch?v=Dv6OtEnIAQk
Check out your good friend Ringo Dingrando! He loves Astrophysics as
well. http://www.youtube.com/watch?v=_90_wmXw_E8&list=PL7FD7F1082F45C268&inde
x=1
E.1.1Outline the general structure of the solar system.
NASA Site – Tons of great stuff here, just got to look.
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mars
1. What is the solar system?
2. What are planets?
3. What shape are their orbits?
4. How are the planes of their orbits orientated?
5. In what order are the planets?
6. Disregarding Pluto, which was probably not formed with the other planets, how could you group the
remaining 8 into two groups? Give three properties of these groups.
7. What are moons?
8. What are comets?
9. How do their orbits differ from the orbits of the planets?
10.
What is, and where is the asteroid belt?
11.
Give one theory for its formation.
E.1.2 Distinguish between a stellar cluster and a constellation
Pg 917 (Giancoli) / Ringo / Nothing Nerdy
The Pleiades is a stellar cluster, but the Great Bear is a constellation. They both appear to be groups of stars
close to each other in the sky, why are they different?
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E.1.3 Define the light year.
Pg 915 (Giancoli) / Ringo / Nothing Nerdy
What is an AU? Can you convert between an AU and a ly with out using an online converter?
How many AU are in 3.2ly? How many meters are in 3.2ly?
E.1.4 Compare the relative distances between stars within a galaxy and between galaxies, in terms of
order of magnitude.
Pg 915, 918 table 33-1 (Giancoli) / Ringo / Nothing Nerdy
http://scaleofuniverse.com - look at the relative size of objects
- Navigate to the "Observable Universe" tab at the top. Zoom in to the Earth on the
far left and work your way to the right. Notice that the Milky Way is that band of
white that you see in the night sky. When you get to the "Local Galactic Group" try
and find Ursa Minor and Ursa Major. You probably know these as being part of the
big and little dippers. Now try and find the Andromeda Galaxy. That is the closest
galaxy to us.
- Navigate to the "The Scale of the Universe" tab at the top. Zoom in and find
the smallest distance, zoom out and find the largest distance.
How close is the average distance between stars?
What is the closest star? How far is it in terms of km? ly? AU?
What is the closest galaxy? How far way is it in terms of km? ly?
How wide is a star? How about a galaxy?
E.1.5 Describe the apparent motion of the stars/constellations over a period of a night and over a period
of a year, and explain these observations in terms of the rotation and revolution of the Earth. ***Special
Note*** This is the basic background for stellar parallax. Other observations, for example, seasons and
the motion of planets, are not expected.
Ringo / Nothing Nerdy
http://physics.weber.edu/schroeder/ua/StarMotion.html - Text Book web site
1. Why do the stars appear to move in heavenly circles around the North Star (Polaris)
throughout the night? How long do they take to go around once?
2. Why do nearby stars appear to change position over a 12 month period?(This will
lead you onto knowing what parallax is)
Other Possible Resources:
An amazing collection of resources at your finger tips, just reach out and touch them.
http://physicspedagogics.pbworks.com/w/page/34408432/Option%20E%20%20Astrophysics#Topicpowerpointsnbsp
A simple PPT
http://www.docstoc.com/docs/112343337/Astrophysics-E1-Introduction-to-the-UniverseIB-Physics-HL-Dublin
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