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.
- 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
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. -
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 2.5x106ly 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
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
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
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.
Check out your good friend Ringo Dingrando! He loves Astrophysics as well.
E.1.1Outline the general structure of the solar system.
NASA Site – Tons of great stuff here, just got to look.
- What is the solar system?
- What are planets?
- What shape are their orbits?
- How are the planes of their orbits orientated?
- In what order are the planets?
- DisregardingPluto, 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.
- What are moons?
- What are comets?
- How do their orbits differ from the orbits of the planets?
- What is, and where is the asteroid belt?
- Give one theory for its formation.
E.1.2Distinguish 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 bothappear tobe groups of stars close to each other in the sky, why arethey different?
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
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
- Text Book web site
- 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?
- 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.
A simple PPT
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