Chapter 28.1 Tools of Astronomy Notes
Vocabulary:
- Refracting telescope
- Reflecting telescope
- Interferometry
- Spinoff
It is difficult to study the objects in our universe as they are so far away. In most cases, the only way to study them is by the radiation they emit.
Radiation
Electromagnetic spectrum arrangement of waves according to their wavelengths and frequencies.
- gamma Short wavelength High frequency
- x-rays
- ultravoilet radiation
- visible light
- infrared
- microwaves
- radiowaves Long wavelength Low frequency
Electromagnetic radiation spectrum song
mhttp://www.youtube.com/watch?v=bjOGNVH3D4Y&feature=related
Doppler Effect the change in frequency of a wave due to movement of the source of the wave.
Big Bang Theory
mhttp://www.youtube.com/watch?v=Tn35SB1_NYI&feature=related
Fun Science
mhttp://www.youtube.com/watch?v=LIvVzJ6KZpk
Wavelength are shortened as the source moves toward the observer and lengthened as the source moves away from the observer.
Short wavelengths are blue in color, long waves lengths are red in color.
What color would be the shift if a galaxy is moving away from Earth?
RED
Spectroscopy is the study of the properties of light that depend on wavelength.
Continuous spectrum includes
ROYGBIV
Optical Telescopes
| Type of telescope | Pros and cons | |
| Refracting | Uses lenses | Needs expensive lensesGlass lenses limit size |
| Reflecting | Uses mirrors | Best optical quality- no size limit |
Chromatic Aberration the property of a lens where different colors are not in focus at the same time
Detecting “Invisible” Light
| Type of telescope | Pros and cons | |
| Radio telescope | Uses antennae to capture incoming radio waves | Not affected by cloudsCan use 24 hours a dayCan detect cool clouds and gases |
| Space telescope | Orbit above Earth’s atmosphere | Produce clearer images than Earth telescopes |
| Special purpose | Examples X-ray telescope to study black holes Compton Gamma-Ray to study exploding stars | Can “see” objects outside of visible light spectrum |
Review video: NOVA Hunting the Edge of Space: Part 1
https://www.youtube.com/watch?v=sqwgpsXII0s
Chapter 29.4 Formation of Our Solar System
mhttps://www.youtube.com/watch?v=HEheh1BH34Q
Objectives:
- Summarize the properties of the solar system that support the theory of the solar system’s formation
- Describe how the planets formed from a disk surrounding the young sun
- Explore the remnants of solar system formation
Vocabulary:
planetessimal
asteroid
meteroid
meteor
meteorite
comet
coma
nucleus
meteor shower
A Collapsing Interstellar Cloud
Stars and planets formed from clouds of dust and gas called interstellar clouds. The clouds, consisting of mostly hydrogen and helium, are located in the space between stars.
The Nebular Theory states that the sun and planets formed from a rotating disk of dust and gases.
As the speed of the rotation increased, the center disk began to flatten concentrating matter in the center, where the sun eventually formed.
Sun and Planet Formation
The disk of dust and gas that formed the sun and planets is called the solar nebula. The dense concentration of gas at the center of the disk became the sun.
Temperature varied around the disk with the highest temperatures closet to the sun. As the disk began to cool, various elements began to condense according to their melting points.
The Growth of Objects
As condensing began to slow, solids and gases began to accrete (stick to together). Objects would collide and stick to form planetessimals hundreds of kilometers wide.
Merging of Planets
Jupiter was the first planet to form by gathering icy planetessimals. As Jupiter’s size increased, so did its gravity and it collected even more planetessimals. Saturn and the other gas giants did not reach Jupiter’s size as Jupiter had already accumulated most of the material by the time the other planets formed.
Debris
Eventually planetary debris thinned out as it accreted into planets or left the solar system.
Planetessimals between Mars and Jupiter remained and became known as the asteroid belt.
Asteroids
Pieces if asteroids
- meteoroid any piece of interplanetary material that falls toward Earth and enters Earth’s atmosphere
- meteor when it falls and produces light in Earth’s atmosphere by burning, it is called a meteor
- meteorite if ti does not completely burn, and parts collide with the Earth, it is called a meteorite
Meteor crater in Arizona
The crater is 50,000 years old. Why has it not eroded?
Chapter 30.2 Measuring Stars
Objectives:
- Describe star distribution and distance
- Classify the types of stars
- Summarize the interrelated properties of stars
Basic Properties of Stars
The basic properties of stars include
1. diameter
2. mass
Binary stars can be used to determine the stellar mass
3. brightness or magnitude
apparent magnitude is how bright the star appears to be from Earth.
Three factors control apparent brightness.
- how big the star is
- how hot the star is
- how far away the star is
absolute magnitude is the brightness a star would appear if placed at a distance of 10 pc. You must know the distance the star is from Earth on order to calculate the absolute magnitude
4. Luminosity energy output (power) energy output from the surface of a star per second
5. Surface temperature and composition
Surface temperature is determined by spectral class (color) in the following order: O, B, A, F, G, K, and M
6. Distance star is from Earth can be calculated using parallax
- The closer the star is to Earth, the greater the parallax
- You cannot use a parallax to measure the distance to all stars as some stars may be so far away that the parallax angle is too small to measure.
- It takes 6 months to measure a star by its parallax as you have to wait for the Earth to reach the maximum distances of its orbit
What relationship is shown on a Hertzsprung-Russell diagram?
Shows the relationships between the absolute magnitude and the temperature of stars.
Watch a short animation of the HR diagram.
What color stars are the hottest? Coolest?
Blue are the hottest
Red are the coolest
How do the stars on the left hand side of the diagram differ from stars on the right hand side of the diagram?
The stars on the left are the hottest, the stars on the right are the coolest
How do the stars on the top of the diagram differ from stars on the bottom of the diagram?
The stars toward the top are giant stars while the stars toward the bottom are smaller stars and dwarf stars
Use this link to answer 17 questions about the HR diagram.
Chapter 30.3 Stellar Evolution
Objectives:
1. What stage marks the birth of a star?
When the protostar reaches 10 million degrees K and nuclear fusion occurs. The star is “self-sufficient” and producing its own energy.
2. Why do all stars eventually die?
All stars eventually die because they run out of fuel
3. What stages make up the life cycle of a low, medium, and high mass star?
This chart lists the stages but does not include details you will be expected to know.
Video:
The Universe: The Life and Death of Stars
mhttp://www.history.com/shows/the-universe/videos/the-universe-life-and-death-of-a-star
http://www.history.com/shows/the-universe/videos/the-universe-life-and-death-of-a-star
Chapter 31.2 Other Galaxies in the Universe
Objectives:
- Describe how astronomers classify galaxies
- Identify how galaxies are organized into clusters and super clusters
- Describe the expansion of the universe
Describe how astronomers classify galaxies
Galaxies are classified according to their shapes.
How do galaxies get their shape?
http://www.discovery.com/tv-shows/other-shows/videos/how-the-universe-works-the-shape-of-galaxies/
Disk like galaxies with spiral arms are called spiral galaxies. They can be divided into two sub classes:
- normal spirals with no bar denotes as “S”
- barred spirals which have a central bar passing through the nucleus denoted as “SB”
Spiral galaxies are further divided by how tightly the spiral arms are wound as well as brightness of the nucleus.
“a” represents tightly wound arms and a large, bright nucleus
“c” represents loosely wound arms and a dim nucleus
“b” is somewhere in between a and b
Elliptical galaxies are divided into two subclasses based on the apparent ratio of their major and minor axes.
Round are classified as E0 and very long elliptical galaxies are classified as E7.
Some galaxies do not fit either pattern and are classified as irregular “Irr”
http://sings.stsci.edu/Publications/sings_poster.html
Describe the expansion of the universe
Hubble’s Law
Hubble determined that universe is expanding by graphing the velocity of various galaxies versus the distance.
The result was a straight line
Chapter 31.3 Cosmology
The Big Bang
http://www.discovery.com/tv-shows/other-shows/videos/other-shows-how-the-universe-works-videos/
Ch 31.3 Cosmology
Objectives
Sequence the events of the Big Bang Theory
- The universe began as a small, dense sphere
- It began to expand
- It is still expanding today at an ever increasing rate
Describe the Big Bang Theory
Know 3 pieces of evidence supporting the Big Bang Theory
- Cosmic background radiation (remember the unexplainable “heat” from the video)
- Doppler red shifts of neighboring galaxies
- Quasars Quasistellar Radio Sources (meaning “star-like radio sources”)
Quasars were once thought to be nearby stars but had unusual optical spectra.It was later found that the “stars” were not as close as previously believed and the large Doppler shift indicated they were moving at a fraction of the speed of light
Quasars are not stars but object emitting radiowaves
Interesting video:
Activities
Lab: Our expanding universe
Activity: Hubble’s Law worksheet
Conclusion questions:
1. Study the velocity of the galaxy closest to Earth to that of the galaxy . How do the velocities compare? What can you infer about the expansion of the galaxy?
2. The Milky Way galaxy shows a velocity of 0 km/sec. Does that mean our galaxy is the center of the universe and all expansion occurs from the Milky Way? Explain.
Ch 25.3 Study guide
11:20 am
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