stars, galaxies & the electromagneti c spectrum 4.f. describe the hierarchical structure (stars,...
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Stars, Galaxies & The Electromagnetic Spectrum
4.f. Describe the hierarchical structure (stars, cluster, galaxies, galactic clusters) of the universe & examine the expanding universe to include its age & history & the modern techniques (e.g. radio, infrared, ultraviolet & x-ray astronomy) used to measure objects & distances in the universe. (DOK 2)2.e. Contrast various components of the electromagnetic spectrum (e.g. infrared, visible light, ultraviolet) & predict their impacts on living things. (DOK 2)
Vocabulary Words – Chapter 4 & 211. Electromagnetic wave2. Electromagnetic radiation3. Electromagnetic spectrum4. Radio waves5. Microwaves6. Radar7. Infrared rays8. Visible light9. Ultraviolet rays10.X-rays11.Gamma rays12. Incandescent light13.wavelength
14.Spectrum15.Constellation16.Light-year17.Apparent brightness18.Absolute brightness19.Spectrograph20.Parallax21.Hertzsprung-Russell
diagram22.Main sequence23.Open cluster24.Globular cluster25.Galaxy26.Milky Way27.Universe
Definitions 1. Electromagnetic wave – transverse waves that transfer
electrical and magnetic energy2. Electromagnetic radiation – the energy transferred through
space by electromagnetic waves3. Electromagnetic spectrum – the complete range of
electromagnetic waves placed in order of increasing frequency4. Radio waves – electromagnetic waves with the longest
wavelengths and lowest frequencies5. Microwaves – radio waves with the shortest wavelengths and
the highest frequencies6. Radar – a system that uses reflected radio waves to detect
objects and measure their distance and speed7. Infrared rays – electromagnetic waves with wavelengths
shorter than radio waves, but longer than visible light
Definitions 8. Visible light – electromagnetic waves that are visible to the
human eye9. Ultraviolet rays – electromagnetic waves with wavelengths
shorter than visible light, but longer than x-rays10. X-rays – electromagnetic waves with wavelengths shorter than
ultraviolet rays, but longer than gamma rays11. Gamma rays – electromagnetic waves with the shortest
wavelengths and highest frequencies12. Incandescent light – light bulb that glows when a filament inside it
gets white hot13. Wavelength – the distance between the crest of one wave and the
crest of the next wave14. Spectrum – the range of wavelengths of electromagnetic waves15. Constellation – an imaginary pattern of stars in the sky
Definitions 16. Light-year – the distance that light travels in one year, about
9.5 trillion kilometers17. Apparent brightness – the brightness of a star as seen from
Earth18. Absolute brightness – the brightness a star would have if it
were at a standard distance from Earth19. Spectrograph – an instrument that separates light into colors
and makes an image of the resulting spectrum20. Parallax – the apparent change in position of an object when
seen from different places21. Hertzsprung-Russell diagram – a graph relating the surface
temperatures and absolute brightness of stars22. Main sequence – a diagonal area on a H-R diagram that
includes more than 90% of all stars
Definitions 23.Open cluster – a star cluster that has a loose,
disorganized appearance and contains no more than a few stars
24.Globular cluster – a large, round, densely-packed grouping of older stars
25.Galaxy – a huge group of single stars, star systems, star clusters, dust and gas bound together by gravity
26.Milky Way – a spiral galaxy that contains our solar system
27.Universe – all of space and everything in it
The electromagnetic spectrum (EM spectrum) The complete range of electromagnetic
waves placed in order of increasing frequency
Made up of radio waves, infrared rays, visible light, UV rays, x-rays, and gamma rays
Electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light
Speed = wavelength x frequency Wavelength – the distance between the
crest of one wave and the crest of the next wave
Frequency – the number of occurrences of a repeating event per unit of time
The speed of all electromagnetic waves is the same Wavelength decreases, frequency increases Wavelength increases, frequency decreases
Waves with long wavelengths have lower frequencies
Waves with shorter wavelengths have higher frequencies
The amount of energy carried by an electromagnetic wave increases with frequency The higher the frequency of a wave, the
higher its energy
Parts of the EM Spectrum1. Radio waves
Electromagnetic waves with the longest wavelengths and lowest frequencies
Includes: 1. Broadcast waves
Radio and TV waves Longer wavelengths
2. Microwaves Shorter wavelengths Cellular devices Radar
Parts of the EM Spectrum2. Infrared rays
Electromagnetic waves with wavelengths shorter than those of radio waves
If you turn on a burner on an electric stove, you can feel it warm up before the heating element starts to glow
The invisible heat you feel is infrared rays Have a higher frequency than radio waves, so they have
more energy You feel the energy as heat Examples:
1. Heat lamps2. Infrared cameras
Thermograms
3. Visible light Shorter wavelengths and higher
frequencies than infrared rays Electromagnetic waves that you can see Only make up a small part of the EM
Spectrum
Visible lightVisible light waves with the longest
wavelengths appear redAs the wavelengths decrease, you can see
other colors of lightThe shortest wavelengths of visible light
appear violet in colorColors in order of longest wavelength to
shortest wavelength Red, orange, yellow, green, blue, violet
4. Ultraviolet rays (UV rays) Electromagnetic waves with
wavelengths just shorter than those of visible light
Higher frequencies than visible light, so they carry more energy
The energy of UV rays is great enough to damage or kill living cells
UV lamps are often used to kill bacteria on hospital equipment
UV rays Small doses of UV rays are useful
Example: UV rays cause skin cells to produce vitamin D, which is needed for healthy bones and teeth However, too much exposure to UV rays is
dangerous UV rays can burn your skin, cause skin
cancer, and damage your eyes Wear sunscreen to block UV rays
5. X-rays Electromagnetic waves with
wavelengths just shorter than those of UV rays
Higher frequency than UV rays, so they carry more energy
They can penetrate through most matter
X-rays Bone and lead are considered dense
matter They absorb x-rays and do not allow them
to pass through X-rays are used to make images of bones
inside the body or of teeth
X-rays Too much exposure to x-rays can cause
cancer If you’ve ever had a dental x-ray, you’ll
remember that the dentist gave you a lead apron to wear
The lead prevents the x-ray from reaching your body
X-rays are also used in industry and engineering
6. Gamma rays Electromagnetic waves with the shortest
wavelengths and highest frequencies Greatest amount of energy Some radioactive substances and certain
nuclear reactions produce gamma rays Can be used to kill cancer cells inside the
body Some objects in space give off bursts of
gamma rays, but they are blocked by Earth’s atmosphere
Discussion Questions1. Why are shorter
wavelengths more damaging than longer wavelengths
2. Does exposure to any type of energy on the EM Spectrum cause cellular damage? Why or why not?
3. Which wavelengths are visible to the human eye and which are not?
4. Which part of the EM Spectrum has the shortest wavelengths?
5. What is the order of visible light from longest wavelengths to shortest?
6. How are wavelengths and frequency related?
7. How are frequency and the amount of energy present related?
8. What is the best way to avoid skin cancer?
9. How do we feel the energy of infrared rays?
The Universe4.f. describe the hierarchical structure of the universe and examine the expanding universe to include its age and history and the modern techniques used to measure objects and distances in the universe (DOK 2)
Hierarchical structure of the universe Smallest to largest
1. Stars2. Clusters3. Galaxies4. Galactic clusters
Classifying stars Characteristics used to classify stars
include:1. Color 2. Temperature3. Size4. Composition5. Brightness
Color and temperature If you look at the night sky, you can see
slight differences in the colors of the stars Example:
Betelgeuse (BAY tul jooz), the bright star in Orion’s shoulder, looks reddish
Rigel, the star in Orion’s heel, is blue-white
Color and temperature Like hot objects on Earth, a star’s color
reveals its surface temperature If you watch a toaster heat up, you can see
the wires glow red-hot The wires inside a light bulb are even hotter
and glow white Similarly, the coolest stars appear reddish in
the sky The hottest stars appear bluish Medium temperature stars appear yellow
Size When you look at stars in the sky, they all
appear to be points of light of the same size
Many stars are about the same size of the sun, which is a medium sized star
Some stars are much larger than the sun Very large stars are called giant stars or
supergiant stars Giant stars are 10 to 100 times larger than the
sun
Size If the supergiant star Betelgeuse were
located where our sun is, it would be as far out as Jupiter Betelgeuse is 420 million kilometers in
diameter
Size Most stars are much smaller than the
sun White dwarf stars are about the size of
Earth Neutron stars are even smaller
20 kilometers in diameter
Composition Astronomers use spectrographs to determine the
elements found in stars A spectrograph is a device that breaks light into
colors and produces an image of the resulting spectrum
Brightness of stars Depends upon both its size and
temperature The hotter the star, the brighter it
shines The bigger the star, the brighter it
shines How bright a star looks from Earth
depends on both its distance from Earth and how bright the star truly is
Brightness of a star Because of this, the brightness of a star
can be described in 2 ways:1. Apparent brightness2. Absolute brightness
Apparent brightness A star’s brightness as seen from Earth Astronomers can measure apparent
brightness fairly easily using electronic devices
However, astronomers can’t tell how much light a star gives off just from the apparent brightness
Apparent brightness Just as a flashlight looks brighter the
closer it is to you, a star looks brighter the closer it is to Earth
Example: the sun looks very bright This does not mean the sun gives off more
light than all other stars The sun looks so bright simply because it is
so close In reality, the sun is a star of only average
brightness
Measuring distances to stars Imagine that you could travel to the
stars at the speed of light (300,00 km/s) To travel from Earth to the sun would
take about 8 minutes! The next nearest star, Proxima Centauri,
is much farther away A trip there at the speed of light would
take 4.2 years!
The light-year Distances on Earth’s surface are often
measured in kilometers However, distances to the stars are so
large that kilometers are not very practical
Astronomers use a unit called a light year to measure distances between the stars
A light-year In space, light travels at a speed of
about 300,000km/s A light-year is the distance that light
travels in one year 9.5 million million kilometers
A light-year is a unit of distance, NOT TIME!
Clusters Many stars belong to larger groupings
called clusters There are 2 types of clusters
1. Open clusters2. Globular clusters
Open Clusters Have a loose disorganized appearance
and contain no more than a few thousand stars
They often contain many bright supergiants and much gas and dust
Globular clusters Large grouping of older stars Are round and densely packed with stars Some may contain more than a million
stars
Galaxies A huge group of singe stars, star systems, star
clusters, dust and gas bound together by gravity There are billions of galaxies in the universe The largest galaxies have more than a trillion
stars Significantly larger than our solar system Astronomers classify most galaxies into the
following types: 1. Spiral2. Elliptical3. irregular
Spiral galaxies Galaxies that have a bulge in the middle
and arms that spiral outward, like pinwheels.
The spiral arms contain many bright, young stars as well as gas and dust
Most new stars in spiral galaxies form in these spiral arms
Relatively few new stars are forming in the central bulge
The Milky Way Our solar system is located in a spiral
galaxy called the Milky Way The center of the galaxy is about 25,000
light-years away
Galactic clusters A structure that consists of hundreds of
galaxies bound by gravity Hold the greatest number of stars in the
universe Are the largest known gravitationally
bound objects in the universe
Our Solar System Our solar system includes:
The sun – center of our solar system Planets Belts of rock, ice and dust
The Milky Way name derives from its appearance as a
dim "milky" glowing band arching across the night sky
Contains our solar system Contains about 200 billion stars Almost everything that we can see in
the sky belongs to the Milky Way We are located on one of its spiral arms
out towards the edge
The Universe All of space and everything in it ENORMOUS! Almost beyond imagination Older than our solar system and the
Milky Way
The expanding universe Most astronomers believe the universe is
expanding in size Edwin Hubble studied the spectrums of many
galaxies at various distances from Earth By examining a galaxy’s spectrum, Hubble could
tell how fast the galaxy is moving and whether it is moving toward our galaxy or away from it
Hubble discovered that, with the exception of a few nearby galaxies, all galaxies are moving away from us and from each other
The expanding universe Hubble found that there is a relationship
between the distance to a galaxy and its speed
Hubble’s law states that the further away a galaxy is, the faster it is moving away from us.
Red shift or blue shift? Red shift
When an object is moving away, it appears red in color The wavelengths increase and the color
SHIFTS towards the red end of the spectrum Giving the star a reddish color
Blue shift When an object is moving toward our
galaxy, it appears blue in color The wavelengths decrease and this SHIFTS
the color from the red end of the spectrum to the blue end Giving the star a bluish color
Cosmic background radiation Leftover thermal energy that is
distributed in every direction as the universe expands
Age of the universe Since astronomers can measure
approximately how fast the universe is expanding now, the can infer how long it has been expanding.
Based on careful measurements of how fast distant galaxies are moving away from us and the cosmic background radiation, astronomers estimate that the universe is about 13.7 billion years old
The future of the universe1. The universe will continue to expand and
eventually all of the stars will run out of fuel and burn out. The universe will be cold and dark
2. The force of gravity will begin to pull the galaxies back together. All of the matter in the universe would be crushed into an enormous black hole
3. New observations lead many astronomers to conclude that the universe will likely expand forever