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)

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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 SpectrumObjective 2.e.

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

the higher thefrequency of awave, 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

Visible light Visible light that appears white is

actually a mixture of many colors

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

Apparent brightness

Absolute brightness The brightness the star would have if it

were at a standard distance from Earth

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

Spiral galaxies

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

The Universe, The Milky Way, & Our Solar System

Sequence from smallest to largest

1.Our solar system2.The Milky Way3.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 Milky Way

The Universe All of space and everything in it ENORMOUS! Almost beyond imagination Older than our solar system and the

Milky Way

Is the universe expanding?

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.

The expanding universe

How can we tell if a star/galaxy is moving toward or 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