4 f Describe the hierarchical structure stars cluster

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) Stars, Galaxies & The Electromagnetic Spectrum

Vocabulary Words – Chapter 4 & 21 Electromagnetic wave 2. Electromagnetic radiation 3. Electromagnetic spectrum 4. Radio waves 5. Microwaves 6. Radar 7. Infrared rays 8. Visible light 9. Ultraviolet rays 10. X-rays 11. Gamma rays 12. Incandescent light 13. wavelength 1. Spectrum 15. Constellation 16. Light-year 17. Apparent brightness 18. Absolute brightness 19. Spectrograph 20. Parallax 21. Hertzsprung-Russell diagram 22. Main sequence 23. Open cluster 24. Globular cluster 25. Galaxy 26. Milky Way 27. Universe 14.

Definitions 1. 2. 3. 4. 5. 6. 7. Electromagnetic wave – transverse waves that transfer electrical and magnetic energy Electromagnetic radiation – the energy transferred through space by electromagnetic waves Electromagnetic spectrum – the complete range of electromagnetic waves placed in order of increasing frequency Radio waves – electromagnetic waves with the longest wavelengths and lowest frequencies Microwaves – radio waves with the shortest wavelengths and the highest frequencies Radar – a system that uses reflected radio waves to detect objects and measure their distance and speed Infrared rays – electromagnetic waves with wavelengths shorter than radio waves, but longer than visible light

Definitions 8. 9. 10. 11. 12. 13. 14. 15. Visible light – electromagnetic waves that are visible to the human eye Ultraviolet rays – electromagnetic waves with wavelengths shorter than visible light, but longer than x-rays X-rays – electromagnetic waves with wavelengths shorter than ultraviolet rays, but longer than gamma rays Gamma rays – electromagnetic waves with the shortest wavelengths and highest frequencies Incandescent light – light bulb that glows when a filament inside it gets white hot Wavelength – the distance between the crest of one wave and the crest of the next wave Spectrum – the range of wavelengths of electromagnetic waves Constellation – an imaginary pattern of stars in the sky

Definitions 16. 17. 18. 19. 20. 21. 22. Light-year – the distance that light travels in one year, about 9. 5 trillion kilometers Apparent brightness – the brightness of a star as seen from Earth Absolute brightness – the brightness a star would have if it were at a standard distance from Earth Spectrograph – an instrument that separates light into colors and makes an image of the resulting spectrum Parallax – the apparent change in position of an object when seen from different places Hertzsprung-Russell diagram – a graph relating the surface temperatures and absolute brightness of stars 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 Objective 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 the frequency of a wave, the higher its energy

Parts of the EM Spectrum 1. Radio waves Electromagnetic waves with the longest wavelengths and lowest frequencies 1. 2. Includes: Broadcast waves Radio and TV waves Longer wavelengths Microwaves Shorter wavelengths Cellular devices Radar

Parts of the EM Spectrum 2. 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: Heat lamps Infrared cameras 1. 2. 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 light waves with the longest wavelengths appear red As the wavelengths decrease, you can see other colors of light The shortest wavelengths of visible light appear violet in color Colors in order of longest wavelength to shortest wavelength Red, orange, yellow, green, blue, violet

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 Questions 1. 2. 3. 4. Why are shorter wavelengths more damaging than longer wavelengths Does exposure to any type of energy on the EM Spectrum cause cellular damage? Why or why not? Which wavelengths are visible to the human eye and which are not? Which part of the EM Spectrum has the shortest wavelengths? 5. 6. 7. 8. 9. What is the order of visible light from longest wavelengths to shortest? How are wavelengths and frequency related? How are frequency and the amount of energy present related? What is the best way to avoid skin cancer? How do we feel the energy of infrared rays?

The Universe 4. 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 1. 2. 3. 4. to largest Stars Clusters Galaxies Galactic clusters

Classifying stars Characteristics 1. 2. 3. 4. 5. used to classify stars include: Color Temperature Size Composition 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. 2. Apparent brightness 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, 000 km/s A light-year is the distance that light travels in one year 9. 5 A million kilometers 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. 2. Open clusters 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. 2. 3. Spiral Elliptical 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 lightyears 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 system 2. The Milky Way 3. 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 universe 1. 2. 3. The universe will continue to expand eventually all of the stars will run out of fuel and burn out. The universe will be cold and dark 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 New observations lead many astronomers to conclude that the universe will likely expand forever