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Unit 7: Astronomy & Capstone

Unit 7: Astronomy & Capstone. Our Place in Space. What is a Planet?. Planet: celestial body which revolves around a star and was massive enough to melt and form a spheroid shape. What is the Sun? Why does it look so big?. The Sun is a STAR

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Unit 7: Astronomy & Capstone

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  1. Unit 7: Astronomy & Capstone Our Place in Space

  2. What is a Planet? • Planet: celestial body which revolves around a star and was massive enough to melt and form a spheroid shape

  3. What is the Sun? Why does it look so big? • The Sun is a STAR • very hot, massive ball of gas (mostly hydrogen and helium, fusion at core produces energy • Closest star to earth so it looks much bigger!

  4. List planets in order from closest to Sun to farthest from Sun

  5. What keeps planets in orbit around the Sun? • Gravity! • Why don’t they all fall into the Sun? • Moving too fast, no friction in space • Orbit=perfect balance between pull in from gravity and pushing out from forward motion

  6. If Pluto is NOT a planet, what is it?! • Dwarf planet 2006 • Kuiper Belt Object (KBO) • Kuiper belt=frozen zone of ice and dust at edge of solar system • Why dwarf “planet” instead of other object? Big enough to be sphere shape

  7. What other important “celestial objects” are there in our solar system? • Comets • Asteroids • Meteors • Moons

  8. What is the farthest humans have ever travelled in space?

  9. How do we know about the other planets? • Telescopes • Unmanned space craft: • Rovers • Probes

  10. Rotation vs. Revolution • Rotation • Turning on its own axis, not orbiting around anything. • Causes the day/night cycle • All planets rotate on an axis, so does the moon and the Sun • Revolution • To move in an elliptical (cicrle-ish) path around another object, to “orbit” that object. • Causes the year to occur and because of our tilted axis, is responsible for the timing of the seasons • Planets revolve around stars, moons revolve around planets.

  11. Our Place in Space • Earth is a planet which revolves around our Sun. Our Sun is a star which is is part of a Galaxy along with billions of others. Our galaxy is one of billions of galaxies that are spread throughout our universe. Our universe is mostly empty space .

  12. Simple Definitions • Planet: celestial body which revolves around a star and was massive enough to melt and form a spheroid shape • Moon: celestial body which revolves around a planet (may or may not be spherical) • Galaxy: group of billions of stars (and there planets) that are held together in space by gravity • Solar System: a star and all of the celestial objects that revolve around it • Universe: Everything. All the energy and light that we know about and can observe and all the nothingness in between • Star: celestial object that is so massive that fusion goes on in the inside and gives off energy making it so hot it is gas and gives off radiation into space

  13. How do we measure distances in space? • Paralax=geometry! • Why do we describe distances in light year’s? what are light years? • Light year is the distance light can travel in one year at the speed of light (which is about 299,792,458 m/s) • Used because distances in space are so enormous…they don’t call it space for nothing! A light year isabout 9.5 trillion km

  14. Star Characteristics What is a star? What is the nearest star? Nearest star other than sun= Proxima centauri (4.3 light years) (9.5 trillion km=1 ly) Looking at this star we are seeing light that was released 4.3 years ago…so we are seeing an image that is 4.3 years old! It is like looking back in time! Mass Color: red=cool, blue=hot Brightness=stellar magnitude based on: how big, how hot, how far

  15. Are we alone?

  16. Size Pattern

  17. Density=amount of mass per volume Tennis ball vs. baseball Density Pattern

  18. Jovian vs. Terrestrial Planets • Earth-Like Planets • Include Mercury, Venus, Earth, Mars • Called “terrestrial” or inner • Similar in composition (rocks and metals, not a lot of hydrogen and helium) • Similar in size (smallish) • Similar in density (denser than other planets) • Jupiter-like planets • Include Jupiter, Saturns, Uranus, Neptune • Called “Jovian” or outer • Similar in composition (high percentage of hydrogen and helium) • Similar in size (big) • Similar in density (not very dense!)

  19. Other interesting patterns • All planets revolve around the Sun in the same direction… • counter-clockwise • All planets, except … • Venus, rotate on their axis in the same direction • Is there a model of solar system formation that is consistent with these patterns and helps to explain why they might occr? • YES! Nebular Hypothesis

  20. Formation of the Solar System • Nebular Hypothesis (1944) • 5 Billion yrs. Ago rotating gas & dust cloud • As cloud collapsed, spins faster, disc spins out • Compression of matter in center led to fusion=sun • Mass collects (10%) into clumps, protoplanets

  21. Nebula • Big cloud of dust and gas that the solar system formed from

  22. Where did the Gasses come from • Older stars explode and their matter gets flung out into space • You are all stars!

  23. What happened to form the Sun and planets? • Center of nebula got hot through compression and fusion began… • Disk spun out and got cool, dust solids began to form but too hot for hydrogen and helium to stick to rest of matter in inner part, blown out to outer edge of disk • Collisions of matter due to gravity, small planets start to form, crash into others and become a few big planets! • Planets in the outer region able to capture the hydrogen and helium and grow huge!!!

  24. The night sky Window to the universe During day, “sun” star is so much brighter we can’t see the rest of the universe Moon, planets, stars, galaxies, star clusters, galaxy clusters, nebula Study the light that reaches us:

  25. Why do Stars rise and set and circle Polaris? • Most dramatic motions caused by EARTH motions: • Rotation,revolution • Rotation causes: rising/setting • Revolution causes: seasons/path of sun, difference in stars viewable during the night

  26. The “Big Bang” • “to make an apple pie from scratch you must first invent the universe” –Carl Sagan • 13.7 billion years ago all matter and energy expanded from a single hot, dense point in time “singularity”

  27. The Big Bang • Hot dense ball suddenly exploded 14 bya • Cooled 10 billion C, much cooler, much less dense, basic atomic particles form (protons & neutrons) • Simple elements formed (H, He) • H & He formed clouds which became galaxies with stars including milky way • Galaxies continue to spread and age. Stars explode and create new heavier elements (Fe, C, O) • Our solar nebula begins to collapse and form our sun and planets

  28. Expanding Universe • Expansion is not just galaxies moving through space…. • Space itself is expanding! • No center of universe, just appears to be center everywhere… • Every galaxy is moving away from every other galaxy! • Evidence? • All galaxies moving apart • Farther galaxies moving apart faster/more

  29. What evidence is there in support of Big Bang? • Space is expanding: • All galaxies moving apart • Farther galaxies moving faster/more! • There was a big, quick explosion/expansion at the beginning: • Cosmic background radiation (faint radio signals throughout space in all directions)

  30. How do we know this stuff?! • Study of electromagnetic spectrum energy that we collect with telescopes (radio, light, xray telescopes for example) • In order from longest to shortest… • Radio, microwave, infrared, visible, ultravioet, xray, gamma ray • Within the part of spectrum we see with our eyes (visible) • Red is longer! • What is redshift??

  31. The Doppler Effect • Wavelength=squished/shortened as emitter approaches observer • Wavelength=stretched/lengthened as emitter moves away from observer

  32. The Doppler Effect and Red-shifted light • Evidence that all galaxies are moving apart and farther galaxies are moving faster/more which means space is expanding comes from observations that their energy is “red-shifted” • Doppler effect: as an object moves away, energy it gives off seems to be longer wavelength than it is (wavelength is stretched!) • Light from distant galaxies is “red-shifted” all energy given off is longer wavelengths than we would expect

  33. Cosmic Background Radiation • Nearly uniform energy scattered throughout space, microwave wavelength detected with radio telescopes • Evidence of initial, all direction inflation of universe from singularity…from first few seconds of time…atoms and energy came to be at same time. • Just like matter spread and cooled, energy wavelength has grown…

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