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GALAXY & BEYOND OVERVIEW & OBJECTIVES Know about: • • • • • • • • Pluto Asteroids Comets Meteors Milky Way Galaxy & where we are in it Black Holes Other Galaxies Other Objects in Space Chapter 3, Lesson 4 Chapter 4, Lesson 1 & 2 PLUTO Downgraded to a “dwarf planet” in 2006 CHAPTER 3, LESSON 4 PLUTO • Size? • Smaller than Earth’s Moon • Orbit is eccentric • Elliptical • Averages 40 Astronomical Units (AUs) from the Sun (can range from 30 - 50 Aus) Astronomical Unit (AU) - is distance b/w Earth & Sun (about 93 million miles) PLUTO’S ORBIT & ATMOSPHERE • Pluto has an atmosphere, but not year-round • At perihelion it “warms up” • At aphelion it receives so little solar energy that its surface is below the temperature where methane freezes! PLUTO’S MOON CHARON • Charon & Pluto are locked in a synchronous orbit • No Moon rise or set – always same face in same spot ASTEROIDS • Remains of a planet? • Most likely matter that never formed into a planet • Asteroid belt orbit in region b/w Mars & Jupiter • Jupiter’s gravitational pull creates gaps & stirs it up COMETS • 1705, Edmund Halley predicted a comet’s return in 1758 • On Christmas night of 1758, Comet Halley appeared in the sky again • Scientists have traced Halley Comet sightings back to 239 BC CHAPTER 3, LESSON 4 A COMET’S 3 MAIN PARTS 1. Head: nucleus (solid core) 2. Coma: diffuse gas & dust 3. Tail: gas & dust swept away from comet’s head Comet Hale Bopp 1997 Hartley Nucleus CHAPTER 3, LESSON 4 SHELL OF COMETS Kuiper belt • Billions of short-period Comets • 100,000 icy worlds 60 miles diameter • Disk-shaped region beyond Neptune Oort Cloud • Billions & billions of comet nuclei • Far, far beyond Neptune • Kuiper Belt exists w/n Oort cloud CHAPTER 3, LESSON 4 Sun METEORS VS. METEORITES Meteor (falling star) • Falling space rock/particle that emits light as it streaks through • Heated by immense friction through Earth’s atmosphere • Video Fireball: extremely bright meteor video 1 Meteorite? • Meteor that has struck the Earth • Video Courtesy NASA/JPL THE MILKY WAY GALAXY & OUR SUN’S PLACE IN IT • Our Sun is one of about 200 billion stars in the Milky Way Galaxy • Diameter: • 60,000-100,000 light-years across! • Disk-shaped w/ bulging center CHAPTER 4, LESSON 1 GALAXIES • Almost everything you can see in the sky is in the Milky Way Galaxy! • Andromeda • Another galaxy - visible in the autumn sky as a fuzzy spot OTHER GALAXIES • Edwin Hubble divided galaxies into 3 major groups: 1. Spiral Sombrero Galaxy Barred Galaxy 2. Elliptical 3. Irregular Megellanic Cloud STARS Different sizes – identified by color: • White – “Dwarf” (very small) • Yellow – small/medium-size • Our Sun “Sol” • Orange – medium/large • Blue - giant • Red – super giant CHAPTER 3, LESSON 4 OTHER STAR SIZES Remember COMPARED TO OUR SUN This? LIFE CYCLE OF A STAR • When small stars die: • • Grow to Red Giants and shrink to White Dwarves When large stars die: • Supernova or Black Hole CHAPTER 3, LESSON 4 Video BLACK HOLES • Gravity is so great that light can’t escape! • Escape velocity • Speed Object (or molecule) must travel to “escape” gravity • Earth – rockets, Nitrogen, O2 • Black hole gravity – speed of light not fast enough • 186,000 MPS • Video • Because of great energy detected there, scientists believe center of Milky Way & other galaxies is a super massive-black-hole! OTHER OBJECTS IN SPACE • Nebula • Interstellar cloud of dust or gas Horse Head Nebula Eagle Nebula Crab Nebula CHAPTER 4, LESSON 2 OTHER OBJECTS IN SPACE PULSARS • Pulsating radio source • Like a lighthouse beacon • Believed to be a rapidly rotating neutron star Courtesy NASA CHAPTER 4, LESSON 2 OTHER OBJECTS IN SPACE BINARY STARS • Pair of stars that revolve around each other