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GALAXY & BEYOND
OVERVIEW & OBJECTIVES
Know about:
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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
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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
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When small stars die:
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Grow to Red Giants and shrink to White Dwarves
When large stars die:
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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