Transcript Unit 1 The Universe

Big Idea:
The sun is one of billions of stars in
one of billions of galaxies in the
universe.
Unit 1 The Universe
Mrs. Williams
8th Grade
Unit 1 Lesson 1 Structure of the Universe
Our Place in Space
•Universe-space & all the
matter & energy in it.
•Galaxy- a large collection
of stars, gas, & dust
• There are an estimated 100 billion galaxies in
the universe.
Unit 1 Lesson 1 Structure of the Universe
Types of Galaxies
• Irregular galaxies appear as splotchy,
irregularly shaped “blobs.” They are
very active areas of star formation.
• Spiral galaxies are shaped like
pinwheels. They have a central bulge
from which two or more spiral arms
extend.
• Elliptical galaxies look like spheres or
ovals and do not have spiral arms.
http://library.thinkquest.org/C0110277/images/galaxies.gif
Unit 1 Lesson 1 Structure of the Universe
What Makes Up the Universe?
• Solar system- the collection of large &
small bodies that orbit our central star,
the sun.
• Planet-spherical body that orbits the sun.
Unit 1 Lesson 1 Structure of the Universe
Terrestrial Planets
• Terrestrial Planets- rocky, dense,
and relatively small.
• Mercury, Venus, Earth and Mars
http://ut-images.s3.amazonaws.com/wp-content/uploads/2008/04/mercurycomparison.jpg
Unit 1 Lesson 1 Structure of the Universe
• Gas giant planets - have thick,
gaseous atmospheres; small, rocky
cores; and ring systems of ice, rock,
and dust.
• Jupiter, Saturn, Uranus, and Neptune.
Unit 1 Lesson 1 Structure of the Universe
Small Bodies in the Universe
• Moons- orbit most of the planets.
Earth has only one moon, but Jupiter has
more than 60.
• The solar system has other small bodies,
including
• Dwarf planets
• Comets
• Asteroids
• Meteoroids
•
http://home.earthlink.net/~meshellwg/w/www/images/comet.jpg
Unit 1 Lesson 1 Structure of the Universe
Measuring the Universe
• Distances between most objects in the universe are so
large that astronomers measure distances using the
speed of light.
• Light-year -the distance that light
travels through space in one year.
• Light travels through space at about
300,000 km/s, or about 9.5 trillion kilometers in one year.
Unit 1 Lesson 1 Structure of the Universe
Reach For The Stars!
• Star - large celestial body that is
composed of gas & emits light.
• Most stars are composed almost entirely of
hydrogen and helium.
• Stars emit light and vary in brightness, size
and temperatures.
http://www.le.ac.uk/ph/faulkes/web/images/stars.jpg
Unit 1 Lesson 2 Stars
You’re a Shining Star
How is star brightness measured?
• Apparent magnitude -measure of a star’s
brightness as seen from Earth.
– Luminosity- actual brightness of a star.
• Absolute magnitude -measure of how bright a
star would be if the star were located at a
standard distance.
Unit 1 Lesson 2 Stars
Stars differ greatly in size
• White dwarfs - Very small stars
have about the same radius as Earth,
which is approximately 0.01 solar
radius.
• Giant stars - Very large stars,
typically have sizes between 10 and
100 times the sun’s radius.
• Supergiants - Some rare, extremely
large stars have sizes of up to 1,000
solar radii.
Unit 1 Lesson 2 Stars
Too HOT to Handle
• Surface temperatures of Stars
are measured by their COLOR
COLOR
SURFACE TEMPERATURE (˚C)
Blue
Above 25,000
Blue-white
10,000-25,000
White
7,500-10,000
Yellow-white
6,000-7,500
Yellow
5,000-6,000
Orange
3,500-5,000
Red
Below 3,500
Unit 1 Lesson 3 The Life Cycle of Stars
A Star Is Born
What is the life cycle of a star?
• Stars form in nebulae.
• Nebula -large cloud of gas and dust. It is
composed mainly of hydrogen and helium, with
small amounts of heavier elements.
•
Gravity caused the solar
• Nebula to collapse toward the
• center, causing the center of
the sun to be dense & creates
friction making things hot.
http://dsc.discovery.com/convergence/hubble/hits/gallery/garden4_lrg.jpg
Unit 1 Lesson 3 The Life Cycle of Stars
Birth of a Star
• Nuclear fusion –high temp & pressure
cause two or more low-mass atomic nuclei
to form a heavier nucleus. Gives off light.
• Occurs for most of the stars life.
Unit 1 Lesson 3 The Life Cycle of Stars
The Lightweights
• Low-mass stars- The sun is a low mass,
medium size star.
– Giants-large red stars due to star’s outer
atmosphere expanding after active fusion ends.
– Planetary nebula -forms when a star can no
longer support itself by fusion reactions in its
center
– White dwarf -hot, dense core of matter that
remains from the collapse of a low-mass star. It
is about the size of Earth.
– Black dwarf-white dwarf that stopped glowing.
Unit 1 Lesson 3 The Life Cycle of Stars
The Heavyweights
• High mass stars
– Red supergiant-produces heavier elements
like carbon
– Supernova -gigantic explosion in which a
high-mass star collapses, throwing its outer
layers into space. But its core remains.
– Neutron star -small, incredibly dense ball
of closely packed neutrons.
– Black hole -invisible object with gravity so
great that nothing, not even light, can
escape it.
Unit 1 Lesson 3 The Life Cycle of Stars
A Graphic Display
• H-R diagram –graph that shows the
relationship between the stars
surface temperature & absolute
magnitude (brightness/luminosity)
Main sequence -region of the diagram where stars
spend most of their lives. (actively fusing hydrogen)