UNIT 3 UNIVERSE
Study Guide
Main Topics:
1. Scientific Notation
 Into and out of scientific notation
 Always 1 x 10+ or –X
 If a number is >1, then 101, etc.; if <1, then 10-1, etc.
a. 5.4 x 103 =
5,400
b. 5.4 x 10-3 =
.0054
c. 6.101x106 =
6,101,000
d. 6.101x10-6 =
.0006101
2. The Big Bang
Theory
 The universe formed in an instant from a small, very hot and
dense singularity in a single explosion.
Evidence
 Edwin Hubble discovered galaxies. He said that as galaxies move
away from us, they moving away faster.
 The remnants of the heat given off by the big bang is known as
cosmic background radiation
 This event occurred approximately 13.7 billion years ago.
3. The Universe
90% of the universe is composed of dark matter.
The unknown force that causes the universe to expand is dark
energy
Dark matter is considered ‘dark’ because there are no EMS
emissions.
4. Galaxies
 Place in order from Small to large: solar system, star, galaxy,
universe. star, solar system, galaxy, universe
 The three types of galaxies are:
spiral, elliptical, irregular
 A typical galaxy has 200 billion stars, is 30 million light years
from Earth, and is 500 light years in diameter.
 Our galaxy is called the Milky Way galaxy, and is a spiral galaxy.
 Light travels at approximately 300,000 km/s.
 Light can be broken up into its composite colors and viewed
using a spectroscope.
5. Star Classification
 5 classifications: T.C.C.B.S
Temperature, color, composition, brightness, size
 Binary star systems, clusters, globualrs
How do we know star systems are binary?
By one star eclipsing another causing alternating changes in brightness
as well as gravitational effects on each other
 Apparent magnitude and Absolute brightness
Apparent magnitude is how bright a star is compared to our sun in
its current position; Absolute brightness is how bright a star would
be if it were as far away from us as out sun.
 Parallax and Hertzsprung-Russell diagram
A parallax measures a star’s distance by viewing it from two different
angles
The HR diagram graphs stars’ relative absolute brightness,
temperature, and color. Stars in the middle of the graphs, showing
medium characteristics, are called the main sequence stars.
 EMS spectrum: R.M.I.V.U.X.G
Radio waves, microwaves, infrared waves, visible light (ROYGBIV),
ultra violet waves, x-rays, and gamma rays
 The EMS spectrum are types of radiant energy.
 This energy is in the form of waves.
 The EMS spectrum is organized by its energy or wavelength.
 Visible light: R.O.Y.G.B.I.V
Red, orange, yellow, green, blue, indigo, and violet
Short, long, high, low
Blue light has a short wavelength and high energy. Red light has a
long wavelength and low energy.
6. Star Life Cycle

Star’s life cycle is determined by its size.
 Stars start from a nebula, which is a large cloud of gas and
dust.
 Stars form due the pulling force of gravity acting on matter.
 A star that has begun to form and generate heat protostar
 When hydrogen atoms in a star’s core are pushed close
enough together, they combine to form helium, and nuclear
fusion begins
 A star that has begun nuclear fusion, is said to be in its
main sequence.
 At the end of its life cycle a medium star will form a red
giant.
 As the star loses its atmosphere, a planetary nebula is
formed.
 When a star’s atmosphere is lost, a hot core of carbon
remains, and is called a white dwarf.
 When the core has cooled it is called a black dwarf.
 A massive star forms a super giant when it starts to die.
 As a star starts runs out of hydrogen, it starts to fuse
atoms of helium.
 When a star up to 10 times the mass of our sun loses its
atmosphere, the star collapses so rapidly a super nova occurs,
scattering gas and trace elements throughout the galaxy.
 The remaining core of a massive star is called a neutron star,
because the pressure is so great that the protons and
electrons have fused to form neutrons.
 A neutron star that emits radio waves due to its fast
rotation is called a pulsar.
 When a massive star more than 10 times the mass of our
sun collapses, a singularity is formed called a black hole.
7. Vocabulary