Space Study Guide
Name ___________________________
LT 1: I can explain how gravity affects objects on Earth and in Space.
Gravity plays many roles in space. The following is a list of main roles gravity plays.
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Gravity is responsible for the accretion (the coming together of particles due to gravity) of planets and stars. If it
was not for gravity, planets and stars would not have been able to form.
Gravity is responsible for holding things in orbit around each other. It is responsible for
o Holding the moon in orbit around the Earth (important for daily cycles of many living things).
o Holding artificial satellites in orbit around the Earth (important part of our daily lives including
technology, TV, cell phones, weather, and research)
o The Earth in orbit around the sun (responsible for our calendar year)
o Our solar system revolving around other solar systems and
o Our galaxy revolving around other galaxies.
Gravity is responsible for holding gases around a planet and forming the atmosphere. If it were not for this,
there could be no life on Earth.
The Earth’s gravity is responsible for things being held to the earth- living and non-living things.
The moons gravitational attraction to the Earth is responsible for our ocean tides.
LT 2: I can explain the theory on the formation of the solar system.
The nebular hypothesis is the current scientific model for the formation of our solar system.
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Scientists believe that our solar system began 5 billion years ago as a huge spinning cloud of dust and gas called
a nebula.
The dust and gas collapsed in on itself because of accretion (the coming together because of gravity) and
formed the sun (same process as other stars).
As the cloud collapsed, it formed into a rotating disk and spun faster and faster which caused it to flatten.
Planetesimals, or particles that become planets, began to form in the disk.
As the planetesimals grew larger, their gravitational attraction also grew, and collected more gas and dust from
the nebula.
Some planetesimals collided with larger ones and combined to form larger and more stable planets.
The warmer, inner planets were rocky (terrestrial), while the cold, outer planets accumulated lightweight gases.
Each planet was massive enough to sweep up the material in its region, so their orbits are separate from each
other.
Asteroids and other rock are leftover debris from the formation of the solar system.
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LT 3: I can describe and give evidence for the Big Bang Theory.
The Big Bang Theory is the current scientific model that explains the formation of the universe with evidence we have
observed. The Big Bang Model is summarized in the following:
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The universe began 13-15 billion years ago when it expanded rapidly from a single point.
At that moment, all matter and energy was created. Before then, there was nothing.
Right after the “Big Bang” event (which scientists think was not like an explosion as the name suggests), the
temperature was VERY hot.
BBT says that the universe would be abundant in the lightest elements of Hydrogen (H) and Helium (He).
As technology increased, scientists made more and more observations that supported the Big Bang Model.
1. In 1929, Edwin Hubble observed that the spectral lines from other galaxies tended to always shift toward the red
end of the spectrum. According to the Doppler Effect, causes this change of observed frequency of
electromagnetic radiation when the object or the observer is moving. When objects are moving away from us,
we call it red shifting because the spectra appear redder. When objects are moving toward us, the spectral lines
are shifted toward the blue end of the spectrum, and we call it blue shifting. Due to this red shifting of nearly
every other galaxy, Hubble announced that the universe is expanding and that nearly every other galaxy was
moving away from us.
2. Scientists using radio telescopes have observed that no matter where in the sky they look, they pick up cosmic
background radiation (CBR). This radiation is leftover microwave radiation leftover from the Big Bang event and
fills the universe. The universe has an average temperature of 2-3˚ Kelvin, which is what the Big Bang Model
predicts would be the temperature after cooling from the event.
3. Scientists have observed an abundance of Hydrogen and Helium throughout the universe. The amount of H
and He isotopes is a very close match to predictions of the Big Bang Model since H and He have the least amount
of mass, they would be the first elements to form. These elements are necessary to make the heavier elements.
4. The age of the universe as predicted by the Big Bang Model is consistent with data we have observed. No item
identified in the universe is older than 13-15 billion years, the age predicted by the model.
LT 4: I can compare and contrast several theories on the origin of the universe.
There are many different theories on the origin of the universe. The following is just a short list of the more popular
ones leading up to what we know today.
Theory
Creationism/ Intelligent
Design
Static Theory
Summary
 God or a higher power created the universe and everything
in it.
 Relatively recent correlations ongoing that link Creationism
with the Big Bang Theory
 Theory popularized/ believed by Einstein (1917).
 Says that the universe has always been here
 Says space is neither expanding nor contracting.
“Problem”
Lacks quantitative data
We now have evidence
that the universe IS in
fact expanding (red
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Space Study Guide
shifting of galaxies).
Steady State Theory
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Many Bang Theory
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Multiverse Theory
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Also known as the Infinite Universe Theory or Continuous
Creation Theory.
Believed in by Edwin Hubble and is an offshoot of the Static
Theory.
Thought that new matter is continuously created as the
universe expands and that most matter created is
Hydrogen.
Similar to the Big Bang Theory, but instead of one “big
bang,” explosions on all scales occur continuously.
More recent theory
Instead of having one universe, there are multiple
universes- a different universe for every possible outcome
for anything that has happened.
Does not explain the
presence of cosmic
background radiation.
Lacks evidence
Currently impossible to
collect data for
LT 5: I can explain the life cycle of a star.
Stars begin as a cloud of dust and gas called a nebula. As the gas spins and starts to condense and come together, the
beginnings of a star are formed in the stage called a protostar. As the star further condenses, temperatures rise and the
hydrogen atoms begin violently colliding. These collisions result in nuclear fusion where the hydrogen atoms combine to
form helium and a huge amount of energy is given off. At this point, the star is “born,” and is classified as a main
sequence star. Our sun in about half way through the main sequence. As fuel for the star begins to run out, the star
pushes gas outward and becomes a red giant. What comes after the red giant stage depends on the mass of the star.
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Smaller stars that are equivalent to 0-8 of our suns mass will enter the white dwarf stage where the star
appears smaller and shines brightly. When its fuel runs out it becomes dark cold and is called a black dwarf.
Medium sized stars that are 8-20 of our solar masses will go from a red giant stage into a supernova. From
there, it can go into a neutron star, or a spinning neutron star, called a pulsar.
Large and massive stars, that of more than 20 or more of our suns mass, go from a red giant into the supernova
stage. Then, because of their large mass, can condense in on themselves and form a black hole.
LT 6: I can explain where and how different elements are formed in a star.
All matter is made up of atoms. The number of protons within the nucleus determines the type of element. An
element can have different forms, called isotopes, based on the number of neutrons in the nucleus. For example, an
ordinary hydrogen nucleus contains just one proton. But deuterium, an isotope of hydrogen, has one proton and one
neutron in its nucleus.
The entire universe shares a common set of elements. In the very early universe, the only elements were
hydrogen and helium. But since the formation of stars, lighter elements within the stars began fusing to create
heavier elements, producing all the other naturally occurring elements. Under the extremely high temperatures and
pressures within the core of stars, atoms collide at high enough speeds to overcome the usual electromagnetic repulsion
of nuclei, allowing nuclear fusion to occur.
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All stars live by fusing hydrogen into helium. In the first step of the process, two hydrogen atoms fuse to form
deuterium. In the next step, another hydrogen atom fuses with the deuterium, creating a rare isotope of helium that has
two protons and one neutron in its nucleus. In the third step, two of the rare helium atoms fuse to create a single
normal helium atom and two hydrogen atoms. The fusion pathway described above requires six hydrogen atoms to
create one helium atom -- however, there are two hydrogen atoms left over at the end of the process. The net result is
that it takes four hydrogen atoms to make one helium atom. The energy that fuels a star is a result of the difference in
mass between the original four hydrogen atoms and the resulting helium atom. Following Einstein's mass-energy
relationship, E=mc2, the missing mass is converted to energy.
At even higher temperatures and pressures, heavier elements are able to form. Many are made from a process
called "helium capture," in which a heavier element fuses with a helium atom. For example, helium fuses with carbon to
make oxygen, and helium fuses with oxygen to make neon. Heavier nuclei can also fuse with each other, such as when
carbon and oxygen fuse to make silicon or two silicon atoms fuse to make iron. Eventually, the interior of a massive star
begins to resemble an onion, with different elements being created in different layers. However, elements heavier than
iron are only produced in the extraordinary conditions created by the collapse and explosion of a star -- a supernova.
LT 7: I can understand how the speed of light is used to measure distances in space.
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While we think of the planets in our solar system being far away, distances within our solar system are relatively
very close. To measure distances in our solar system, units that we are familiar with (such as miles or
kilometers) would be way too small. Light years (ly) that are used in the solar system would be too large. For
this reason, distances in our solar system are measured in Astronomical Units (AU). One AU is the distance
from Earth to the Sun.
Once outside our solar system, AU’s are too small of a unit, so we use light years (ly). A light year is the distance
that light travels in one earth year. To get an idea, in one second, light can travel around the Earth about 7
times. In one year, light can travel 9.46 trillion kilometers or 5.86 trillion miles (240 million times around the
Earth). Often stars are referred to as x number of light years away. For example, if a star is 7 light years away,
the light leaving the star took 7 years to reach Earth for us to be able to see. Because of this, looking at stars is
like looking back in time. By the time the light reaches us, the star could have changed and be completely
different.
To give you another idea, our Sun is 8.3 light minutes away and the moon is 1.3 light seconds away.
Interesting tidbit… According to NASAs website, the parsec (1 parsec = 3.26 light years) is actually the more
common unit used to measure distance by astronomers. The units of light years are only used by astronomers
when talking to the general public or teaching a class.
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Space Study Guide