Space #1: Big Bang/Galaxies/Stars/Planets
| 38 Questions
Note from the author:
Weekly classwork/homework instructions: This assignment will be broken into parts--some will be done in class and some parts will be done as homework. Remember that any work you do not finish in class immediately becomes homework.

Points Possible: 50 assignment points (10 for each section)

The Universe
Content adapted from
What is the universe?
The universe contains everything that exists including the Earth, planets, stars, space, and galaxies. This includes all matter, energy, and even time.
How big is the universe?
No one knows for sure just how big the universe is. It could be infinitely large. Scientists, however, measure the size of the universe by what they can see. They call this the "observable universe." The observable universe is around 93 billion light years across. One light year is how far light (the fastest thing there is) can travel in one year. Only one light year is 5,878,625,373,183.6 miles (that's more than 5.8 TRILLION miles!).
The Universe is Expanding
One of the interesting things about the universe is that it is currently expanding. It's growing larger and larger all the time. Not only is it growing larger, but the edge of the universe is expanding at a faster and faster rate. As the universe expands, the objects in it are getting farther and farther apart from each other. Evidence supports that the edge of the universe is expanding faster than the speed of light.

What is the universe made of?
Even though the Earth seems really big to us, it's actually a very tiny part of the universe. The Sun has a mass of 330,000 times the Earth. The Sun is just one star in the Milky Way galaxy that contains over 300 billion stars and scientists estimate that there are over 170 billion galaxies in the universe!
However, most of the universe is what we think of as empty space. All the stars together only make up around half a percent of the universe. The majority of the universe consists of something scientists call dark matter and dark energy.
What are dark matter and dark energy?
We mentioned above that the majority of the universe is made up of dark matter and dark energy, but what exactly are these things?
  • Dark matter - Scientists aren't sure exactly what dark matter is, but they believe that it exists due to experiments. Dark matter gets its name because it cannot be seen with any type of instrument that we have today. Around 27% of the universe is made up of dark matter. Dark matter is thought to help hold galaxies together.
  • Dark energy - Dark energy is something that scientists believe fills all space. It turns out that "empty space" is more than just nothing, but is really dark energy. The theory of dark energy helps scientists to explain why the universe is expanding. Around 68% of the universe is dark energy. Dark energy is thought to push objects like galaxies farther apart from each other.
How old is the universe?
Scientists think that the universe began between 13 and 14 billion years ago with the start of a massive expansion called the Big Bang.
Interesting Facts about the Universe
  • Distant galaxies are constantly moving further and further away from us as the universe expands.
  • Every galaxy in the universe is moving away from every other galaxy. There is no center to the universe.
  • Albert Einstein said that the shape of the universe was open, closed, or flat. Many scientists today think that the universe is flat.
  • The universe appears to be cooling and may eventually freeze, and many scientists think that is how the universe will "end". Some scientists think there could eventually be a reverse Big Bang (called the "Big Crunch") where the universe collapses back to a singularity point. This is just a hypothesis. The truth is that no one knows for sure what will happen, but whatever does happen won't happen for billions and billions of years.
  • Large empty spaces in the universe are called voids. Voids contain no matter and are pure "nothingness".
  • The most abundant, or common, element in the universe is hydrogen. The second most abundant element is helium.
Picture above: The shape of the whole universe may be closed (top image), open (middle image), or flat (bottom image). Astronomers, or scientists who study space, use observations and complex math to understand the shape of the universe. Most scientists agree that the universe is most likely flat.
1 pt
What is included in the Universe?
Stars and planets
All energy
All matter
All of the above
1 pt
What do scientists call the parts of the Universe they can see?
Viewable universe
Visible universe
Observable universe
Basic universe
Timely universe
1 pt
True or False? The universe is expanding at a faster and faster rate.
1 pt
What percentange of the universe do the stars make up?
Less than 1%
1 pt
What do scientists believe fills up the "empty space" in the universe?
Dark energy
Dark matter
Hydrogen gas
Dark force
1 pt
What do scientists call matter that can't be seen with our current instruments?
Dark energy
Dark matter
Hydrogen gas
Dark force
1 pt
How fast is the edge of the universe expanding?
So slowly we can hardly measure it
Around 1 mile/hour
At the speed of light
Faster than the speed of light
The universe is not expanding, it's actually collapsing
1 pt
What do scientists call the big expansion that started the universe?
Original Boom
The First Explosion
Big Bang
Initial Blast
Ground Zero
1 pt
What shape do scientists think the universe is?
1 pt
What is the most abundant, or common, element in the universe?

The universe has been around for a long time and it will continue to exist for a very long time. One of the biggest questions humans have always asked is where did everything come from?

We can go on to ask even more questions: What caused the universe to form in the first place? Where did the atoms that make up matter come from? Where did energy come from? What was the beginning of time? Will the universe ever end or will it literally exist forever? If the universe will end, what will happen?

Watch the two video clips and observe the "Timeline of the Universe Image" below to answer the questions in this section.
1 pt
What is the name of the teeny, tiny, super hot and dense particle that the whole universe expanded from during the Big Bang?
The Origin Point
The Center of the Universe
The Big Bang Core
The Singularity
1 pt
How long ago did the Big Bang occur?
Thousands of years ago
Millions of years ago
Billions of years ago
Trillions of years ago
Quadrillions of years ago

1 pt
The universe is currently...
Expanding and getting hotter
Expanding and getting colder
Shrinking and getting hotter
Shrinking and getting colder
Functionalized Placeholder
1 pt
Put the following events in the timeline of the universe in order from oldest at the top to the most recent at the bottom
  1. The first atoms, mostly hydrogen, form
  2. The parts that make up atoms, such the protons and neutrons in nuclei form
  3. Life begins on Earth
  4. Our solar system formed
  5. The first stars formed
  6. The "Big Bang" occurs from an infinitely small, hot, and dense point called the singularity
  7. Today
Use your notes and Jilbert's notes presentation, "Big Bang Notes" to answer the following question:
1 pt
Select all the answers that are evidence to support The Big Bang.
The Earth revolves around the Sun
Redshift, or stretching of light waves as objects in space get farther away from each other
We can't find anything in the universe older than 13.7 billion years old
Plants make use carbon dioxide and sunlight to make oxygen and sugar in photosynthesis
Cosmic background radiation
Black holes are extremely dense and small
1 pt
Put the following objects in order from smallest at the top to the biggest on the bottom.
  1. The Earth
  2. The continent of North America
  3. The Universe
  4. Jilbert's room in B6
  5. An atom
  6. Shandin Hills Middle School
  7. The Milky Way Galaxy
  8. The Sun
  9. California
  10. San Bernardino County
  11. The city of San Bernardino
  12. Our solar system
  13. The United States of America
  14. A skin cell
  15. A single proton
  16. You

Now that we've talked about the universe, which is all the matter, energy, and time that exists, let's look at something smaller: a galaxy.

Scientists used to think that all the stars in the universe were part of one giant grouping of stars. Then, in 1917, Thomas Wright suggested that there might be lots of different large groups of stars. A few years later this was proven by other astronomers and the idea of the galaxy became real.
What is a Galaxy?
A galaxy is a group of stars and other space stuff like the planets, asteroids, and comets that orbit individual stars. The stars tend to spin around a center of high gravity, sort of like the planets spin around the Sun in the Solar System. Galaxies are huge and can have trillions (way bigger than billions!) of stars. Galaxies are often defined by their shape, the most common being spiral, barred, elliptical, and irregular galaxies.
As big as galaxies are, they are generally separated by large areas of empty space. There are even clusters of galaxies that are separated by even larger areas of space. Scientists think there are over 100 billion galaxies. Wow, the universe is huge!
Milky Way
We live in the galaxy called the Milky Way. The Milky Way is part of cluster of around 3,000 galaxies called the Local Group. The Milky Way is a spiral shaped galaxy and is estimated to be made up of around 200 to 400 billion stars.
Types of Galaxies
There are four main types of galaxies depending on their shape:
  • Spiral - The spiral galaxy has a number of long arms that are spiraling around the center. In the center of the spiral galaxy are older stars while the arms are generally made of new stars. At the center is a large black hole. Its intense gravity helps hold the galaxy together.
  • Barred spiral - This type of galaxy is similar to the spiral but has a long bar in the middle with spirals coming off the ends.
  • Elliptical - A mass of stars clumped together in the shape of an elliptical disc, or stretched-out circle shape.
  • Irregular - Any other shaped galaxy is generally lumped into the category of irregular. It is thought that most irregular galaxies are formed by two of the other three types of galaxies crashing into each other.
  • Fun Facts about Galaxies
  • The word galaxy comes from the Greek word for "milky".
  • Some scientists think that most of the mass of a galaxy is made up of a mysterious substance called dark matter.
  • It is thought that there is a massive black hole in the center of galaxies.
  • The closest galaxy to the Milky Way is Andromeda, which is around 2.6 million light years away from us.
  • Many galaxies are more than 100,000 light years across in distance.
  • It takes over two hundred million years for the sun to orbit the center of the galaxy. This is called a galactic year.
1 pt
Which of the following best defines a galaxy?
A giant star
An area of high gravity where even light cannot escape
A large group of stars spinning around a center of high gravity
A star and its planets
A large area of empty space
1 pt
What is the name of the galaxy we live in?
Whirlpool galaxy
Elliptical galaxy
Messier 82
Sombrero galaxy
Milky Way galaxy
Tadpole galaxy
1 pt
The galaxy we belong to is a part of a larger group of galaxies called __________________.
Ursa Major Group
The Local Group
The Universe
The Solar System
Magellanic Clouds
1 pt
What type of galaxy is formed by a massive grouping of stars in the shape of a disk?
Spiral galaxy
Barred spiral galaxy
Elliptical galaxy
Irregular galaxy
None of the above
1 pt
What type of galaxy is formed when two other galaxies crash into each other?
Spiral galaxy
Barred spiral galaxy
Elliptical galaxy
Irregular galaxy
None of the above
1 pt
What type of galaxy is the Milky Way
Spiral galaxy
Barred spiral galaxy
Elliptical galaxy
Irregular galaxy
None of the above
1 pt
What type of galaxy has a long bar in the middle with spirals coming off the ends?
Spiral galaxy
Barred spiral galaxy
Elliptical galaxy
Irregular galaxy
None of the above
1 pt
What is at the center of galaxies?
A super giant star
Empty space
A massive black hole
Dark matter
1 pt
What galaxy is the closest to the Milky Way?
Solar System
1 pt
How long does it take the Sun to orbit (go all the way around) our galaxy?
1 year
100 years
365 years
1 million years
Over 200 million years

As you've learned, a galaxy is a group of stars and space objects. But what exactly IS a star? We see them at night and we know they shine. What makes stars shine and give off light and other waves of energy?

What is a star?
Stars are giant spheres of superhot gas made up mostly of hydrogen and helium. Stars get so hot by burning hydrogen into helium in a process called nuclear fusion (we will learn about this later). This is what makes them so hot and bright. Our Sun is a star.
Lifecycle of a star
  • Birth - Stars start out in giant clouds of dust called nebulae. Gravity forces the dust to bunch together. As more and more dust bunches up, gravity gets stronger and it starts to get hot and becomes a protostar. Once the center gets hot enough, nuclear fusion will begin and a young star is born.
  • Main Sequence Star - Once a star, it will continue to burn energy and glow for billions of years. This is the state of the star for the majority of its life and is called the "main sequence". During this time a balance is met between gravity wanting to shrink the star and heat wanting to make it grow bigger. The star will remain this way until it runs out of hydrogen.
  • Red Giant - When the hydrogen runs out, the outside of the star expands and it becomes a red giant.
  • Collapse - Eventually the core of the star will start to make iron. This will cause the star to collapse. What happens to the star next depends on how much mass it had (how big it was). The average star (like the Sun) will become a white dwarf star. Larger stars (like Betelguese, pronounced "Beetlejuice" Ha ha.) will create a huge nuclear explosion called a supernova. After the supernova it may become a black hole or a neutron star.
Picture Above: The Horsehead Nebula. Stars form from massive clouds of dust called nebulae. A single cloud of dust and gases is called a nebula. Author: ESA/Hubble [CC 4.0]

Types of Stars
There are many different types of stars. Stars that are in their main sequence (normal stars) are categorized by their color. The smallest stars are red and don't give off much of a glow. Medium size stars are yellow, like the Sun. The largest stars are blue and are hugely bright. The larger the main sequence star, the hotter and brighter they are.
Dwarfs - Smaller stars are called dwarf stars. Red and yellow stars are generally called dwarfs. A brown dwarf is one that never quite got large enough for nuclear fusion to occur. A white dwarf is the remnants of the collapse of a red giant star.
Giants - Giant stars may be main sequence stars like a blue giant, or stars that are expanding like red giants. Some supergiant stars are as big as the entire Solar System!
Neutrons - A neutron star is created from the collapse of a giant star. It's very tiny, but very dense and has the same huge amount of gravity the giant star had.
An image of a cross section of a star like the Sun. Source: NASA
Fun facts about Stars
  • Most of the stars in the universe are red dwarfs.
  • They twinkle because of movement in the Earth's atmosphere and interference of clouds of dust and gas in space that get in the way.
  • Many stars come in pairs called binary stars. There are some groupings with up to 4 stars.
  • The smaller they are the longer they live. Giant stars are bright, but tend to burn out fast.
  • The nearest star to Earth is Proxima Centauri. It is 4.2 light-years away, meaning you would have to travel at the speed of light for 4.2 years to get there.
  • The Sun is around 4.5 billion years old.

1 pt
Stars are made up mostly of what two elements?
Iron and nickel
Oxygen and hydrogen
Silicon and sulfur
Hydrogen and helium
Helium and magnesium
1 pt
What process allows stars to produce so much heat and energy?
Fossil fuels
Nuclear fusion
Electric wind
1 pt
What is it called when a large star collapses and creates a massive nuclear explosion?
Main Sequence Star
Red Giant
1 pt
What stage in the life cycle of a star lasts the longest?
Main Sequence Star
Red Giant
1 pt
What is a giant cloud of space dust and gases that will form into a new star in the future?
Main Sequence Star
Red Giant
1 pt
What do we call a star that has run out of hydrogen and expanded?
Main Sequence Star
Red Giant
1 pt
What type of star is the Sun?
Red dwarf star
Yellow dwarf star
Super giant star
Neutron star
Brown dwarf star
1 pt
What type of star is the most common star in the universe?
Red dwarf star
Yellow dwarf star
Super giant star
Neutron star
Brown dwarf star
1 pt
What color are the largest stars?

What is a planet?
While many people can point to a picture of Jupiter or Saturn and call it a "planet," the definition of this word is much more subtle and has changed over time. Many astronomers decided on a new definition in 2006 after the discovery of several worlds at the far edges of the solar system.

The International Astronomical Union defined a planet as an object that:
  • orbits (goes around) a star
  • has enough mass for gravity to pull it into a round, or nearly round shape
  • is not a satellite (moon) of another object
  • has removed debris and small objects from the area around its orbit, or path around its Sun. In other words, it has a clear path around the star it orbits.
A planet can also be defined by what it is not or what it can't do. A planet will never:
  • Shine or make its own light. Only stars do that. However, light from stars does reflect, or bounce off, the surface of a planet often making it look like a star that does not twinkle when seen from a distance. A few of the brightest "stars" you can see at night are not stars at all, but distant planets in our solar system.
  • Just float around in space without a star to orbit. There are objects in space called "rogue planets" or "orphan planets" that do drift but they do not qualify as proper planets based on this defintion.
  • Be a shape that is not round or almost round. Some objects in space, such as asteroids, are too small for gravity to pull them into a round shape and this disqualifies them as planets.

What kind of planets are there?

The solar system we live in consists of the Sun, which is at the center, and 8 planets that orbit it. There are 2 catagories and 3 types of planets in our solar system. The four planets closest to the Sun are Mercury, Venus, Earth, and Mars. Although they vary in size and appearance, all four planets are considered rocky, or terrestrial planets. This means that they are solid, dense, and made out of rocky or metallic material. Terrestrial planets are also small compared to other types of planets. They do not have rings like Saturn does and they tend to have few, if any, moons.

The picture below shows the terrestrial planets in our solar system: Mercury, Venus, Earth, and Mars. Earth's moon and Mars's two moons are not shown in this picture. Mercury and Venus do not have a moon.

The four planets farthest from the Sun are Jupiter, Saturn, Uranus, and Neptune and they are called Jovian planets. "Jovian" means they are all similar to the planet Jupiter in that they are made of gases instead of rocky material. Jovian, or gas planets, tend to be very large, very cold, have rings, and have many moons orbiting them. Even though Saturn's rings are the biggest and most beautiful, Jupiter, Uranus, and Neptune have their own rings but they are harder to see. Jupiter and Saturn are made of light, cold liquid gases such as hydrogen and helium. Gas planets are often called gas giants because they are much, much bigger than terrestrial planets like Earth. Jupiter and Saturn are actually mostly liquid gases about as dense as water--this means you could not stand on Jupiter or Saturn. If anything tried to land on a gas planet, it would sink and eventually be crushed by the weight of its atmosphere. Uranus and Neptune also made of extremely cold, heavier gases such as methane, oxygen, nitrogen and are called ice giants. Like gas giants, ice giants do not have a solid surface that you could stand on.

The picture below shows the Jovian planets in our solar system: Jupiter, Saturn (gas giants) and Uranus and Neptune (ice giants). Jupiter's 69 moons, Saturn's 62 moons, Uranus's 27 moons, and Neptune's 14 moons are not shown.
1 pt
Sort the planets in our solar system as "Terrestrial" or "Jovian" or "Not a Planet"
  • Jupiter
  • Venus
  • Mars
  • Uranus
  • Mercury
  • The Sun
  • Neptune
  • Earth
  • Saturn
  • The Moon
  • Terrestrial Planets
  • Jovian Planets
  • Not a Planet
Are there planets outside our solar system?


As of March 8, 2018, humans have identified 3,743 planets outside of our solar system. Planets that exist outside of our solar system are called exoplanets ("exo" means "outside"). Most stars have at least one planet orbiting them, and it is thought that there are hundreds of billions, or even trillions, of planets in our own Milky Way Galaxy. There is an uncountable number of planets in other galaxies. New exoplanets are being discovered all the time. Most of the exoplanets that have been found belong to the 2,796 different solar systems that have been discovered so far; 625 of these solar systems have more than one planet.

Some exoplanets are similar to the planets we see in our own solar system. Some of the planets we have discovered are terrestrial and rocky; others are cold, Jovian-type planets like Jupiter. Other exoplanets are very different from the planets in our solar system. Here are some of those different types:

Super-Earths: "Super-Earths" are between 1-10 times more massive than Earth. They have features that are similar to Earth--many have some form of water and a fairly thin atmophere like our home planet. Even through they are Earth-like, it does not mean they have life on them or that they could support life. Some super-Earths are very icy and cold.

Ocean Planets: These are terrestrial planets that are completely covered in water and have no land.

Desert Planets: These planets have no water on the surface at all. They are terrestrial planets that may have had water at some point in the past but lost it for various reasons.

Hot Jupiters: So called "hot Jupiters" are gas giant planets that are close to the star they orbit, causing them to have a high temperature. When hot Jupiters were first discovered, it was a big surprise because it was thought that a gas planet had to be cold and very far away from its host star to exist.

The picture below is an artist's idea of what some of the exoplanets that have been discovered look like. There is an image of Earth in the top right so you can get an idea of how large these exoplanets are. These particular exoplanets have some features that could support life. However, no life has been discovered outside Earth.
1 pt
Write a paragraph that describes the types of planets found in our own solar system.

1 pt
Write a paragraph that describes the types of planets found outside of our solar system.

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