Aboriginal Knowledge of the Solar System
Galaxies are collections of stars, gas, and dust held together by gravity. Scientists believe there are about 125 billion of these structures in our universe. Galaxies occur in three basic shapes: spiral, elliptical, and irregular. The Milky Way galaxy, where our Sun is located, is a spiral galaxy. Just as gravitational force pulls stars together to form a galaxy, so it pulls individual galaxies together into galaxy clusters and those clusters into even larger clusters
Before getting started, let's take a moment to stop and see what we already know about Galaxies:
Your predictions should be recorded in your individual Google document, Space Exploration – Galaxies.
Once you have finished your brainstorming you should move on to Time to Research portion of this activity. While you are reading the notes below and watching the videos, you should be making notes in your individual Google Document, Space Exploration – Personal Notes, if you prefer you can record your "personal notes" on paper.
- What is a galaxy?
- What galaxy do we inhabit?
- What are other galaxy names you have heard?
Your predictions should be recorded in your individual Google document, Space Exploration – Galaxies.
Once you have finished your brainstorming you should move on to Time to Research portion of this activity. While you are reading the notes below and watching the videos, you should be making notes in your individual Google Document, Space Exploration – Personal Notes, if you prefer you can record your "personal notes" on paper.
Important Terms
|
|
Time to Research (Read, Watch, and Take Notes)
The Number of Galaxies in the UniverseFor a long time, astronomers thought that our galaxy was the only one in the universe.
A discovery by Edwin Hubble in 1925 changed this notion. While observing what he thought was just a bright nebula, a cloud of gas and dust, Hubble realized he was looking into a massive collection of stars. He had identified another galaxy, the one now named Andromeda. It is our nearest neighbouring galaxy. Astronomers now estimate that the whole universe contains at least 125 billion galaxies. The Hubble Space Telescope transmits images of thousands of these galaxies to Earth. Each of the 1500 or so galaxies in this region of space, close to Earth, contains at least 100 billion stars. |
Did You Know?
|
Galaxy Shapes
There are 3 basic shapes of galaxies:
- spiral
- elliptical
- irregular
Spiral Galaxies
These appear like pinwheels with many long arms spiralling out from the centre.
The centre bulge is made up of stars formed long ago, while the circling disc is made up of gasses and dust. This area is called the “halo.”
The centre bulge is made up of stars formed long ago, while the circling disc is made up of gasses and dust. This area is called the “halo.”
Milky Way
|
Galaxy UGC12158
NGC 4564 Profile
|
Elliptical Galaxies
These galaxies contain some of the oldest stars in the universe. They range in shape from a football field to a cigar.
Over half of the galaxies are elliptical and many are also the largest.
Over half of the galaxies are elliptical and many are also the largest.
NGC 3597
|
ECO Centaurus A
|
Irregular GalaxiesThese are made up of a mixture of new and old stars. They do not have distinguishing shapes like the elliptical or spiral galaxies.
|
Irregular Galaxy: NCG 1427A
|
Other Differences Between Galaxies
Galaxies can also differ in size, mass, colour, brightness, and speed they spin. These differences are determined by;
Some galaxies grow into supergiants while others remain dwarf.
- number of stars
- amount and type of gas
- dust
Some galaxies grow into supergiants while others remain dwarf.
Most galaxies also contain two types of distinct formations of stars, called star clusters.
One type is called a “globular cluster.” These are composed of as many as one million stars held together by their mutual gravity in a spherical shape.
The other type is called an “open cluster.” These only contain between a few hundred and tens of thousands of stars.
One type is called a “globular cluster.” These are composed of as many as one million stars held together by their mutual gravity in a spherical shape.
The other type is called an “open cluster.” These only contain between a few hundred and tens of thousands of stars.
Globular Cluster: Messier 80
|
Open Cluster: NGC 346
|
Videos
- List of Videos with hyperlinks
Check-In - To Be Completed Before Moving On
Let's have a check in. Take the time to answer the questions provided to you; record your answers on the worksheet provided. (You should be able to answer the questions without having to refer to your notes).