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Galaxy is a gravitationally bound entity, typically consisting of dark matter, gas, dust, and stars. Galaxies populate the Universe, mainly residing in clusters and groups.
See the fact file below for more information on the Galaxy or alternatively, you can download our 19-page Galaxy worksheet pack to utilise within the classroom or home environment.
Key Facts & Information
- There are thought to be over 100 billion galaxies in the observable Universe, and the most well-known galaxy is our own Milky Way. The term galaxy comes from the Greek “gala,” meaning “milk.”
- Nearly all large galaxies are thought to contain supermassive black holes at their centers.
- Our sun is just one of about 100 to 400 billion stars that spin around Sagittarius A*, a supermassive black hole that contains as much mass as four million suns.
- The universe’s first stars ignited some 180 million years after the big bang, the explosive moment 13.8 billion years ago that marks the origins of the universe as we know it.
- Gravity had sculpted the first galaxies into shape by the time the universe turned 400 million years old, or less than 3 percent of its current age.
- Astronomers now think that nearly all galaxies—with possible exceptions—are embedded in vast haloes of dark matter. Theoretical models also suggest that in the early universe, vast tendrils of dark matter provided ordinary matter the gravitational scaffold it needed to coalesce into the first galaxies.
- However, there are still open questions about how galaxies form. Some believe galaxies were formed from smaller clusters of about one million stars, known as globular clusters, while others hold that galaxies formed first, and later birthed globular clusters. It is also challenging to figure out how many galaxy’s stars formed in situ from its own gas, versus forming in another galaxy and joining the party later.
- ELLIPTICAL GALAXY
- Elliptical galaxies are shaped as their name suggests: they are generally round but can stretch longer along one axis than along the other, so much so that some take on a cigar-like appearance. The universe’s largest known galaxies — giant elliptical galaxies — can contain up to a trillion stars and span two million light-years across. Elliptical galaxies may also be small, in which case they are called dwarf elliptical galaxies.
- Elliptical galaxies contain many older stars, but little dust and other interstellar matter. Their stars orbit the galactic center, like those in the disks of spiral galaxies, but they do so in more random directions. Few new stars are known to form in elliptical galaxies. They are common in galaxy clusters.
- SPIRAL GALAXY
- More than two-thirds of all observed galaxies are spiral galaxies.
- A spiral galaxy has a flat, spinning disk with a central bulge surrounded by spiral arms. That spinning motion, at speeds of hundreds of kilometers a second, may cause matter in the disk to take on a distinctive spiral shape, like a cosmic pinwheel. Our Milky Way, like other spiral galaxies, has a linear, starry bar at its center.
- When Hubble, an American astronomer, developed his classification system for galaxies based on their appearance in optical light, he divided the spirals into those in which the spiral arm radiated from a central bulge (classic spirals), and those where the arms radiated from a central bar (barred spirals).
- These two regions can be seen clearly in color images of face-on spirals. The central bulge or bar is yellow indicating older stars, while the bright nebulae and young blue stars formed from gas and dust in the galaxy, trace out the spiral arms within the disk. Dust is also visible in edge-on spirals as dark lanes, similar to the dark lanes we see in our own Milky Way when we observe the night sky.
- IRREGULAR GALAXY
- Galaxies that are not spiral or elliptical are called irregular galaxies. They have no defined shape nor structure and may have formed from collisions, close encounters with other galaxies or violent internal activity. They contain both old and young stars, significant amounts of gas and usually exhibit bright knots of star
- Irregular galaxies — such as the Large and Small Magellanic Clouds that flank our Milky Way — appear misshapen and lack a distinct form, often because they are within the gravitational influence of other galaxies close by. They are full of gas and dust, which makes them great nurseries for forming new stars.
This is a fantastic bundle which includes everything you need to know about Galaxy across 19 in-depth pages. These are ready-to-use Galaxy worksheets that are perfect for teaching students about the Galaxy which is a gravitationally bound entity, typically consisting of dark matter, gas, dust, and stars. Galaxies populate the Universe, mainly residing in clusters and groups.
Complete List Of Included Worksheets
- Galaxy Facts
- A Recall
- Three Types
- Choose What?
- Hubble Telescope
- Galaxy Formation
- That’s a Galaxy!
- Keep Us Posted
- Acrostic Facts
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Link will appear as Galaxy Facts & Worksheets: https://kidskonnect.com - KidsKonnect, August 12, 2019
Use With Any Curriculum
These worksheets have been specifically designed for use with any international curriculum. You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards.