Galaxies - Definition, Examples, Quiz, FAQ, Trivia
Discover how billions of stars form giant islands in space!
What is a Galaxy?
A galaxy is a huge collection of gas, dust, and billions of stars held together by gravity. Think of it as a "city of stars" in space! Each galaxy is like its own island universe, separated by vast empty spaces.
Galaxies come in different shapes and sizes. Our home galaxy is called the Milky Way, which contains our solar system. The universe has billions of galaxies, each containing millions or even trillions of stars!
Space Fact!
The largest known galaxy, IC 1101, contains about 100 trillion stars - that's 1,000 times more than our Milky Way!
Types of Galaxies
Astronomers classify galaxies into three main types based on their shapes:
Spiral Galaxies
Have flat, spinning disks with spiral arms. Our Milky Way and the Andromeda Galaxy are spirals.
Elliptical Galaxies
Round or oval shaped with older stars and less gas. They look like fuzzy footballs in space.
Irregular Galaxies
No definite shape. Often form after galaxy collisions. The Large Magellanic Cloud is irregular.
Galaxies also group together. Our Milky Way is part of the Local Group, which contains about 50 galaxies. Groups of galaxies form even larger structures called galaxy clusters.
Hubble's Discovery!
In the 1920s, astronomer Edwin Hubble discovered that the Andromeda "nebula" was actually another galaxy beyond our own!
Our Home: The Milky Way
The Milky Way is our cosmic home - a barred spiral galaxy about 100,000 light-years across. Here's what makes it special:
Billions of Stars
Contains 100-400 billion stars, including our Sun
Supermassive Black Hole
Sagittarius A* at the center has 4 million times the Sun's mass
Spiral Structure
Has several spiral arms where new stars form
Galactic Neighborhood
Part of the Local Group with Andromeda and other galaxies
Our solar system is located in the Orion Arm, about 27,000 light-years from the galactic center. In about 4 billion years, the Milky Way will collide with the Andromeda Galaxy to form a new elliptical galaxy!
Dark Matter Mystery!
Most of the Milky Way's mass is invisible "dark matter" that we can only detect by its gravitational effects!
Galaxy Quiz
Test your galaxy knowledge with this cosmic quiz! Answer all 5 questions to see how much you've learned.
Frequently Asked Questions
Here are answers to some common questions about galaxies:
Galaxy Trivia
Discover some amazing facts about galaxies!
Time Travel
When we look at the Andromeda Galaxy, we're seeing it as it was 2.5 million years ago because that's how long its light takes to reach us!
Size Record
The largest known galaxy is IC 1101, which is 6 million light-years across - about 60 times wider than our Milky Way!
Deep Field Image
The Hubble Space Telescope's Deep Field image revealed over 3,000 galaxies in a tiny patch of sky that appeared empty to previous telescopes!
Supermassive Black Holes
Nearly every large galaxy has a supermassive black hole at its center. The one in our Milky Way has a mass 4 million times greater than our Sun!
