What Is a Galaxy? What Is the Milky Way? — For Kids
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What Is a Galaxy? — Elementary
The short answer
A galaxy is a big group in space.
It has stars.
It has gas.
It has dust.
Gravity holds them all together as a group.
Gravity is the pull that holds the group together.
So many stars, so many galaxies
One galaxy may have millions of stars.
One galaxy may even have billions of stars.
And there are billions of galaxies in the universe.
The universe is all of space.
How big is a galaxy?
A galaxy may be as little as a thousand light-years across.
A galaxy may be as much as a million light-years across.
A light-year is the distance light travels in one year, 9.5 trillion (9,500,000,000,000) kilometers.
Four shapes of galaxies
Galaxies are named by their shape.
A spiral galaxy looks like a giant pinwheel.
An elliptical galaxy looks like a flat ball.
An irregular galaxy does not really have a shape.
A starburst galaxy is a galaxy where new stars burst out very quickly.
Our home galaxy: the Milky Way
We live in a galaxy.
Its name is the Milky Way.
The Milky Way is a spiral galaxy.
It looks like a giant pinwheel.
It contains more than 200 billion stars.
It is about 100,000 light-years across.
Words to know
- Galaxy
- A group of stars, gas, and dust held together by gravity. One galaxy may have millions, or even billions, of stars.
- Gravity
- The pull that holds the stars, gas, and dust in a galaxy together as a group.
- Spiral
- A galaxy shape that looks like a giant pinwheel. The Milky Way is a spiral galaxy.
- Elliptical
- A galaxy shape that looks like a flat ball.
- Irregular
- A galaxy that does not really have a shape.
- Starburst
- A galaxy where new stars burst out very quickly.
- Light-year
- The distance light travels in one year, 9.5 trillion (9,500,000,000,000) kilometers.
- Milky Way
- The galaxy we live in. It is a spiral galaxy.
What Is a Galaxy? — Middle
The short answer
A galaxy contains stars, gas, and dust which are held together as a group by gravity.
There may be millions, or even billions, of stars in one galaxy, and there are billions of galaxies in the universe.
How big galaxies can be
The size of a galaxy may be as little as a thousand light-years across or as much as a million light-years across.
A light-year is the distance light travels in one year. It is 9.5 trillion (9,500,000,000,000) kilometers.
Galaxies are labeled by shape
Galaxies are labeled according to their shape, and there are four kinds named here.
Some galaxies are called “spiral”, because they look like giant pinwheels in the sky.
Some galaxies are called “elliptical”, because they look like flat balls.
A galaxy may be called “irregular” if it doesn’t really have a shape.
A new type of galaxy was discovered recently, called a “starburst” galaxy. In this type of galaxy, new stars just seem to ‘burst out’ very quickly.
The Milky Way, the galaxy we live in
The galaxy we live in, the Milky Way, is a spiral galaxy, so it has the pinwheel shape described above.
The Milky Way contains more than 200 billion stars, and its diameter is about 100,000 light-years.
That makes our home galaxy one of the billions of galaxies in the universe, each one a group of stars, gas, and dust held together by gravity.
Words to know
- Galaxy
- A group of stars, gas, and dust held together as a group by gravity. There may be millions, or even billions, of stars in one galaxy, and there are billions of galaxies in the universe.
- Gravity
- The force that holds the stars, gas, and dust in a galaxy together as a group.
- Spiral
- A galaxy that looks like a giant pinwheel in the sky. The galaxy we live in, the Milky Way, is a spiral galaxy.
- Elliptical
- A galaxy that looks like a flat ball.
- Irregular
- A galaxy that doesn’t really have a shape.
- Starburst
- A type of galaxy in which new stars just seem to ‘burst out’ very quickly.
- Light-year
- The distance light travels in one year. It is 9.5 trillion (9,500,000,000,000) kilometers.
- Milky Way
- The galaxy we live in. It is a spiral galaxy. It contains more than 200 billion stars, and its diameter is about 100,000 light-years.
You can also read the page called “What Is a Light-Year? — For Kids”
You can also read the page called “What Is a Black Hole? — For Kids”
Sources
This page was built only from these sources:
NASA StarChild — “Galaxies” — Universe Level 1 — https://starchild.gsfc.nasa.gov/docs/StarChild/universe_level1/galaxies.html
NASA / Amazing Space — Student Background Reading: About Galaxies — https://docent.calacademy.org/sites/default/files/assets/docs/pdf/stud_read_aboutgals_nasa.pdf
Checked November 2, 2026.