A galaxy is a huge collection of stars , gas, dust , and dark matter , all held together by gravity . Our home galaxy is called the Milky Way. On a very clear , dark night you can see part of it as a hazy band of light stretching across the sky — that glow is the combined light of countless distant stars .
✨ The Milky Way contains between 100 and 400 billion stars . Our Sun is just one of them — a perfectly ordinary star in one of the galaxy's outer spiral arms .
Our Milky Way is so wide that light , the fastest thing in the universe , takes about 100,000 years to cross from one side to the other. Our Sun sits roughly halfway out from the centre , and it takes around 230 million years to make one full lap around the galaxy . The last time the Sun was in this exact spot , dinosaurs had not yet appeared !
Galaxies come in different shapes . Spiral galaxies , like the Milky Way, have curved arms of stars sweeping out from a bright centre . Elliptical galaxies are rounder blobs , often filled with older stars . Irregular galaxies have no set shape at all, frequently because they have been tugged out of shape by a neighbour's gravity .
📷 ESA/Hubble NASA, R. Chandar, J. Lee and the PHANGS-HST team · Public domain🃏 Flip each card to learn about galaxy shapes.
? Spiral galaxy Curved arms sweeping from a bright centre — like the Milky Way
? Elliptical galaxy A rounded blob of stars, no spiral arms
? Irregular galaxy No set shape — often smaller and messier
? Barred spiral A spiral galaxy with a straight bar of stars through its centre
Tap each card to see the answer.
🗂️ Sort each description into the right galaxy shape.
Has curved arms from a bright centre
? Spiral Elliptical Irregular
The Milky Way is one of these
? Spiral Elliptical Irregular
A smooth, rounded blob of older stars
? Spiral Elliptical Irregular
No particular shape at all
? Spiral Elliptical Irregular
✨ The nearest large galaxy to ours is the Andromeda Galaxy , about 2.5 million light-years away . One light-year is roughly 9.5 trillion kilometres — Andromeda is extraordinarily far!
At the heart of almost every large galaxy lurks a supermassive black hole . The one at the centre of the Milky Way is called Sagittarius A*, and it weighs about four million times as much as our Sun. Far from tearing the galaxy apart , it sits quietly at the centre while billions of stars orbit around it.
📷 Taavi Niittee · CC BY-SA 4.0💡 In about 4.5 billion years , the Milky Way and Andromeda will slowly collide and merge into one giant new galaxy . The stars are so spread out that very few will actually crash into each other!
Astronomers estimate there are at least two trillion galaxies in the observable universe . That means there are more galaxies out there than there are grains of sand on all of Earth's beaches put together . The universe is almost impossibly large — and every one of those galaxies is filled with billions of stars .
✍️ Fill in the galaxy facts.
Our home galaxy is called the _____ . Its nearest large neighbour is the _____ galaxy . At the centre of most large galaxies sits a supermassive _____ hole .
Milky Way Andromeda black Solar System Orion
