Know that the Milky Way is one of many billions of galaxies making up the Universe and that the diameter of the Milky Way is approximately 100000 light-years

6.2.3 The Universe

🌌 The Universe is an enormous collection of galaxies, stars, planets and all the matter that exists.

Our home, the Milky Way, is just one of the billions of galaxies that make up this cosmic tapestry.

The Milky Way Galaxy

Think of the Milky Way as a bustling city of stars. It contains about 100–400 billion stars, many of which are similar to our Sun.

The galaxy is roughly a flat disk with a diameter of about \$100\,000\$ light‑years (≈9.46 × 10²⁰ m).

That’s the distance light travels in 100,000 years – a truly mind‑blowing scale!

• ⭐ Size comparison: If the Milky Way were the size of a football field, the Sun would be a tiny pin in the middle.
• 🚀 Travel time: Even at the speed of a spacecraft like Voyager 1 (≈17 km/s), it would take over 70,000 years to cross the galaxy.
• 🌍 Our position: We sit about 26,000 light‑years from the galactic centre, in the Orion Arm.

The Universe Beyond the Milky Way

The Universe contains an estimated 2 × 10¹¹ galaxies, each with its own stars, planets and mysteries.

Some galaxies are tiny (a few thousand stars), while others are super‑massive, spanning millions of light‑years.

Exam Tips

1. Remember the key fact: \$\text{Milky Way diameter} \approx 100\,000\ \text{light‑years}\$.
2. Use analogies (e.g., city, football field) to explain scale in written answers.
3. When comparing galaxy sizes, mention the range (dwarf to giant) and relate to the Milky Way.
4. Show understanding of “billions of galaxies” by giving an approximate number (≈2 × 10¹¹).
5. Include a simple diagram or table if allowed, but keep it clear and concise.