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How far is the Sun?

Space and time · level 2, lesson 3 of 6

A question to start

The Sun and the Moon look about the same size in the sky. Are they really the same size?

The idea

No. The Sun is far, far bigger, and far, far farther away.

  • The Sun is about 150 million km away: about 390 times as far as the Moon.
  • It is about 1,392,000 km across: about 109 Earths side by side.

They look the same size only because the Sun is so much farther away. A car driving at 100 km an hour would take about 170 years to get there.

The Sun is a star, a huge ball of hot, glowing gas. All the other stars are suns too, much farther away still.

the Earth, to scalethe Sun109 Earths would fitacross the Sun

Worked examples

1. How many Earths across. \(1{,}392{,}000 \div 12{,}756 \approx 109\).

2. Moon or Sun. \(150{,}000{,}000 \div 384{,}400 \approx 390\). The Sun is about 390 times as far as the Moon.

3. Driving there. \(150{,}000{,}000 \div 100 = 1{,}500{,}000\) hours. That is about 62,000 days, about 170 years.

Try it

  1. About how far away is the Sun?
  2. About how many Earths would fit across the Sun?
  3. Why do the Sun and Moon look about the same size?
  4. What is the Sun?
Answers
  1. About 150 million km.
  2. About 109.
  3. The Sun is much bigger, but also much farther away.
  4. A star: a huge ball of hot, glowing gas.

Common mistake

"The Sun is not a star; stars are tiny." Stars only look tiny because they are so far away. The Sun is an ordinary star that happens to be close.

Where it leads