Polaris
Star · Yellow supergiant
Polaris is the North Star. It isn’t the brightest star, but it’s special: Earth’s axis points almost straight at it, so while all other stars circle through the night, Polaris stays put. For centuries it guided sailors and travellers.
- 430 light-years awayEven light – the fastest thing there is – needs 430 years to get here.
- North StarAlso called
- Cepheid variableType
Take a closer look
A real giant
Polaris looks fairly ordinary because it is so far away – about 430 light-years. Up close it is a yellow supergiant, dozens of times wider than our Sun and more than a thousand times brighter. In fact it is only around the 50th brightest star in the night sky.
Not quite on target
Polaris is not exactly above Earth’s North Pole. It is slightly off to one side – a little more than the width of the full Moon – so it actually draws a very tiny circle in the sky each night. It will be at its closest to the pole around the year 2100.
A cosmic measuring tape
Polaris belongs to a family of pulsing stars called Cepheids. In 1912, Henrietta Leavitt discovered that the slower a Cepheid pulses, the brighter it truly is. That lets astronomers work out how far away Cepheids are – even in other galaxies – and Polaris is the closest Cepheid of all.
How we found out
- For centuries
Navigators use Polaris to find north and to estimate their latitude at sea.
- 1780
William Herschel discovers that Polaris has a companion star. We now know it is a triple star system.
- 1911
Astronomers discover that Polaris gently pulses in brightness – it is a Cepheid variable.
Will Polaris always be the North Star?
No! Earth’s axis slowly wobbles like a spinning top. In about 12,000 years, the bright star Vega will be close to the pole instead.
See it yourself
Only from the Northern Hemisphere. Follow the two “pointer stars” at the end of the Big Dipper.
From the encyclopedia
Read the full article on Wikipedia ↗Got it?
Mark Polaris as explored to earn 10 XP.