Polaris has been an important navigation star for many centuries. But it isn't just one star, it's a triple star system. The main star is a luminous supergiant – it's now called Polaris A. In the 18th century William Herschel discovered a companion star (Polaris B). They were far enough apart that he was able to see the companion with a good telescope. Today good binoculars will do the job.
The big surprise was that there is a third star. It was invisible, but in the early 20th century was discovered by analyzing the light spectrum of Polaris. The third star (Polaris Ab) is so close to the bright supergiant that it's lost in its glare. But – at last! - nearly eighty years later,
Hubble Space Telescope managed to image it in 2006.
