Polaris

Polaris, aka the North Star (Pole Star, α UMi) is a star known for being close to the celestial north pole, currently about 40 arcminutes apart. Amateur astronomers and casual observers of the stars often orient themselves to the celestial sphere by finding Polaris, first finding the Big Dipper (an asterism that is part of the standard constellation, Ursa Major), then using two of its stars that form a line with Polaris.

Celestial north (the direction of Earth's axis, toward the north) shifts with the precession of the equinoxes (a slow wobble of the Earth's rotation), such that in the past and future, it was not so close to Polaris. It has been close to Polaris over the past few centuries and will be closest in about the year 2100. It shifts a degree roughly every couple of hundred years, and two thousand years ago, it was on the order of ten degrees away from Polaris, and no star nearly as prominent as Polaris was closer.

Polaris is a triple star, the prominent member that we see (α UMi Aa) being an F-type giant Cepheid variable. The nearer companion (α UMi Ab) orbits it roughly every 30 years. The further companion (α UMi B) is on the order of 2500 astronomical unit distant and I haven't found an orbital period estimate. Characteristics (of α UMi Aa):

• Constellation: Ursa Minor
• 02h31m49.09s - right ascension.
• +89deg15m50.8s - declination.
• +1.98 - apparent magnitude (V).
• 446.5 ly - distance.
• F7b - spectral type.
• 5.13 - mass(solar).
• 1260 - luminosity(solar).
• 46.27 - radius(solar).
• +0.42 - B-V color index.