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Pole Star

Polaris is next to the sky's north pole and can therefore easily be used to locate directions.
It is a system made of a weakly pulsating Cepheid variable (Aa) and a yellow main sequence star (B). The bigger star A has another very close companion (Ab), which was made visible by the Hubble telescope.

Constellation: Ursa Minor
Distance: 430 light-years
Radial velocity: -17.4 km/sec
Space between Polaris A and B: 2646 AU
Space between Polaris Aa and Ab: 18.5 AU
Orbit period of Polaris Aa and Ab: 30 years

Polaris Aa

Spectral class: F7
Visual magnitude: 2.10
Luminosity: 2204 * Sun
Mass: 6 * Sun
Diameter: 43.9 * Sun

Polaris B

Spectral class: F3
Visual magnitude: 8.40
Luminosity: 6.65 * Sun
Mass: 1.5 * Sun

Back: List of big and giant stars
Polaris A and B
Photo: Nasa
Polaris Ab
Polaris Aa and Ab
Photo: NASA / STScI / N. Evans (CfA)

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