There are many remarkable things about Polaris, the North Star. It lies less than one degree from the North Celestial Pole, and has been used for navigation for thousands of years. Polaris A is a very young star. It’s only about 100 million years old, about the same age as the Pleiades star cluster in Taurus (the Bull).

Polaris is moving closer to the North Celestial Pole, and will continue to do so until 2102. Polaris is a triple star system. The brightest star, Polaris A, is a supergiant star, about 5 times more massive than the sun. Polaris A is the star seen from Earth. It has almost the same surface temperature as the sun and is nearly the same color. Polaris A is a Cepheid, a star that pulsates or changes in brightness. It pulsates brighter about every 4 days, but it isn’t as regular as most Cepheids. It’s the closest Cepheid to Earth, at a distance of 430 light years away. The European satellite Hipparcos measured its parallax in 1997 and calculated the distance.

Polaris B is a main sequence star and is easy to see using a small telescope. It’s about 60 times the distance of Pluto to our sun, or 2,400 Astronomical Units from Polaris A. An Astronomical Unit is Earth’s distance to the sun, 93 million miles. Polaris B takes tens of thousands of years to make one orbit of Polaris A. The Hubble Space Telescope discovered the third star, Polaris C, in 2005. It’s a main sequence star that’s in orbit around Polaris A at about the same distance that Uranus orbits our sun. It orbits every 29.6 years, and affects the velocity of Polaris A with its gravity and close proximity.

Polaris A is very bright. It releases 2,400 times more light than our sun releases in three months! Polaris grows brighter over time too. It’s twice as bright as it was 2,000 years ago. Scientists believe Polaris A may be changing into a red or blue supergiant star.