Due to the Earth’s self-rotation around its axis, stars constantly change positions in the sky, rising and setting. However, the Earth’s axis is pointed directly towards Polaris, making it appear as though it never moves.
Polaris is located 434 light-years from Earth and shines 4,000 times brighter than the Sun. It is the 48th brightest star in the sky, with an apparent magnitude of 2.02.
Apparent magnitude is the measure of a star’s brightness as seen from Earth. The smaller the number, the brighter the star. The Moon and Venus have negative magnitudes.
According to astronomers, the phenomenon of precession (the wobble of the Earth’s axis) causes the Earth’s axis to shift direction each year. In about 500 years, it will no longer point towards Polaris.
Polaris is a Cepheid variable star, which means it pulsates and changes brightness in cycles of several days. The small point we see with the naked eye is actually the combined light from a system of three stars orbiting a common center of mass.
The first star, Polaris A, is a supergiant weighing six times more than the Sun. The second companion star, Polaris Ab, orbits it at a distance of about 2 billion kilometers. The third star, Polaris B, is even farther away.
Polaris is actually a system of three stars orbiting a common center.
In Vietnam, Polaris is often confused with the “Northern Dipper.”
The Northern Dipper actually refers to a constellation in ancient Eastern astronomy, consisting of seven bright stars (the Seven Stars of the Northern Dipper), which are the seven stars forming the handle of the Big Dipper constellation.
Because it is located near Polaris and is easily recognizable, ancient people often used this constellation to find Polaris (by extending the outer edge of the dipper five times to reach Polaris) to determine the northern direction.
