What Is The North Star?
QUICK ANSWER
The North Star is Polaris, a star located almost directly above Earth's north pole. Because Polaris sits so close to the north celestial pole, it appears nearly stationary in the sky while other stars rotate around it. Polaris is at the end of the Little Dipper's handle and has been used for navigation for centuries.
The North Star, formally called Polaris, is the most famous star in the Northern Hemisphere sky. It's not particularly bright, but its near-perfect alignment with Earth's rotational axis makes it stay almost still while other stars circle around it through the night. This has made Polaris invaluable for navigation for thousands of years. Surprisingly, Polaris hasn't always been the North Star and won't always be.
Where is Polaris?
At the end of the Little Dipper's handle. According to NASA, Polaris sits at the end of the handle of the Little Dipper (also the tail of the constellation Ursa Minor). It's about 430 light years from Earth. To find Polaris from a dark sky location, locate the Big Dipper first. The two stars at the end of the Big Dipper's bowl are called pointer stars; drawing a line from them upward leads directly to Polaris, about five times the distance between the two pointer stars.
Why does it appear to stay still?
Because it sits almost directly above Earth's north pole. Polaris is positioned within about three-quarters of a degree of the north celestial pole, the imaginary point in the sky where Earth's rotational axis points. As Earth rotates through the night, all other stars appear to circle around Polaris while it stays nearly fixed. Long-exposure photographs of the night sky show this as star trails forming concentric circles around the North Star. This unique behavior has made Polaris essential for navigation throughout history.
How bright is Polaris?
Not particularly bright. Polaris is only about the 50th brightest star visible from Earth, dimmer than the stars in the Big Dipper. Many people first seeing it are surprised. Polaris stands out because of its location and its near-immobility, not its brilliance. The star is actually a triple-star system; NASA's Hubble Space Telescope confirmed the closest companion in 2006. The main star is a yellow supergiant about 2,500 times more luminous than the Sun, but distance reduces its apparent brightness.
Has it always been the North Star?
No. Earth's rotational axis slowly wobbles through a 26,000-year cycle called precession. This means the celestial pole points to different stars over time. Around 3000 BCE, the pole star was Thuban (in Draco). By about 14,000 CE, Vega will be the pole star. Polaris is currently in its position as North Star for an extended period because the wobble brings the pole nearly to it. The star will gradually drift from the pole over the next several thousand years, becoming less reliable for navigation.
The North Star is Polaris, located almost directly above Earth's north pole. It appears nearly stationary while other stars circle around it through the night, making it valuable for navigation. Polaris sits at the end of the Little Dipper's handle and can be found using the Big Dipper's pointer stars. It's not particularly bright. Due to Earth's axial precession, Polaris hasn't always been the North Star and won't be in the distant future.
More Sun & Stars Questions
Mystery Question?
Mystery Question?
Mystery Question?