Polaris is quite an unusual star. First, Polaris [
http://einstein.stc…] is the nearest bright star to the north spin axis [
http://antwrp.gsfc.…] of the Earth. Therefore, as the Earth turns, stars appear to rotate around Polaris [
http://www.physics.…], making it the North Star [
http://www.physics.…]. Since no bright star is near the south spin axis of the Earth, there is currently no South Star [
http://antwrp.gsfc.…]. Thousands of years ago, Earth's spin axis pointed in a slightly different direction [
http://www.fourmila…], and Vega [
http://antwrp.gsfc.…] was the North Star. Although Polaris [
http://www.seds.org…] is not the brightest star [
http://www.astro.wi…] on the sky, it is easily located because it is nearly aligned with two stars in the cup of the Big Dipper [
http://www.astro.wi…], and is the last star in the handle of the Little Dipper [
http://www.astro.wi…]. In the above picture, Polaris [
http://www.astro.wi…] is the brightest star on the right, above the fleeting streak of a Perseid meteor [
http://antwrp.gsfc.…]. The surface of Polaris slowly pulsates [
http://adsbit.harva…], causing the star to change its brightness by a few percent over the course of a few days. This rare Cepheid variability [
http://antwrp.gsfc.…] of Polaris is, oddly enough, itself changing [
http://adsabs.harva…].
Explanation
Polaris is quite an unusual star. First, Polaris [
http://einstein.stc…] is the nearest bright star to the north spin axis [
http://antwrp.gsfc.…] of the Earth. Therefore, as the Earth turns, stars appear to rotate around Polaris [
http://www.physics.…], making it the North Star [
http://www.physics.…]. Since no bright star is near the south spin axis of the Earth, there is currently no South Star [
http://antwrp.gsfc.…]. Thousands of years ago, Earth's spin axis pointed in a slightly different direction [
http://www.fourmila…], and Vega [
http://antwrp.gsfc.…] was the North Star. Although Polaris [
http://www.seds.org…] is not the brightest star [
http://www.astro.wi…] on the sky, it is easily located because it is nearly aligned with two stars in the cup of the Big Dipper [
http://www.astro.wi…], and is the last star in the handle of the Little Dipper [
http://www.astro.wi…]. In the above picture, Polaris [
http://www.astro.wi…] is the brightest star on the right, above the fleeting streak of a Perseid meteor [
http://antwrp.gsfc.…]. The surface of Polaris slowly pulsates [
http://adsbit.harva…], causing the star to change its brightness by a few percent over the course of a few days. This rare Cepheid variability [
http://antwrp.gsfc.…] of Polaris is, oddly enough, itself changing [
http://adsabs.harva…].
Explanation
