If you’ve ever seen the Northern Hemisphere’s night sky, you could have spotted that glistening object that gives the impression that everything is moving around it. The star you are observing is the Polaris Star, sometimes referred to as the North Star. It is a component of the Ursa Minor constellation and is located around 430 light-years from Earth.
Due to its near-stationary nature and the appearance of other stars revolving around it in the night sky, Polaris has been an essential navigational reference for countless years, helping travelers make their way due north. Let’s examine this bright beacon’s features and discover how to find it with ease.
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A well-known star in the Northern Hemisphere, the Polaris Star is often referred to as the North Star, Northern Star, or Pole Star. It is especially located in the Ursa Minor constellation, sometimes known as the Little Bear or the Little Dipper. It is positioned almost exactly in line with the axis of rotation of Earth and stays above the North Pole.
Instead than being a single star, Polaris is really a trinary system made up of two lesser companion stars, Polaris B and Polaris Ab, plus the main star, Polaris A. (In astronomy, three celestial objects that are gravitationally connected to one another make up a trinary system.)
Despite being well-known for appearing to be unwavering in our sky, Polaris A is really a supergiant star that is around 323 light-years away from Earth and has a mass roughly six times that of the sun. It is classified as a Cepheid variable star as it pulses and changes in brightness in a cycle that is predictable.
Even though Polaris is now the North Star, this designation is temporary because to axial precession, a slow shift in the Earth’s axial position. Another brilliant star, Vega, will replace Polaris as our primary night sky marker in around 12,000 years.
No Rise or Set for Polaris
According to astronomer and former communications officer of the American Astronomical Society Rick Fienberg, who received his training at Harvard, the reason the North Star got its name is because it lies practically directly overhead the North Pole in the night sky.
Thus, Fienberg writes in an email, “If you were to stand at the North Pole, which is latitude 90 degrees north, at night and look straight up, you would see Polaris directly overhead.” If you reside in Portland, Oregon, which is located at a latitude of 45 degrees north, you may see Polaris glowing there if you face north at night and stare at the same angle above the horizon as your latitude (for example, look approximately halfway up — 45 degrees).”
According to Fienberg, Polaris is distinctive because, in contrast to all the other stars in the sky, it is always visible in the same spot from nightfall to dawn and never rises or sets. Because of its imposing appearance, some people incorrectly believe it to be the brightest star in the sky, but it is really the 48th brightest.
Even yet, due to its greater mass and girth, it is almost 2,500 times more bright than our sun. However, the fact that Polaris is far distant for a star that can be seen with the unaided eye also lessens the brilliance of the light.
Has the North Star Always Been Polaris?
Though it may seem unbelievable, Polaris hasn’t always been a realm of heavenly aristocracy. According to Giulio Magli’s book, “Architecture, Astronomy and Sacred Landscape in Ancient Egypt,” Egyptian astronomers of the Old Kingdom, between 4,700 and 4,100 years ago, really had a distinct North Star, which they symbolically symbolized with a female hippopotamus.
This is due to the fact that our perception of the North Star has evolved throughout time.
As the Earth spins, “if you picture a line connecting Earth’s North and South Poles as the axis around which Earth rotates, that axis is slowly moving in its own circle,” says Christopher Palma, an assistant dean at Penn State University’s Eberly College of Science. This is often likened to what occurs when a coin or a top begins to ‘wobble’ before toppling over onto its side. Earth’s North Pole is ‘precessing,’ meaning that a circle with a period of 26,000 years is traced by the line connecting the North and South Poles.”
Consequently, “the North Pole moves with respect to the stars over very long time periods (more than a few thousand years)” says Palma. “So thousands of years ago, people on Earth saw the star Thuban in [the constellation] Draco appear due north, instead of Polaris.”
How to Locate the Sky’s North Star
Being able to locate the North Star may be a valuable and enjoyable talent, particularly while traveling at night. Make sure you’re in an area with less light pollution before starting your stargazing expedition. The higher Polaris is in the sky the further north you are. Polaris is always straight north and is nearly aligned with your latitude.
Find the Great Dipper. Start with recognizing the most well-known constellation in the northern sky, the Big Dipper. Search for the “dipper” shape, which is made up of a cluster of seven brilliant stars: The “bowl” is formed by four stars, and the “handle” by three.
Observe the guidelines. Pay attention to the two stars that make up the bowl’s outer edge on the Big Dipper. Known as the “pointer stars” because they direct you to Polaris, these are Dubhe and Merak. Picture a straight line passing through Dubhe, the top star, and Merak, the bottom star.
Acquire Polaris. Stretch the fictitious line outward from the points by roughly five times the separation between Dubhe and Merak. Polaris is the bright star in this line. It should be somewhat far from nearby brilliant stars.
Verifying the Polaris. At the end of the Little Dipper’s (Ursa Minor) handle is Polaris. You may be able to confirm it by seeing a smaller dipper-shaped group of stars, with Polaris being noticeably brighter.
The Navigator’s North Star
The astronomer Claudius Ptolemy, who flourished in the second century CE, appears to have been the first to map Polaris. Navigators ultimately found the star’s proximity to the celestial North Pole to be advantageous.
“At night, in the Northern Hemisphere, if you can see Polaris, you can always tell which way is north (and, by extension, which ways are south, east and west),” Fienberg asserts. “It is true today, it has been true for hundreds of years (including the 15th through 17th century, when exploration was at its height), and it will continue to be true for hundreds of years beyond that. Since the angle from the horizon to Polaris equals your latitude (to within a degree, anyhow), you may also determine your latitude. However, Polaris disappears below the horizon as you move south of the equator, making it useless as a navigational aid.”
However, as astronomy professor Rich Schuler notes in an email conversation, a navigator using Polaris must consider that the star has an offset of 39 arc-minutes and is not exactly above the North Pole. (This 2002 Scientific American primer on the North Star is written by him.) According to him, it translates to a 44.7-mile (72-kilometer) inaccuracy.
The North Star Twinkles for This Reason
The fact that Polaris is a Cepheid Variable—a kind of star that pulses radially, changing in diameter and temperature and causing variations in brightness with a clearly determined constant time and amplitude—is another fascinating aspect of this star.
“This star pulsates because it is in a state that is unstable,” Palma explains. “It will expand, and as it does, the star cools down because its outer layer becomes transparent. It will cool down and contract until it turns opaque once more, at which point it will reheat and expand once more. It will repeatedly pulse in and out like this, changing its brightness in the process.”