Polaris, also known as the North Star, is more or less fixed in our sky. We can find the North Star in the constellation Ursa Minor, which is also known as the Little Dipper. Polaris is located at the end of the handle of the Little Dipper.
The stars of the Little Dipper are rather faint when viewed with the naked eyes!
In the sky, Polaris can be located by drawing a line between two stars Dubhe and Merak of the Big Dipper. This line, when extended further around five times, will end up at Polaris.
The stars in the Big Dipper are brighter than the stars of the Little Dipper. Other than this, the Big Dipper is upright, and the Little Dipper is upside down.
Usually, it is easily visible by the naked eye even on the full moon day. As far as size is concerned, do you know that Polaris is a supergiant with six times the mass of our Sun?
Scientists have explored that Polaris is 2400 times as luminous as our Sun!
The North Star has special importance for all those who reside in the Northern Hemisphere. If you view it from the equator, which is at 0 degrees latitude, you will find it on the northern horizon. Moving further down the southern hemisphere (say Australia or Brazil), you will not be able to see it because of the Earth’s curvature.
Currently, we are endowed with the GPS for our navigation whether in sea, land or air, but several centuries back, it was a terrible task to sail in the sea without any navigational aid. Compass also did not exist several centuries back.
The Pole Star is unique in the sense that while all other celestial objects keep changing their locations in the night, The North Star remains stationary hour after hour and night after night!
Sailors would take advantage of this constancy of the Star picking right direction while navigating in the sea. Sailors could also guess their latitudinal location by measuring the degree of the North Star in the sky!
It is not that the North Star does not move. It does make its small circle, but for all practical purposes, it appears fixed at one point because it is located along the north axis of the Earth.
The North Star or Polaris is unique in the sense that there is no parallel to it along the Southern Axis or pole of the Earth, and that is not likely to occur for another 2000 years at least.
As we move toward northward, the North Star also moves up and above, and close to the North Pole one can see it just overhead.
Many people assume that Polaris is the most luminous star in our sky. But, that is not true! By the way, the label of the most luminous star goes to Sirius!
According to the scientists, Polaris ranks at the 50th spot among the brightest stars in our sky, and it can be spotted with the naked eye. But be aware that the increasing light pollution in the cities may sometimes prevent you to see it with the naked eyes!
Do you know that some 6,000 years ago, Polaris was not the North Star?
Thuban, also known as Alpha Draconis, in the Draco constellation, enjoyed the status of the North Star then! And almost 19,000 years later, Thuban will again regain the label of the pole star replacing Polaris. This occurs due to the effects of axial ‘precession’ of the Earth.
You might be interested to know what exactly the precession is!
Well, the example of a spinning top can help you understand this phenomenon. When one gives a slight ‘nudge’ to the spinning top, its axis will start making a small circle taking a conical shape. This shift in the axis of the rotated top is known as precession.
Our Earth is not a true sphere instead it bulges in the middle; its equatorial diameter is higher than the polar diameter. Due to this bulging, the gravitational force of the Sun, Moon, and Jupiter exerts a required nudge causing precession of the Earth axis over time.
In 130 B.C, Hipparchus, the Greek astronomer, first informed the world about the precession of the Earth. It takes almost 26,000 years for the axis of the earth to complete one cycle.
Do you know at what distance Polaris is from the Earth!
The distance of Polaris from the Earth is estimated at 434 light-years, and one light-year is a distance that light travels in a year. The speed of light is astonishingly high to the tune of 186,000 miles per second! This means if we could travel with such a high speed it would take us 434 years to reach Polaris!
As a hypothetical case, if a couple rides on a plane that is destined to go to Polaris with the speed of the light, then their 18th or 19th generation will reach Polaris.
Another astonishing fact is that when we see Polaris any night, we are essentially viewing a historical Polaris that existed 434 years back in the past.
Conversely, the current Polaris can be viewed only after 434 years from now! This means if Polaris dies today, we can know about its death only after 434 years from now!
Paying tribute to the genius of Einstein, space and time are not two separate entities, but they form a single entity in the space-time continuum.
Some Other Astonishing Facts about Polaris
When you target your telescope on Polaris, you will also notice another star nearby called Polaris B (for our clarity, we will call Polaris as Polaris A). In 1780, William Herschel discovered this companion star for the first time.
Incidentally, Herschel also discovered the planet Uranus only a year later!
The distance between Polaris A and Polaris B is estimated close to 2,400 astronomical units (AU). One AU measures the average distance between our Sun and the Earth.
In 1929, a third companion star – a white dwarf called Polaris C, was also discovered. The distance between Polaris A and Polaris C is just 18.5 AU, which is indeed a small distance in this infinite universe!
Perhaps that was the reason why Polaris C went unnoticed for such a long time. Even being a white dwarf, its mass is 1.4 times higher than that of our Sun!
In a clear night, with a good telescope, we will be able to see Polaris C as well!
Is Polaris a Cepheid Star?
An interesting property of Polaris is that it is a Cepheid star! Cepheid stars brighten and dim at regular intervals. In case of Polaris, this interval is little over three days. Leavitt first noted this phenomenon of Cepheid stars in 1912.
Cepheid stars are very special stars in the sense scientists can identify them even if they are in other galaxies and help estimate the distance of that galaxy from our location.
The Pole Star in Mythology
The Pole Star is mentioned in the ancient scriptures and mythology profusely!
In Greek mythology, they called it Kynosoura. It means “the Dog’s Tail.” The word cynosure in English is said to have come from this Greek word.
In Hindu mythology, the North Star is called ‘Dhruva’ meaning an object that does not change over time. According to the story, God was so pleased with the boy named Dhruva that He granted him a permanent place in the sky when he died!
In the Arabian world, ‘Al Kiblah’ is the word used for the North Star meaning it is at the least distance from the North Pole. In the deserts, the Pole Star helped travelers to travel in the right direction with their caravan of camels.