The North Star is perhaps one of the most frequently mentioned stars. It is mentioned on the pages of fiction, in the notes of sailors, scientific research. The luminosity owes its fame, even popularity, primarily to the direction that the North Star shows. Its unique position for several hundred years helps travelers to navigate both by sea and by land. In addition, it plays a role in determining distances in space, and therefore is the subject of many scientific studies. But first things first.
Dancing stars
The answer to the question, which direction does the North Star show, is inextricably linked with the place of the star in an imaginary celestial sphere. If you watch the stars from the Earth, it seems as if they are moving around the planet, then descending below the horizon, then emerging again. In the images taken by the camera with a high shutter speed, it is clear that the stars move along circular paths of different diameters. The smaller they are, the closer the star is to the pole of the celestial sphere. In the center of the circles formed by the movement of stars in the Northern Hemisphere, there is a fixed point. This is the North Star, or, as some people called it, the Northern Nail, Funny Star, Iron or Heavenly stake, Golden Pile.
Features of the situation
The “nail” metaphor is very successful: if we continue the imaginary metal rod from the “hat”, then it is easy to understand what direction the North Star shows. This “nail” pierces the globe exactly at the North Pole, passes through all the inner layers of the planet and reappears at the point of the South Pole. Thus, the North Star in the sky is located on the continuation of the earth's axis. Less than 1º separates it from the North Pole.
It should be noted that the North Star moves in the same way as the rest of the stars. Its seemingly fixed place for us is connected precisely with the location on the extension of the axis. Indeed, in fact, the rather rapid movement of stars is associated not only with their own movement, but also with the rotation of the planet. Making revolutions around the axis, the Earth turns to the stars one side or the other. And only luminaries located above the poles always see the same part of the surface. By the way, the South Pole also has its own polar star - Sigma Octant, but it is very dim in comparison with others. However, after a while, everything can change.
Post passed - post accepted
The North Star has been showing north since about 1100 AD. It will be as close to the pole of the world as possible only in 2100, and then it will begin to move away. So, from the beginning of time, the post of the main index has been transferred from one star to another. This is due to the proper motion of the stars, as well as to such a phenomenon as the precession of the earth's axis. The imaginary rod piercing the planet also moves: it slowly describes the circles. The reason lies in the peculiarities of the shape of the globe and the action of gravity. The axis passes one circle in almost 26 thousand years.
About 15 thousand years ago, the role of the Northern Nail was Vega, the brightest point of the constellation Lyra. And after a little less than 11 thousand years, she will again occupy this position. In the near future, Alrai (Gamma Cephei) will replace the Pole Star, it will be in 3200. And in 5000 Alrai will be replaced by Beta of the same constellation, Alfirk, and then, in 6500, Alderamin (Alpha Cepheus). Between 8500 and 13,000 years, the position of the North Star will be occupied by Deneb and Sadr from the constellation Cygnus.
How to find the North Star?
There is one very persistent myth associated with the Northern Nail, generated by its fame and popularity. It seems that the star, which is on everyone’s lips, should be, if not the brightest in the sky, then at least overshadowing many others. However, it is not. The North Star is located in the constellation Ursa Minor and among other luminaries in its composition really stands out. Moreover, in the list of the brightest points of the whole night sky, it takes only 46th place. Therefore, it is important to know how to find the North Star.
The main guideline is Ursa Major. The constellation is familiar to almost everyone since childhood. To detect the Northern Nail, it is necessary to mentally connect one extreme two extreme stars of the Big Bucket - Dubge and Merak. If we continue the line to a distance of approximately five segments between Dubge and Merak, then at its end we will find the North Star. She crowns the tail of Ursa Minor.
How to navigate the area by the North Star?
From the moment the Northern Nail was in close proximity to the pole of the world, it began to be used as a convenient guide. The North Star indicates the direction to the north, and even more accurately than another compass. Determining the cardinal points is quite simple. It is necessary to lower the perpendicular to the surface of the North Star. If you face him, then the south will be exactly behind, east - on the right, west - on the left.
Not only does the North Star show north, it also serves as an indication of the geographical latitude of the area. To determine it, you need to measure the height of the star above the horizon. The lower the value, the closer to the equator. At the North Pole, the North Star is at its zenith. At the equator, it almost merges with the horizon line. Specifically, determining the angle between the North Star and the horizon in the north direction, the sailors of the past centuries were guided by the terrain, laid and corrected their route.
On other planets
In the open spaces there are many analogues of our North Star. Rotation around the axis is an integral property of all planets, and therefore, if you observe the movement of stars from their surface, it is easy to find fixed points pointing to the South and North poles. For Mercury, for example, the polar star is Omicron Ophiuchus, its southern counterpart is the Alpha of the constellation Painter. There is a Northern Nail and the Moon is the Golden Fish Delta.
Importance for Astronomy
The North Star, or Alpha Ursa Minor, has a whole range of features that make it unique. Among them are periodic pulsations, which make it possible to attribute the luminary to the class of Cepheids. They are characterized by a change in gloss, temperature and size. The period of the pulsation of the North Star is 3.97 days. At the same time, changes in brightness from the Earth are imperceptible.
Studies have shown that there is a relationship between periods of pulsation and the luminosity of Cepheids. It turned out that the longer the period, the greater the luminosity. This ratio is used in astronomy to determine the distance to distant objects. And since the North Star is the closest Cepheid to the solar system, its role in the calculations can hardly be overestimated, especially considering that with increasing distance to the periodic star, the accuracy of the data decreases.
Non-standard
This property of the North Star attracted the attention of many researchers to it. In the process of studying, it became known that the Northern Nail - Cepheid is not easy. Its pulsations have a peculiarity: they gradually fade. At the end of the last century, there was an assumption that in the early 2000s a star may cease to be a Cepheid, which has never happened in scientific history. However, this did not happen: in 1993, changes in the amplitude of the pulsations stopped. In addition, during this time, the star became brighter by 15%.
Cosmic infinity
To determine the distance to distant objects, data on the luminosity and location of all the nearest Cepheids are used. Using this method, in the first quarter of the last century, the famous Edwin Hubble determined the distance to the Andromeda nebula and proved the existence of other galaxies. Today, on the basis of the technique, the sizes of many stellar "communities" have been calculated. It is based on the modern understanding of the scale of the universe.
Little but
The catch is that today there is no consensus among researchers about the distance to the North Star itself. The accepted figure, 400 with a small light-year, was received by the Hipparkos satellite in 1990. However, at the beginning of our century, this estimate underwent changes: first it was reduced to 330, then increased to 359 light years. Finally, in 2012, David Turner put forward a new assumption - 323 light years.
As already noted, the North Star is the closest Cepheid to the solar system. With a decrease or increase in the distance to it, our understanding of cosmic scales also changes. Decreasing the value not only makes the stars and galaxies a little closer, but also affects the estimation of the size of the Universe. Clarification of the distance to the North Star will make its own corrections in understanding the scale of space, make it necessary to overestimate the mass of dark matter, and may result in a revision of some aspects of the theory of expansion of the Universe.
Astronomical features
The direction that the North Star shows is generally little dependent on some of its cosmic characteristics. However, it is they who, one might say, compensate for the modesty of the brilliance of the body so important for orienting the terrain .
The North Star is brighter and larger than the Sun. It belongs to the class of supergiants, has a radius exceeding the solar by 46 times. The luminosity of the Northern Nail is 2500 times greater than the similar parameter of our star.
But that’s not all: the Polar is not a solitary star. It is part of a system of three bodies, differing in size and brightness. Polar A is the center of the system, that same supergiant, at an impressive distance from it is Polar B. This star is much smaller, its mass is only 1.39 solar (the mass of Polar A is 4.5 solar). Very close to the supergiant is his companion, Polar Ab (1.26 solar masses). Due to the small distance separating the two luminaries, the "modest companion" could not be detected for a long time. His image was only obtained using the Hubble telescope.
It turns out, not only where the North Star shows, makes it unique in the sky. A non-standard Cepheid and a triple system, it occupies the minds of many astronomers. And it looks very symbolic. For a long time in history, the direction of the North Star (the path indicated by it) helped to navigate at night on the expanses of the ocean or in unfamiliar terrain.
Today, when instead of natural signs, various devices and gadgets are still more often used, the North Star remains a reference point in outer space. And although the Northern Nail in its new quality does not indicate the direction, but helps to determine the distance, its value and significance for man and science as a whole does not decrease. And therefore, researchers are working on an accurate determination of how far the North Star is from the Sun, why its pulsation dies, and do not disregard this small and even inconspicuous, in the opinion of a simple earth observer, star.