The popularization of knowledge from the field of astronomy today is largely promoted by interest in astrology, horoscopes and secret knowledge. But novels such as the Map (Mystery) of the Celestial Sphere, or the Secret Meridian by the famous Spanish novelist Arturo Perez-Reverte, who has become a bestseller since 2007, do not fill up knowledge from the field of classical astronomy. In the article, we consider the concept of the celestial sphere. And, of course, its characteristics are the celestial meridian and the equator.
Midday
That is how the very word "meridian" is translated from Latin. It is understood as a line of section of any surface by a plane that passes through the axis of symmetry of the body.
There are astronomical, geographical, magnetic meridians. In folk healing there are concepts of the meridians of the human body.
The development of astrology as a science of the relationship between the location of stars at the time of the birth of a person and their influence on fate is associated with the concept of meridian. That is how the ancient astrologers identified every 16 degrees in the ecliptic strip, which formed the twelve zodiac signs-constellations.
And although today our knowledge about the location of stars on the vault of heaven is much wider, but the zodiacal signs continue to be used in astronomy.
So different meridians
The mentioned novel refers to a secret heavenly meridian, the decoding of which is associated with the hidden treasures of the Jesuits. And how many really meridians?
In astronomy, the following are distinguished:
- Meridian astronomical or true. This is a line on the surface of the earth where all points are characterized by the same astronomical longitude. The plane of this meridian passes through the direction of the plumb line at any point and is parallel to the axis of rotation of the planet.
- The celestial meridian is a circle on the celestial sphere, which passes through the poles of the world and is connected to the zenith of the observation point.
- Meridian Greenwich. This is a conditional line that passes through the Greenwich Observatory (England). It is from him that astronomical longitude is being accounted for in the western and eastern directions.
Secret Meridian
But this was not always the case, but only since 1884, when it was the Greenwich Meridian that was accepted in all countries as zero. And this happened in accordance with the decision of the first International Meridian Conference.
Prior to this event, in the Russian Empire it was used as the zero Pulkovo meridian, in France - the Paris, in many countries - the Ferro meridian.
And in the Middle Ages, in general, anyone could take the zero meridian. It is in connection with this that there is a legend about the secret meridian.
Vault of heaven
It seems to the observer that all the stars are located on the surface of a huge sphere that rotates from east to west. This was noticed in ancient times, and the first astronomers (Aristotle, Ptolemy) designated the concept of the celestial sphere with a clear arrangement of celestial bodies on it.
It was then that a sphere appeared - a science about the position of stars and the compilation of their catalogs and maps. And although the ideas of ancient astronomers were erroneous, but such a model of the celestial sphere was very successful.
Key Terms
So, today the celestial sphere is called an imaginary sphere with an arbitrary radius on which the arrangement of celestial bodies is projected.
Elements of the celestial sphere are:
- A vertical line is a straight line that passes through the center of the sphere and coincides with the direction of the vertical line at the point of observation. The intersection of this line with the celestial sphere is called zenith, and at a point on the surface of the planet or under the feet of an observer - nadir.
- The true horizon is the plane of the circle of the celestial sphere perpendicular to the vertical line.
- The vertical of the luminary is the semicircle of a sphere that passes through the luminary and connects the nadir with the zenith.
Concepts related to the rotation of the celestial sphere
- The axis of the world is an imaginary straight line that passes through the center and intersects with the surface of the sphere itself at the poles (north and south).
- The sky equator is a large circle perpendicular to the axis of the world. It divides the sphere into the northern and southern hemispheres.
- The circle of a sphere that passes through a vertical line and axis is the celestial meridian. Its plane also divides the sphere into two hemispheres - eastern and western.
- The midday line is a conditional straight line where the planes of the meridian and the horizon intersect.
How the axis of the world is located relative to the celestial meridian is illustrated in the figure below.
It becomes clear that the axis of the world is parallel to the axis of rotation of the planet and is in the plane of the meridian. And the celestial meridian itself intersects with the horizon at the points of the north and south.
Spherical coordinate systems
Each star corresponds to a point on the celestial sphere with the corresponding coordinates. In this case, the position and movement of the bodies can be studied in different systems of spherical coordinates, for example:
- Horizontal topocentric. In this case, the observer's position is considered the fundamental reference point, and the true (mathematical) horizon is the central plane.
- The first and second equatorial systems take the equator for the fundamental plane.
- The ecliptic uses the plane of the ecliptic (a large circle of the celestial sphere along which the sun moves throughout the year).
- The galactic coordinate system is based on using the plane on which our galaxy is located.
The climax of the stars
Each star in the celestial sphere passes the celestial meridian twice a day. Moreover, in its upper position, the luminary is located to the south, and in the lower position - north of the poles. It is the phenomena when the center of the star passes the celestial meridian that are called the climax. It is worth noting that the phenomena are available for observation only in ascending and descending luminaries.
To observe the movements of the stars use telescopes mounted in their plane (passive instruments).
For the amateur astronomer
But even without special instruments and with minimal astronomical knowledge, one can observe the movement of the stars and even measure the distances between them.
As you know, the distances between the stars are measured in angular degrees. A full circle for the luminary is 360 degrees. For example, a change in the distance between the stars can be, albeit approximately, observed when comparing the angle between them.
In addition, knowledge of the coordinates of the star in a given time interval greatly simplifies their search in the vault for the amateur astronomer. In a home telescope, one can see Mercury (for a very short time), Venus (and then only in the form of a sickle) and Mars (only once every two years - during the confrontation). And the most exciting will be the observations of Jupiter and Saturn.
Summarize
The greatest discoveries of our civilization are related to the concept of celestial coordinates. The precession and nutation of our planet, aberrations and parallaxes of stars, black holes and multi-colored dwarfs - these and other discoveries continue to excite the minds of scientists and amateurs. The knowledge of the celestial coordinates gave mankind the opportunity to solve the problems of time, determine the geographical position on the planet, compile catalogs and star maps.
The importance of this knowledge can hardly be overestimated in astronomy, astrophysics, and astronautics.
And in astrology as well. Indeed, it was the discovery of the thirteenth zodiac sign - Ophiuchus - that brought a lot of skepticism into astrology. And this constellation appeared in the ecliptic due to the fact that the Earth’s precession has changed. But this topic is a completely different article.