The popularization of knowledge in the field of astronomy today is largely facilitated by interest in astrology, horoscopes and secret knowledge. But novels such as The Map (Mystery) of the Celestial Sphere, or the Secret Meridian by renowned Spanish novelist Arturo Pérez-Reverte, which has been a bestseller since 2007, do not make up for the knowledge of classical astronomy. In the article we will consider the concept of the celestial sphere. And, of course, its characteristics are the celestial meridian and the equator.
Midday indicator
This 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, geographic, magnetic meridians. In folk healing there are concepts of the meridians of the human body.
The development of astrology as a science of communication is connected with the concept of the meridianthe location of the stars at the time of the birth of a person and their influence on fate. This is how the ancient astrologers singled out every 16 degrees in the ecliptic band, which formed the twelve zodiac signs-constellations.
And although today our knowledge of the location of stars in the firmament is much wider, but the zodiacal designations continue to be used in astronomy.
Such different meridians
In the mentioned novel we are talking about the secret celestial meridian, the decoding of which is connected with the hidden treasures of the Jesuits. How many meridians are there really?
In astronomy, the following are distinguished:
- Meridian astronomical or true. This is a line on the surface of the earth on which 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 that passes through the poles of the world and is connected to the zenith of the observation point.
- Greenwich Meridian. This is a conditional line that passes through the Greenwich Observatory (England). It is from him that today the astronomical longitude is counted in the western and eastern directions.
Secret meridian
But this was not always the case, but only since 1884, when the Greenwich meridian was accepted in all countries as the zero one. And this happened in accordance with the decision of the first International Meridian Conference.
In the Russian Empire before this eventwas used as the zero Pulkovo meridian, in France - the Paris meridian, in many countries - the Ferro meridian.
And in the Middle Ages, in general, anyone could be taken as the zero meridian. It is in connection with this that the legend of the secret meridian exists.
Vault of Heaven
To the observer, it seems that all the stars are located on the surface of a huge sphere that rotates in the direction 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 the sphere appeared - the science of the position of stars and the compilation of their catalogs and maps. And even if the ideas of ancient astronomers were wrong, but such a model of the celestial sphere turned out to be very successful.
Basic terms
So, today the celestial sphere is an imaginary sphere with an arbitrary radius, on which the location of celestial bodies is projected.
The elements of the celestial sphere are:
- A plumb line is a straight line that passes through the center of the sphere and coincides with the direction of the plumb line at the observation point. The intersection of this line with the celestial sphere is called the zenith, and at a point on the surface of the planet or under the feet of the observer - nadir.
- The true horizon is the plane of the circle of the celestial sphere, perpendicular to the plumb line.
- The star's vertical is a semicircle of a sphere that passes through the star and connects the nadir with the zenith.
Concepts,associated with 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 celestial equator is a large circle perpendicularly intersecting the axis of the world. It divides the sphere into northern and southern hemispheres.
- The circle of the sphere that passes through the plumb line and the 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, illustrates 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 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 luminaries can be studied in different systems of spherical coordinates, for example:
- Horizontal topocentric. In this case, the position of the observer is considered to be the fundamental reference point, and the true (mathematical) horizon is considered the central plane.
- The first and second equatorial systems take the equator as the fundamental plane.
- Ecliptic uses the plane of the ecliptic (the great circle of the celestial sphere along which the Sun moves throughout the year).
- Galacticthe coordinate system is based on using the plane on which our galaxy is placed.
Climaxes of the Luminaries
Each star in the celestial sphere passes the celestial meridian twice a day. At the same time, in its upper position, the luminary is located to the south, and in its lower position, to the north of the poles. It is the phenomena when the center of the luminary passes the celestial meridian that are called culminations. At the same time, it should be noted that the phenomena are available for observation only in ascending and setting luminaries.
To observe the movements of the stars, telescopes installed in their plane (passing instruments) are used.
For an 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 stars are measured in angular degrees. A full circle for the luminary is 360 degrees. For example, a change in the distance between stars can be noticed, albeit approximately, when comparing the angle between them.
Besides, knowing the coordinates of the luminary in a particular time interval greatly simplifies their search in the firmament for an amateur astronomer. In a home telescope, you 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 opposition period). And the most exciting will be observations of Jupiter and Saturn.
Summarize
The greatest discoveries of our civilization are connected with the concept of celestial coordinates. The precession and nutation of our planet, the aberrations and parallaxes of stars, black holes and multi-colored dwarfs - these and other discoveries continue to haunt the minds of scientists and amateurs. Knowledge of celestial coordinates gave mankind the opportunity to solve problems of time, determine the geographical position on the planet, and compile catalogs and maps of the stars.
The value of this knowledge is difficult to overestimate in astronomy, astrophysics, astronautics.
And also in astrology. After all, it was the discovery of the thirteenth sign of the zodiac - Ophiuchus - that introduced a lot of skepticism into astrology. And this constellation appeared in the ecliptic due to the fact that the precession of the Earth has changed. But this is a topic for a completely different article.
