People in ancient times believed that all the stars are located on the celestial sphere, which, as a whole, revolves around the Earth. Already more than 2,000 years ago, astronomers began to use methods that made it possible to indicate the location of any star in the celestial sphere in relation to other space objects or ground landmarks. The notion of a celestial sphere is convenient to use even now, although we know that this sphere does not really exist.

celestial sphere -an imaginary spherical surface of an arbitrary radius, in the center of which is the observer's eye, and on which we project the position of the celestial bodies.

The concept of the celestial sphere is used for angular measurements in the sky, for the convenience of reasoning about the simplest visible celestial phenomena, for various calculations, for example, calculating the time of sunrise and sunset of the luminaries.

Let's build a celestial sphere and draw a ray from its center towards the star BUT.

Where this ray intersects the surface of the sphere, place a point A 1 depicting this star. Star AT will be represented by a dot IN 1 . By repeating a similar operation for all the observed stars, we will get an image of the starry sky on the surface of the sphere - a star globe. It is clear that if the observer is in the center of this imaginary sphere, then for him the direction to the stars themselves and to their images on the sphere will coincide.

• What is the center of the celestial sphere? (Eye of the beholder)
• What is the radius of the celestial sphere? (Arbitrary)
• What is the difference between the celestial spheres of two neighbors on the desk? (Center position).

For solving many practical problems, distances to celestial bodies do not play a role, only their apparent location in the sky is important. Angular measurements are independent of the radius of the sphere. Therefore, although the celestial sphere does not exist in nature, astronomers use the concept of the celestial sphere to study the visible location of the stars and phenomena that can be observed in the sky during the day or many months. Stars, the Sun, the Moon, planets, etc. are projected onto such a sphere, abstracting from the actual distances to the luminaries and considering only the angular distances between them. The distances between stars on the celestial sphere can only be expressed in angular measure. These angular distances are measured by the value of the central angle between the rays directed to one and the other star, or by the arcs corresponding to them on the surface of the sphere.

For an approximate estimate of the angular distances in the sky, it is useful to remember the following data: the angular distance between the two extreme stars of the Ursa Major bucket (α and β) is about 5 °, and from α Ursa Major to α Ursa Minor (Polar Star) - 5 times more - approximately 25°.

The simplest visual estimates of angular distances can also be made using the fingers of an outstretched hand.

Only two luminaries - the Sun and the Moon - we see as disks. The angular diameters of these disks are almost the same - about 30 "or 0.5 °. The angular dimensions of the planets and stars are much smaller, so we see them simply as luminous points. To the naked eye, an object does not look like a point if its angular dimensions exceed 2 -3". This means, in particular, that our eye distinguishes each separately luminous point (star) in the event that the angular distance between them is greater than this value. In other words, we see an object not as a point only if the distance to it exceeds its size by no more than 1700 times.

plumb line Z, Z' , passing through the eye of the observer (point C), located in the center of the celestial sphere, intersects the celestial sphere at points Z - zenith,Z' - nadir.

Zenith- this is the highest point above the observer's head.

Nadir -point of the celestial sphere opposite the zenith.

The plane perpendicular to the plumb line is calledhorizontal plane (or horizon plane).

math horizoncalled the line of intersection of the celestial sphere with a horizontal plane passing through the center of the celestial sphere.

With the naked eye, you can see about 6,000 stars in the entire sky, but we see only half of them, because the Earth closes the other half of the starry sky from us. Do stars move across the sky? It turns out that they all move at the same time. This is easy to verify by observing the starry sky (focusing on certain objects).

Due to its rotation, the appearance of the starry sky changes. Some stars are just emerging from the horizon (rising) in its eastern part, others are high above your head at this time, and still others are already hiding behind the horizon in the western side (setting). At the same time, it seems to us that the starry sky rotates as a whole. Now everyone is well aware that The rotation of the firmament is an apparent phenomenon caused by the rotation of the Earth.

The picture of what happens to the starry sky as a result of the daily rotation of the Earth, allows you to capture the camera.

In the resulting image, each star left its mark in the form of an arc of a circle. But there is also such a star, the movement of which throughout the night is almost imperceptible. This star was named Polaris. It describes a circle of small radius during the day and is always visible at almost the same height above the horizon in the northern side of the sky. The common center of all concentric traces of stars is in the sky near the North Star. This point, to which the axis of rotation of the Earth is directed, is called north pole of the world. The arc described by the North Star has the smallest radius. But this arc, and all the others - regardless of their radius and curvature - constitute the same part of the circle. If it were possible to photograph the paths of the stars in the sky for a whole day, then the photograph would turn out to be full circles - 360 °. After all, a day is the period of a complete revolution of the Earth around its axis. In an hour, the Earth will turn 1/24 of the circle, i.e., 15 °. Consequently, the length of the arc that the star will describe during this time will be 15 °, and in half an hour - 7.5 °.

During the day, the stars describe the larger circles, the farther from the North Star they are.

The axis of the daily rotation of the celestial sphere is calledaxis of the world (RR").

The points of intersection of the celestial sphere with the axis of the world are calledthe poles of the world(dot R - north celestial pole point R" - south pole of the world).

The polar star is located near the north celestial pole. When we look at the North Star, more precisely, at a fixed point next to it - the north pole of the world, the direction of our gaze coincides with the axis of the world. The south pole of the world is in southern hemisphere celestial sphere.

Plane EAWQ, perpendicular to the axis of the world PP" and passing through the center of the celestial sphere is calledplane of the celestial equator, and the line of its intersection with the celestial sphere -celestial equator.

Celestial equator - a circle line obtained from the intersection of the celestial sphere with a plane passing through the center of the celestial sphere perpendicular to the axis of the world.

The celestial equator divides the celestial sphere into two hemispheres: northern and southern.

The axis of the world, the poles of the world and the celestial equator are similar to the axis, poles and equator of the Earth, since the listed names are associated with the apparent rotation of the celestial sphere, and it is a consequence of the actual rotation of the globe.

The plane passing through the zenithZ , center FROM celestial sphere and pole R peace, they callplane of the celestial meridian, and the line of its intersection with the celestial sphere formscelestial meridian line.

sky meridian - a great circle of the celestial sphere passing through the zenith Z, the celestial pole P, the south celestial pole R", nadir Z"

In any place on Earth, the plane of the celestial meridian coincides with the plane of the geographic meridian of that place.

noon line NS - this is the line of intersection of the planes of the meridian and the horizon. N - north point, S - south point

It is so named because at noon the shadows from vertical objects fall in this direction.

• What is the rotation period of the celestial sphere? (Equal to the period of rotation of the Earth - 1 day).
• In what direction does the apparent (apparent) rotation of the celestial sphere take place? (Opposite to the direction of the Earth's rotation).
• What can be said about the relative position of the axis of rotation of the celestial sphere and earth's axis? (The axis of the celestial sphere and the earth's axis will coincide).
• Are all points of the celestial sphere involved in the apparent rotation of the celestial sphere? (Points lying on the axis are at rest).

The earth moves in an orbit around the sun. The axis of rotation of the Earth is inclined to the plane of the orbit at an angle of 66.5°. Due to the action of gravitational forces from the side of the Moon and the Sun, the axis of rotation of the Earth is shifted, while the inclination of the axis to the plane of the Earth's orbit remains constant. The axis of the Earth, as it were, slides along the surface of the cone. (the same happens with the y-axis of an ordinary top at the end of rotation).

This phenomenon was discovered as early as 125 BC. e. Greek astronomer Hipparchus and named precession.

One rotation of the earth's axis takes 25,776 years - this period is called the Platonic year. Now near P - the north pole of the world is the North Star - α Ursa Minor. The polar star is the one that is currently located near the North Pole of the world. In our time, from about 1100, such a star is the alpha Ursa Minor - Kinosura. Previously, the title of the Polar was alternately assigned to π, η and τ Hercules, the stars of Tuban and Kochab. The Romans did not have the North Star at all, and Kokhab and Kinosuru (α Ursa Minor) were called Guardians.

At the beginning of our reckoning - the pole of the world was near α Draco - 2000 years ago. In 2100, the celestial pole will be only 28" from the North Star - now 44". In 3200, the constellation Cepheus will become polar. In 14000, Vega (α Lyrae) will be polar.

How to find the North Star in the sky?

To find the North Star, you need to mentally draw a straight line through the stars of the Big Dipper (the first 2 stars of the "bucket") and count 5 distances between these stars along it. In this place, next to the straight line, we will see a star, almost the same in brightness with the stars of the "dipper" - this is the Polar Star.

In the constellation, which is often called the Little Dipper, the North Star is the brightest. But just like most of the stars of the Big Dipper bucket, the Polaris is a star of the second magnitude.

Summer (summer-autumn) triangle = star Vega (α Lyra, 25.3 light years), star Deneb (α Cygnus, 3230 light years), star Altair (α Eagle, 16.8 light years)

Celestial coordinates

To find a luminary in the sky, you need to indicate in which side of the horizon and how high above it it is. For this purpose, it is used horizontal coordinate system – azimuth and height. For an observer located anywhere on the Earth, it is not difficult to determine the vertical and horizontal directions.

The first of them is determined using a plumb line and is depicted in the drawing by a plumb line ZZ", passing through the center of the sphere (point O).

The Z point directly above the observer's head is called zenith.

A plane that passes through the center of the sphere perpendicular to the plumb line forms a circle when it intersects with the sphere - true, or mathematical, horizon.

Height the luminary is counted along a circle passing through the zenith and the luminary , and is expressed by the length of the arc of this circle from the horizon to the luminary. This arc and the angle corresponding to it are usually denoted by the letter h.

The height of the luminary, which is located at the zenith, is 90 °, on the horizon - 0 °.

The position of the luminary relative to the sides of the horizon is indicated by its second coordinate - azimuth, denoted by a letter BUT. Azimuth is measured from the south point in clockwise direction, so the azimuth of the south point is 0°, the west point is 90°, and so on.

The horizontal coordinates of the luminaries continuously change over time and depend on the position of the observer on the Earth, because in relation to world space the horizon plane at a given point on the Earth rotates with it.

The horizontal coordinates of the luminaries are measured to determine the time or geographical coordinates of various points on Earth. In practice, for example, in geodesy, height and azimuth are measured with special goniometric optical instruments - theodolites.

To create a star map depicting constellations on a plane, you need to know the coordinates of the stars. To do this, you need to choose a coordinate system that would rotate with the starry sky. To indicate the position of the luminaries in the sky, a coordinate system is used similar to that used in geography, - equatorial coordinate system.

The equatorial coordinate system is similar to the geographic coordinate system on the globe. As you know, the position of any point on the globe can be specified With using geographical coordinates - latitude and longitude.

Geographic latitude - is the angular distance of the point from the earth's equator. Geographic latitude (φ) is measured along the meridians from the equator to the poles of the Earth.

Longitude- the angle between the plane of the meridian of the given point and the plane of the initial meridian. Geographic longitude (λ) is measured along the equator from the initial (Greenwich) meridian.

So, for example, Moscow has the following coordinates: 37°30" east longitude and 55°45" north latitude.

Let's introduce equatorial coordinate system, which indicates the position of the luminaries on the celestial sphere relative to each other.

Let us draw a line through the center of the celestial sphere parallel to the axis of rotation of the Earth, - axis of the world. It will cross the celestial sphere at two diametrically opposite points, which are called the poles of the world - R and R. The North Pole of the world is called the one near which the North Star is located. A plane passing through the center of the sphere parallel to the plane of the Earth's equator, in cross section with the sphere, forms a circle called celestial equator. The celestial equator (like the earth's) divides the celestial sphere into two hemispheres: Northern and Southern. The angular distance of a star from the celestial equator is called declension. The declination is measured in a circle drawn through the luminary and the poles of the world, it is similar to geographic latitude.

declination- angular distance of the luminaries from the celestial equator. Declension is denoted by the letter δ. In the northern hemisphere, declinations are considered positive, in the southern - negative.

The second coordinate, which indicates the position of the star in the sky, is similar to geographic longitude. This coordinate is called right ascension . Right ascension is measured along the celestial equator from the vernal equinox point γ, in which the Sun annually occurs on March 21 (on the day of the vernal equinox). It is counted from the point of the spring equinox γ counterclockwise, i.e., towards the daily rotation of the sky. Therefore, the luminaries ascend (and set) in ascending order of their right ascension.

right ascension - the angle between the plane of a semicircle drawn from the celestial pole through the luminary(circle of declination), and the plane of a semicircle drawn from the celestial pole through the point of the vernal equinox lying on the equator(the initial circle of declinations). Right ascension is denoted by the letter α

Declension and right ascension(δ, α) are called equatorial coordinates.

Declination and right ascension are conveniently expressed not in degrees, but in units of time. Considering that the Earth makes one revolution in 24 hours, we get:

360° - 24 h, 1° - 4 min;

15° - 1 h, 15" -1 min, 15" - 1 s.

Therefore, a right ascension equal, for example, to 12 hours is 180°, and 7 hours and 40 minutes corresponds to 115°.

If special accuracy is not needed, then the celestial coordinates for the stars can be considered unchanged. With the daily rotation of the starry sky, the vernal equinox also rotates. Therefore, the positions of the stars relative to the equator and the vernal equinox do not depend either on the time of day or on the position of the observer on Earth.

The equatorial coordinate system is depicted on a moving map of the starry sky.

§ 48. Celestial sphere. Basic points, lines and circles on the celestial sphere

A celestial sphere is a sphere of any radius centered at an arbitrary point in space. For its center, depending on the statement of the problem, take the eye of the observer, the center of the tool, the center of the Earth, etc.

Consider the main points and circles of the celestial sphere, for the center of which the eye of the observer is taken (Fig. 72). Draw a plumb line through the center of the celestial sphere. The points of intersection of the plumb line with the sphere are called the zenith Z and the nadir n.

Rice. 72.

The plane passing through the center of the celestial sphere perpendicular to the plumb line is called true horizon plane. This plane, intersecting with the celestial sphere, forms a circle of a great circle, called the true horizon. The latter divides the celestial sphere into two parts: the above-horizon and sub-horizon.

A straight line passing through the center of the celestial sphere parallel to the earth's axis is called the axis of the world. The points of intersection of the axis of the world with the celestial sphere are called the poles of the world. One of the poles, corresponding to the poles of the Earth, is called the north pole of the world and is denoted by Pn, the other - south pole peace Ps.

The plane QQ" passing through the center of the celestial sphere perpendicular to the axis of the world is called plane of the celestial equator. This plane, intersecting with the celestial sphere, forms a circle of a large circle - celestial equator, which divides the celestial sphere into northern and southern parts.

The great circle of the celestial sphere passing through the poles of the world, zenith and nadir, is called meridian of the observer PN nPsZ. The axis of the world divides the meridian of the observer into noon PN ZPs and midnight PN nPs parts.

The meridian of the observer intersects with the true horizon at two points: the north point N and the south point S. The straight line connecting the north and south points is called noon line.

If you look from the center of the sphere to point N, then the east point O st will be on the right, and the west point W will be on the left. Small circles of the celestial sphere aa "parallel to the plane of the true horizon are called almucantarates; small bb" parallel to the plane of the celestial equator, - celestial parallels.

Circles of the celestial sphere Zon passing through the zenith and nadir points are called verticals. The vertical passing through the points east and west is called the first vertical.

Circles of the celestial sphere PNoPs passing through the celestial poles are called declination circles.

The meridian of the observer is both a vertical and a circle of declination. It divides the celestial sphere into two parts - eastern and western.

The pole of the world, located above the horizon (below the horizon), is called the elevated (lowered) pole of the world. The name of the elevated pole of the world is always of the same name with the name of the latitude of the place.

The axis of the world with the plane of the true horizon makes an angle equal to geographic latitude of the place.

The position of the luminaries on the celestial sphere is determined using spherical coordinate systems. In nautical astronomy, horizontal and equatorial coordinate systems are used.

Circle of the celestial sphere large

the intersection of the celestial sphere with an arbitrary plane passing through the center of the celestial sphere.

Astronomical dictionary. EdwART. 2010 .

See what the "Circle of the celestial sphere is large" in other dictionaries:

A great circle of the celestial sphere (See celestial sphere) passing through the zenith and nadir of the observation site and a given point on the celestial sphere. K. v., passing through the points of the north and south, coincides with the celestial meridian; K. v., passing through the points ... ...

A large circle of the celestial sphere passing through the poles of the world and a given point of the celestial sphere ... Great Soviet Encyclopedia

A great circle of the celestial sphere (See Celestial Sphere), passing through the poles of the ecliptic and a given point on the celestial sphere ... Great Soviet Encyclopedia

The celestial sphere is divided by the celestial equator. The celestial sphere is an imaginary auxiliary sphere of arbitrary radius onto which heavenly bodies: serves for solving various astrometric problems. Behind the center of the celestial sphere, like ... ... Wikipedia

The celestial sphere is divided by the celestial equator. The celestial sphere is an imaginary auxiliary sphere of arbitrary radius onto which celestial bodies are projected: it serves to solve various astrometric problems. Behind the center of the celestial sphere, like ... ... Wikipedia

The celestial sphere is divided by the celestial equator. The celestial sphere is an imaginary auxiliary sphere of arbitrary radius onto which celestial bodies are projected: it serves to solve various astrometric problems. Behind the center of the celestial sphere, like ... ... Wikipedia

The celestial sphere is divided by the celestial equator. The celestial sphere is an imaginary auxiliary sphere of arbitrary radius onto which celestial bodies are projected: it serves to solve various astrometric problems. Behind the center of the celestial sphere, like ... ... Wikipedia

The celestial sphere is divided by the celestial equator. The celestial sphere is an imaginary auxiliary sphere of arbitrary radius onto which celestial bodies are projected: it serves to solve various astrometric problems. Behind the center of the celestial sphere, like ... ... Wikipedia

Circle, the main meaning is the part of the plane bounded by a circle. In a figurative sense, it can be used to denote cyclicity. Krug is also a common surname. Contents 1 Term 2 Surname 3 Other signs ... Wikipedia

Books

• Calculation and construction of a horoscope using tables. Tables of Michelsen's ephemeris, RPE, tables of Placidus houses, A. E. Galitskaya. A cosmogram is a snapshot of the ecliptic with the signs of the Zodiac marked on it and projections of the positions of the planets and fictitious points. It is important to remember that on the cosmogram we indicate the positions ...

2.1.1. Basic planes, lines and points of the celestial sphere

The celestial sphere is an imaginary sphere of arbitrary radius centered at a chosen point of observation, on the surface of which the luminaries are located as they are visible in the sky at some point in time from a given point in space. In order to correctly imagine an astronomical phenomenon, it is necessary to consider the radius of the celestial sphere to be much greater than the radius of the Earth (R sf \u003e R Earth), i.e., to assume that the observer is in the center of the celestial sphere, and the same point of the celestial sphere (one and the same star) is visible from different places earth's surface in parallel directions.

The firmament or sky is usually understood as the inner surface of the celestial sphere, on which celestial bodies (luminaries) are projected. For an observer on Earth during the day, the Sun is visible in the sky, sometimes the Moon, even more rarely Venus. On a cloudless night, stars, the Moon, planets, sometimes comets and other bodies are visible. There are about 6000 stars visible to the naked eye. The relative position of the stars almost does not change due to the large distances to them. The celestial bodies belonging to the solar system change their position relative to the stars and each other, which is determined by their noticeable angular and linear daily and annual displacement.

The vault of heaven rotates as a whole with all the luminaries located on it about an imaginary axis. This rotation is diurnal. If you observe the daily rotation of stars in the northern hemisphere of the Earth and face the north pole, then the rotation of the sky will occur counterclockwise.

The center O of the celestial sphere is an observation point. The straight line ZOZ "coinciding with the direction of the plumb line at the point of observation is called a plumb or vertical line. The plumb line intersects with the surface of the celestial sphere at two points: at the zenith Z, above the observer's head, and at the diametrically opposite point Z" - nadir. The great circle of the celestial sphere (SWNE), whose plane is perpendicular to the plumb line, is called the mathematical or true horizon. The mathematical horizon is a plane tangent to the Earth's surface at the point of observation. The small circle of the celestial sphere (aMa"), passing through the luminary M, and whose plane is parallel to the plane of the mathematical horizon, is called the almucantar of the luminary. The large semicircle of the celestial sphere ZMZ" is called the circle of height, the vertical circle, or simply the vertical of the luminary.

Diameter PP", around which the celestial sphere rotates, is called the axis of the world. The axis of the world intersects with the surface of the celestial sphere at two points: at the north pole of the world P, from which the rotation of the celestial sphere occurs clockwise, if you look at the sphere from the outside, and at the south celestial pole R". The axis of the world is inclined to the plane of the mathematical horizon at an angle equal to the geographical latitude of the observation point φ. The great circle of the celestial sphere QWQ "E, whose plane is perpendicular to the axis of the world, is called the celestial equator. The small circle of the celestial sphere (bMb"), whose plane is parallel to the plane of the celestial equator, is called the celestial or daily parallel of the luminary M. The large semicircle of the celestial sphere PMP * is called hourly circle or circle of declination of the luminary.

The celestial equator intersects with the mathematical horizon at two points: at the east point E and at the west point W. The circles of heights passing through the points of east and west are called the first verticals - east and west.

The great circle of the celestial sphere PZQSP "Z" Q "N, the plane of which passes through the plumb line and the axis of the world, is called the celestial meridian. The plane of the celestial meridian and the plane of the mathematical horizon intersect in a straight line NOS, which is called the noon line. The celestial meridian intersects with the mathematical horizon at the north point N and at the south point S. The celestial meridian intersects with the celestial equator also at two points: at the upper point of the equator Q, which is closer to the zenith, and at the lower point of the equator Q ", which is closer to the nadir.

2.1.2. Luminaries, their classification, visible movements.
Stars, sun and moon, planets

To navigate the sky bright stars grouped into constellations. There are 88 constellations in the sky, of which 56 are visible to an observer located in the middle latitudes of the northern hemisphere of the Earth. All constellations have their own names associated with the names of animals (Ursa Major, Leo, Dragon), the names of heroes Greek mythology(Cassiopeia, Andromeda, Perseus) or the names of objects whose outlines resemble (Northern Crown, Triangle, Libra). Individual stars in the constellations are designated by the letters of the Greek alphabet, and the brightest of them (about 200) received "own" names. For example, a Big Dog- "Sirius", α Orion - "Betelgeuse", β Perseus - "Algol", α Ursa Minor - "Polar Star", near which the point of the north pole of the world is located. The paths of the Sun and the Moon against the background of the stars almost coincide and come along the twelve constellations, which are called zodiac, since most of them are called animals (from the Greek "zoon" - animal). These include the constellations of Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces.

The trajectory of the movement of Mars in the celestial sphere in 2003

The sun and moon also rise and set during the day, but, unlike the stars, at different points on the horizon during the year. From short observations it can be seen that the Moon moves against the background of stars, moving from west to east at a speed of about 13 ° per day, making a full circle in the sky in 27.32 days. The sun also travels this path, but during the year, moving at a speed of 59" per day.

Even in ancient times, 5 luminaries were noticed, similar to stars, but “wandering” through the constellations. They were called planets - "wandering luminaries." Later, 2 more planets and a large number of smaller celestial bodies (dwarf planets, asteroids) were discovered.

The planets most of the time move through the zodiac constellations from west to east (direct movement), but part of the time - from east to west (reverse movement).

Your browser does not support the video tag. The movement of stars in the sky