During their diurnal movement, the stars cross the celestial meridian twice - above the points of the south and north. The moment of crossing the celestial meridian is called the culmination of the star. At the moment of the upper culmination above the south point, the luminary reaches its highest height above the horizon. As you know, the height of the pole of the world above the horizon (angle PON): hp \u003d f. Then the angle between the horizon (NS) and the celestial equator (QQ1) will be 180 ° - f - 90 ° \u003d 90 ° - f. The angle MOS, which expresses the height of the luminary M at its climax, is the sum of two angles: Q1OS and MOQ1. We have just determined the magnitude of the first of them, and the second is nothing more than the declination of the luminary M, equal to 8. Thus, we get the following formula linking the height of the star at its culmination with its declination and the geographical latitude of the place of observation:
h \u003d 90 ° - f + 5.
Knowing the declination of the luminary and having determined from observations its height at the culmination, you can find out the geographical latitude of the place of observation. Let's continue our imaginary journey and go from mid-latitudes to the equator, whose latitude is 0 °. As follows from the just derived formula, here the axis of the world is located in the plane of the horizon, and the celestial equator passes through the zenith. At the equator, during the day, all the stars will visit the horizon.
Even in ancient times, observing the Sun, people discovered that its midday height changes throughout the year, as does the appearance of the starry sky: at midnight above the southern part of the horizon at different times of the year, stars of different constellations are visible - those that are visible in summer are not visible in winter and vice versa. On the basis of these observations, it was concluded that the Sun moves across the sky, passing from one constellation to another, and completes a full revolution within a year. The circle of the celestial sphere, along which the apparent annual movement of the Sun takes place, was called the ecliptic. The constellations along which the ecliptic passes are called zodiacal (from the Greek word "zoon" - animal). The Sun crosses each zodiacal constellation in about a month. In the XX century. one more was added to their number - Ophiuchus.
The movement of the Sun against the background of stars is an apparent phenomenon. It occurs due to the annual revolution of the Earth around the Sun. Therefore, the ecliptic represents the circle of the celestial sphere along which it intersects with the plane of the earth's orbit. During the day, the Earth passes about 1/365 of its orbit. As a result, the Sun moves in the sky by about 1 ° every day. The period of time during which it goes around a full circle in the celestial sphere was called a year. You know from the course of geography that the axis of rotation of the Earth is inclined to the plane of its orbit at an angle of 66 ° 30 ". Therefore, the Earth's equator has an inclination of 23 ° 30" relative to the plane of its orbit. This is the inclination of the ecliptic to the celestial equator, which it crosses at two points: the spring and autumn equinoxes.
These days (usually March 21 and September 23) the Sun is at the celestial equator and has a declination of 0 °. Both hemispheres of the Earth are illuminated by the Sun in the same way: the border of day and night passes exactly through the poles, and day is equal to night at all points of the Earth. On the day of the summer solstice (June 22), the Earth is turned towards the Sun with its Northern Hemisphere. It is summer here, at the North Pole there is a polar day, and in the rest of the hemisphere the days are longer than night. On the day of the summer solstice, the Sun rises above the plane of the earth's (and celestial) equator by 23 ° 30 ". On the day of the winter solstice (December 22), when the Northern Hemisphere is least illuminated, the Sun is below the celestial equator at the same angle of 23 ° 30". Depending on the position of the Sun on the ecliptic, its height above the horizon changes at noon - the moment of the upper climax. By measuring the midday height of the Sun and knowing its declination on that day, you can calculate the latitude of the observation site. This method has long been used to determine the location of an observer on land and at sea.
The celestial sphere is an imaginary sphere of arbitrary radius, the center of which is at the point of observation (Fig. 1). A plane drawn through the center of the celestial sphere perpendicular to the line vertical to the earth's surface forms a large circle at the intersection with the celestial sphere, called the mathematical or true horizon.
The plumb line intersects with the celestial sphere at two diametrically opposite points - zenith Z and nadir Z '. Zenith is located exactly above the observer's head, the nadir is hidden by the earth's surface.
The daily rotation of the celestial sphere is a reflection of the rotation of the Earth and also occurs around the earth's axis, but in the opposite direction, that is, from east to west. The axis of rotation of the celestial sphere, coinciding with the axis of rotation of the Earth, is called the axis of the world.
The North Pole of the world P is directed to the North Star (0 ° 51 from the North Star). The south pole of the world P 'is located above the horizon of the southern earth hemisphere and is not visible from the northern hemisphere.
Fig. 1. The intersection of the celestial equator and celestial meridian with the true horizon
The great circle of the celestial sphere, the plane of which is perpendicular to the axis of the world, is called the celestial equator, which coincides with the plane of the earth's equator. The celestial equator divides the celestial sphere into two hemispheres - northern and southern. The celestial equator intersects with the true horizon at two points, which are called the points east of E and west of W. At the point east, the celestial equator rises above the true horizon, and at the west point it falls beyond it.
The great circle of the celestial sphere passing through the pole of the world (PP '), zenith and nadir (ZZ') is called the celestial meridian, which is reflected on earth surface in the form of an earthly (geographic) meridian. The celestial meridian divides the celestial sphere into east and west and intersects with the true horizon at two diametrically opposite points - the south point (S) and the north point (N).
A straight line passing through the points of the south and north and which is the line of intersection of the plane of the true horizon with the plane of the celestial meridian is called the midday line.
A large semicircle passing through the poles of the Earth and any point on its surface is called the meridian of this point. The meridian passing through the Greenwich Observatory, Britain's main observatory, is called the prime or prime meridian. The prime meridian and the meridian, 180 ° apart from the zero, divide the Earth's surface into two hemispheres - eastern and western.
The great circle of the celestial sphere, the plane of which coincides with the plane of the earth's orbit around the sun, is called the ecliptic plane. The line of intersection of the celestial sphere with the plane of the ecliptic is called the ecliptic line or simply the ecliptic (Fig. 3.2). Ecliptic is a Greek word and in translation means an eclipse. This circle was named so because eclipses of the Sun and Moon occur when both stars are near the plane of the ecliptic. For a terrestrial observer, the apparent annual motion of the Sun occurs along the ecliptic. The line, perpendicular to the plane of the ecliptic and passing through the center of the celestial sphere, forms at the points of intersection with it the North (P) and South (P ') poles of the ecliptic.
The line of intersection of the plane of the ecliptic with the plane of the celestial equator intersects the surface of the earth's sphere at two diametrically opposite points, called the points of spring and autumn equilibrium. The vernal equinox is usually denoted (Aries), the autumnal equinox is (Libra). The sun at these points occurs on March 21 and September 23, respectively. On these days on Earth, day is equal to night. The ecliptic points that are 90 ° from the equinox are called solstice points (July 22 - summer, December 23 - winter).
The plane of the celestial equator is inclined to the plane of the ecliptic at an angle of - 23 ° 27 ′. The inclination of the ecliptic to the equator does not remain constant. In 1896, when approving the astronomical constants, it was decided to consider the inclination of the ecliptic equal to 23 ° 27 ′ 8.26 ".
Due to the influence on the Earth of the forces of attraction of the Sun and the Moon, it gradually changes in the range from 22 ° 59 ′ to 24 ° 36 ′.
Figure: 2. The plane of the ecliptic and its intersection with the plane of the celestial equator
Celestial coordinate systems
To determine the location of a celestial body, one or another system of celestial coordinates is used. Depending on which of the circles of the celestial sphere is selected to build a coordinate grid, these systems are called ecliptic coordinate system or equatorial. To determine coordinates on the earth's surface, use geographic system coordinates. Consider all of these systems.
Ecliptic coordinate system.
The ecliptic coordinate system is most commonly used by astrologers. This system is laid down in all the old atlases of the starry sky. The ecliptic system is built on the ecliptic plane. The position of a celestial body in this system is determined by two spherical coordinates - ecliptic longitude (or simply longitude) and ecliptic latitude.
Ecliptic longitude L is measured from the plane passing through the poles of the ecliptic and the vernal equinox in the direction of the annual motion of the Sun, i.e. along the signs of the zodiac (fig. 3.3). Longitude is measured from 0 ° to 360 °.
Ecliptic latitude B is the angular distance from the ecliptic towards the poles. The B value is positive towards the north pole of the ecliptic, negative towards the south. Measured from + 90 ° to –90 °.
Fig. 3. Ecliptic celestial coordinate system.
Equatorial coordinate system.
The equatorial coordinate system is also sometimes used by astrologers. This system is built on the celestial equator, which coincides with the earth's equator (Fig. 4). The position of a celestial body in this system is determined by two coordinates - right ascension and declination.
Right ascension is counted from the vernal equinox 0 ° in the direction opposite to the daily rotation of the celestial sphere. It is measured either in the range from 0 ° to 360 °, or in units of time - from 0 hour. up to 24 hours. Declination? Is the angle between the celestial equator and the pole (similar to latitude in the ecliptic system) and is measured from –90 ° to + 90 °.
Fig. 4. Equatorial celestial coordinate system
Geographic coordinate system.
Determined by geographic longitude and geographic latitude. In astrology, it is used for the coordinates of the place of birth.
Geographic longitude? reckoned from the Greenwich meridian with a + sign to the east and - to the west from - 180 ° to + 180 ° (Fig. 3.5). Sometimes geographic longitude is measured in units of time from 0 to 24 hours, counting it east of Greenwich.
Geographic latitude? is measured along the meridians in the direction of the geographic poles with a + sign to the north, with a sign - south of the equator. Geographic latitude ranges from - 90 ° to + 90 °.
Fig. 5. Geographical coordinates
Precession
Ancient astronomers believed that the axis of rotation of the Earth was motionless relative to the stellar sphere, but Giparchus (160 BC) discovered that the vernal equinox was slowly moving towards the annual motion of the Sun, i.e. against the course of the zodiacal constellations. This phenomenon is called precession.
The offset is 50'3.1 "per year. The vernal equinox makes a full circle in 25,729 years, i.e. 1 ° takes about 72 years. The reference point on the celestial sphere is the north pole of the world. Due to precession, it slowly moves among the stars around the pole of the ecliptic along a circle of spherical radius 23 ° 27 ′. In our time, he is getting closer and closer to the North Star.
Now the angular distance between the North Pole of the world and the North Star is 57 ′. On the most close quarters (28 ′) it will come up in 2000, and in 12,000 years it will be near the brightest star in the northern hemisphere, Vega.
Time measurement
The issue of measuring time has been decided throughout the history of human development. It is difficult to imagine a more complex concept than time. The greatest philosopher of the ancient world, Aristotle, four centuries BC wrote that among the unknown in the nature around us, time is the most unknown, for no one knows what time is and how to control it.
Time measurement is based on the rotation of the Earth around its axis and on its revolution around the Sun. These processes are continuous and have fairly constant periods, which allows them to be used as natural units of time measurement.
Due to the fact that the Earth's orbit is an ellipse, the movement of the Earth along it occurs at an uneven speed, and, therefore, the speed of the apparent movement of the Sun along the ecliptic is also uneven. All the luminaries in a day in their visible movement cross the celestial meridian twice. The intersection of the celestial meridian by the center of the luminary is called the culmination of the luminary (culmination is a Latin word and in translation means "top"). Distinguish between the upper and lower culmination of the luminary. The time interval between climaxes is called a half day. The moment of the upper culmination of the center of the Sun is called true noon, and the moment of the lower one is called true midnight. Both the upper and lower culminations can serve as the beginning or end of the time interval (day) we have chosen as a unit.
If we choose the center of the true Sun as the main point for determining the length of the day, i.e. the center of the solar disk that we see on the celestial sphere, we get a unit of time called the true solar days.
When choosing the so-called mean equatorial sun as the main point, i.e. some fictitious point moving along the equator with a constant speed of the Sun along the ecliptic, we get a unit of time called the average solar day.
If we choose the vernal equinox point as the main point in determining the length of the day, then we get a unit of time called sidereal days. Sidereal days are shorter than solar days by 3 minutes. 56.555 sec. Local sidereal day is the period of time from the moment of the upper culmination of the Aries point on the local meridian to a given moment in time. In a certain area, each star always culminates at the same height above the horizon, because its angular distance from the pole of the world and from the celestial equator does not change. The sun and moon, on the other hand, change the altitude at which they climax. The intervals between the culminations of stars are four minutes shorter than the intervals between the culminations of the Sun. The sun per day (the time of one revolution of the celestial sphere), manages to move relative to the stars to the east - in the direction opposite to the diurnal rotation of the sky, by a distance of about 1 °, since the celestial sphere makes a full revolution (360 °) in 24 hours (15 ° - in 1 hour, 1 ° - in 4 minutes).
The climax of the Moon is as much as 50 minutes late every day, as the Moon makes approximately one revolution towards the rotation of the sky per month.
In the starry sky, the planets do not occupy a constant place, just like the Moon and the Sun, therefore on the starry sky map, as well as on the maps of cosmograms and horoscopes, the position of the Sun, Moon and planets can be indicated only for a certain moment in time.
Zone time. Zone time (Tp) of any point is the local mean solar time of the main geographic meridian of the time zone in which this item is located. For the convenience of determining the time, the Earth's surface is divided by 24 meridians - each of them is located exactly 15 ° in longitude from the neighboring one. These meridians define 24 time zones. The time zone boundaries are 7.5 ° east and west from each of the corresponding meridians. The time of the same belt at every moment is considered the same for all its points. The Greenwich meridian is considered to be zero. A date line was also set, i.e. a conditional line, to the west of which the calendar date for all time zones of east longitude will be one day longer than countries located on time zones of west longitude.
In Russia, standard time was introduced in 1919. Taking as a basis the international system of time zones and the then existing administrative boundaries, time zones from II to XII inclusive were plotted on the map of the RSFSR (see Appendix 2, Table 12).
The local time. Time in any dimension, be it sidereal, true solar or mean solar time of some meridian, is called local sidereal, local true solar and local mean solar time. All points lying on the same meridian at the same moment will have the same time, which is called the local time LT (Local Time). The local time is different on different meridians, because The Earth, rotating around its axis, sequentially turns to the Sun different parts of the surface. The sun rises and the day does not come in all places of the globe at the same time. To the east of the Greenwich meridian, local time increases, and to the west, it decreases. Local time is used by astrologers to find the so-called fields (houses) of the horoscope.
World Time. The local solar mean time of the Greenwich meridian is called universal or world time (UT, GMT). The local mean solar time of any point on the earth's surface is determined by the geographical longitude of this point, expressed in hourly units and measured from the Greenwich meridian. To the east of Greenwich, time is considered positive, i.e. it is larger than in Greenwich, and to the west of Greenwich it is negative, i.e. time in the areas west of Greenwich is less than Greenwich.
Daylight saving time (td) - time entered throughout the territory Soviet Union June 21, 1930 Canceled on March 31, 1991. Reintroduced in the CIS and Russia from March 19, 1992.
Daylight saving time (T) is the time introduced in the former Soviet Union from April 1, 1991.
Ephemeris time. The unevenness of the universal time scale has led to the need to introduce a new scale, determined orbital movements bodies Solar system and representing the scale of change in the independent variable of the differential equations of Newtonian mechanics, which form the basis of the theory of motion of celestial bodies. The ephemeris second is equal to 1 / 31556925.9747 of the tropical year (see) of the beginning of our century (1900). The denominator of this fraction corresponds to the number of seconds in the tropical year 1900. The epoch of 1900 is chosen as the zero point of the ephemeris time scale. The beginning of this year corresponds to the moment when the Sun had a longitude of 279 ° 42 ′.
Sidereal, or sidereal year. This is the period of time during which the Sun, with its apparent annual movement around the Earth along the ecliptic, describes a full revolution (360 °) and returns to its previous position relative to the stars.
Tropical year. This is the time interval between two successive passages of the Sun through the vernal equinox. Due to the precessional movement of the vernal equinox towards the movement of the Sun, the tropical year is somewhat shorter than the sidereal one.
An abnormal year. It is the time interval between two successive passages of the Earth through perihelion.
Calendar year. The calendar year is used to count time. It contains an integer number of days. The length of the calendar year was chosen with an orientation to the tropical year, since the correct periodic return of the seasons is associated precisely with the length of the tropical year. And since the tropical year does not contain an integer number of days, we had to resort to the system of inserting additional days when constructing the calendar, which would compensate for the days accumulated due to the fractional part of the tropical year. In the Julian calendar, introduced by Julius Caesar in 46 BC. with the assistance of the Alexandrian astronomer Sosigenes, simple years contained 365 days, leap years - 366. Thus, the average length of a year in the Julian calendar was 0.0078 days longer than the duration of a tropical year. Because of this, if, for example, the Sun in 325 passed through the vernal equinox on March 21, then in 1582, when the calendar reform was adopted by Pope Gregory XIII, the equinox fell on March 11. Reform of the calendar, made at the suggestion of the Italian physician and astronomer Luigi Lilio, provides for the omission of some leap years. The years at the beginning of each century were taken as such years, for which the number of hundreds is not divisible by 4, namely: 1700, 1800 and 1900. Thus, the average length of the Gregorian year was equal to 365.2425 average solar days. In a number of European countries, the transition to the new style was carried out on October 4, 1582, when October 15 was considered the next day. In Russia, the new (Gregorian) style was introduced in 1918, when, by order of the Council of People's Commissars on February 1, 1918, it was ordered to count February 14.
In addition to the calendar system for counting days, in astronomy, a system of continuous counting of days from a certain starting date has become widespread. Such a system was proposed in the 16th century by the Leiden professor Scaliger. It was named in honor of Scaliger's father Julius, therefore it is called the Julian period (not to be confused with the Julian calendar!). Greenwich noon on January 1, 4713 BC was taken as the starting point. according to the Julian calendar, so the Julian day begins at Greenwich noon. Every day according to this time count has its own serial number. In ephemeris - astronomical tables - Julian days are counted from 01.01.1900 1.01.1996 - 2450 084th Julian day.
The planets of the solar system
There are nine major planets in the solar system. In order of distance from the Sun, these are Mercury, Venus, Earth (with the Moon), Mars, Jupiter, Saturn, Uranus, Neptune and Pluto (Fig. 6).
Fig. 6. Orbits of the planets of the solar system
The planets revolve around the Sun in ellipses in almost the same plane. Between Mars and Jupiter, small planets, the so-called asteroids, circulate, the number of which is approaching 2,000. The space between the planets is filled with rarefied gas and cosmic dust. It is penetrated by electromagnetic radiation, which are carriers of magnetic, gravitational and other force fields.
The sun is about 109 times the diameter of the Earth and 330 thousand times more massive than the Earth, and the mass of all the planets combined is only about 0.1 percent of the mass of the Sun. The sun by the force of its attraction controls the movement of the planets of the solar system. The closer a planet is to the Sun, the greater its linear and angular velocity of revolution around the Sun. The period of the planet's revolution around the Sun in relation to the stars is called the stellar, or sidereal period (see Appendix 2, Table 1.2). The period of revolution of the Earth relative to the stars is called a sidereal year.
Until the 16th century, the so-called geocentric system of the world of Claudius Ptolemy existed. In the 16th century, this system was revised by the Polish astronomer Nicolaus Copernicus, who put the sun in the center. Galileo, who built the first telescope, a prototype telescope, based on his observations, confirmed the theory of Copernicus.
At the beginning of the 17th century, Johannes Kepler, a mathematician and astrologer of the Austrian royal court, established three laws of motion of bodies in the solar system.
Kepler's first law. The planets move along ellipses, in one of the focuses of which is the Sun.
Kepler's second law. The radius vector of a planet for equal time intervals describes equal areas, therefore, the closer the planet is to the Sun, the faster it moves, and, conversely, the further it is from the Sun, the slower its motion.
Kepler's third law. The squares of the orbital times of planets are related to each other as cubes of their average distances from the Sun (semi-major axes of their orbits). Thus, Kepler's second law quantitatively determines the change in the speed of the planet's motion along an ellipse, and Kepler's third law connects the average distances of planets from the Sun with the periods of their stellar revolutions and allows the semi-major axes of all planetary orbits to be expressed in units of the semi-major axis of the earth's orbit.
Based on observations of the motion of the moon and Kepler's laws, Newton discovered the law universal gravitation... He found that the type of orbit that the body describes depends on the speed of the celestial body. Thus, Kepler's laws, which make it possible to determine the orbit of the planet, are a consequence of a more general law of nature - the law of universal gravitation, which is the basis of celestial mechanics. Kepler's laws are observed when the motion of two isolated bodies is considered, taking into account their mutual attraction, but not only the attraction of the Sun, but also the mutual attraction of all nine planets operates in the solar system. In this regard, there is a deviation from the motion, albeit a rather small one, which would occur if Kepler's laws were strictly followed. Such deviations are called disturbances. They have to be taken into account when calculating the apparent position of the planets. Moreover, it was thanks to the perturbations that the planet Neptune was discovered; it was calculated, as they say, at the tip of a pen.
In the 40s of the XIX century, it was discovered that Uranus, discovered by W. Herschel at the end of the XVIII century, barely noticeably deviates from the path along which it should follow, taking into account the disturbances from all already known planets. Astronomers Le Verrier (in France) and Adam (in England) have suggested that Uranus is being pulled by some unknown body. They calculated the orbit of the unknown planet, its mass and even indicated the place in the sky where the unknown planet should be at this time. In 1846, this planet was found with a telescope at the location indicated by the German astronomer Halle. This is how Neptune was discovered.
The apparent motion of the planets. From the point of view of an earthly observer, at certain intervals the planets change their direction of motion, in contrast to the Sun and the Moon, which move across the sky in the same direction. In this regard, there is a distinction between the direct motion of the planet (from west to east, like the Sun and the Moon), and backward, or retrograde motion (from east to west). At the moment of the transition from one type of motion to another, an apparent stop of the planet occurs. Based on the above, the apparent path of each planet against the background of the stars is a complex line with zigzags and loops. The shapes and sizes of the described loops are different for different planets.
There is also a difference between the motions of the inner and outer planets. The inner planets include Mercury and Venus, whose orbits lie within the Earth's orbit. The inner planets in their motion are closely connected with the Sun, Mercury moves away from the Sun no further than 28 °, Venus - 48 °. The configuration in which Mercury or Venus passes between the Sun and the Earth is called the lower conjunction with the Sun, during the upper conjunction the planet is behind the Sun, i.e. The sun is between the planet and the Earth. Outer planets include planets whose orbits lie outside the Earth's orbit. The outer planets move against the background of the stars as if independently of the Sun. They describe loops when they are in the opposite region of the sky from the Sun. The outer planets have only the upper conjunction. In cases where the Earth is between the Sun and the outer planet, the so-called opposition occurs.
The opposition of Mars at a time when the Earth and Mars are as close to each other as possible is called the great opposition. Great confrontations are repeated 15-17 years later.
Characteristics of the planets of the solar system
Terrestrial planets. Mercury, Venus, Earth and Mars are called Earth-type planets. They differ from giant planets in many respects: smaller size and mass, higher density, etc.
Mercury is the planet closest to the Sun. It is 2.5 times closer to the Sun than Earth. For a terrestrial observer, Mercury is no more than 28 ° away from the Sun. Only near extreme positions can the planet be seen in the rays of the evening or morning dawn. For the naked eye, Mercury is a bright point, and in a strong telescope it looks like a crescent or an incomplete circle. Mercury is surrounded by an atmosphere. Atmosphere pressure at the surface of the planet is approximately 1,000 times less than at the surface of the Earth. The surface of Mercury is dark brown and lunar-like, strewn with ring mountains and craters. Sidereal day, i.e. the period of rotation around the axis relative to the stars, equal to 58.6 of our days. A solar day on Mercury lasts two Mercury years, that is, about 176 Earth days. The length of the day and night on Mercury results in a dramatic temperature difference between midday and midnight. The daytime hemisphere of Mercury is heating up to 380 ° C and above.
Venus is the closest planet in the solar system to Earth. Venus is almost the same size as the earth. The surface of the planet is always obscured by clouds. The gas shell of Venus was discovered by M.V.Lomonosov in 1761. The atmosphere of Venus differs sharply in chemical composition from the earthly and completely unfit for breathing. It consists of approximately 97% carbon dioxide, nitrogen - 2%, oxygen - no more than 0.1%. Solar days are 117 Earth days. There is no change of seasons on it. At its surface, the temperature is close to + 450 ° C, and the pressure is about 100 atmospheres. The axis of rotation of Venus is almost exactly directed to the pole of the orbit. The daily rotation of Venus occurs not in the forward direction, but in the opposite direction, i.e. in the direction opposite to the motion of the planet in its orbit around the Sun.
Mars is the fourth planet in the solar system, the last of the planets terrestrial group... Mars is almost half the size of Earth. The mass is about 10 times less than the mass of the Earth. Free fall acceleration on its surface is 2.6 times less than on Earth. Solar days on Mars are 24 hours and 37.4 minutes, i.e. almost like on Earth. The duration of daylight hours and the midday height of the Sun above the horizon change throughout the year in about the same way as on Earth, due to the almost identical inclination of the equatorial plane to the orbital plane of these planets (Mars has about 25 °). When Mars is in opposition, it is so bright that it can be distinguished from other stars by its red-orange color. On the surface of Mars, two polar caps are visible, when one grows, the other decreases. It is dotted with ring mountains. The surface of the planet is shrouded in haze, clouds cover it. On Mars, powerful dust storms rage, sometimes lasting for months. The pressure of the atmosphere is 100 times less than that of the Earth. The atmosphere itself is mostly carbon dioxide. Daily temperature changes reach 80-100 ° C.
The giant planets. The giant planets include the four planets of the solar system: Jupiter, Saturn, Uranus and Neptune.
Jupiter is the largest planet in the solar system. It is twice as massive as all the other planets combined. But Jupiter's mass is small compared to the Sun. It is 11 times larger than the Earth in diameter, and more than 300 times in mass. Jupiter is at a distance of 5.2 AU from the Sun. The period of revolution around the Sun is about 12 years. The equatorial diameter of Jupiter is about 142 thousand km. The angular velocity of this giant's daily rotation is 2.5 times that of the Earth. The period of Jupiter's rotation at the equator is 9 hours 50 minutes.
By its structure, chemical composition and physical conditions at the surface, Jupiter has nothing to do with the Earth and the terrestrial planets. It is not known what surface Jupiter has - solid or liquid. Through the telescope, you can observe the light and dark bands of variable clouds. The outer layer of these clouds is made up of frozen ammonia particles. The temperature of the above-cloud layers is about –145 ° С. Above the clouds, Jupiter's atmosphere appears to be made of hydrogen and helium. The thickness of the gas envelope of Jupiter is extremely large, and the average density of Jupiter, on the contrary, is very small (from 1,260 to 1,400 kg / m3), which is only 24% of the average density of the Earth.
Jupiter has 14 moons, the thirteenth was discovered in 1974, and the fourteenth in 1979. They move in elliptical orbits around the planet. Of these, two satellites stand out for their size, Callisto and Ganymede - the largest of the satellites in the solar system.
Saturn is the second largest planet. It is located twice as far from the Sun as Jupiter. Its equatorial diameter is 120 thousand km. Saturn is half the mass of Jupiter. A small admixture of methane gas is found in the atmosphere of Saturn, as on Jupiter. The temperature on the visible side of Saturn is close to the freezing point of methane (-184 ° C), of the solid particles of which the cloudy layer of this planet most likely consists. The period of axial rotation is 10 hours. 14 minutes Rotating rapidly, Saturn has acquired a flattened shape. Flat system rings encircles the planet around the equator, never touching its surface. Three zones are distinguished in the rings, separated by narrow slits. The inner ring is very transparent and the middle ring is the brightest. The rings of Saturn are a mass of small satellites of the giant planet located in the same plane. The plane of the rings has a constant inclination to the orbital plane of approximately 27 °. The thickness of Saturn's rings is about 3 km, and the diameter along the outer edge is 275 thousand km. The period of Saturn's revolution around the Sun is 29.5 years.
Saturn has 15 satellites, the tenth was discovered in 1966, the last three - in 1980 by the American automatic spacecraft Voyager 1. The largest of these is Titan.
Uranus is the most eccentric planet in the solar system. It differs from other planets in that it rotates as if lying on its side: the plane of its equator is almost perpendicular to the plane of its orbit. The inclination of the axis of rotation to the orbital plane by 8 ° exceeds 90 °, so the direction of rotation of the planet is reversed. The moons of Uranus are also moving in the opposite direction.
Uranus was discovered by the English scientist William Herschel in 1781. It is located twice as far from the Sun as Saturn. Hydrogen, helium and a small admixture of methane are found in the atmosphere of Uranus. The temperature at the sunflower point near the surface is 205-220 ° C. The period of revolution around the axis at the equator is 10 hours 49 minutes. Due to the unusual location of the axis of rotation of Uranus, the Sun there rises high above the horizon almost to the zenith, even at the poles. The polar day and the polar night reach 42 years at the poles.
Neptune - found himself by the force of his attraction. Its location was first calculated, after which the German astronomer Johann Halle discovered it in 1846. The average distance from the Sun is 30 AU. The circulation period is 164 years 280 days. Neptune is completely covered with clouds. It is assumed that the atmosphere of Neptune contains hydrogen with an admixture of methane, and the surface of Neptune is mostly water. Neptune has two moons, the largest of which is Triton.
Pluto - the planet farthest from the Sun, the ninth in a row, was discovered in 1930 by Clyde Tombaugh at the Lowell Astrological Observatory (Arizona, USA).
Pluto looks like a point object of the fifteenth magnitude, i.e. it is about 4 thousand times fainter than those stars that are at the limit of visibility with the naked eye. Pluto moves very slowly, only 1.5 ° per year (4.7 km / s) in an orbit that has a large inclination (17 °) to the plane of the ecliptic and is strongly elongated: at perihelion it approaches the Sun for a shorter distance, than the orbit of Neptune, and in aphelion it departs 3 billion km further. With an average distance of Pluto from the Sun (5.9 billion km), our daylight looks from this planet not as a disk, but as a shining point and gives illumination 1,560 times less than on Earth. And therefore, it is not surprising that studying Pluto is very difficult: we know almost nothing about it.
Pluto is 0.18 Earth masses, and is half the Earth in diameter. The period of revolution around the Sun is 247.7 years on average. The period of axial daily rotation is 6 days 9 hours.
The sun is the center of the solar system. His energy is enormous. Even that tiny part that falls on the Earth is very large. The Earth receives from the Sun tens of thousands of times more energy than all power plants in the world if they were working at full capacity.
The distance from the Earth to the Sun is 107 times its diameter, which in turn is 109 times larger than that of the Earth and is about 1,392 thousand km. The mass of the Sun is 333 thousand times greater than the mass of the Earth, and its volume is 1 million 304 thousand times. Inside the Sun, matter is strongly compressed by the pressure of the overlying layers and is ten times denser than lead, but the outer layers of the Sun are hundreds of times more rarefied than air at the Earth's surface. The gas pressure in the interior of the Sun is hundreds of billions of times greater than the air pressure at the Earth's surface. All substances on the Sun are in a gaseous state. Almost all atoms completely lose their electrons and turn into "naked" atomic nuclei. Free electrons, detached from atoms, become part of gas. This gas is called plasma. Plasma particles move at tremendous speeds - hundreds and thousands of kilometers per second. Nuclear reactions are constantly going on on the Sun, which are the source of the inexhaustible energy of the Sun.
The sun is made up of the same chemical elements, as the Earth, but there is incomparably more hydrogen on the Sun than on the Earth. The sun has not used up even half of its hydrogen nuclear fuel. It will shine for many billions of years until all hydrogen in the interior of the Sun turns into helium.
The radio emission of the Sun reaching us arises in the so-called corona of the Sun. The solar corona extends over a distance of several solar radii, it reaches the orbits of Mars and Earth. Thus, the Earth is immersed in the solar corona.
From time to time in sunny atmosphere active areas appear, the number of which changes regularly, with a cycle on average of about 11 years.
The moon is a satellite of the Earth, with a diameter 4 times smaller than the Earth. The Moon's orbit is an ellipse with the Earth in one of its focuses. The average distance between the centers of the Moon and the Earth is 384,400 km. The Moon's orbit is tilted 5 ° 9 ′ to Earth's orbit. The average angular velocity of the Moon is 13 °, 176 per day. The inclination of the lunar equator to the ecliptic is 1 ° 32.3 ′. The time the Moon turns around its axis is equal to the time it turns around the Earth, as a result of which the Moon always faces the Earth with one side. The moon's movement is uneven: in some parts of its visible path, it moves faster, in others it moves more slowly. During its orbital motion, the distance of the Moon to the Earth varies from 356 to 406 thousand km. The uneven orbital motion is associated with the influence of the Earth on the Moon, on the one hand, and the powerful gravitational force of the Sun, on the other. And if we take into account that Venus, Mars, Jupiter and Saturn influence its motion, it is understandable why the Moon continuously changes, within certain limits, the shape of the ellipse along which it revolves. Due to the fact that the Moon has an elliptical orbit, it either approaches the Earth or moves away from it. The point of the lunar orbit closest to the Earth is called perigee, and the most distant one is apogee.
The lunar orbit crosses the ecliptic plane at two diametrically opposite points, called lunar nodes. The ascending (North) node crosses the ecliptic plane, moving from south to north, and the descending (South) node - from north to south. The lunar nodes move continuously along the ecliptic in the direction opposite to the course of the zodiacal constellations. The period of rotation of the lunar nodes along the ecliptic is 18 years and 7 months.
There are four periods of the Moon's revolution around the Earth:
a) sidereal month - the period of the Moon's revolution around the Earth relative to the stars, it is 27.3217 days, i.e. 27 days 7 hours 43 minutes;
b) lunar, or synodic month - the period of the Moon's revolution around the Earth relative to the Sun, i.e. the interval between two new moons or full moons, it averages 29.5306 days, i.e. 29 days 12 hours 44 minutes. Its duration is not constant due to the uneven movement of the Earth and the Moon and ranges from 29.25 to 29.83 days;
c) draconic month - the time interval between two successive passages of the Moon through the same node of its orbit, it is 27.21 average days;
d) anomalistic month - the time interval between two successive passages of the Moon through the perigee, it is 27.55 average days.
During the movement of the Moon around the Earth, the conditions for illuminating the Moon by the Sun change, the so-called change of lunar phases occurs. The main phases of the moon are new moon, first quarter, full moon and last quarter. The line on the disk of the Moon separating the illuminated part of the hemisphere facing us from the unlit one is called the terminator. Due to the excess of the synodic lunar month over the sidereal month, the Moon rises every day about 52 minutes later, the moon rises and sets occur at different hours of the day, and the same phases occur at different points of the lunar orbit alternately in all signs of the zodiac.
Lunar and solar eclipses. Lunar and solar eclipses occur when the Sun and Moon are near the nodes. At the time of the eclipse, the Sun, Moon and Earth are located almost on one straight line.
A solar eclipse occurs when the moon passes between the earth and the sun. At this time, the Moon is facing the Earth with its unlit side, that is solar eclipse occurs only during the new moon (Fig. 3.7). The apparent sizes of the Moon and the Sun are almost the same, so the Moon can cover the Sun with itself.
Fig. 7. Solar eclipse diagram
The distances of the Sun and the Moon from the Earth do not remain constant, since the orbits of the Earth and the Moon are not circles, but ellipses. Therefore, if at the time of a solar eclipse the Moon is at the smallest distance from the Earth, then the Moon will completely cover the Sun. Such an eclipse is called total. The total phase of the solar eclipse lasts no more than 7 minutes 40 seconds.
If during an eclipse the Moon is at the greatest distance from the Earth, then it has a slightly smaller apparent size and does not completely cover the Sun, such an eclipse is called annular. The eclipse will be total or annular if the Sun and Moon are almost at a node during the new moon. If the Sun at the time of the new moon is at some distance from the node, then the centers of the lunar and solar disks will not coincide and the Moon will partially cover the Sun, such an eclipse is called partial. There are at least two solar eclipses every year. The maximum possible number of eclipses in a year is five. Due to the fact that the shadow from the Moon during a solar eclipse does not fall on the entire Earth, a solar eclipse is observed in a certain area. This explains the rarity of this phenomenon.
A lunar eclipse occurs during a full moon, when the Earth is between the Moon and the Sun (Figure 8). The diameter of the Earth is four times the diameter of the Moon, so the shadow from the Earth is 2.5 times the size of the Moon, i.e. The moon can completely plunge into the shadow of the earth. The longest total lunar eclipse is 1 hour 40 minutes.
Fig. 8. Lunar eclipse diagram
Lunar eclipses are visible in the hemisphere where the moon is currently above the horizon. One or two happen throughout the year lunar eclipses, in some years they may not be at all, and sometimes there are three lunar eclipses a year. Depending on the distance from the node of the lunar orbit the full moon occurs, the moon will more or less plunge into the earth's shadow. There are also total and partial lunar eclipses.
Each particular eclipse is repeated after 18 years 11 days 8 hours. This period is called saros. During Saros, 70 eclipses occur: 43 solar, of which 15 are partial, 15 are annular and 13 are complete; 28 are lunar, of which 15 are partial and 13 are full. At the end of the Saros, each eclipse repeats about 8 hours later than the previous one.
The stars are extremely distant from the Earth. Observing them even through a telescope, it is impossible to determine which one is farther and which one is closer. When studying the starry sky, a mathematical model of the starry sky is used - the celestial sphere.
Heavenly sphere is called an imaginary sphere of arbitrary radius centered at the point of observation on which the celestial bodies are projected.
Angular distance between two points of the sphere is the angle between the radii drawn at these points. Note that the circle obtained by intersecting the celestial sphere with a plane passing through the center of the sphere is calledbig circle , and if the plane does not pass through the center -small circle .
The consequence of the rotation of the Earth around its axis is the apparent rotation of the celestial sphere in the opposite direction. This is easy to verify. During the night, the stars describe arcs of concentric circles (with a common axis), the axis passes near the Polar star (α Ursa Minor). The very same Polar (m \u003d 2; from the Greek field - I rotate) remains almost motionless. To study the movement of stars in more detail, you need to familiarize yourself with the basic elements of the celestial sphere.
The diameter of the celestial sphere around which its apparent rotation is carried out is calledaxis of the world (PP ′ see Fig. 1).
The axis of the world crosses the celestial sphere at two points -poles of the world (from greekstripes - axis ): north (R - near it you can see the North Star) and the southern (R' - there are no bright stars near it). In 2000, the angular distance between the North Pole of the world and the Pole Star was only 42`. Polaris is called the compass star because it is a reference point that indicates the direction to the north.
Celestial equator called the great circle of the celestial sphere, perpendicular to the axis of the world.
The diameter of the celestial sphere along which gravity acts and passing through the observation point is calledvertical , orplumb line ( ZZ). The points of intersection of the plumb line with the celestial sphere arezenith (from Arabiczemt ararass - the top of the way ) andnadir (from Arabic -foot direction ).
The great circle of the celestial sphere, perpendicular to the vertical, is calledmathematical , orreal, horizon .
The celestial equator divides the celestial sphere into the northern and southern hemispheres, and the horizon into the visible and invisible hemispheres. The visible hemisphere of the celestial sphere is also calledthe firmament .
The great circle of the celestial sphere passing through the poles of the world - zenith and nadir - is calledheavenly meridian ... The horizon intersects with the celestial meridian at points north (N ) and south (S ), and with the celestial equator - at the points of the east (E ) and west (W ) ... The diameter of the celestial sphere connecting the points of the north and south is calledmidday line ( N S ).
The angular distance of the star from the horizon is calledluminary height h ... For example, the height of a star at its zenith is 90 °.
In fig.1 O - observation point,R - pole of the world,N - north point,T is the center of the Earth, andL - a point on the earth's equator. AngleOTL equals latitude? pointsABOUT and the anglePON is the height of the pole of the worldh p (or the North Star, which is almost the same). The axis of the world is parallel to the axis of rotation of the Earth, and the plane of the celestial equator is parallel to the plane of the earth.
So, the height of the pole of the world is equal to the geographical latitude of the area: h p =φ .
At different points on the Earth, the movement of stars in the celestial sphere looks different. For an observer at the pole of our planet, the pole of the world is at the zenith, the axis of the world coincides with the vertical. Stars move in circles parallel to the horizon. Some luminaries are always visible, others are never seen, here the stars do not rise or set and their height is always the same.
On the earth's equator, the poles of the world are located on the horizon, and the axis of the world coincides with the midday line. Stars move in circles perpendicular to the horizon plane. All the luminaries rise and set, being in the sky for half a day. If it were not for the Sun "interfered", then in a day from the Earth's equator one could see all the bright stars of the sky.
Observing the sky from mid-latitudes, you will notice that some stars rise and set, while others do not set at all. There are also stars that never appear above the horizon.
The stars located at the celestial equator above the horizon are as long as they are below it. The sun moves among the stars, describing a line that is calledeklitiki. Twice a year (in spring - March 20-21 and in autumn - September 22-23) it is located at the celestial equator at the points of the spring and autumn equinoxes. At this time, day is equal to night.
Each star crosses the celestial meridian twice a day. The phenomenon of the passage of luminaries through the celestial meridian is calledculmination ... INupper climax the height of the luminary is the highest, at the bottom - the lowest (see Fig.6 ). The movement of the luminaries between neighboring climaxes continues for half a day. At the pole, the height of the star in both culminations is the same (see Fig. 3). At the equator, only the upper culmination is visible, but all the stars (see Fig. 4). In the middle latitudes of the Earth, for circumpolar stars, both culminations are visible (if not for the Sun), for others (in particular, for the Sun) - only the upper one, and for stars that do not descend - none (see Fig. 5). The moment of the upper culmination of the center of the Sun is called real noon, and in the lower - real north. At noon, the shadow of a vertical object falls along the noon line.
To construct star maps, you must enter a celestial coordinate system. In astronomy, several such systems are used, each of which is convenient for solving various scientific and practical problems. In this case, special planes, circles and points of the celestial sphere are used. On it, the position of the star is uniquely set by two angles. If (the plane in which and from which these angles are deposited is the plane of the celestial equator, then the coordinate system is calledequatorial ... In it, the coordinates are the declination and direct ascent of the stars.
The declination δ is the angular distance of the star from the celestial equator (see Fig. 7). The declination is within -90 °< δ < 90° и принимается положительным в северном полушарии небесной сферы и
отрицательным - в южной. Например, для точек на небесном экваторе δ = 0°, а для
полюсов мира 
,
.
Around declination called the great circle of the celestial sphere passing through the poles of the world and this luminary.
Direct ascent (orright ascension ) α is the angular distance of the declination circle of the star from the vernal equinox. This coordinate is counted in the direction opposite to the direction of rotation of the celestial sphere and is expressed in hourly measure. Right ascension varies within 0 h.< α < 24 час. Всему кругу небесного экватора соответствует 24 часа (или, что то же самое, 360 °). Тогда 1 ч = 15 °, а 4 мин = 1 °. Например, α γ = 0 hour., α Ω \u003d 12 hours.
One of the most famous and simplest celestial coordinate systems is horizontal. The main plane in it is the mathematical horizon, and the coordinates are the azimuthAND luminaries and the height of the luminary above the horizonh ... The disadvantage of the horizontal system is that the coordinates of the luminary are constantly changing.
Time determines the order of change of phenomena. The need to measure and store time arose at the beginning of civilization. For this, periodic processes occurring in nature were used. The movement of our planet produces the visible movement of the luminaries, in particular the Sun on the celestial sphere, which we observe. The most ancient unit of time is a day, the duration of which is determined by the rotation of the Earth around its axis.
The time interval between two successive upper (or lower) culminations of the center of the Sun is calledreal days (or real sunny days) .
The duration of a complete revolution of the Sun along the ecliptic is a unit of time in astronomy.Tropical year is called the time interval between two successive passages of the center of the Sun's disk through the vernal equinox. The tropical year lasts approximately 365.2422 days. In everyday life, they use the calendar year, which is almost equal to the tropical one.
It has been established that the Earth revolves around the Sun unevenly. Therefore, the duration of a real solar day changes periodically, albeit insignificantly. It is longer in winter and shorter in summer. The longest true solar days are about 51 seconds long from short ones. To eliminate this inconvenience in measuring time, usemiddle equatorial sun - an imaginary point that moves uniformly along the ecliptic and makes a full revolution along it in a tropical year. The time interval between two successive climaxes of the middle equatorial sun is calledaverage days (or average sunny days). The average solar day begins at the time of the lower climax of the average equatorial sun. The middle equatorial sun is a fictitious point, not marked in any way in the sky. Therefore, it is impossible to observe its movement, and the necessary calculations are made to determine its coordinates.
The measurement of time by solar days depends on geographic longitude. For all points on a given meridian, the time is the same, but it differs from the local time on other meridians. For example, if we have north according to local time (i.e. the day begins), then on the opposite meridian according to their local time it is already noon. In 1884, in many countries, a belt system was introduced. The surface of the Earth was divided into 24 time zones. INeach of them lies the main meridian, the local time of which is T n considerwaist whole belt time. Distance between major meridians of neighboringbelts 15 ° or 1 hour. For convenience, time zone boundaries pass throughstate and administrative boundaries, and on the seas of sparsely populated areas along the meridians, which are removed from the main ones by 7.5 ° to the east and 7.5 ° to the west.
The Greenwich meridian (passes through the former Greenwich Observatory near London, because it has now been moved to another place) is the main one for the zero time zone. Further to the east, the zones are assigned numbers from 1 to 23. Ukraine lies in the second time zone. Time T 0 time zone zero is calleduniversal time (or Western European). Fair ratio: T n \u003d T 0 + n wheren - time zone number.
The zone time of some time zones has special names.European (or Central European) is the time of the first time zone,eastern European - the second.
In order to efficiently use sunlight and save energy, some countries introduce daylight saving time, which starts every year on the last Sunday in March at 2:00 am by setting the clock hands one hour ahead. At 3 am on the last Sunday in September, the clock is set back one hour, canceling daylight saving time.
It is known that the basic unit of time in SI is the second. Previously, 1/86400 of a solar day was taken in one second. After discovering changes in the duration of solar days, the problem arose of finding a new time scale. In 1967, at the International Conference of Weights and Measures, the atomic second was adopted as a unit of time - a time equal to 9192631770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom. The atomic time scale is based on the data of the cesium atomic clock, which are in some observatories and laboratories of the time services. Atomic clocks are extremely accurate - they make an error of 1 s in a million years.
Astronomy solution for grade 11 for lesson number 2 ( workbook) - Heavenly sphere
1. Complete the sentence.
A constellation is a section of the starry sky with a characteristic observed group of stars.
2. Using the map of the starry sky, enter in the corresponding columns of the table constellation schemes with bright stars. In each constellation, select the brightest star and indicate its name.
3. Complete the sentence.
Star charts do not indicate the position of the planets, since the charts are intended to describe the stars and constellations.
4. Place the following stars in decreasing order of magnitude:
1) Betelgeuse; 2) Spica; 3) Aldebaran; 4) Sirius; 5) Arcturus; 6) Capella; 7) Procyon; 8) Vega; 9) Altair; 10) Pollux.
| 4 | 5 | 8 | 6 | 7 | 1 | 3 | 9 | 2 | 10 |
5. Complete the sentence.
Stars of the 1st magnitude are 100 times brighter than stars of the 6th magnitude.
The ecliptic is the apparent annual path of the Sun among the stars.
6. What is called the celestial sphere?
An imaginary sphere of arbitrary radius.
7. Indicate the names of points and lines of the celestial sphere, indicated by numbers 1-14 in Figure 2.1.
- North pole of the world
- zenith; zenith point
- vertical line
- celestial equator
- west; west point
- center of the celestial sphere
- midday line
- south; point south
- skyline
- east; point east
- south pole of the world
- nadir; toka nadir
- north point
- line of the celestial meridian
8. Using Figure 2.1, answer the questions.
How is the axis of the world located relative to the earth's axis?
Parallel.
How is the axis of the world located relative to the plane of the celestial meridian?
Lies on a plane.
At what points does the celestial equator intersect with the horizon line?
At the points of the east and west.
At what points does the celestial meridian intersect with the horizon line?
At points north and south.
9. What observations convince us of the daily rotation of the celestial sphere?
If you watch the stars for a long time, the stars appear to be a single sphere.
10. Using a moving star chart, write in the table two or three constellations visible at latitude 55 ° in the Northern Hemisphere.
The solution to task 10 corresponds to the reality of the events of 2015, however, not all teachers check the solution of each student's task on the star map for compliance with reality
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2.1.2. Celestial sphere. Special points of the celestial sphere.
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 landmarks. It is convenient to use the concept of the celestial sphere even now, although we know that this sphere does not really exist.
Heavenly sphere - an imaginary spherical surface of arbitrary radius, in the center of which is the observer's eye, and onto 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.
Let's construct a celestial sphere and draw a ray from its center towards the star AND (Figure 1.1).
Where this ray crosses the surface of the sphere, place a point A 1depicting this star. Star INwill be represented by a dot IN 1 .Repeating a similar operation for all observed stars, we get on the surface of the sphere an image of the starry sky - 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 Observer)
- 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 the solution of many practical problems, the 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 apparent arrangement of the luminaries and phenomena that can be observed in the sky during the day or many months. The stars, the Sun, the Moon, planets, etc., are projected onto such a sphere, abstracting from the actual distances to the stars and considering only the angular distance between them. Distances between stars in the celestial sphere can be expressed only 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 the corresponding arcs 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 bucket Big Dipper (α and β) is about 5 ° (Fig. 1.2), and from α Ursa Major to α Ursa Minor (Polar Star) - 5 times more - about 25 °.
The simplest eye estimates of angular distances can also be carried out 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 sizes of 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 as non-point only if the distance to it exceeds its dimensions 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, crosses the celestial sphere at points Z - zenith,Z '- nadir.
Zenith- this highest point above the head of the observer.
Nadir -opposite the zenith point of the celestial sphere.
The plane perpendicular to the plumb line is calledhorizontal plane (or horizon plane).
Mathematical horizon is called the line of intersection of the celestial sphere with a horizontal plane passing through the center of the celestial sphere.
With the naked eye, about 6,000 stars can be seen in the entire sky, but we see only half of them, because the other half of the starry sky is covered by the Earth. Are the stars moving across the sky? It turns out that everyone is moving and, moreover, 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 at this time are high above our heads, 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 knows well that the rotation of the firmament is an apparent phenomenon caused by the rotation of the Earth.
A picture of what happens to the starry sky as a result of the Earth's daily rotation can be captured by a camera.
In the resulting image, each star left its trail in the form of a circular arc (Fig. 2.3). But there is also such a star, the movement of which is almost imperceptible throughout the night. This star was named Polar. During the day, it describes a circle of small radius 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 star trails 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 Polaris has the smallest radius. But this arc and all the others - regardless of their radius and curvature - make up 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 have turned out to be full circles - 360 °. After all, a day is a period of complete revolution of the Earth around its axis. In an hour, the Earth will rotate 1/24 of a circle, that is, 15 °. Therefore, the length of the arc, which the star will describe during this time, will be 15 °, and in half an hour - 7.5 °.
The stars during the day describe the larger circles, the farther from the Pole Star they are.
The axis of the diurnal rotation of the celestial sphere is calledaxis of the world (PP ").
The points of intersection of the celestial sphere with the axis of the world are calledpoles of the world (dot R - north pole of the world, point R" - south pole of the world).
Polaris is located near the North Pole of the world. When we look at the North Star, or rather, 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 located in the southern hemisphere of the celestial sphere.
Plane EAWQ, perpendicular to the axis of the world PP "and passing through the center of the celestial sphere, is calledthe plane 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: north and south.
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 zenith pointZ , center FROM celestial sphere and pole R the world is calledplane of the celestial meridian, and the line of its intersection with the celestial sphere formssky meridian line.
Heavenly meridian - a large circle of the celestial sphere passing through the zenith Z, the pole of the world P, the south pole of the world P ", nadir Z"
Anywhere on Earth, the plane of the celestial meridian coincides with the plane of the geographical meridian of this 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 rotation of the Earth).
- What can be said about relative position the axis of rotation of the celestial sphere and the earth's axis? (The axis of the celestial sphere and the earth's axis will coincide).
- Do all points of the celestial sphere participate 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 Earth's axis of rotation is tilted to the orbital plane at an angle of 66.5 °.Due to the action of gravitational forces from 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 seems to slide along the surface of the cone. (the same happens with the 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.
The earth's axis makes one revolution in 25,776 years - this period is called the Platonic year. Now, near P - the northern pole of the world, there is the Pole Star - α Ursa Minor. Polar is the name of the star that today is located near the North Pole of the world. In our time, since about 1100, such a star is the Ursa Minor alpha - Kinosura. Previously, the title of Polar was alternately assigned to π, η and τ of Hercules, to the stars Tuban and Kohab. The Romans did not have the North Star at all, and Kohab and Kinosura (α Ursa Minor) were called Guardians.
At the beginning of our chronology - the pole of the world was near the α Dragon - 2000 years ago. In 2100, the pole of the world 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 "bucket" - this is the North Star.
In the constellation, which is often called the Small Bucket, the North Star is the brightest. But just like most of the stars of the Big Dipper dipper, Polaris is a second-magnitude star.
Summer (summer-autumn) triangle \u003d star Vega (α Lyrae, 25.3 light years), star Deneb (α Cygnus, 3230 light years), star Altair (α Eagle, 16.8 light years)