What is the orbit of a planet? Can a planet fall out of orbit? What happens if the planet leaves orbit? Which planet is bigger - Mars or Earth? Planets of the Solar System and their sizes What orbits are the planets in?
The planets of the Solar System revolve around the Sun in elliptical orbits (see. Kepler's laws) and are divided into two groups. Planets that are closer to the Sun than Earth are called lower. These are Mercury and Venus. Planets that are located further from the Sun than Earth are called top. These are Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
Planets in the process of revolving around the Sun can be located relative to the Earth and the Sun in an arbitrary manner. This mutual arrangement The Earth, Sun and Planets are called configuration. Some of the configurations are highlighted and have special names (see Fig. 19).
The lower planet can be located on the same line with the Sun and Earth: either between the Earth and the Sun - bottom connection, or behind the Sun - top connection. At the moment of inferior conjunction, a planet may pass across the disk of the Sun (the planet is projected onto the disk of the Sun). But due to the fact that the orbits of the planets do not lie in the same plane, such passages do not occur every inferior conjunction, but quite rarely. Configurations in which the planet, when observed from Earth, is at its maximum angular distance from the Sun (these are the most favorable periods for observing the lower planets) are called greatest elongations, western And eastern.
The upper planet can also be in line with the Earth and the Sun: behind the Sun - compound, and on the other side of the Sun - confrontation. Opposition is the most favorable time to observe the upper planet. Configurations in which the angle between the directions from the Earth to the planet and to the Sun is 90 o, are called quadratures, western And eastern.
The time interval between two successive planetary configurations of the same name is called its synodic circulation period P, in contrast to the true period of its revolution relative to the stars, therefore called sidereal S. The difference between these two periods arises due to the fact that the Earth also revolves around the Sun with a period T. The synodic and sidereal periods are interconnected:
for the top.
10.2. Kepler's laws
The laws by which the planets revolve around the Sun were empirically (i.e., from observations) established by Kepler, and then theoretically substantiated on the basis of the law universal gravity Newton.
First law. Each planet moves in an ellipse, with the Sun at one focus.
Second law. When a planet moves, its radius vector describes equal areas in equal periods of time.
Third law. The squares of the sidereal revolution times of the planets are related to each other as the cubes of the semimajor axes of their orbits (as the cubes of their average distances from the Sun):
Kepler's third law is an approximate one; it was derived from the law of universal gravitation refined Kepler's third law:
Kepler's third law is satisfied with good accuracy only because the masses of the planets are much less than the mass of the Sun.
Ellipse is geometric figure(see Fig. 20), which has two main points - tricks F 1 , F 2, and the sum of the distances from any point of the ellipse to each of the foci is a constant value equal to the major axis of the ellipse. The ellipse has center O, the distance from which to the most distant point of the ellipse is called semi-major shaft a, and the distance from the center to the nearest point is called minor axis b. The quantity that characterizes the oblateness of the ellipse is called eccentricity e:
A circle is a special case of an ellipse ( e=0).
The distance from the planet to the Sun varies from the smallest, equal to
perihelion) to the greatest, equal
(this point of the orbit is called aphelion).
10.3. Movement of artificial celestial bodies
The movement of artificial celestial bodies is subject to the same laws as natural ones. However, a number of features need to be noted.
The main thing is that the dimensions of the orbits of artificial satellites are, as a rule, comparable to the dimensions of the planet around which they orbit, therefore they often talk about the height of the satellite above the surface of the planet (Fig. 21). It should be taken into account that the center of the planet is at the focus of the satellite’s orbit.
For artificial satellites, the concept of first and second escape velocity is introduced.
First escape velocity or circular velocity is the speed of circular orbital motion at the surface of the planet at altitude h:
Second escape velocity or parabolic speed is the speed that needs to be given spacecraft, so that he can leave the sphere of gravity of a given planet in a parabolic orbit:
The speed of a celestial body at any point in the elliptical orbit at a distance R from the gravitating center can be calculated using the formula:
Questions
4. Could Mars pass across the Sun? Transit of Mercury? Transit of Jupiter?
5. Is it possible to see Mercury in the east in the evening? And Jupiter?
Tasks
Solution: The orbits of all planets lie approximately in the same plane, so the planets move in celestial sphere approximately along the ecliptic. At the moment of opposition, the right ascensions of Mars and the Sun differ by 180 o :
. Let's calculate for May 19th. On March 21 it is 0 o. The sun's right ascension increases by about 1 per day o. 59 days passed from March 21 to May 19. So, , a . On sky map you can see that the ecliptic with such a right ascension passes through the constellations Libra and Scorpio, which means Mars was in one of these constellations.
47. The best evening visibility of Venus (its greatest distance east of the Sun) was on February 5th. When is Venus next visible under the same conditions, if its sidereal orbital period is 225 d ?
Solution: Venus's best evening visibility occurs during its eastern elongation. Therefore, the next best evening visibility will occur during the next easterly elongation. And the time interval between two successive eastern elongations is equal to the synodic period of revolution of Venus and can be easily calculated:
or P=587 d. This means that the next evening visibility of Venus under the same conditions will occur in 587 days, i.e. September 14-15 next year.
48. (663) Determine the mass of Uranus in units of the mass of the Earth, comparing the movement of the Moon around the Earth with the movement of the satellite of Uranus - Titania, orbiting around it with a period of 8 d.7 at a distance of 438,000 km. Orbital period of the Moon around the Earth 27 d.3, and its average distance from the Earth is 384,000 km.
Solution: To solve the problem, it is necessary to use Kepler's third refined law. Since for any body with mass m, orbiting another body of mass at an average distance a with period T:
 |
(36) |
Then we have the right to write down the equality for any pair of celestial bodies revolving around each other:
Taking Uranus and Titania as the first pair, and the Earth and the Moon as the second, and also neglecting the mass of the satellites compared to the mass of the planets, we obtain:
49. Taking the Moon's orbit as a circle and knowing the Moon's orbital speed v L = 1.02 km/s, determine the mass of the Earth.
Solution: Let us recall the formula for the square of circular velocity () and substitute the average distance of the Moon from the Earth a L (see previous problem):
50. Calculate mass double star Centauri, whose period of revolution of the components around the common center of mass is T = 79 years, and the distance between them is 23.5 astronomical units (AU). An astronomical unit is the distance from the Earth to the Sun, equal to approximately 150 million km.
Solution: The solution to this problem is similar to the solution to the problem of the mass of Uranus. Only when determining the masses of double stars are they compared with the Sun-Earth pair and their mass expressed in solar masses.
51. (1210) Calculate linear speeds spaceship at perigee and apogee, if above the Earth at perigee it flies at an altitude of 227 km above the ocean surface and the major axis of its orbit is 13,900 km. The radius and mass of the Earth are 6371 km and 6.0 10 27 g.
Solution: Let's calculate the distance from the satellite to the Earth at apogee ( greatest distance from the earth). To do this, it is necessary, knowing the distance at perigee (the shortest distance from the Earth), to calculate the eccentricity of the satellite’s orbit using formula () and then determine the required distance using formula (32). We get h a= 931 km.
The most important (and most massive!) member of the Solar System is the Sun itself. Therefore, it is no coincidence that the great luminary occupies a central position in the solar system. It is surrounded by numerous satellites. The most significant of them are the large planets.
The planets are spherical" heavenly lands"Like the Earth and the Moon, they do not have their own light - they are illuminated exclusively by the sun's rays. Nine are known major planets, distant from the central luminary in the following order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Five planets - Mercury, Venus, Mars, Jupiter and Saturn - have been known to people since time immemorial due to their bright brilliance. Nicolaus Copernicus included our Earth among the planets. And the most distant planets - Uranus, Neptune and Pluto - were discovered using telescopes.
|
Solar system, a system of cosmic bodies, including, in addition to the central luminary - Sun- nine large planets, their satellites, many small planets, comets, small meteoroids and cosmic dust, moving in the region of the prevailing gravitational action of the Sun. The Solar system was formed about 4.6 billion years ago from a cold cloud of gas and dust. Currently, using modern telescopes (in particular the Hubble Space Telescope), astronomers have discovered several stars with similar protoplanetary nebulae, which confirms this cosmogonic hypothesis. |
Our Earth is in third place from the Sun. Its average distance from it is 149,600,000 km. It is taken as one astronomical unit (1 AU) and serves as a standard in measuring interplanetary distances. Light travels 1 a. i.e. in 8 minutes and 19 seconds, or in 499 seconds.
The average distance of Mercury from the Sun is 0.387 AU. That is, it is 2.5 times closer to the central luminary than our Earth, and the average distance of distant Pluto is almost 40 such units. A radio signal sent from Earth towards Pluto would take almost 5.5 hours to travel. The further a planet is from the Sun, the less radiant energy it receives. That's why average temperature planets fall rapidly with increasing distance from the radiant star.
By physical characteristics The planets are clearly divided into two groups. The four closest to the Sun - Mercury, Venus, Earth and Mars - are called planets terrestrial group . They are relatively small, but their average density is high: about 5 times the density of water. After the Moon, the planets Venus and Mars are our closest cosmic neighbors. Jupiter, Saturn, Uranus and Neptune are significantly far from the Sun more massive than planets terrestrial group and even more surpass them in volume. In the interiors of these planets, the matter is highly compressed, however, their average density is low, and Saturn has even less than the density of water. Hence, giant planets consist of lighter (volatile) substances than terrestrial planets.
At one time, astronomers considered Pluto to be a planet like Earth. However latest research forced scientists to abandon this view. Frozen methane was detected on its surface using spectroscopy. This discovery indicates the similarity of Pluto with the large satellites of the giant planets. Some researchers are inclined to think that Pluto is a “runaway” satellite of Neptune.
Even Galileo, who discovered the four largest satellites of Jupiter (they are called Galilean satellites), imagined the remarkable Jupiterian family as a miniature Solar System. Today natural satellites are known from almost all major planets (with the exception of Mercury and Venus), and their total number has increased to 137. The giant planets have especially many moon satellites.
If we had the opportunity to look at the solar system from its perspective north pole, then one could observe a picture of the ordered movement of the planets. They all move around the Sun in almost circular orbits in the same direction - opposite to the clockwise rotation. This direction of movement in astronomy is usually called straight movement. But the revolution of the planets does not occur around the geometric center of the Sun, but around the general center of mass of the entire Solar System, in relation to which the Sun itself describes a complex curve. And very often this center of mass ends up outside the solar globe.
The solar system is far from being limited to the central luminary - the Sun and nine large planets with their satellites. There are no words, the major planets are the most important representatives of the Sun family. However, our great luminary still has many other “relatives”.
The German scientist Johannes Kepler spent almost his entire life searching for the harmony of planetary movements. He was the first to draw attention to the fact that between the orbits of Mars and Jupiter there is an empty space. And Kepler was right. Two centuries later, in this interval, a planet was actually discovered, only not a large one, but a small one. In terms of its diameter, it turned out to be 3.4 times smaller, and in terms of volume, 40 times smaller than our Moon. The new planet was named after the ancient Roman goddess Ceres, the patroness of agriculture.
Over time, it became clear that Ceres has thousands of celestial “sisters” and most of them move just between the orbits of Mars and Jupiter. There they form a kind of belt of minor planets. Mostly these are tiny planets with a diameter of about 1 km. Second belt of minor planets recently discovered on the outskirts of our planetary system - beyond the orbit of Uranus. It is possible that the total number of these celestial bodies in the Solar System reaches several million.
But the family of the Sun is not limited to just the planets (large and small). Sometimes tailed “stars” are visible in the sky - comets. They come to us from afar and usually appear suddenly. According to scientists, on the outskirts of the solar system there is a “cloud” consisting of 100 billion potential, that is, not manifested, cometary nuclei. This is what serves as a constant source of the comets we observe.
Occasionally we are “visited” by giant comets. The bright tails of such comets stretch almost across the entire sky. Thus, the comet of September 1882 had a tail reaching a length of 900 million km! When the nucleus of this comet flew near the Sun, its tail went far beyond the orbit of Jupiter...
As you can see, our Sun turned out to have a very large family. In addition to the nine large planets with their satellites, under the leadership of the great luminary there are at least 1 million small planets, about 100 billion comets, as well as countless meteor bodies: from blocks several tens of meters in size to microscopic dust grains.
The planets are located at enormous distances from each other. Even Venus, which is adjacent to the Earth, is never closer to us than 39 million km, which is 3000 times the diameter of the globe...
You can’t help but wonder: what is our solar system? A space desert with individual worlds lost in it? Emptiness? No, the solar system is not empty. An incalculable number of particles of solid matter of the most varied sizes, but mostly very small, with a mass of thousandths and millionths of a gram, are moving in interplanetary space. This meteor dust. It is formed by the evaporation and destruction of cometary nuclei. As a result of the fragmentation of colliding small planets, fragments of various sizes arise, the so-called meteoroids. Under the pressure of solar rays, the smallest particles of meteoric dust are swept to the outskirts of the solar system, and larger ones spiral towards the Sun and, before reaching it, evaporate in the vicinity of the central star. Some meteoroids fall to Earth as meteorites.
The circumsolar space is permeated by all types of electromagnetic radiation and corpuscular flows.
Their very powerful source is the Sun itself. But on the outskirts of the Solar system, radiation emanating from the depths of our Galaxy predominates. By the way: how to establish the boundaries of the solar system? Where do they go?
It may seem to some that the boundaries of the solar domain are delineated by the orbit of Pluto. After all, there seem to be no large planets beyond Pluto. This is where it’s time to “dig in” the boundary pillars... But we must not forget that many comets go far beyond the orbit of Pluto. Aphelia- the farthest points of their orbits lie in a cloud of primordial ice cores. This hypothetical (alleged) cometary cloud is apparently 100 thousand AU away from the Sun. e., that is, 2.5 thousand times further than Pluto. So the power of the great luminary extends here too. The solar system is here too!
Obviously, the Solar System reaches those places in interstellar space where the gravitational force of the Sun is commensurate with the gravitational force of the nearest stars. The closest star to us, Alpha Centauri, is 270 thousand AU away from us. e. and its mass is approximately equal to the Sun. Consequently, the point at which the gravitational forces of the Sun and Alpha Centauri are balanced is located approximately in the middle of the distance separating them. This means that the boundaries of the solar domain are at least 135 thousand AU away from the great luminary. e., or 20 trillion kilometers!
The moment when the planets are at their closest approach to each other is called opposition. The distance between planets can change even in opposition. The closest distance from Earth to Venus is 38 million kilometers.
And the farthest is 261 million km. While this seems surprisingly large, it is nothing compared to the distance between other planets. Try to imagine how far the Earth is from Neptune.
Venus's relative proximity helps explain why it is the second brightest object in the night sky. It has an apparent magnitude of about -4.9. It can also completely disappear from the night sky when it is at its farthest point in its orbit from us.
Visible magnitude depends also on the reflectivity of the sulfuric acid clouds that dominate its atmosphere. These clouds reflect most of the visible light, increasing the planet's albedo.
Planet transits
Venus will periodically pass across the disk of the Sun. This is called a transit across the solar disk. These transits occur in pairs at intervals of more than a century. With the advent of the telescope, transits were discovered in 1631, 1639, 1761, 1769 and 1874, 1882. The most recent occurred on June 8, 2004 and June 6, 2012.
Venus is always brighter than any star. When the distance from it to the Earth is smallest, the brightness of the planet in the Earth's sky is greatest.
It can be easily noticeable when the Sun is low on the horizon. It is always approximately 47° from the Sun.
The planet rotates faster than the Earth, so it overtakes it every 584 days. When this happens, it is easier to see in the morning, just after sunrise.
| · · · · | |
People have always been interested in the unknown expanses of space. Research on other planets attracted many scientists, and to the common man An interesting question is what is there in space? First of all, scientists pay attention to the planets of the solar system. Since they are closest to Earth and are easier to study. The mysterious red planet Mars is being especially actively studied. Let's find out which planet is larger - Mars or Earth, and try to understand what is red heavenly body That's how it attracts us.
Brief description of the planets of the solar system. Their sizes
From Earth, all the planets of our system appear to us as small luminous points that are difficult to see naked eye. Mars is different from everyone else - it seems larger to us than the others and sometimes even without telescopic equipment you can see its orange light.
Which planet is bigger: Mars or Earth? Do we see Mars so well because it is huge, or is it simply closer to us? Let's look into this issue. To do this, we will sequentially consider the sizes of all planets belonging to the Solar system. They were divided into two groups.
Terrestrial group of planets
Mercury is the smallest planet. In addition, it is closest to the Sun than anyone else. Its diameter is 4878 km.
Venus is the planet next farthest from the Sun and closest to Earth. Its surface temperature reaches +5000 degrees Celsius. The diameter of Venus is 12103 km.
The earth is different in that it has an atmosphere and water reserves, which made it possible for life to arise. Its size is slightly larger than Venus and is 12,765 km .
Mars is the fourth planet from the Sun. Earth and has a diameter at the equator of 6786 km. Its atmosphere is almost 96% composed of Mars and has a more elongated orbit of rotation than Earth.
Giant planets
Jupiter is the largest of the planets in the solar system. Its diameter is 143,000 km. It consists of gas, which is in a vortex motion. Jupiter rotates around its axis very quickly; it makes a full revolution in about 10 Earth hours. It is surrounded by 16 satellites.
Saturn is a planet that can justifiably be called unique. Its structure has the lowest density. Saturn is also known for its rings, which are 115,000 km wide and 5 km thick. It is the second largest planet in the solar system. Its size is 120,000 km.
Uranus is unusual in that with a telescope it can be seen in blue-green color. This planet also consists of gases that move at a speed of 600 km/h. The diameter is just over 51,000 km.
Neptune is made up of a mixture of gases, most of which are methane. It is because of this that the planet acquired Blue colour. Neptune's surface is shrouded in clouds of ammonia and water. The size of the planet is 49,528 km.
The most distant planet from the Sun is Pluto; it does not belong to any of the groups of planets in the Solar System. Its diameter is half that of Mercury and is 2320 km.
Characteristics of the planet Mars. Features of the Red Planet and comparison of its size with the size of the Earth
So we looked at the sizes of all the planets in the solar system. Now we can answer the question of which planet is larger - Mars or Earth. A simple comparison of the diameters of the planets can help with this. The sizes of Mars and Earth differ by half. The Red Planet is almost half the size of our Earth.
Mars is a very interesting space object to study. The mass of the planet is 11% of the Temperature on its surface varies throughout the day from +270 to -700 degrees C. The sharp drop is due to the fact that the atmosphere of Mars is not so dense and consists mainly of carbon dioxide.
The description of Mars begins with an emphasis on its rich red color. I wonder what caused this? The answer is simple - the soil composition is rich in iron oxides and the increased concentration of carbon dioxide in its atmosphere. For such a specific color, ancient people called the planet bloody and gave it a name in honor of the Roman god of war - Ares.
The surface of the planet is mostly desert, but there are also dark areas, the nature of which has not yet been studied. Mars is a plain, and the southern one is slightly raised from the average level and is dotted with craters.
Many people do not know, but on Mars there is the highest mountain in the entire solar system - Olympus. Its height from base to top is 21 km. The width of this hill is 500 km.
Is it possible
All the works of astronomers are aimed at finding signs of life in space. In order to study Mars for the presence of living cells and organisms on its surface, rovers have repeatedly visited this planet.
Numerous expeditions have already proven that water was previously present on the Red Planet. It is still there, only in the form of ice, and it is hidden under a thin layer of rock soil. The presence of water is also confirmed by photographs in which the beds of Martian rivers are clearly visible.
Many scientists want to prove that humans can adapt to life on Mars. The following facts are provided to support this theory:
- Almost the same speed of movement of Mars and Earth.
- Similarity of gravitational fields.
- Carbon dioxide can be used to produce vital oxygen.
Perhaps in the future, the development of technology will allow us to easily make interplanetary travel and even settle on Mars. But first of all, humanity must preserve and protect its home planet - the Earth, so that it never has to wonder which planet is bigger - Mars or the Earth, and whether the red planet can accept all the migrants who want it.