How do asteroids move? Asteroid movement

Small planets

The galaxy is inhabited by many small asteroid planets. Asteroids are solid cosmic bodies that move like planets in elliptical orbits around the Sun. The term “asteroid,” which means “star-like,” was introduced by the famous astronomer of his time, William Herschel (1738-1822), to characterize these objects when observing them through a telescope. Asteroids are so small that even with the most powerful telescopes and the largest asteroids, it is impossible to discern visible disks.

Asteroids look like small point sources of light, although, like all other planets, they do not emit it themselves, but only reflect light falling from the Sun. The largest of all asteroids is Ceres. It was discovered by the Sicilian astronomer Giuseppe Piazzi from Palermo. On the night of January 1, 1801, when the New Year of the 19th century was celebrated on Earth, Piazzi observed the stars in the zodiac constellation Taurus.

First asteroid

Suddenly he noticed that between the orbits of Jupiter and Mars, one of the stars had moved to the west and was moving. Therefore, this is not a star, but some other celestial body, but this body does not have a noticeable disk, which a planet should have, or a hazy appearance characteristic of comets... Piazzi named his brainchild Ceres in honor of the ancient Roman goddess agriculture and fertility, considered the patroness of Sicily.

This first asteroid discovered by an astronomer also turned out to be the largest asteroid in the Solar System, its diameter is 932 kilometers. And the mass is 1.17 × 10 21 kilograms, which is approximately a third of the total mass of the asteroid belt.

Ceres' orbit is 2.77 astronomical units from the Sun and lies in the main asteroid belt, with Ceres' distance from the Sun ranging from 2.55 to 3.05 AU. e. The asteroid's brightness is equal to its maximum magnitude - 6.9, although the albedo (characteristic of surface reflectivity) of Ceres is only 9%.

The rotation period is 9 hours, and during this time the color and brightness change very little (this leads to the correct idea that this asteroid has a spherical shape and a uniform gray color).

Currently

Modern astronomical science has discovered about 20,000 asteroids, but only about 10,000 of them are registered, that is, they are given numbers and names. And the bulk of these asteroids are located between the orbits of Jupiter and Mars at a distance of 2.2-3.2 AU. e. from the Sun.

The first photographs of asteroids taken by spacecraft show that the surface of these cosmic bodies is riddled with craters and craters of various sizes. It is assumed that such a surface of small planets was formed as a result of collisions of asteroids with other celestial bodies.

Asteroids have been known to astronomers for a long time, but the world community started talking about them seriously only after 2004, when information appeared in the media that this could have been a disaster, destroying about 25% of life on the planet. Then the trajectory of the asteroid was recalculated, everyone calmed down, but interest in asteroids and others remained. So, ?
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Diameter is about 950 km. What this celestial body has been since its discovery (which happened, for a moment, in 1801!): a full-fledged planet, an asteroid, and since 2006 it has been considered a dwarf planet - for being the largest in the asteroid belt. Ceres is spherical in shape, which is completely uncharacteristic of asteroids; the core consists of rock, and the crust is made of minerals and water ice. The closest point of its orbit is at a distance of 263 million km from Earth, so it is unlikely that a collision should be expected - at least in the next few thousand years.

Its diameter is 532 km. It also forms part of the asteroid belt and is very rich in silicon - in the future it may become a source of minerals for earthlings.

530 km in diameter. Even though Vesta is smaller in size than previous asteroids, it is the heaviest asteroid. Its core consists of heavy metal, its crust is made of rock. Due to the characteristics of this rock, Vesta reflects 4 times more sunlight than the leader of our top - Ceres, so sometimes, once every 3-4 years, Vesta’s movements can be observed from Earth with the naked eye.

Its diameter is considerable - 407 km, but this asteroid is so dim that it was discovered later than the others. Hygea is a typical representative of the most common type of asteroid - with carbonaceous content. At the moment of its maximum approach to the Earth, this celestial body can be observed not through a telescope, but through binoculars.

Diameter – 326 km. Despite the fact that Interamnia is a very large asteroid, it still remains a very little-studied celestial body. First of all, because they belong to asteroids of the rare spectral class F, neither their exact composition nor the internal structure is known to modern science. As for Interamnia, even its exact form is unknown! Complete mysteries...

The diameter of this asteroid is 302.5 km, and it was discovered a long time ago - in 1858. It has a very elongated orbit, so the distance from Europa to the Sun can change very significantly (if there was life here, it would be some super-adaptive mutants!). Its density index is only slightly greater than that of water, which means that the surface of this celestial body is porous. It's like a giant pumice stone rotating in the Great Asteroid Ring.

Its diameter, according to various estimates, ranges from 270 to 326 km. Where does such a strange name come from? The discoverer of this asteroid, Raymond Dugan, named the celestial body he discovered in honor of astronomy professor David Todd, but the name was remade into a “female” version - “David”, since at that time only female names were given to asteroids (and, as you already might note, most are from Greek mythology).

Diameter – 232 km. This asteroid, like Europa, has a large porosity - essentially, it is a pile of rubble that is held together by gravity. Sylvia is the first triple asteroid known to us, because it has at least 2 satellites!

A very strange space object with dimensions of 370 × 195 × 205 and a shape that looks like either a peanut or a dumbbell, and in addition to everything, it also has its own (as yet unnamed) moon. Its origin is interesting: the fact is that Hector consists of a mixture of rock and ice. The Kuiper belt objects Pluto and its satellite Triton have this composition. This means that Hector arrived from the Kuiper Belt (the region of space beyond Pluto), most likely at the dawn of the formation of the Solar System, when the planets were actively migrating.

Size – according to various sources, from 248 to 270 km – is a large and rapidly rotating asteroid. It has a very high density, but this is due to its large size.
And just recently - on July 19 - asteroid UW-158 with a core containing about 100 million tons of platinum passed very close to Earth (2.4 million km, nothing for space)! Such wealth is gone... So asteroids continue to surprise us!

At the very beginning of the 19th century. Italian astronomer Piazzi (1746-1826) accidentally discovered the first minor planet (asteroid). She was named Ceres. Subsequently, many other small planets were discovered, forming the asteroid belt between the orbits of Mars and Jupiter.

Asteroid movement

In photographs of the starry sky taken with long exposures, they appear as light lines. More than 5,500 minor planets have been registered. The total number of asteroids should be tens of times greater. Asteroids whose orbits have been established receive designations (serial numbers) and names. Some new asteroids are named after great people (1379 Lomonosov), states (1541 Estonia, 1554 Yugoslavia), observatories (1373 Cincinnati - an American observatory that is the International Asteroid Observation Center), etc.

Asteroids move around the Sun in the same direction as the large planets. Their revolutions have larger eccentricities (on average 0.15) than the orbits of large planets. Therefore, some small planets extend far beyond the asteroid belt. Some of them move beyond the orbit of Saturn at aphelion, while others approach Mars and Earth at perihelion. For example, in October 1937, Hermes passed from the Earth at a distance of 580,000 km (only one and a half times further than the Moon), and the asteroid Icarus, discovered in 1949, even moves inside the orbit of Mercury and approaches the Earth every 19 years . The last time this happened was in June 1987. Then Icarus approached the Earth at a distance of several million kilometers and was observed at many observatories. Of course, this is not the only case. It is possible, for example, that the collision of an asteroid with the Earth led to the death of dinosaurs 65 million years ago. And in March 1989, an asteroid measuring about 300 m passed from the Earth at a distance of less than 650 thousand km. Therefore, it is no coincidence that scientists have begun to develop effective methods for the timely detection and, if necessary, destruction of dangerous asteroids.

Physical characteristics of asteroids

Asteroids are not visible to the naked eye. The largest asteroid is Ceres (diameter 1000 km). In general, asteroids have diameters from several kilometers to several tens of kilometers, and most asteroids are shapeless blocks. The masses of asteroids, although different, are too small for these celestial bodies to retain an atmosphere. The total mass of all asteroids collected together is about 20 times less than the mass of the Moon. All the asteroids would make one planet with a diameter of less than 1500 km.

In recent years, it has been possible to discover satellites (!) on some asteroids. The asteroid was first photographed from a distance of only 16 thousand km on October 29, 1991, from the American spacecraft Galileo, launched on October 18, 1982 to study Jupiter. Crossing the asteroid belt, Galileo photographed the minor planet 951 - the Gaspra asteroid. This is a typical asteroid. The semimajor axis of its orbit is 2.21 AU. It turned out to be irregular in shape and may have been formed as a result of the collision of larger bodies in the asteroid belt. The photographs show craters (their diameter is 1-2 km, the consecrated part of the asteroid is 16x12 km). In the images, it is possible to discern details of the surface of the Gaspra asteroid with a size of 60-100 m.

For a long time, humanity had no idea about the real composition of the solar system. It was assumed that the only celestial bodies were planets, their satellites and comets. One could only guess about the existence of smaller formations, judging by the traces that fallen asteroids left on the surface of our planet. There were neither technical means nor capabilities for a more accurate study of outer space. Progress came only at the beginning of the 19th century, when mathematics came to the aid of astronomers. The first mathematical calculations confirmed the assumption of astronomers that there are many small space objects within the boundaries of near space.

Such objects were called asteroids by accident, at the suggestion of William Herschel. Having compared these dim celestial bodies with distant stars, the English astronomer gave them the appropriate name. Asteroid, translated from ancient Greek, means “like a star.”

History of the discovery of asteroids

Even Johannes Kepler in 1596, studying the calculations made by Copernicus, noted the following feature in the position of the orbits of the known planets of the solar system. All terrestrial planets had orbits located approximately at the same interval from each other. The region of outer space between the orbits of Mars and Jupiter clearly did not fit into a strict order and looked quite wide. This gave the scientist the idea that there must probably be another planet in this part of space, or at least some traces of its existence. Kepler's speculations, made many years ago, remained unresolved until 1801, when the Italian astronomer Piazii managed to detect a small, dim object in this part of space.

All the scientists known at that time, including the mathematician Gauss, began to calculate the exact location of the new object. In 1802, another meeting with a new celestial body took place, and, thanks to the joint efforts of mathematicians and astronomers, the object was discovered.

The first asteroid was named Ceres in honor of the ancient Roman goddess. All subsequent discovered asteroids received names consonant with the names of the goddesses of the ancient Roman pantheon. Pallas appeared next to Ceres on the cosmic map.

A little later, this list was supplemented by two other similar bodies. In 1804, Astronomer Harding discovered Juno, and three years later, the same Heinrich Olbers put the name of the fourth astroid - Vesta - on the star map. For convenience, new space objects were named after characters from ancient Roman mythology. Fortunately, ancient Roman mythology had a sufficient number of characters who gave names to asteroids. Thus began the campaign for small celestial bodies, of which there were a huge number in the Solar System.

Asteroid belt in the solar system

After scientists were able to discover Ceres, Pallas, Juno and Vesta - the largest and largest asteroids in the Solar System - the fact of the existence of a whole cluster of similar objects becomes obvious.

Thanks to Gauss's calculations, Olbers obtained accurate astronomical data for new objects. It turned out that both Ceres and Pallas move around the Sun in identical orbits, making a full revolution around the central body in 4.6 Earth years. The inclination of the asteroids' orbit to the ecliptic plane was 34 degrees. All newly discovered celestial bodies were located between the orbits of Mars and Jupiter.

At the end of the 19th century, the discovery of new objects in this part of space continued. By 1957, 389 other smaller objects were known to exist. Their nature and physical parameters gave every reason to classify such bodies as asteroids. Such a massive accumulation of solid celestial bodies, reminiscent in their shape and structure of fragments of a large celestial body, is called the “asteroid belt”.

The orbits of the asteroids are approximately in the same plane, the width of which is 100 thousand km. Such an array of fragments in space led scientists to a version of a planetary catastrophe that occurred in the system of our star billions of years ago. Scientists agree that large and small asteroids are the legendary planet Phaeton, which split into small pieces. Even the ancient Greeks had a myth that there was a planet in space that became a victim of the gravitational confrontation between Jupiter and the Sun. Probably, the asteroid belt between Mars and Jupiter is real confirmation that we are dealing with the remains of a once-existing planet.

After it was possible to determine the real scale and size of the asteroid belt, it became clear where the threat to our planet could come from. A huge array of stone fragments is a real source of meteorite danger, which threatens the peaceful existence of earthly civilization. The main problem is that celestial bodies of small mass do not have sufficient stability for a stable position in orbit. Constantly under the influence of their larger neighbors Jupiter and Mars, asteroids can shoot out of the asteroid belt like a rock fired from a sling. Where this huge cosmic boulder will fly next is anyone's guess.

Now it is impossible to guess and calculate where the asteroid will fall, what consequences the fall of asteroids threatens for earthlings. We will have very little time left to make any decisions in terms of salvation. Probably for the same reason, dinosaurs disappeared from the face of planet Earth at one time. Our planet millions of years ago could have collided with an asteroid, as a result of which the living conditions on Earth radically changed.

Astronomical and physical data of the largest asteroids

As for the largest objects of Ceres, Pallas, Juno and Vesta, they were given a separate box in the astronomical catalog. The first of them, the largest, was classified as a dwarf planet. The reason for this decision was the rotation of this celestial body around its own axis. In other words, in addition to their orbital path, large asteroids undergo their own rotational motion. It is not possible to determine exactly what caused it. Probably, the bodies continue to rotate by inertia, having received a powerful impulse at the moment of formation. However, unlike Pluto and other dwarf planets, Ceres has no moons. The shape of a dwarf planet is traditionally planetary, typical of all planets in the Solar System. Astronomers admit that the spherical shape of Ceres contributed to the development of planetary magnetism. Accordingly, a body rotating around its own axis must have its own center of gravity.

It turned out that the discovered celestial bodies are significantly smaller in size than the planets, and also have an irregular, stone-like shape. The sizes of asteroids are very diverse, as is the mass of these fragments. So the size of Ceres is 960 x 932 km. It is not possible to determine the exact diameter of asteroids due to the lack of a spherical shape. The mass of this giant rock is 8.958E20 kg. Although Pallas and Vesta are smaller in size than Ceres, they have three or four times more mass. Scientists admit the different nature of these objects. Ceres is a rocky body that arose when the planetary crust fractured. Pallas and Vesta may be remnants of the planet's ruptured iron-dominated core.

The surface of asteroids is heterogeneous. For some objects it is quite even and smooth, like a cobblestone melted by high temperature. Other asteroids have surfaces with clear features missing. Craters are often observed on the surface of large asteroids, indicating the ancient nature of such objects. There can be no talk of any atmosphere on such small-sized celestial bodies. These are ordinary fragments of building material that rotate in orbit around the Sun under the influence of gravitational forces.

The total mass of all celestial bodies found in the asteroid belt is approximately 2.3-3.2 astronomical units. At the moment, science knows more than 20,000 asteroids from this cluster. The average orbital speed of space objects located in this area is 20 km/s. The period of rotation around the Sun varies in the range of 3.5-9 Earth years.

Dangerous asteroids: what threatens the Earth from a collision with an asteroid

In order to have an idea of what we are dealing with, it is enough to look at the physical parameters of some asteroids that are located on the inner edge of the asteroid belt. It is these celestial objects that pose the greatest threat to our planet. These include:

Amur asteroid group;
group of Apollo objects;
Aten asteroid group.

All of these objects have unstable orbits, which at different times can intersect not only with Mars, but also with the orbits of other terrestrial planets. Scientists admit that in the process of orbital evolutions under the influence of gravity of Jupiter and other large bodies of the Solar System, the orbits of Amurs, Apollos and Atons can intersect with the orbital path of the planet Earth. Scientists have already calculated that the orbits of some asteroids from the listed groups at a certain period are inside the orbital ring of the Earth and even Venus.

It has been established that up to 800 such objects tend to change their orbital path. However, one should take into account hundreds, thousands of small asteroids, with a mass of 10.50, 1000 and 10000 kg, which are also moving in this direction. Accordingly, through mathematical calculations one can assume the probability of a collision between the Earth and such a space hulk. The consequences of such a rendezvous would be catastrophic. Even small asteroids, the size of an ocean liner, falling to Earth will lead to a global catastrophe.

In conclusion

Exploring remote areas of space has allowed scientists to discover a new asteroid belt beyond Pluto. This region lies between the orbits of Pluto and the Kuiper Belt. It is physically impossible to determine the exact number of objects in this area. These distant space objects constitute a small retinue of our star system and do not pose a real threat to humanity.

Much more dangerous are the asteroids that revolve around us. A giant scar on the body of Mars may be the exact site of a collision between the red planet and one of the uninvited space guests that left the asteroid belt billions of years ago.

We are not immune from such collisions; moreover, in the history of planet Earth there have been many such unpleasant encounters. The close location of our planet to such a massive accumulation of stone fragments and fragments always poses a certain danger.

All asteroids discovered so far have direct motion: they move around the Sun in the same direction as the large planets (i

The boundaries of the ring are somewhat arbitrary: the spatial density of asteroids (the number of asteroids per unit volume) decreases with distance from the central part. If, as the asteroid moves along its orbit, the mentioned zr plane is rotated (around an axis perpendicular to the ecliptic plane and passing through the Sun) following the asteroid (so that it remains in this plane all the time), then the asteroid will describe a certain loop in this plane in one revolution .

Most of these loops lie within the shaded region, like those of Ceres and Vesta, moving in slightly eccentric and slightly inclined orbits. For a few asteroids, due to the significant eccentricity and inclination of the orbit, the loop, like Pallas’s (i = 35o), extends beyond this region or even lies entirely outside it, like the Atonians. Therefore, asteroids are also found far outside the ring

The volume of space occupied by the ring-torus, where 98% of all asteroids move, is enormous - about 1.6 1026 km3. For comparison, we point out that the volume of the Earth is only 1012 km3. The semi-major axes of the orbits of asteroids belonging to the ring lie in the range from 2.2 to 3.2 a. e. Asteroids move in orbits with a linear (heliocentric) speed of about 20 km/s, spending from 3 to 9 years per revolution around the Sun.

Their average daily motion is in the range of 400-1200. The eccentricity of these orbits is small - from 0 to 0.2 and rarely exceeds 0.4. But even with a very small eccentricity, only 0.1, the heliocentric distance of the asteroid during its orbital movement changes by several tenths of an astronomical unit, and with e = 0.4 by 1.5 - 3 a. That is, depending on the size of the orbit, the inclination of the orbits to the ecliptic plane is usually from 5° to 10°.

But with an inclination of 10°, the asteroid can deviate from the ecliptic plane by about 0.5 AU. That is, at an inclination of 30°, move away from it by 1.5 AU. According to the average daily motion, asteroids are usually divided into five groups. Numerous in composition, groups I, II and III include asteroids moving, respectively, in the outer (farthest from the Sun), central and inner zones of the ring.

In the central zone, asteroids of the spherical subsystem predominate, while in the inner zone, 3/4 of the asteroids are members of the flat system. As we move from the inner to the outer zone, more and more circular orbits become: in group III, the eccentricity is e

Only bodies in less eccentric orbits, unreachable for this giant of the solar system, have survived. All asteroids in the ring are, so to speak, in a safe zone. But they also experience disturbances from the planets all the time. Of course, Jupiter has the strongest influence on them. Therefore, their orbits are constantly changing. To be completely strict, it must be said that the path of an asteroid in space is not ellipses, but open quasi-elliptical turns that lie next to each other. Only occasionally - when approaching a planet - do the orbits noticeably deviate from one another. The planets, of course, disturb the movement not only of asteroids, but also of each other. However, the disturbances experienced by the planets themselves are small and do not change the structure of the Solar System.

They cannot cause planets to collide with each other. With asteroids the situation is different. Due to the large eccentricities and inclinations of the orbits of asteroids, they change quite strongly under the influence of planetary disturbances, even if there are no approaches to the planets. Asteroids deviate from their path, first in one direction, then in the other. The farther away, the greater these deviations become: after all, the planets are continuously “pulling” the asteroid, each towards itself, but Jupiter is the strongest.

Observations of asteroids cover too short periods of time to detect significant changes in the orbits of most asteroids, with the exception of some rare cases. Therefore, our ideas about the evolution of their orbits are based on theoretical considerations. Briefly, they boil down to the following: The orbit of each asteroid oscillates around its average position, spending several tens or hundreds of years on each oscillation. Its semi-axis, eccentricity and inclination change synchronously with a small amplitude. Perihelion and aphelion either approach the Sun or move away from it. These fluctuations are included as a component in fluctuations of a larger period - thousands or tens of thousands of years.

They have a slightly different character. The semimajor axis does not experience additional changes. But the amplitudes of eccentricity and tilt fluctuations can be much greater. With such time scales, one can no longer consider the instantaneous positions of planets in orbits: as in an accelerated film, an asteroid and a planet appear to be smeared along their orbits.

It becomes reasonable to consider them as gravitating rings. The inclination of the asteroid ring to the ecliptic plane, where the planetary rings are located - the source of disturbing forces - leads to the fact that the asteroid ring behaves like a top or a gyroscope. Only the picture turns out to be more complex, because the asteroid’s orbit is not rigid and its shape changes over time. The asteroid's orbit rotates so that the normal to its plane, restored at the focus where the Sun is located, describes a cone. In this case, the line of nodes rotates in the ecliptic plane with a more or less constant speed clockwise. During one revolution, the inclination, eccentricity, perihelion and aphelion distances experience two fluctuations.

When the line of nodes coincides with the asp line (and this happens twice in one revolution), the inclination is maximum and the eccentricity is minimum. The shape of the orbit becomes closer to circular, the semi-minor axis of the orbit increases, the perihelion is moved away from the Sun as much as possible, and the aphelion is closer to it (since q+q’=2a=const). Then the line of nodes shifts, the inclination decreases, the perihelion moves towards the Sun, the aphelion moves away from it, the eccentricity increases, and the semi-minor axis of the orbit shortens. Extreme values are reached when the line of nodes is perpendicular to the asp line. Now perihelion is closest to the Sun, aphelion is farthest from it, and both of these points deviate the most from the ecliptic.

Studies of the evolution of orbits over long periods of time show that the described changes are included in changes of an even longer period, occurring with even greater amplitudes of oscillations of the elements, and the asp line is also included in the movement. So, each orbit continuously pulsates, and besides, it also rotates. At small e and i, their oscillations occur with small amplitudes. Almost circular orbits, which also lie close to the ecliptic plane, change barely noticeably.

For them, it all comes down to a slight deformation and a slight deviation of one or the other part of the orbit from the ecliptic plane. But the greater the eccentricity and inclination of the orbit, the stronger the disturbances appear over large periods of time. Thus, planetary disturbances lead to continuous mixing of the orbits of asteroids, and therefore to the mixing of objects moving along them. This makes it possible for asteroids to collide with each other. Over the past 4.5 billion years, since asteroids have existed, they have experienced many collisions with each other. The inclinations and eccentricities of the orbits lead to non-parallelism of their mutual movements, and the speed with which the asteroids rush past one another (the chaotic velocity component) averages about 5 km/s. Collisions at such speeds lead to the destruction of bodies.