I want to say right away that I did not set out to scare the reader with scary stories about a cosmic threat with a colorful description of the fall of a comet to Earth and the death of all living things. I think it’s unlikely that anyone will be able to do this better than in the movie “Armageddon” in the near future. Here I simply collected and systematized in a popular form the basic information about the small bodies of the Solar System and tried to objectively answer the question: “Is it possible to sleep peacefully at night or should we be afraid that at any moment a rock the size of a house or an entire city and will destroy, if not half the planet, then some small country?”

The world of asteroids and comets.

I have two news for you - good and bad. I'll start with the bad: around the Sun, within a sphere with a radius of 1 light year (this is the sphere in which the Sun can hold small bodies with its gravity), they are constantly circling trillions(!!!) blocks ranging in size from tens of meters to hundreds and even thousands of kilometers!

The good news is that the solar system has existed for 4.5 billion years and the original mess of cosmic matter has long been structured into the stable system of planets, asteroids, comets, etc. that we observe. The period of massive meteorite bombardment that the Earth and other planets experienced remained in the distant prehistoric past. Almost everything large that was supposed to fall to Earth from space, fortunately for us, has already fallen. Now the situation in the solar system is generally calm. Occasionally, a comet will delight you with its appearance - a guest from the very outskirts of the possessions of our luminary.

All large asteroids have been discovered, recorded, registered, their orbits have been calculated, and they pose no danger.

It’s more difficult with small ones - there are more of them in space than there are ants in all anthills. It is simply impossible to register every space rock. Due to their small size, they are detected only in the immediate vicinity of the Earth. And very small ones are not detected at all before entering the atmosphere. But they don’t do much harm, at most they can scare you with a loud bang before almost completely burning out. Although they can break glass in houses, as the same Chelyabinsk meteorite did, which demonstrated the reality of the threat from space.

The greatest concern is caused by asteroids over 150 meters in size. Theoretically, their number is only in "main belt" can be in the millions. It is very difficult to detect such a body at a distance large enough to have time to do something. A meteorite 150-300 meters in size is guaranteed to destroy a city if it hits it.

Thus, the threat from space is more than real. Meteorites have fallen on Earth throughout its history, and sooner or later it will happen again. To assess the level of danger, I propose to understand in more detail the structure of this heavenly economy.

Terminology.

• Small bodies of the Solar System- all natural objects orbiting the Sun, except planets, dwarf planets and their satellites.

• Dwarf planets- bodies with a mass sufficient to, due to their own gravity, maintain a shape close to spherical (from 300-400 km), but not dominant in their orbit.

• - small bodies measuring more than 30 meters.
• Small bodies less than 30 meters in size are called meteoroids.
• Further, as the size decreases, there are micrometeoroids(less than 1-2 mm), and then cosmic dust(particles smaller than 10 microns).
• Meteorite- what remains of an asteroid or meteoroid after it falls to Earth.
• Bolide- a flash visible when a small body enters the atmosphere.
• Comet- icy small body. As it approaches the Sun, ice and frozen gas evaporate, forming the comet's tail and coma (head).
• Aphelion— the most distant point of the orbit.
• Perihelion— the point of the orbit closest to the Sun.
• a.e.— Astronomical unit of distance, this is the distance from the Earth to the Sun (150 million km).

Place of mass concentration of small bodies. This is a wide strip between the orbits of Mars and Jupiter, along which the bulk of the asteroids of the central part of the Solar System rotate:

Most of the small bodies in the Solar System fly around the Sun in groups in close orbits. This is due to the fact that over billions of years they experience gravitational influences from the planets (especially Jupiter) and gradually shift from unstable orbits, where such influences are maximum, to stable ones, where gravitational disturbances are minimal. Also, groups of asteroids arise during collisions, when a large asteroid falls apart into many small ones, or it remains intact, but many fragments break off from it. At the moment, dozens of groups (or families) of asteroids are known, but most of them belong to the main belt.

IN main belt There are 4 known bodies with a size of more than 400 km, about 200 bodies with a size of more than 100 km, about 1000 with a size of 15 km or more. It is theoretically calculated that there should be about 1-2 million asteroids larger than 1 km there. Despite the huge number, the total mass of these stones is only 4% of the mass of the Moon.

It was previously assumed that the main asteroid belt arose from the debris of the exploded planet Phaeton. But now a more likely version is that the planet in this area simply could not arise due to the proximity of the giant Jupiter.

Millions of asteroids in this belt, many of which could cause Armageddon on Earth, do not pose a danger to us, since their orbits lie beyond the orbit of Mars.

Collisions.

But sometimes they collide with each other, then some fragment can accidentally fall into the Earth. The probability of such an accident is extremely low. If you calculate it for a time period equal to the life of 2-3 generations, then these generations need not worry too much.

But the Earth has existed for billions of years, during which time everything has happened. For example, the extinction of about 80% of all living things and 100% of dinosaurs 65 million years ago. It has been practically proven that the crater of which is located in the area of ​​the Yucotan Peninsula (Mexico) is to blame for this. Judging by the crater, it was a meteorite about 10 km in size. Presumably it belonged to the Baptistina family of asteroids, which was formed when a 170-km asteroid collided with another fairly large one.

How often do such collisions occur? I propose to turn on your spatial imagination and imagine the main asteroid belt reduced by 100 thousand times. At this scale, its width will be approximately equal to the width of the Atlantic Ocean. An asteroid with a diameter of 1 km will turn into a ball 1 cm in size. Four giant bodies - Ceres, Vesta, Pallas and Hygiea with sizes of 950, 530, 532 and 407 km, respectively, will become balls with sizes of approximately 10, 5 and 4 meters. 100-meter asteroids (the minimum size that poses a serious enough threat) will become 1-mm crumbs. Now let’s mentally scatter them throughout the Atlantic and imagine that they smoothly cruise in approximately one direction, for example, first from north to south, then back. Their trajectories are not exactly parallel - let some sail from London to the lower tip of South America, and others from New York to southern Africa. Moreover, they complete their journey there and back (orbital period) in 4-6 years (on this scale, this approximately corresponds to a speed of 1 km/h).

Have you imagined this picture? On the same scale, the Earth in its closest position relative to any asteroid will be a 130-meter island in the Indian Ocean. What is the probability that two asteroids collide and a fragment hits her directly!? Now, I think you will sleep more peacefully. At the very least, the anxiety about cosmic Armageddon, constantly fueled by the media, should recede further into the background. Even if you pour several million balls ranging in size from 1 millimeter to tens of centimeters and only a few hundred larger than a meter into the Atlantic Ocean, then with such a movement that we were talking about, intuition suggests that collisions and fragments hitting the Earth in the near future cannot be expected. And mathematical calculations give the following data: asteroids over 20 km in size hit each other once every 10 million years.

One of the typical pictures that is usually given as an illustration when describing the asteroid belt:

Now I think you understand that in real life it looks completely different. In fact, the ratio of the distances between neighboring blocks and their sizes is much greater there than in this figure. It measures thousands of kilometers, maybe sometimes hundreds, so interplanetary spacecraft have so far easily flown through this belt without any complications.

However, despite all that has been said, it is from the Main Asteroid Belt that more than 99% of meteorite fragments found on Earth come from. They made a significant contribution to the “development” of life on Earth, periodically causing mass extinctions of species on it. Well, that’s why he’s the Chief...

Asteroids approaching the Earth.

As mentioned above, most asteroids belong to some family, that is, bodies of the same group fly in similar orbits. There are families of orbits that approach the Earth's orbit, or even cross it. The most dangerous of them are the families of Amur, Apollo and Aten:

Amur Group- the least threatening of these three, since it does not cross the Earth’s orbit, but only approaches it. This is enough to pose a potential danger, since during such approaches, Earth’s gravity unpredictably changes the orbit of asteroids, and therefore the threat can turn from potential into real. Mars has the same effect on them, since they cross its orbit, and therefore sometimes come close to it. About 4000 asteroids of this group are known, naturally most of them have not yet been discovered. The largest of them is Ganymede (not to be confused with the satellite of Jupiter), its diameter is 31.5 km. Another member of this group, Eros (34 X 11 km), is famous for being the first spacecraft in history to land on it, the NEAR Shoemaker (NASA).

Apollo group. As can be seen in the diagram, the asteroids of this group, as well as the “cupids”, go into the Main Belt at aphelion (maximum distance from the Sun), and at perihelion they enter the Earth’s orbit. That is, they cross it in two places. More than 5,000 members are known in this family, mostly small ones, the largest being 8.5 km.

Aton Group. There are about 1,000 known “Atonov” (the largest is 3.5 km). On the contrary, they cruise inside the Earth’s orbit, and only at aphelion do they go beyond its limits, also crossing our orbit.

In fact, the diagram shows projections of typical orbits of “Apollos” and “Atons”. Each of the asteroids has a certain orbital inclination, so not all of them cross the Earth's orbit - most pass under or above it (or slightly to the side). But if it crosses, then there is a possibility that at some point the Earth will be at the same point with it - then a collision will occur.

This is how this cosmic carousel spins from year to year. Astronomers around the world are monitoring every suspicious object, constantly discovering more and more. On the website of the Center for Minor Planets I found a list of asteroids that threaten the Earth (potentially dangerous). The asteroids in it are sorted starting with the most dangerous.

Apophis.

“Apophis” is one of the “atons”, leading the list of the most dangerous asteroids, since the estimated distance at which it will pass by the Earth is the smallest of all known - only 30-35 thousand km from the surface of our planet. Since there is a possibility of errors in calculations due to inaccurate data, there is also some probability of a “hit”.

Its diameter is about 320 meters, the period of revolution around the Sun is 324 Earth days. That is, once every 162 days it practically flies through the Earth’s orbit, but since the total length of the Earth’s orbit is almost a billion kilometers, risky approaches rarely occur.

Apophis was discovered in July 2004 and approached Earth again in December. The July data was compared with the December data, the orbit was calculated and... a big commotion began! Calculations have shown that in 2029 Apophis will fall to Earth with a 3% probability! This was tantamount to a scientifically based prediction of the end of the world. Close observations of Apophis began, each new refinement of the orbit reducing the likelihood of Armageddon. The possibility of a collision in 2029 was practically refuted, but the approach in 2036 came under suspicion. In 2013, the next flight of Apophis near the Earth (about 14 million km) made it possible to clarify its size and orbital parameters as much as possible, after which NASA scientists completely refuted the information about the threat of this asteroid falling to Earth.

A little about other small bodies of the Solar System.

The most asteroid-dangerous part of our planetary system is left behind, we are moving towards its outskirts. As the distance increases, the potential danger of objects located there decreases accordingly. In other words, if, according to NASA, there is no need to be afraid of any Apophis, then the danger of small bodies, which will be discussed below, tends to zero.

"Trojans" and "Greeks".

Each major planet in the Solar System has points in its orbit where bodies with low mass are in equilibrium between this planet and the Sun. These are the so-called Lagrange points, there are 5 of them in total. Two of them, which are located 60° in front and behind the planet, are inhabited by “Trojan” asteroids.

Jupiter has the largest Trojan groups. Those that are ahead of him in orbit are called “Greeks”, those that lag behind are called “Trojans”. About 2000 “Trojans” and 3000 “Greeks” are known. All of them are not, of course, located at one point, but are scattered throughout the orbit in areas extending tens of millions of kilometers.

In addition to Jupiter, Trojan groups have been discovered near Neptune, Uranus, Mars and Earth. Venus and Mercury most likely have them too, but they have not yet been discovered, since the proximity of the Sun prevents astronomical observations in these areas. By the way, at the Lagrange points of the Moon relative to the Earth there are also at least clumps of cosmic dust, and possibly small fragments of meteorites caught in a gravitational trap.

Kuiper Belt.

Further, as you move away from the Sun, beyond the orbit of Neptune (the farthest planet in the Solar System), that is, at a distance of more than 30 AU. from the center, another vast asteroid belt begins - the Kuiper belt. It is approximately 20 times wider than the Main Belt and 100-200 times more massive. Conventionally, its outer boundary is assumed to be a distance of 55 AU. from the Sun. As can be seen in the figure, the Kuiper Belt is a huge torus (donut) lying beyond the orbit of Neptune: More than 1000 Kuiper Belt Objects (KBOs) are already known. Theoretical calculations say that there should be about 500,000 objects with a size of 50 km, about 70,000 with a size of 100 km, several thousand small planets (and maybe large ones) with a size of more than 1000 km (so far only 7 of these have been discovered).

The most famous Kuiper Belt object is Pluto. According to the new definition of the term “planet”, it is no longer considered a full-fledged planet, but is classified as a dwarf planet, since it clearly does not dominate its orbit.

Scattered disk.

The outer boundary of the Kuiper Belt smoothly transitions into the Scattered Disk. Here small bodies rotate in much more elongated and even more inclined orbits. At aphelion, scattered disk objects can move hundreds of AU away.

That is, objects in this region do not adhere to any strict system in their rotation, but move in very different orbits. Therefore, in fact, the disk is called scattered. For example, objects with orbital inclinations of up to 78° have been discovered there. There is also an object that enters the orbit of Saturn and then moves away to 100 AU.

The largest known dwarf planet, Eris, rotates in the scattered disk; its diameter is about 2500 km, which is larger than that of Pluto. At perihelion it enters the Kuiper belt, at aphelion it moves away to a distance of 97 AU. from the Sun. Its orbital period is 560 years.

The most extreme known object in this region is the dwarf planet Sedna (diameter 1000 km), at its maximum distance it leaves us at a distance of 900 AU. It takes 11,500 years to orbit the Sun.

It seems that all this is an unattainable distant distance, but!. There are currently two man-made objects in this area - the Voyager spacecraft, launched back in 1977. Voyager 1 has gone a little further than its partner, now it is at a distance of 19 billion kilometers from us (126 AU). Both devices still successfully transmit information about the level of cosmic radiation to Earth, while the radio signal reaches us in 17 hours. At this rate, Voyagers will fly 1 light year (a quarter of the distance to the nearest star) in 40,000 years.

And you and I, mentally of course, can overcome this distance in an instant. Let's move on..

Oort cloud.

The Oort cloud begins where the scattered disk ends (the distance is conventionally assumed to be 2000 AU), that is, it does not have a clear boundary - the scattered disk becomes more and more scattered, and smoothly turns into a spherical cloud consisting of a wide variety of bodies rotating in a wide variety of areas. orbits around the Sun. At a distance of more than 100,000 au. (about 1 light year) The Sun can no longer hold anything with its gravity, so the Oort cloud gradually fades away and interstellar emptiness begins.

Here is an illustration from Wikipedia, which clearly shows the comparative sizes of the Oort Cloud and the inner part of the Solar System:

For comparison, the orbit of Sedna (Scattered Disc Object, a dwarf planet with a diameter of about 1000 km) is also shown. Sedna is one of the most distant objects currently known, the perihelion of its orbit is 76 AU, and the aphelion is 940 AU. Opened in 2003. By the way, it would hardly have been discovered if it were not now in the perihelion region of its orbit, that is, at the closest distance to us, although this is twice as far as Pluto.

What is a comet?

A comet is an icy small body (water ice, frozen gases, some meteorite matter), the Oort Cloud mainly consists of these bodies. Although at such enormous distances modern telescopes cannot see objects about a kilometer in size, it is theoretically predicted that there are several trillion (!!!) small bodies in the Oort Cloud. All of them are potential comet nuclei. However, with such enormous dimensions of the cloud, the average distance between neighboring bodies there is measured in millions, and on the outskirts in tens of millions of kilometers.

Everything that is said about the Oort cloud is revealed “at the tip of the pen”, since although we are inside it, it is very far from us. But every year, astronomers discover dozens of new comets approaching the Sun. Some of them, the longest-period ones, were thrown into our part of the Solar System precisely from the Oort cloud. How could this happen? What exactly brought them here?

The options are:

• There is a large planet(s) in the Oort Cloud that disrupts the orbits of small Oort Cloud Objects.
• Their orbits were scattered when another star passed near the Sun (at an early stage in the evolution of the Solar System, when the Sun was still inside the star cluster that gave birth to it).
• Some long-period comets were captured by the Sun from a similar “Oort Cloud” of another, smaller star that passed nearby.
• All of these options are true at the same time.

Be that as it may, every year newly discovered comets approach their perihelion, both short-period comets arriving from the Kuiper belt and the Scattered Disk (the period of revolution around the Sun is up to 200 years), and long-period comets from the Oort cloud (they, for revolution around the Sun takes tens of thousands of years). Basically, they do not fly too close to the Earth, so only astronomers see them. But sometimes such guests put on a beautiful space show:

What if..

What will happen if a comet or asteroid falls to Earth, because this has happened many times in the past? About this in

Asteroid Apophis may fall to Earth in 2068, and in 2029 it will pass at a distance ten times closer to the planet than the distance from the Earth to the Moon, according to the Department of Celestial Mechanics of St. Petersburg State University. They prepared a corresponding report for the Moscow Royal Readings on Cosmonautics, quotes from it are given RIA Novosti .

“The unique feature of this asteroid is its precisely determined close approach to the Earth on April 13, 2029, at a distance of 38 thousand kilometers (the Moon is 384 thousand kilometers away from the Earth). This convergence causes a significant scattering of possible trajectories, among them there are trajectories containing a convergence in 2051.

The corresponding resonant returns contain many (about hundreds) possible collisions of Apophis with the Earth today, the most dangerous - in 2068,”

- says the abstract of the report, which will be announced at the readings at the end of January.

Before a possible collision with Earth in 2068, the asteroid will approach our planet by 16 million kilometers in 2044, by 760 thousand kilometers in 2051, and by 5 million kilometers in 2060.

The Apophis asteroid was discovered in 2004 by specialists at the Kitt Peak Observatory in Arizona. Its diameter is about 325 m, the asteroid reflects only 23% of the light incident on its surface.

According to researchers, the TNT equivalent of an explosion when an asteroid falls on Earth would be 506 megatons. For comparison, the energy release during the fall of the Tunguska meteorite is estimated at 10-40 Mt, the energy of the explosion of the Tsar Bomb is 57-58.6 Mt, the explosion of the Krakatau volcano in 1883 was equivalent to approximately 200 Mt.

The effect of the explosion could vary depending on the asteroid's composition and the location and angle of impact. In any case, the explosion would cause massive destruction over an area of ​​thousands of square kilometers, but would not create long-term global effects like an “asteroid winter.”

If it fell into the seas or large lakes, such as Ontario, Michigan, Baikal or Ladoga, there would not be a devastating tsunami.

All populated areas located at a distance of 3-300 km, depending on the topography of the impact area, would have been completely destroyed.

He noted that at the moment, instead of civil defense, a life safety course is being taught.

“We can say in the resolution that we need to contact the Ministry of Education to jointly discuss the issue of minimizing damage from space threats,” Sergeev said.

Corresponding Member of the Russian Academy of Sciences A. FINKELSTEIN, Institute of Applied Astronomy RAS (St. Petersburg).

Asteroid Ida has an elongated shape, approximately 55 km long and 22 km wide. This asteroid has a small moon, Dactyl (pictured: light dot on the right), about 1.5 km across. Photo by NASA

The Eros asteroid, on the surface of which the NEAR spacecraft landed in 2001. Photo by NASA.

The orbit of the asteroid Apophis intersects the orbit of the Earth. According to calculations, on April 13, 2029, Apophis will pass at a distance of 35.7-37.9 thousand km from Earth.

For two years now, the “Online Interview” section has been running on the website of the journal “Science and Life”. Experts in the field of science, technology, and education answer questions from readers and site visitors. We publish some interviews on the pages of the magazine. We present to our readers an article prepared on the basis of an Internet interview with Andrei Mikhailovich Finkelshtein, director of the Institute of Applied Astronomy of the Russian Academy of Sciences. We are talking about asteroids, observations of them and the possible threat posed by small space objects in the Solar System. Over the four-billion-year history of its existence, our planet has been repeatedly hit by large meteorites and asteroids. The fall of cosmic bodies is associated with global climate changes that occurred in the past and the extinction of many thousands of species of living beings, in particular dinosaurs.

How great is the risk of a collision between the Earth and an asteroid in the coming decades and what consequences could such a collision lead to? The answers to these questions are of interest not only to specialists. In 2007, the Russian Academy of Sciences, together with Roscosmos, the Ministry of Defense of the Russian Federation and other interested departments, prepared a draft Federal Target Program “Asteroid Hazard Prevention”. This national program is designed to organize systemic monitoring of potentially dangerous space objects in the country and provides for the creation of a national early warning system for a possible asteroid threat and the development of means of protection against the possible destruction of civilization.

The solar system is nature's greatest creation. Life arose in it, intelligence arose and civilization developed. The solar system consists of eight major planets - Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune - and more than 60 of their satellites. Small planets, of which more than 200 thousand are currently known, rotate between the orbits of Mars and Jupiter. Outside the orbit of Neptune, in the so-called Kuiper belt, trans-Neptunian dwarf planets move. Among them, the most famous is Pluto, which until 2006 was considered, according to the classification of the International Astronomical Union, the most distant major planet in the solar system. Finally, comets move within the solar system, the tails of which create the impressive effect of “star showers” ​​when the Earth’s orbit crosses them and many meteors burn up in the earth’s atmosphere. This entire system of celestial bodies, rich in complex movements, is perfectly described by celestial-mechanical theories, which reliably predict the position of bodies in the solar system at any time and in any place.

“Star-like”

Unlike the large planets of the solar system, most of which have been known since ancient times, asteroids, or small planets, were discovered only in the 19th century. The first minor planet, Ceres, was discovered in the constellation Taurus by the Sicilian astronomer, director of the Palermo Observatory, Giuseppe Piazzi, on the night of December 31, 1800 to January 1, 1801. The size of this planet was approximately 950 km. Between 1802 and 1807, three more minor planets were discovered - Pallas, Vesta and Juno, whose orbits, like the orbit of Ceres, lay between Mars and Jupiter. It became clear that they all represented a new class of planets. At the suggestion of the English royal astronomer William Herschel, small planets began to be called asteroids, that is, “star-like,” since telescopes could not distinguish the disks characteristic of large planets.

In the second half of the 19th century, due to the development of photographic observations, the number of discovered asteroids increased sharply. It became clear that a special service was needed to monitor them. Before the outbreak of World War II, this service operated at the Berlin Computing Institute. After the war, the tracking function was taken over by the US Minor Planet Center, currently located in Cambridge. The calculation and publication of ephemeris (tables of planetary coordinates for a specific date) was carried out by the Institute of Theoretical Astronomy of the USSR, and since 1998 by the Institute of Applied Astronomy of the Russian Academy of Sciences. To date, about 12 million observations of minor planets have been accumulated.

More than 98% of small planets move at a speed of 20 km/s in the so-called main belt between Mars and Jupiter, which is a torus, at distances from 300 to 500 million km from the Sun. The largest minor planets of the main belt, in addition to the already mentioned Ceres, are Pallas - 570 km, Vesta - 530 km, Hygiea - 470 km, Davida - 326 km, Interamnia - 317 km and Europa - 302 km. The mass of all asteroids taken together is 0.04% of the mass of the Earth, or 3% of the mass of the Moon. I note that, unlike large planets, the orbits of asteroids deviate from the ecliptic plane. For example, the asteroid Pallas has an inclination of about 35 degrees.

NEAs - near-Earth asteroids

In 1898, the small planet Eros was discovered, orbiting the Sun at a distance less than Mars. It can approach Earth's orbit to within a distance of about 0.14 AU. (AU - astronomical unit equal to 149.6 million km - the average distance from the Earth to the Sun), closer than all small planets known at that time. Such bodies came to be called near-Earth asteroids (NEAs). Some of them, those that approach the Earth's orbit but do not enter the depths of the orbit, constitute the so-called Amur group, named after their most typical representative. Others penetrate deep into Earth's orbit and form the Apollo group. Finally, the Aten group of asteroids rotate within the Earth's orbit, rarely leaving its boundaries. The Apollo group includes 66% of NEAs, and they are the most dangerous for the Earth. The largest asteroids in this group are Ganymede (41 km), Eros (20 km), Betulia, Ivar and Sisyphus (8 km each).

Since the middle of the 20th century, astronomers began to discover NEAs on a large scale, and now dozens of such asteroids are being discovered every month, some of which are potentially dangerous. Let me give you a few examples. In 1937, the Hermes asteroid with a diameter of 1.5 km was discovered, which flew at a distance of 750 thousand km from Earth (then it was “lost” and rediscovered in October 2003). At the end of March 1989, one of the asteroids crossed the Earth's orbit 6 hours before our planet entered this region of space. In 1991, the asteroid flew at a distance of 165 thousand km from Earth, in 1993 - at a distance of 150 thousand km, in 1996 - at a distance of 112 thousand km. In May 1996, an asteroid 300 m in size flew by at a distance of 477 thousand km from the Earth, which was discovered only 4 days before its closest approach to the Earth. In early 2002, the 300 m diameter asteroid 2001 YB5 passed at a distance of only twice the distance from the Earth to the Moon. In the same year, asteroid 2002 EM7 with a diameter of 50 m, flying at a distance of 460 thousand km from the Earth, was discovered only after it began to move away from it. These examples are far from exhausting the list of ASZs that arouse professional interest and generate public concern. It is only natural that astronomers point out to their colleagues, government agencies and the general public that the Earth may be considered a vulnerable cosmic target for asteroids.

About collisions

To understand the meaning of collision predictions and the consequences of such collisions, it is necessary to keep in mind that an encounter between the Earth and an asteroid is a very rare occurrence. According to estimates, a collision of the Earth with asteroids 1 m in size occurs annually, 10 m in size - once every hundred years, 50-100 m - once every several hundred to thousands of years, and 5-10 km - once every 20-200 million years . At the same time, asteroids larger than several hundred meters in diameter pose a real danger, since they are practically not destroyed when passing through the atmosphere. Now on Earth there are several hundred known craters (as-troblem - “star wounds”) with diameters from tens of meters to hundreds of kilometers and ages from tens to 2 billion years. The largest known are the crater in Canada with a diameter of 200 km, formed 1.85 billion years ago, the Chicxulub crater in Mexico with a diameter of 180 km, formed 65 million years ago, and the Popigai Basin with a diameter of 100 km in the north of the Central Siberian Plateau in Russia, formed 35.5 million years ago. All these craters resulted from the fall of asteroids with diameters of the order of 5-10 km at an average speed of 25 km/s. Of the relatively young craters, the most famous is the Berringer crater in Arizona (USA), with a diameter of 2 km and a depth of 170 m, which appeared 20-50 thousand years ago as a result of the fall of an asteroid with a diameter of 260 m at a speed of 20 km/s.

The average probability of death of a person due to a collision of the Earth with an asteroid or comet is comparable to the probability of death in a plane crash and is of the order of (4-5) . 10 -3%. This value is calculated as the product of the probability of the event and the estimated number of victims. And in the event of an asteroid impact, the number of victims could be a million times greater than in a plane crash.

The energy released when an asteroid with a diameter of 300 m is struck has the TNT equivalent of 3,000 megatons, or 200,000 atomic bombs similar to the one dropped on Hiroshima. A collision with an asteroid with a diameter of 1 km releases energy with the TNT equivalent of 106 megatons, while the ejection of matter is three orders of magnitude greater than the mass of the asteroid. For this reason, a collision of a large asteroid with the Earth will lead to a catastrophe on a global scale, the consequences of which will be amplified by the destruction of the artificial technical environment.

It is estimated that among the near-Earth asteroids, at least a thousand have a diameter greater than 1 km (about half of them have already been discovered to date). The number of asteroids ranging in size from hundreds of meters to a kilometer exceeds tens of thousands.

The probability of a collision of asteroids and comet nuclei with the ocean and seas is significantly higher than with the earth's surface, since the oceans occupy more than 70% of the earth's area. To assess the consequences of a collision of asteroids with a water surface, hydrodynamic models and software systems have been created that simulate the main stages of the impact and propagation of the resulting wave. Experimental results and theoretical calculations show that noticeable, including catastrophic, effects occur when the size of the falling body is more than 10% of the depth of the ocean or sea. Thus, for the 1 km-sized asteroid 1950 DA, a collision with which may occur on March 16, 2880, modeling showed that if it falls into the Atlantic Ocean at a distance of 580 km from the US coast, a wave 120 m high will reach the beaches of America in 2 hours, and in 8 hours a wave 10-15 m high will reach the shores of Europe. A dangerous consequence of a collision of an asteroid of noticeable size with a water surface can be the evaporation of a large amount of water, which is released into the stratosphere. When an asteroid with a diameter of more than 3 km falls, the volume of evaporated water will be comparable to the total amount of water contained in the atmosphere above the tropopause. This effect will lead to a long-term increase in the average temperature of the Earth's surface by tens of degrees and destruction of the ozone layer.

About ten years ago, the international astronomical community was tasked with determining the orbital parameters of at least 90% of NEAs with diameters of more than 1 km by 2008 and to begin work on determining the orbits of all NEAs with diameters of more than 150 m. For this purpose, new telescopes were created and are being created, equipped with modern highly sensitive recording systems and hardware and software for transmitting and processing information.

Drama of Apophis

In June 2004, asteroid (99942) Apophis was discovered at the Keith Peak Observatory in Arizona (USA). In December of the same year it was observed at the Siding Spring Observatory (Australia), and at the beginning of 2005 - again in the USA. The Apophis asteroid with a diameter of 300-400 m belongs to the class of Aten asteroids. Asteroids of this class make up several percent of the total number of asteroids whose orbits are inside the Earth's orbit and go beyond it at aphelion (the point of the orbit farthest from the Sun). A series of observations allowed the preliminary orbit of the asteroid to be determined, and calculations showed an unprecedentedly high probability of this asteroid colliding with Earth in April 2029. According to the so-called Turin Asteroid Hazard Scale, the threat level corresponded to 4; the latter means that the probability of a collision and subsequent regional disaster is about 3%. It is this sad forecast that explains the name of the asteroid, the Greek name of the ancient Egyptian god Apophis (“Destroyer”), who lives in the dark and seeks to destroy the Sun.

The drama of the situation was resolved by the beginning of 2005, when new observations were brought in, including radar ones, and it became clear that there would be no collision, although on April 13, 2029 the asteroid will pass at a distance of 35.7-37.9 thousand km from Earth, that is, at the distance of a geostationary satellite. At the same time, it will be visible to the naked eye as a bright point from Europe, Africa and western Asia. After this close approach to the Earth, Apophis will turn into an Apollo-class asteroid, that is, it will have an orbit that penetrates into the orbit of the Earth. Its second approach to Earth will occur in 2036, and the probability of a collision will be very low. With one exception. If, during the first approach in 2029, the asteroid will pass through a narrow area (“keyhole”) with a size of 700-1500 m, comparable to the size of the asteroid itself, then the Earth’s gravitational field will lead to the fact that in 2036 the asteroid with a probability close to unity will collide with the Earth. For this reason, the interest of astronomers in observing this asteroid and more and more accurately determining its orbit will increase. Observations of the asteroid will make it possible to reliably estimate the probability of hitting the “keyhole” long before its first approach to the Earth and, if necessary, to prevent it ten years before approaching the Earth. This can be done using a kinetic impactor (a “blank” weighing 1 ton launched from the Earth, which will hit the asteroid and change its speed) or a “gravitational tractor” - a spacecraft that will affect the orbit of the asteroid due to its gravitational field.

The Unsleeping Eye

In 1996, the Parliamentary Assembly of the Council of Europe adopted a resolution pointing out the real danger to humanity from asteroids and comets and calling on European governments to support research in this area. She also recommended the creation of an international association “Space Guard”, the founding act of which was signed in Rome in the same year. The main task of the association is to create a service for observing, tracking and determining the orbits of asteroids and comets approaching the Earth.

Currently, the most extensive studies of ASZ are being conducted in the United States. There is a service there, supported by the National Space Agency (NASA) and the US Department of Defense. Asteroid observation is carried out according to several programs:

The LINEAR (Lincoln Near-Earth Asteroid Research) program, carried out by the Lincoln Laboratory in Soccoro (New Mexico) in cooperation with the US Air Force on the basis of two 1-meter optical telescopes;

NEAT (Near Earth Asteroid Tracking) program conducted by the Jet Propulsion Laboratory on the 1-meter telescope in Hawaii and on the 1.2-meter telescope at Mount Palomar Observatory (California);

The Spacewatch project, which involves reflecting telescopes with diameters of 0.9 and 1.8 m at the Kitt Peak Observatory (Arizona);

LONEOS (Lowell Observatory Near-Earth Object Search) program on the 0.6-meter telescope at the Lovell Observatory;

The CSS program, carried out at the 0.7-meter and 1.5-meter telescopes in Arizona. Simultaneously with these programs, radar observations of more than 100

near-Earth asteroids on radars at Arecibo (Puerto Rico) and Goldstone (California) observatories. Essentially, the United States currently plays the role of a global outpost for detecting and tracking NEAs.

In the USSR, regular observations of asteroids, including those approaching the Earth, were carried out at the Crimean Astrophysical Observatory of the USSR Academy of Sciences (CrAO). By the way, for many years it was CrAO that held the world record for the discovery of new asteroids. With the collapse of the USSR, our country lost all the southern astronomical bases where asteroid observations were carried out (KrAO, Nikolaev Observatory, Evpatoria Space Communications Center with a 70-meter planetary radar). Since 2002, observations of NEAs in Russia have been carried out only on a modest semi-amateur 32-centimeter astrograph at the Pulkovo Observatory. The work of the group of Pulkovo astronomers evokes deep respect, but it is obvious that Russia needs significant development of astronomical resources to organize regular observations of asteroids. Currently, organizations of the Russian Academy of Sciences, together with organizations of Roscosmos and other ministries and agencies, are developing a draft Federal program on the problem of asteroid-comet hazard. Within its framework, it is planned to create new tools. As part of the Russian space program, it is planned to create a radar based on the 70-meter radio telescope of the Space Communications Center in Ussuriysk, which can also be used for work in this area.

TsNIIMash and NPO im. S. A. Lavochkina proposed projects for the creation of space systems for monitoring NEAs. All of them involve the launch of spacecraft equipped with optical telescopes with mirrors up to 2 m in diameter into various orbits - from geostationary to those located at distances of tens of millions of kilometers from the Earth. However, if these projects are implemented, it will be only within the framework of the largest international space cooperation.

But now a dangerous object has been discovered, what to do? Currently, several methods of combating ASZ are being theoretically considered:

Deflection of an asteroid by impacting it with a special spacecraft;

Removing an asteroid from its original orbit using a space minesweeper or solar sail;

Placing a small asteroid on the trajectory of a large near-Earth asteroid;

The destruction of an asteroid by a nuclear explosion.

All these methods are still very far from real engineering development and theoretically represent a means of combating objects of different sizes, located at different distances from the Earth and with different predicted dates of collision with the Earth. In order for them to become real means of combating NEAs, it is necessary to solve many complex scientific and engineering problems, as well as agree on a number of delicate legal issues relating, first of all, to the possibility and conditions of using nuclear weapons in deep space.