Meteor danger to the earth. Asteroids that pose a serious threat to earth. What does a “dangerous” asteroid mean?
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. Nowadays, several hundred craters (as-troblem - “star wounds”) with diameters from tens of meters to hundreds of kilometers and ages from tens to 2 billion years are known on Earth. 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 (to date, about half of them have already been discovered). 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 increasingly accurately determining its orbit will increase. Observations of the asteroid will make it possible, long before its first approach to the Earth, to reliably estimate the probability of hitting the “keyhole” 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 at the 1-meter telescope in Hawaii and at 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 in 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.
Russian scientists from Irkutsk discovered a new asteroid that flew dangerously close to Earth. We remembered 5 more celestial bodies that pose a threat to humanity
Moscow. September 30th. website - Employees of the astrophysical test site at Irkutsk State University discovered a new asteroid that flew dangerously close to Earth. The celestial body moved at a speed of about 16 km/s 11.3 thousand km above the Earth. The asteroid was closest to the territory between India and Indonesia, over the Indian Ocean. The object with a diameter of 15 m (slightly smaller than the Chelyabinsk meteorite) was named MASD91.
We have discovered 5 more asteroids that threaten our planet
1. 2004 MN4 (Apophis)
The celestial body was discovered in 2004 at the Kitt Peak National Observatory in Arizona. The asteroid is named after the Egyptian god Apophis (in ancient Greek pronunciation - Apophis) - in mythology it is a huge serpent personifying darkness and evil, the eternal enemy of the sun god Ra. The size of the celestial body is about 15 meters in diameter. According to scientists, the asteroid may collide with Earth in 2036. The object was considered one of the most serious threats to our planet, but later NASA practically ruled out the possibility of a collision.
2. 1950 DA
The object was discovered in 1950 by American astronomer Karl Wirtanen and does not yet have its own name. Its dimensions are 1.1 - 1.4 km in diameter. It is expected to approach Earth in 2032. But the closest approach of 1950 DA will occur only on March 16, 2880. According to this version, the asteroid will pass several tens of kilometers from Earth. The chances of a collision are estimated at 1:300.
3. 101955 (1999 RQ36) Bennu
The asteroid was discovered by Americans from the Socorro Observatory in April 2013. The name was given in honor of the bird Bennu (in Egyptian mythology it is an analogue of the phoenix. According to legend, it is the soul of the sun god Ra). According to NASA, this asteroid is the main potentially dangerous object for the Earth. The fall date is between 2169 and 2199. The size of the celestial body is about 510 meters.
4. 2007 VK184
The asteroid was discovered on November 12, 2007 by scientists in Arizona. A celestial body with a diameter of 130 m may collide with the Earth in June 2048. The probability of collision is 1:2700
5. 2011 AG5
Discovered January 8, 2011. The diameter of the asteroid is about 140 m. Visits of this celestial body to our planet at a distance less than the average radius of the Earth (6371.0 km) will take place in 2036, 2040, 2045, 2046, 2051, 2052 and 2057, which seems potentially dangerous . The asteroid will be closest to us in 2040 - 1975 km. However, NASA experts consider the passage of 2052 to be the most risky, when the asteroid will have to fly 4013 km from the earth’s surface, that is, twice as far as in 2040. According to NASA experts, the probability of a collision with Earth in 2040 is 1 in 625
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 News" .
“A 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.