Asteroid-comet hazard

    Hello.

    The catalog of dangerous asteroidsIn the wake of the message on Habrahabr about an asteroid flying past Earth, I would like to briefly talk about the problem as a whole - the problem of asteroid-comet hazard (AKO).

    There are several hundred thousand known asteroids in the solar system. It is estimated that the total number of objects with a radius of more than 1 km is about a million. Most of them are in the Main asteroid belt (between Mars and Jupiter), part are in the Kuiper belt (the region beyond Neptune, Pluto, for example, is an object of the Kuiper belt, like some other dwarf planets - Haumea, Makemake), the part “flies free".



    Quick reference


    The orbit of any object in the solar system has one important parameter - the perihelion distance. This is the minimum distance from an object to the sun. Asteroids approaching the Earth are called asteroids with a perihelion distance of less than 1.3 astronomical units . They are also depending on the parameters divided into three groups (more precisely, already 4):
    • Amurtsy . These asteroids can approach the Earth, but do not go inside its orbit
    • Atonians . Their orbits lie mainly inside the Earth’s orbit and rarely go beyond it.
    • Apollonians . May penetrate the Earth’s orbit
    • X-asteroids . "Fly" in the orbit of the Earth


    To assess the danger of asteroids, a visual Turin scale (analogue of the Richter scale for earthquakes) was developed:
    Turin Asteroid Hazard Scale

    Horizontal - probability of collision, vertical - kinetic energy of collision in megatons. If the object is not 0 on the Turin scale, then this is very, very bad. Even a danger of unity means a chance of collision and almost complete certainty that the object will not burn in the atmosphere.

    Dangerous asteroids


    99942 Apophis


    The most dangerous, at the moment, is the asteroid 99942 Apophis. It was discovered in 2004 at the Kit Peak Observatory. According to preliminary calculations, it turned out that he could collide with the Earth in 2029. As often happens, they “lost” him for a while, and after repeated detection, a collision in 2029 was practically excluded. However, after a series of additional observations and studies, it turned out that he could “collide” with us, though a little later, in 2036, 2037 and subsequent years.

    The name of the asteroid itself is symbolic. Apophis is the name of the not-so-good Egyptian god Apophis, pronounced in the Greek manner. By this, astronomers wanted to show that he would change his type after 2029. It was this asteroid that received a record level of danger - 4 on the Turin scale. Subsequently, the danger decreased first to 1, and then to 0.

    The asteroid itself has a diameter of about 150-300 meters, and, apparently, it “spins” near the Earth for a long time. The main problem associated with this asteroid is the following: observational data (and there are already a lot of them - about 900 + several radar observations at the largest Arecibo radio telescope) are not enough to make an accurate forecast for 2036 and the following years. In 2029, Apophis will fly at a distance of 38,000 km from the center of the Earth (10 times closer than the Moon), and inside its possible trajectories there is a so-called “keyhole” 600 meters in diameter, flying through which in 2029 an asteroid collides with Earth in 2036 (the probability of such a collision is 2-3 per 100,000). To exclude the possible danger of this object, you need accuracy, which is practically unattainable with earth observation means.

    In any case, it was this object that prompted the attention of astronomers to the problem of asteroid-comet hazard. Indeed, nothing has crashed into our planet since the time of the dinosaurs, but according to statistics, it is time.

    2007 VK184 and others

    2007 VK184 - the only object that currently has 1 on the Turin scale. Although the probability of collision is rather low - 1 out of 2700. And the collision time is “later” - 2048. While there are few observations of this object - about a hundred. Until 2014, another series of observations will be carried out and, possibly, it will remove all questions concerning this asteroid and its “meeting” with the Earth.

    Another concern (though not of us, but of our descendants) is two objects - 101955 1999 RQ36 and 153814 2001 WN5. Their rapprochement with the Earth will only be after 2100, but by themselves they are several times more massive than Apophis and 2007 VK184.

    What to do?



    Asteroids sometimes hit the Earth. Even in the 20-21 century there were several similar collisions: the Tunguska meteorite, a meteorite in the Amazon basin, the Vitim car, etc. These objects were mostly burned in the atmosphere. In the case of an asteroid with a diameter of 100-300 meters, mankind is now quite capable of averting the threat without Bruce Willis. There are several ways that you were supposed to try on Apophis or a similar asteroid:
    • Point the spacecraft toward the asteroid and “collide” it with the object so that the orbit of the latter changes slightly and stops passing through the Earth
    • Direct the spacecraft toward the object and change its orbit with a series of directed explosions
    • “Flatten” an asteroid with another planet or satellite (for example, the Moon)


    In principle, with a successful combination of circumstances (“successful combination” = exact mathematical calculation), a mass of 100-200 kg is enough to, for example, move Apophis to a safe distance. However, this must be done before 2020, after which it will be very, very difficult to change the asteroid’s orbit.

    What's next?


    Research on the problem of asteroid-comet hazard has been, is and will be. Russia occupies one of the leading places in the world in this direction. Serious research is being carried out at the Institute of Applied Astronomy of the Russian Academy of Sciences, at the Institute of Astronomy of the Russian Academy of Sciences, at the Pulkovo Observatory, at the Department of Celestial Mechanics, St. Petersburg State University, in Tomsk and other places. I am glad that the engineers of the NGO them. Lavochkina (where many satellites, missiles, etc. are gathering) are also connected to the problem and are ready to implement the tasks. Serious research, including space, is carried out by NASA. Potentially hazardous facilities are constantly monitored, new ones are being opened. Unfortunately, terrestrial surveillance is often not enough, so space missions are being developed. Now we are working on a methodology for working with similar objects, because 15-20 years ago, one could only dream of observing asteroids the size of Apophis. And we can hope that in the event of a real danger, the world community will come up with and implement a space defense program.

    At the moment, it is possible to say with some certainty that in the near future, nothing big and very dangerous will fall to Earth, no matter how hard the film producers, Sitchins, the yellow press and other muck try.

    I would like to end with the phrase from “The Hitchhiker's Guide to the Galaxy”: “Don't panic!”

    Thanks!

    Useful links, literature


    1. Vinogradova T. A., Zheleznov N. B., Kuznetsov V. B. et al. Catalog of potentially dangerous asteroids and comets. St. Petersburg: IPA RAS, 2003.
    2. Nasa JPL Solar System Dynamics
    3. Wikipedia: asteroids approaching the Earth
    4. NASA Asteroids approaching the Earth (updated)
    5. NASA Hazardous Objects Directory
    6. NeoDys - asteroid catalog


    Note. The first figure was prepared using the EPOS program (GAO RAS)

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