On February 12, for only the seventh time in the history of space observations, astronomers managed to detect a small
Although seven seems like a small number in realityIn fact, this is a huge progress. The size of the meteoroid 2023 CX1 or Sar2667 was about a meter. This is about 20 times smaller than the asteroid that caused the famous Chelyabinsk meteorite 10 years ago - the largest collision of the last century.
Most objects of comparable size fiximpact, but the last three predicted impacts occurred in the last 12 months: 2022 WJ1 was spotted in November 2022 three hours before it burned up in the atmosphere over Canada, and 2022 EB5 in March of that year, less than two hours before the collision over the polar Norwegian island of Jan Mayen. This is a testament to how technologies for monitoring near-Earth objects have changed in recent years.
The fall of the meteoroid 2023 CX1. Video: Muhammed Uzzal, ESA
What is an asteroid, meteoroid, and near-Earth object?
Asteroids are one of the smallest objects in the solarsystems, ancient cosmic "rocks" left after the formation of planets from the protoplanetary disk was completed about 4.6 billion years ago. Such objects are much smaller than planets, lack an atmosphere, but may have their own satellites.
Most asteroids revolve around the sun inbelt between Mars and Jupiter in the main belt, but this is not the only area of their "concentration". For example, between the orbits of Jupiter and Neptune, it is estimated that more than 40 thousand asteroids move with unstable orbits larger than 1 km. They are called Centaurs. Even more such objects are located on the outskirts of the solar system beyond the orbits of gas giants in the Kuiper belt.
When traveling through space, asteroids sometimescollide with each other and break into smaller pieces. Comets traveling through the solar system can also leave debris and scatter dust. These “decays” lead to the formation of many small particles and fragments - meteoroids and cosmic dust.
The International Meteor Organization definesasteroids as objects with a size of 1 km or more, and meteoroids are solid objects much smaller than an asteroid and much larger than an atom or molecule. Those objects that, in the process of movement, approach the Sun closer than 1.3 astronomical units (AU), which means that, theoretically, under certain conditions, they can come close to our planet, they are called near-Earth.
What asteroids are dangerous?
The most famous asteroid is Chicxulub, or Chicxulub.Even those who do not know this name will surely remember the story of a space giant that collided with the Earth about 66 million years ago, caused a powerful earthquake and left a huge crater on the territory of modern Mexico, led to the end of the Cretaceous period and the era of dinosaurs.
Impacts of such large asteroids (Chikxulub diameterwas about 10 km) are extremely rare, but smaller stones can also pose a danger to life on Earth. Near-Earth objects are classified as potentially hazardous if they orbit close enough to our planet and are large enough to cause potential damage.
Conventionally, astronomers believe that danger canrepresent objects that approach the Earth at a distance of less than 0.05 AU. or 7.5 million km. Since the size of a distant object is rather difficult to accurately estimate, an absolute star of magnitude less than 22 (approximately corresponding to 150 m objects) is used as the second criterion. This is an indicator that characterizes the brightness of an object for an observer at a standard distance from it.
The probability of a collision between the Earth and meteoroidsasteroids of various sizes: meteoroids with a diameter of about a meter fall every two weeks, and large asteroids more than 1 km in diameter - once every 1–300 million years. Image: ESA, CC BY-SA 3.0 IGO
Why was it not possible to predict the Chelyabinsk meteorite?
An asteroid that collided with Earththe atmosphere formed the Chelyabinsk meteorite, much less than the established limit. Its diameter was only about 10 km. However, the blast from the impact shattered windows in several thousand buildings and glass fragments injured more than 1,500 people.
The unusual thing about this asteroid is that itmoved in the “blind zone” of telescopes - from the direction of the Sun. Exploring the region between the orbits of Earth and Venus is difficult because the star's bright light obscures tiny objects. Favorable opportunities for observation arise only at dawn and dusk during twilight, when this area is still visible from the Earth, and the light of the Sun is not so strong.
Artistic illustration of observing an asteroid against the Sun. Image: DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA/J. da Silva/Spaceengine
Last year, using similar observationsfound three large objects rotating between Earth and Venus, and in total less than 30 of them are known. All of these objects are much larger than the Chelyabinsk one, which means that an unknown number of asteroids may be hidden in the radiance of the Sun, the trajectories of which are unknown and may pose a danger.
Expert of the Space Research Institute of the Russian Academy of SciencesOleg Ugolnikov, in an interview with RIA Novosti, suggested that even in 2023, 10 years later, technology would not have made it possible to detect an asteroid in time and warn local residents. The good news is that, statistically, objects of this size fall to Earth about once every 50-100 years, which means there is still time to prepare.
How does the planetary defense system work?
Elements of an early detection system for asteroidswork in a variety of countries, but in general they are arranged approximately the same. The basis of such a system is a network of ground-based telescopes that automatically scan the night sky in search of moving objects against the background of relatively "fixed" stars. If the system finds an object that was not previously known, it attracts the attention of astronomers.
After discovering a new object, researchersuse additional tools: telescopes that are not busy scanning the entire sky, but can focus on a specific object with greater accuracy. With the help of observations, astronomers specify the approximate size of the object and the trajectory of its movement. Based on these data, the potential risk is assessed: can such an object be in the path of the Earth moving in its orbit, and what power will such a collision lead to an explosion.
Although the list of near-Earth objects with non-zeroAlmost 1,500 objects have been introduced with the probability of a collision; the real danger tends to zero in the coming decades. The maximum impact risk of tracked asteroids is assigned (101955) to Benn. But even for him, the Palermo score (a logarithmic model for assessing collision risk) is -1.59. This means that the probability is 38 times lower than the background danger.
Rotation of asteroid Bennu based on images taken by the OSIRIS-REx mission. Image: NASA's Goddard Space Flight Center/University of Arizona
How will surveillance technology evolve?
Despite the low probability of the nextlarge-scale collision, different countries continue to develop their surveillance systems in order to open objects that so far elude the cameras. The most promising of them involve supplementing ground-based observations with orbital ones.
For example, Roskosmos is creating a new system"Milky Way", which will use satellites to monitor near-Earth space. Among its targets are not only space debris, like the existing ASPOS OKS, but also potentially dangerous asteroids and comets. The system is expected to be completed by 2035.
Avoid a collision like Chelyabinskmeteorite, should help a new program from the European Space Agency - NEOMIR. The researchers plan to send the telescope to the Lagrange point (L1), located between the Earth and the Sun. Being outside the distorting atmosphere of the Earth, the telescope will be able to observe asteroids that can approach the Earth from the direction of the Sun.
Artistic illustration of the NEOMIR satellite. Image: ESA, Pierre Carril
Detection of dangerous objects is only the first step,the next is collision avoidance. One possible solution is to change the orbit of such a celestial body. Previously, Hi-Tech talked about the first experiment in history in which this was achieved.
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