Asteroids vary widely and threaten the Earth differently.

The size of a tall building wipes away the earth… Recently, another asteroid brushed the screen as it flew over the Earth. NASA previously announced that the 2011 ES4 asteroid flew over Earth on September 2, Beijing time, with a diameter of 22 meters to 49 meters, the fastest speed can reach 8.16 kilometers per second, the closest to Earth and the Earth distance of about 120,000 kilometers, less than a third of the distance between the Earth and the moon.

Asteroids vary widely and threaten the Earth differently.

“The media and the general public are often excited to see the asteroid approaching Earth, and scientists generally seem more ‘calm’. From the relevant information, the 2011 ES4 asteroid is likely to just pass by the Earth, and its size is very small, even if it falls on Earth, will be burned up in the atmosphere, with little impact. Dr. Wang Wei, an assistant researcher at the National Space Science Center of the Chinese Academy of Sciences, told Science and Technology Daily.

Asteroids vary widely in size.

Asteroids hit The Earth, not only in sci-fi movies, but also in the real world. Some of the earth’s great craters are the mark they left when they visited the Earth.

It is estimated that about 65 million years ago, an asteroid with a diameter of 10 to 30 kilometers reached the Earth’s “arms” at a speed of 20 to 40 kilometers per second. This unusually violent impact caused the Earth to be dusted for a long time, ending an era in biological history.

Compared with asteroids with a diameter of 10-30 km, the 2011ES4 asteroid with a diameter of 22-49 meters is indeed a “small dot”. One might wonder, it’s all asteroids, why is the volume so different?

Wang explained that the earliest estrogens first formed smaller nucleos and then gradually grew erred by amassing the surrounding material. In the process, the stars collide and converg to form individual planets of varying sizes. Some of these planets are being larger and larger, absorbing the vast majority of objects in their orbits, such as the eight planets in the solar system, but others have not grown enough to gather and empty all objects near their orbits due to factors such as the temperature of their regions. A large number of small objects form asteroid clusters that leave their orbits for other regions with occasional gravitational disturbances, and some of them produce new debris in collisions with each other, which vary in size and natural size.

There are three types of near-Earth asteroids.

According to statistics, more than 1.4 million asteroids have been discovered so far, and this is probably only a small fraction of all asteroids. About 90% of known asteroids orbit the asteroid belt.

“In fact, the biggest concern is the asteroids that may be orbiting earth, or near-Earth asteroids.” In general, near-Earth asteroids are divided into three main categories: Amor, Apollo and Arden, Wang said. ES4 2011 is an Apollo-type asteroid.

Amor asteroid, named after asteroid 1221. These asteroids, which are located outside Earth’s orbit and range from 1.017 to 1.3 astronomical units (AU, about 149.6 million kilometers), are farther away and generally do not threaten Earth.

The Apollo asteroid was named after Apollo 1862. When the asteroid Apollo was discovered in 1932, it was less than 0.07AU from Earth. These asteroids, the closest point of their orbit are in Earth orbit, and the distant point is outside The Earth’s orbit, the orbit often intersects the Earth’s orbit, is also the most dangerous group of asteroids.

The Arden-type asteroid, named after the first asteroid to be discovered, is always within Earth’s orbit, meaning that even the distance from the distant point is less than 1AU.

Closely monitor and prevent potential threats.

What kind of asteroid is a potential threat to Earth? When its distance from Earth’s orbit is less than 0.5AU and its diameter is not less than 150 meters, it is considered a potentially threatening asteroid, Wang said. These asteroids may have their orbits changed due to a variety of factors, causing them to crash into Earth.

How can I prevent intrusion from an asteroid? Scientists have been looking for countermeasures. A global network of near-Earth asteroid observations has been set up to look for and monitor potentially threatening asteroids, often months or even years in advance of when they will approach Earth.

At the same time, once the threat does come, there are plans to take the initiative. For example, the European Union has proposed a “low-Earth orbit shield” to defend against asteroids. The program aims to prevent near-Earth asteroids from hitting Earth through a variety of means, including missile blow-ups, gravitational traction and active collisions.

“In fact, multiple satellites and telescopes have been closely monitoring the movements of near-Earth asteroids, and if a more threatening asteroid appears, it can also launch missiles for active defense. So you don’t have to worry about a small probability event like an asteroid hitting Earth. Wang said.