How serious would it be if an asteroid didn’t hit the earth?

  Beijing, July 18 (Reporter Shangguan Yun) What if one day an asteroid hits the earth? This may be a scene imagined by many science fiction lovers. Earlier, it was reported that an asteroid might hit the earth on September 9 this year, but this possibility was finally ruled out.

  On the 17th, "Asteroids will not hit the Earth in September" boarded a hot search in Weibo, which once again triggered a heated discussion: What is the "asteroid" we often talk about? What will happen if it collides with the earth?

  The probability of "one in seven thousand" colliding with the earth

  The hot search for "asteroids will not hit the earth in September" is related to an announcement issued by the European Space Agency on the 16th. According to media reports, the announcement pointed out that a mysterious asteroid discovered more than ten years ago was originally thought to have a small probability of hitting the earth on September 9 this year, but the latest observation data ruled out this possibility.

  It is understood that this asteroid was discovered by astronomers in 2006, so it was code-named 2006 QV89. According to the observation data at that time, it had a probability of colliding with the earth on September 9 this year.

  However, this asteroid was only observed in a short period of 10 days, and then mysteriously "disappeared". Astronomers never observed it again, which made it difficult to accurately calculate its current position.

  Therefore, in order to judge whether the original observation results of QV89 "collision with the Earth" in 2006 are accurate, researchers have pondered a method: first, assume that the asteroid is still in the orbit that may collide with the Earth, and then observe its possible position in the sky on July 4 and 5, but found nothing.

  Based on all kinds of data, this asteroid was finally considered to be no threat to the earth.

  What the hell is an asteroid?

  As the name implies, asteroids are celestial bodies in the solar system that move around the sun like planets, but their volume and mass are much smaller than those of planets.

  "In 2006, scientists defined planets, asteroids and dwarf planets. For example, the earth is a planet, which basically lives alone, revolves around the sun, and has a relatively round shape. A typical dwarf planet is Ceres, and they are ‘ Live in groups ’ Yes, there are a bunch of celestial friends in the orbit. " Sun Zhengfan, a doctor of astrophysics and a popular science writer, said.

  As for asteroids, compared with the first two, they are simply a group of strange little guys. Sun Zhengfan explained that asteroids also revolve around the sun, but they are not round in shape, and they are grotesque in shape, big and small.

  According to public information, as of 2018, about 1.27 million asteroids have been discovered in the solar system, but due to the limitations of observation methods and other factors, this may be only a small part of all asteroids.

  "If you search for near-earth asteroids or near-earth asteroids on the Internet, the number of them mentioned in relevant popular science articles will definitely surprise people." Sun Zhengfan said.

  Asteroids and the mystery of dinosaur extinction

  The powerful destructive power of asteroids hitting the earth can be known from scientists’ discussion on the mystery of dinosaur extinction. There is a well-known saying that an asteroid hit the earth about 66 million years ago was the direct cause of dinosaur extinction.

  Specifically, this view holds that when an asteroid hit the earth, it triggered a huge tsunami, and the ocean on the surface of the earth suddenly rolled, but this was not the only disaster faced by dinosaurs.

  The impact raised a lot of hot rocks and dust, which triggered a forest fire. Countless flying dust covered the sky, and the earth’s surface was not exposed to sunlight for many years. The global climate became cold and creatures became extinct on a large scale. Dinosaurs couldn’t adapt to the drastic climate change, and in addition, they were short of food and eventually went extinct.

  "There are a pair of astronomers and their sons in the United States. In the strata around 66 million years ago, a metal element was found to have a very high content, but normally it has very little content in the rocks of the earth." Sun Zhengfan said, therefore, astronomers and their sons speculated that this metal element in the stratum exceeded the standard because an asteroid with a diameter of about 10 kilometers hit the earth at that time.

  Of course, there are many different opinions about the reasons for the extinction of dinosaurs, such as volcanic eruption and so on. Sun Zhengfan introduced that some paleontologists believe that the extinction of dinosaurs is not a sudden event, but a process. Because of the long time, it is difficult to find a complete chain of evidence for many claims about the extinction of dinosaurs. The most popular one is "an asteroid hit the earth".

  The disaster caused by "close contact"

  In fact, people are worried about the "close contact" between asteroids and the earth because of the disaster and destructive power they may bring after hitting the earth.

  For example, according to media reports, on February 15, 2013, an asteroid with a diameter of about 20 meters exploded over Chelyabinsk, Russia, which indirectly damaged more than 3,000 buildings and injured more than 1,600 people.

  Astronomically, an object whose orbit is within 1.3 astronomical units from the sun (1 astronomical unit is the average distance between the sun and the earth, which is about 150 million kilometers) and whose distance from the earth’s orbit is less than 0.3 astronomical units is a near-earth object, which is a collection of near-earth asteroids and near-earth comets.

  Among them, the potential impact with a diameter of more than 140 meters and the minimum distance from the earth orbit within 0.05 astronomical unit threatens celestial bodies and poses a direct threat to the earth.

  "An asteroid with a larger diameter can easily cause serious disasters when it hits the earth." Sun Zhengfan explained that "asteroid impact on the earth" is a high-risk event, such as the impact that is thought to have led to the extinction of dinosaurs. There is still a huge crater in Mexico’s Yucatan Peninsula, half on land and half in the sea.

  Asteroids are terrible? There is no need to be overly anxious.

  Based on the possible serious consequences of an asteroid’s visit, the news that an asteroid may hit the earth often causes many people’s worries. But Sun Zhengfan said that there is no need to be too anxious about this.

  "First of all, it can cause extremely serious consequences ‘ Asteroids hit the earth ’ It’s a small probability event, and secondly, our earth has the atmosphere ‘ Protector ’ 。” Sun Zhengfan said.

  Data Map: The picture shows beijing aerospace control center’s real-time monitoring and control mission of "Chang ‘e II" flying over an asteroid on December 13th. Sun zifa

  He explained that the earth is moving in space, and there are always a huge number of things falling on it, mostly in the form of dust, or just like pebbles, some asteroids burn out in the atmosphere. "There are no people in most parts of the earth, such as the sea and the desert. Therefore, it does not have much impact on human beings. "

  Sun Zhengfan also admitted that with the current scientific and technological means, it is still difficult to accurately calculate the running paths of asteroids that may cause harm to the earth, and "we can only estimate their size and quality by reflecting light, and this data itself has errors".

  "Preventing doomsday asteroids is a very important job." Sun Zhengfan said, "Humans can unite to develop aerospace technology and prevent this major disaster through early warning."