Interstellar visitors invade the solar system： does life on earth come from another galaxy？

　　Today viewpoint

　　In the autumn of 2017, the cigar-shaped Oumuamua broke into the solar system and became the first interstellar visitor discovered and confirmed by scientists, which caused a lot of noise and turmoil in the scientific community. Although it is still unknown whether it is an asteroid, a comet or an alien spacecraft, American scientists have recently said that "flying immortals from outer space" like Omo Mo may not be special, and the elements of life on earth may originate from other star systems, which arrived on Earth by hitchhiking with interstellar visitors like Omo Mo Mo.

　　But at present, these are only assumptions. We need to "catch" more celestial bodies similar to Omo Mo for in-depth research with the help of large telescopes in the future to get the final answer.

　　"Omo Mo" is not special

　　The researchers said that "Omo Mo" is the first confirmed interstellar object we have observed in the solar system, but this does not mean that it is the first interstellar object to reach the solar system in history.

　　"We think, like ‘ Omo Mo ’ Such an object … … At any time, there will be one at a distance of one astronomical unit from the sun (the average distance between the earth and the sun is about 150 million kilometers). " At the "Breakthrough Discuss" conference held at the University of California, Berkeley last month, Bill Porter, head of the Department of Space Studies at the Southwest Research Institute in Colorado, said, "This actually has a very meaningful impact, similar to ‘ Omo Mo ’ Objects may bring life from one celestial body to another. "

　　This idea is called "panspermia)— — The theory put forward by scientists in the 1970s that life on earth came from space. At that time, the British physicist Lord kelvin believed that alien bacteria could reach the earth by comet or meteor and thrive on the earth; Other scientists believe that microorganisms can be embedded in dust particles and pass through galaxies, and they run from one planetary system to another through slight stellar radiation pressure.

　　Can provide heat insulation and radiation protection for microorganisms.

　　At present, the exact size of Omo Momo is still unknown, but researchers believe that its longest size is no more than 800 meters. The object will show "non-gravitational acceleration" when it is far away from the sun, which makes people speculate that "Omo Mo" may be some kind of alien spacecraft.

　　But the more common view is that the "intruder" of this solar system is very cold, and its strange movement is caused by the exhaust gas similar to a comet. When the comet approaches the sun, the ice on it will sublimate directly from solid to gas, forming a huge comet head and a long comet tail. When these gases are released, astronomers can use telescopes to study and determine their composition.

　　Karen Mitch, an astrobiologist at the Institute of Astronomy, University of Hawaii, said: "This tells us that ice can be preserved after such a long journey." Previous studies on comets and other small celestial bodies in our solar system show that objects like Omo have good heat insulation and radiation protection functions, which is good news for any microorganism that may "hitchhike". "Living organic matter can be found in ‘ Omo Mo ’ The interior is well protected. "

　　Astronomers have not found the star system that gave birth to Omo, so we don’t know how long ago Omo was ejected into the dark and cold interstellar dust. But Mickey said that it may have traveled through interstellar space for 10 million years or more.

　　Looking for the next interstellar object to study.

　　Of course, it is still unclear whether any hypothetical creature on Omo will survive the collision with the earth. Mickey said that this icy object hit us at a speed of 215,000 km/h relative to our planet. "This is a very high impact speed."

　　In this regard, Stern Sigurdsson, a professor in the Department of Astronomy and Astrophysics at Pennsylvania State University, said in another speech at the "Breakthrough Discussion" conference that "Omo Mo" and its "passengers" may be quite soft, so after hitting the earth, they may land relatively gently and disperse when they break into our atmosphere.

　　Sigurdsson said that the previous work of Ivey Laueber, director of the astronomy department of Harvard University, and others, as well as his own calculations show that in the nearly 4.6 billion years of history of our planet, about 100 celestial bodies like Omo have hit the earth. "So, we don’t know whether there is a biota inside one of these celestial bodies."

　　Laueber added that we don’t know where Omo is now. "Therefore, it is more meaningful to find the next interstellar object." The powerful large-scale weather measuring telescope (SST) is scheduled to take off from Chile next year and begin to observe the sky. When it runs "full of blood", it may find an interstellar object every month for our study.

　　In addition, scientists suggest that it is also possible that life reached the earth only a short distance long ago. Earthlike planets in our solar system exchange rocks quite regularly, as evidenced by the increasing number of Martian meteorites on earth. In fact, some researchers believe that life on earth may have started on the red planet, and a Martian stone reached the earth in a strong impact.

　　Of course, all this is just a hypothesis, and more scientific evidence is needed to reveal one of the ultimate puzzles of mankind — — Where we come from.

　　(Science and Technology Daily, Beijing, May 8 th)