Reported by American Aeronautics and Space website, a latest study shows that the sun bounces every 40 million years when it ranges through the Milky Way Galaxy, which would make a lot of comets rush to the interior of the solar system and bombard the planets like the earth. And such comet collisions resulted in the extinction of abundant ancient species including the dinosaurs.
The scientists guess that such comet collisions maybe promote the life spread on the alien planets at the same time. However, this guess is questioned now. In order to get the data information of comets' bombarding the planets in the solar system, the astronomers have computed the path with which the solar system passes through the Milky Way Galaxy when it circles the core of the Milky Way Galaxy. The researchers point that when the sun passes the most dense area of the Milky Way Galaxy surface, the power of both the surrounding gas and the dust gravity rejects the comets of Oort Cloud outside the solar system and makes these space structures of ice rush to the solar system.
According to the computed results, the sun passes the dense region of the Milky Way Galaxy at intervals ranging from 35 to 40 million years , and the rate of comets' bombarding the internal solar system at this time could be 10 times bigger than that of other time. This bounce circle is in accordance with the phenomena of abundant species extinction and meteorite craters on the earth, which hints that the earth would suffer from more serious comet collision every 36 million years.
William Napier, an astronomer in English Wales Cardiff Centre for Astrobiology,said,"Through this latest research, we have found that the observation results perfectly accord with the astronomical observation records. " And he will issue this research report on recent Monthly Notices of the Royal Astronomical Society with his colleague.
Although it killed many dinasours, invertebrates and plants, this periodical bounce of the sun could also promote the life spread on other celestial bodies. These comets could bring the microbes to other celestial bodies where life could be created. Napier said during the website interview,"When the comets bombard the interior of the solar system, the microbes enter the area formed by stars and planets though the clouds without worrying about the harm from cosmic rays . This viewpoint is very challenging and interesting, and it hints that the life could spread not only in the interior of the solar system, but also in the other galaxies. "
However, some researches questioned this research. Paul Wishman, an astronomer in NASA-JPL,said,"The theory base of the whole research is incorrect. When the sun passes through the Milky Way Galaxy surface, the fast collision would not happen. And any diverse crater would be mild and differ with those caused by the sudden collision. "
Before that, many researchers guess that since the extinction of abundant species happened 30 million years ago and the universe collisions appeared frequently at the same period, there must be a link between them. But Wishman emphasizes that there are quite some doubts about the relation between them.
Other researchers think one of the reasons about the comets' bombard the solar system is that one red dwarf or the tenth planet in the far orbit of the solar system crashed to the Oort Cloud. Wishman said,"Many researchers including me have analyzed this and pointed out the logic errors. Remote red dwarfs are in an unstable orbit and easy to escape from this interstellar space. Besides, it can't be proved that the tenth planet exists in the solar system. The astronomers have searched the solar system so many times, and found no sign of big planets except Neptune."