[ti:Crash of Galaxies May Have Created Solar System] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:00.04]A violent event of a massive size [00:04.60]may have led to the birth of our solar system, scientists say. [00:10.48]That event was the crashing of two galaxies. [00:16.56]The coming together of our galaxy and a smaller one [00:21.68]caused countless stars to form in the Milky Way [00:25.72]more than 4.5 billion years ago, scientists reported last week. [00:33.88]The smaller galaxy is called Sagittarius. [00:38.44]It is 10,000 times smaller than the Milky Way. [00:43.96]A crash between galaxies usually does not involve [00:49.16]stars hitting each other, the scientists noted. [00:53.88]But it can create conditions for star formation. [00:59.68]For example, it can increase the amount of gas in a galaxy [01:06.12]or cause gas clouds to come together. [01:11.08]The Reuters news agency says the two galaxies [01:16.20]first crashed more than six billion years ago. [01:21.52]Since then, Sagittarius has passed through the Milky Way [01:27.20]and its nearly 100 billion stars two more times. [01:34.00]The scientists link all three events [01:37.68]to a sharp jump in Milky Way star formation. [01:42.32]Scientific data show a long period of star-formation [01:49.16]-- from 6.2 billion to 4.2 billion years ago -- linked to the first crash. [01:57.24]That data comes from the European Space Agency's Gaia space observatory. [02:07.12]Scientists believe two other star-formation surges linked to the colliding galaxies [02:14.64]took place 1.9 billion years ago and 1 billion years ago. [02:21.64]Each one lasted a few hundred million years. [02:27.44]Tomás Ruiz-Lara is an astronomer [02:31.96]at the Instituto de Astrofísica de Canarias in Spain. [02:38.92]He was the lead writer of a report on the research. [02:44.12]He says galaxy crashes are not like car crashes. [02:50.64]Some parts of Sagittarius and the Milky Way intersect, [02:55.64]but a crash between stars would be "really, really rare," he said. [03:03.20]The "crash" changed our galaxy's speed of star formation, Ruiz-Lara explained. [03:11.72]"First, we have the addition of material, gas, from Sagittarius [03:18.00]that increases the amount of gas in our galaxy to form new stars," he said. [03:25.44]Second, there is the collision between gas clouds from Sagittarius [03:31.44]and gas clouds from the Milky Way, which also led to star formation. [03:38.52]Third, the crash causes gravitational instabilities [03:44.16]that can lead to star formation, he said. [03:49.40]This happens because of changes in the density of the gaseous matter [03:55.04]in the usually low-density space between star systems. [04:01.24]The report on galactic interactions appears in the publication Natural Astronomy. [04:10.44]I'm Alice Bryant. 更多听力请访问51VOA.COM