Free Astronomy Magazine July-August 2020

JULY-AUGUST 2020 W hen we read a book or a popular article that dis- cusses the formation of the solar system, we usually find the statement that it all started with the explosion of a supernova. The supernova hypothesis is com- monly accepted right now − almost five billion years ago, the explosion millions of years. A supernova is certainly an ideal trigger to produce instability within a cloud of gas and dust, but it is not the only one. An- other mechanism capable of trig- gering the formation of new stars (and their associated planets) is the gravitational interaction between galaxies. An event of this kind oc- of a very massive star compressed a nearby or surrounding interstellar cloud of gas and dust, creating re- gions with greater density that then collapsed in on themselves to generate new stars, including ours. In the accretion disk of the Sun, the Earth and the other planets would then have formed in a few tens of