There's a flaw in the premise here: hundreds of other systems have been detected. However, the information available about just one (our own) is sufficient to speculate on genesis.
Aristarchus of Samos
Scientists theorize that the universe began with the Big Bang around 13.8 billion years ago, when all matter and energy were concentrated into an extremely hot and dense point. This point rapidly expanded, leading to the formation of stars, galaxies, and everything we see today.
big bang: This is the big bang theory
Scientist theorize that a planet-sized object collided with earth and the moon formed
Scientists theorize that life could potentially exist on other planets or moons within our own solar system, such as Mars, Europa, or Enceladus, due to the presence of water or other conditions that could potentially support life. Looking beyond our solar system, exoplanets within the habitable zone of their star are also considered potential candidates for life.
The noun form of "theorize" is "theory."
Alfred Wegener used evidence from fossils, rock formations, and the fit of the continents to theorize Pangaea. He observed similarities in plant and animal fossils found across continents, matching mountain ranges, and how the coastlines of continents seemed to fit together like a jigsaw puzzle.
"I theorize you will soon register and have a real user name." "Experiments with alpha particles led Rutherford to theorize that most of the mass of an atom was concentrated in a small area, the nucleus."
theorize
Scientists theorize that the asteroid belt did not form a planet due to the gravitational influence of Jupiter disrupting planet formation. Jupiter's strong gravity prevented the material in the asteroid belt from accreting into a planet.
scientists theorize that it was jupiters gravity that kept it from forming
Black Dwarfs are still theoretical bodies in the Universe. Belief and scientific observations are two different things. In theory, they will exist, but until one is observed, there existence can not be confirmed. See related question
Scientists theorize that higher global temperatures are do to the greenhouse effect.
Theorize is the verb form of theory. Theorise is the British English spelling.
Hypothesize.
Speculate
Pythagoras