For humans, the chance of giving birth to multiples is less than 2%. The situation is different with stars, especially with particularly heavy stars. Astronomers observe stars that are many times heavier than the sun in more than 80% of cases in double or multiple systems. The key question is whether they were also born as multiples, or whether stars are born alone and approach each other over time.
Multiple births have long been the norm for massive stars. At least on the computer, because in theoretical simulations huge clouds of gas and dust tend to collapse and form multiple systems of massive stars. These simulations depict a hierarchical process in which larger cloud portions contract to form denser cores, and where smaller regions within those “parent cores” collapse to form the separate stars: massive stars, but also numerous less massive stars.
And astronomers do indeed find a wealth of fully formed multiple star systems, especially stars that weigh many times more than the sun. However, this does not yet prove that multiple systems with massive stars are already forming in the primordial cloud, as predicted by simulations.
