Many stars are born inside vast clouds of gas and dust in space. As parts of these clouds collapse under gravity, they create dense regions known as molecular cloud cores where new stars begin to take shape.
Star formation often occurs in groups rather than in isolation. In some cases, two newborn stars become gravitationally bound, creating what astronomers call a binary star system. Observations indicate that many of these systems form very early, before the stars themselves have fully developed. However, researchers have long struggled to understand how two growing protostars can move close enough together to become a binary pair within such a short period of time.
Simulations Reveal the Importance of Magnetic Fields
To investigate this mystery, researchers carried out advanced simulations using several supercomputers, including the National Astronomical Observatory of Japan's ATERUI III system and its predecessor, ATERUI II.
The results showed that magnetic fields threading through the surrounding gas can help draw protostars closer together. Interactions between the magnetic field and the gas remove angular momentum from the pair, allowing the two objects to spiral inward and form a binary system within a realistic timescale.
The simulations also highlighted just how important magnetic fields are to the process. In a test run that excluded magnetic fields entirely, the protostars moved farther apart instead of closer together.
Possible Implications for Black Hole Mergers
The researchers found that a similar mechanism could operate in much larger systems. Massive binary black holes located in the gas rich centers of newly formed galaxies may also lose angular momentum through interactions involving magnetic fields.
Such a process could help explain how pairs of giant black holes move close enough together to eventually merge. These mergers are thought to be an important step in the formation of supermassive black holes after galaxies collide and combine.
Directly simulating the long-term evolution of massive binary black holes remains computationally difficult because of the enormous timescales involved. As a result, researchers say that further studies will be needed to fully determine how magnetic fields influence the behavior and merger of these extreme objects.
