Many stars are born in vast clouds of gas and dust in space. When parts of these clouds collapse under gravity, they form dense regions known as molecular cloud cores, where new stars begin to form.
Star formation often occurs in groups rather than in isolation. In some cases, two newborn stars gravitate together, forming what astronomers call a binary star system. Observations show that many of these systems form very early, before the star itself is fully developed. But researchers have long struggled to understand how two growing protostars can come close enough to form a binary pair in such a short period of time.
Simulations reveal the importance of magnetic fields
To solve this mystery, the researchers conducted sophisticated simulations using multiple supercomputers, including the National Astronomical Observatory of Japan’s Aterui III system and its predecessor, the Aterui II.
The results showed that magnetic fields penetrating the surrounding gas could help pull protostars closer together. The interaction between the magnetic field and the gas removes angular momentum from the pair, allowing the two objects to spiral inward and form a binary star system within a realistic time scale.
The simulations also highlighted how important the magnetic field is to the process. In experiments where the magnetic field was completely removed, the protostars moved further apart instead of closer together.
Possible effects on black hole mergers
The researchers found that a similar mechanism could also operate in much larger systems. Massive binary black holes located in the gas-rich centers of newly formed galaxies can also lose angular momentum through interactions involving magnetic fields.
Such a process could help explain how pairs of supermassive black holes get close enough to each other to eventually merge. These mergers are thought to be a key step in the formation of supermassive black holes after galaxies collide and merge.
Directly simulating the long-term evolution of massive binary black holes remains computationally difficult, as it requires vast time scales. As a result, researchers say more research will be needed to fully understand how magnetic fields affect the behavior and mergers of these extreme objects.
