The Formation of Multiple Stellar Systems Differs in High-Mass Regions
Observations from the ALMA telescope are changing how we understand the birth of stars. While previous data came mainly from nearby and quiet molecular clouds, a new survey delves into extreme environments where massive stars are forged. This scenario, which our own Sun likely experienced, is key to having a complete picture. 🔭
A More Compact Fragmentation Scale
The DIHCA project used ALMA to observe 23 high-mass star-forming regions. Within them, it identified 72 low-mass multiple systems. The crucial finding is the average distance between companion stars: the peak is around 1200 astronomical units (au). This value is significantly lower than the approximately 4000 au typically measured in the most studied low-mass regions. Scientists attribute this difference to the much higher environmental pressure in these chaotic stellar nurseries, driven by intense densities and turbulence.
Key Findings from the DIHCA Study:- The characteristic separation between companion stars is about three times smaller in high-mass environments.
- Fragmentation occurs on a smaller scale due to external pressure conditions.
- The multiplicity fraction (how many stars are born in multiple systems) remains constant despite increasing stellar density.
In quiet neighborhoods, stars form with more space; in more crowded and chaotic stellar nurseries, overcrowding forces them to be born closer together.
The Decisive Role of Turbulence and Interactions
Since the observed separation (1200 au) is much larger than the typical size of a protoplanetary disk, the study concludes that fragmentation does not occur within these disks. Instead, the process arises from the turbulent core fragmentation of the original gas and dust. An interesting counterpoint is that, although stars are born more tightly packed, the overall statistics of multiple systems do not increase in the dense crowd. Researchers propose a balancing mechanism.
Mechanisms Shaping These Systems:- Turbulence in the initial molecular core defines the fragmentation scale.
- Dynamic inter