Astronomers observed a young stellar system with nine stars in the early stages of formation using ALMA telescope data from the CoCCoA survey.
Stars larger than our sun always form in pairs or groups and never alone, although the reasons for this are not fully understood. But a new study featured in arXiv discovered a nascent family of stars, allowing further research into the phenomena.
A system of stars with a variety of age differences
The study was originally about the chemistry of complex organic molecules around hot cores in star-forming regions.
The team were examining 25 hot cores in the telescope, including NGC 6334-43, a hot core over 4,300 light-years away.
Whilst analysing high-resolution dust and gas emissions in NGC 6334-43’s field, researchers spotted nine compact, closely situated sources connected by a single 24,700 AU long filement of gas, suggesting they are part of a single large multiple-star system.
After further analysis, the researchers confirmed that the nine sources are not reandomly scattered and instead are part of a single, gravitationally bound system. This was confirmed by a stability check comparing gravitational and kinetic energy.
The team also found that there were two subgroups within the larger system, with “a range of evolutionary signatures.” The ALMA2 triple- the close hot-core pair ALMA2a/b and the younger ALMA2c- have no evidence of a shared disk, which is consistent with core fragmentation.
The ALMA6 binary has an unusually long spiral-arm-like structure with components 1,530 AU apart and also appears to be formed via core fragmentation. ALMA6a is more evolved than ALMA6b, which is still in the pre-stellar stage.
The other sourcs in the system show behaviour representing a variety of stages- some are driving active outflows, which is a signature of newborn stars.
How do groups of stars form?
There are multiple theories about how groups of stars form and due to our system’s distance from any massive stars, these theories are harder to prove or disprove.
The most common proposed origin theories are disk, core and filament fragmentation.
Filament fragmentation occurs when a long threadlike cloud of gas breaks into clumps along it’s length, which form stars. Initially, the wide range of ages of the nine stars in the identified system suggested they were not formed along a single filament, which only allows for a half-million-year age gap between sibling stars.
But the researchers propose that as the age spread of filament fragmentation is comparable to the span of time needed to form a single massive star, meaning that as the stars observed are not fully grown, “a filament-fragmentation origin for the nine-member system remains feasible.”
