ALMA Helps Answer Questions About How Massive Stars Form

Astronomers have used the Atacama Large Millimeter/submillimeter Array (ALMA) to answer a major question about stars. That question is, do stars that are much more massive than our sun form in the same way as smaller stars. Astronomers have observed still-forming stars similar in mass to the sun as they gain material from the surrounding clouds of dust and gas relatively quickly. The masses of incoming material form a disk orbiting the young star that feeds the star at a fast pace for it to digest.

The remaining material within that orbiting disk eventually forms planets that remain after the growth process of the star is complete. This type of disk is commonly seen around low-mass stars but haven't been found around much more massive stars in the early formation stages. Astronomers have sought to answer the question of whether the process for larger stars is similar to the process smaller stars use or something completely different.

Astronomer Ciriaco Goddi from Radboud University Nijmegen in the Netherlands says his team used ALMA observations to study three high-mass young stars in a star-forming region known as W51. For their study, the team used ALMA with its intent is spread apart to their widest point, providing the power to resolve images ten times sharper than previous studies of objects of the sort.

The astronomers looked for evidence that large, stable discs seen orbiting smaller young stars also orbit more massive stars. With the greater resolving power of ALMA, the researchers expected to see a disk around more massive stars but instead found a feeding zone that looks like a chaotic mess. Researchers concluded that massive stars in the very early stages draw in material for multiple directions at unsteady rates, which is very different from how smaller stars form.

Multiple channels of material coming into the developing star likely prevent the formation of the large, steady discs seen around smaller stars. Scientists weren't exactly surprised at this because the so-called "disordered involved" model was previously proposed based on computer simulations. This marks the first observational evidence to support that model.