Donuts in Space
In the vastness of the universe there are stars, some of which have a hundred solar masses. The crux of the matter: Actually, they shouldn't even exist - at least if you assume their birth and youth to be analogous to less important relatives.
Once a star has formed from the gravitational collapse of a cloud of gas and dust, it continues to grow vigorously in its infancy. Driven by gravity, it draws in surrounding gas and dust on all sides. According to theoretical calculations, this should end at about eight solar masses.
This is due to the radiation emanating from the dense core, which becomes more and more intense with increasing mass. The radiation pressure they generate slows down the infalling matter until it is finally stopped completely. At least that's what the theory demands. But many stars do not stick to this and populate the universe with much larger masses.
Consequently, the astronomical community tried to devise models tailored to non-norm stars. For example, they saw the collision of two low-mass stars as the solution to the problem. Alternatively, they envisioned the star within a toroidal cloud of gas instead of the usual spherical structure. The stellar radiation could escape through the openings without interfering with further mass growth.
For a definitive clarification, a look at the postnatal behavior of massive stars is required. However, to observe the early development, the astronomers need a lot of luck - because of their enormous mass, the massive stars will grow about ten times faster than average stars. Overall, being overweight also means they live much shorter lives, as they burn up their nuclear energy resources much faster. And to make matters worse, they are relatively rare in the universe anyway.
Despite the adverse circumstances, astronomers have been able to examine some of the young colossuses in recent years and detect rotating disks there, even isolated toroidal gas clouds and indications of infalling matter. Now Maria Beltrán and her colleagues from the University of Barcelona are following suit.
They aimed the VLA's giant radio antennae at a cluster of young stars some 25,000 light-years away. G24 A1 turned out to be particularly interesting – a star with twenty times the mass of the sun. He immediately showed three decisive signs for clarifying the question of origin.
So this star had a rotating cloud of gas that appeared in donut shape as desired. So far nothing really new. But analysis of the recorded spectra also revealed that matter was steadily being pulled toward the dense core at a rate of about two kilometers per second. There, in the middle of the gas ring, they made the third discovery: According to the data, G24 A1 sends out two bundled beams into space on each side of the torus.
Beltrán and colleagues found several clues simultaneously for the first time. They conclude that massive stars did indeed form from non-spherical clouds of gas and dust. However, how this process happened in even more massive specimens remains to be seen.