What we thought was a change for star formation doesn’t seem to work that way after all.
New observations from the Hubble Space Telescope show that the powerful astrophysical jets and stellar winds emanating from baby stars do not have the intended effect of disrupting the stellar growth process. This is a major problem for our models of star formation.
Star birth is a very long process on human time frames. It’s not like we can sit and watch a baby star form from go to who. All we can do is find a handful of stars at different stages of the creation process and put the pieces together as a puzzle.
The most common model assumes thus: First, you need to start with a very thick lump of material in a cloud of cool, interspecific molecular gas.
With enough density, the clump collapses under its own depth to form a protostar, which begins to spin. This spinning causes the material in the surrounding cloud to form a disc, which enters the rising star like water down a drain, which is instably drawn in by it. strengthening traction.
But only 30 percent of the mass of the original cloud ends up in the star. So far, we had a pretty good explanation as to why: As the star grows, it begins to emit a strong gust of wind. In addition, material falling into the star begins to interact with the star’s magnetic fields, flowing along magnetic field lines to the poles, where it is exploded. to space in the form of powerful plasma jets.
Pushing out these two forces, called stellar feedback, sculpts a larger and larger cave into the molecular cloud around the star, eventually removing material for further growth, and determines the final size of the star.
Or so we thought.
(RB Andreo / DeepSkyColors.com, NASA, ESA, STScI, N. Habel and ST Megeath / University of Toledo)
In a study of 304 protostars in the star-shaped region of the Orion Complex, highlighted in yellow in the image above, astronomers have found no evidence that the outflow caverns grow steadily. as the star grows rapidly.
“In one model of stellar formation, if you start out with a small cavity, as the protostate grows faster, the outflow creates a growing cavity so that the surrounding gas was blown away, leaving an isolated star, “said astronaut Nolan Habel of the University of Toledo.
“Our observations show that there is no progressive growth that we can detect, so the caves do not grow until they push out all the masses in the cloud. As Then, another process must be underway to get rid of the gas that doesn’t get rid of it and end the star. “
The study required data from several space telescopes. The Herschel Space Observatory and the Spitzer Space Telescope had studied the Orion Center to build a catalog of hundreds of prostates. Based on the light of these stars in the studies, Habel and his team sorted the protostars according to age.
They then looked at the surrounding cloud area in near-infrared using Hubble; some of these can be seen below. Although optical light cannot pass through a protostellar cloud, infrared waves can, and infrared observation is a great tool for scanning into areas with dense clouds.
In this case, the light of the forming star appears off the boundaries of the cave, allowing astronomers to map its size.
(NASA, ESA, STScI, N. Habel and ST Megeath / University of Toledo)
This detailed work resulted in a catalog of Protestants and their caves, sorted by age… and ancient Protestants did not appear to have larger caves.
“We discover that, at the end of the protostellar phase, where most of the gas has fallen from the cloud around the star, several young stars still have very narrow caves,” said astronaut Tom Megeath of the University of Toledo.
“So it is this still commonly held picture of what determines the mass of a star and what stops gas from entering this outflow tract growing up the gas to This has been very fundamental to our idea of how stars form, but it does not seem to fit the data here. “
While it is still possible that winds and jets play a role in star formation, that role does not appear to be as important as we thought, the researchers said. It is possible that a slower outflow with a higher density may be responsible – a similar device, but one that takes longer to clean the cavity – but without more detailed observations, it is impossible to tell.
So, that is one of the next steps. Of course astronomers also look to model and mimic star formation – to try to identify other ways that could stop growth with a much smaller contribution from stellar feedback. Look at this place.
The team’s research is expected to feature The Astrophysical Journal, and is available on arXiv.