Scientists Witness Star Formation Over 18 Years

A team of scientists has witnessed the formation of a young star unfurl over the last 18 years, shedding light on the earliest stages of how these massive stars develop, according to a new study.

Using the National Science Foundation's Karl G. Jansky Very Large Array (VLA), astronomers studied a massive young star called W75N(B)-VLA 2, which is located about 4,200 light-years from Earth. They compared a pair of VLA images taken in 1996 and 2014, revealing a dramatic difference that is providing the team with a unique, "real-time" look at how star formation takes place.

"The comparison is remarkable," lead investigator Carlos Carrasco-Gonzalez, from the Center of Radioastronomy and Astrophysics of the National Autonomous University of Mexico, said in a press release.

The 1996 image shows a compact region of a hot, ionized wind ejected from the young star, whereas the 2014 image shows that ejected wind distorted into a distinctly elongated outflow.

"We're seeing this dramatic change in real time, so this object is providing us an exciting opportunity to watch over the next few years as a very young star goes through the early stages of its formation," Carrasco-Gonzalez explained.

According to the data, W75N(B)-VLA 2 is developing in a dense, gaseous environment surrounded by a doughnut-shaped, dusty torus. In the early stages, the star will eject a hot, ionized wind for several years at a time. At first, that wind will expand and form a spherical shell around the star - a process that will later slow down when the wind hits the dusty torus.

"In the span of only 18 years, we've seen exactly what we predicted," Carrasco-Gonzalez said.

Researchers estimate that W75N(B)-VLA 2 is about eight times more massive than the Sun. Based on observations of less-massive, Sun-like stars, astronomers expected W75N(B)-VLA 2 to display narrower, beam-like outflows. However, that is not the case. Instead, they saw a nearly-spherical expansion of such outflows.

According to theoretical models, the more-uniform outflows are seen in massive young stars in the first few thousand years of their lives, the stage at which W75N(B)-VLA 2 is thought to be.

"Our understanding of how massive young stars develop is much less complete than our understanding of how Sun-like stars develop," Carrasco-Gonzalez said. "It's going to be really great to be able to watch one as it changes. We expect to learn a lot from this object."

The findings were published in the journal Science.

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