HONG KONG: A pair of images of a young star, made 18 years apart, has revealed a dramatic difference that is providing astronomers with a unique, “real-time” look at how massive stars develop in the earliest stages of their formation.
The astronomers used the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) to study a massive young star called W75N(B)-VLA 2, some 4200 light-years from Earth. They compared an image made in 2014 with an earlier VLA image from 1996.
“The comparison is remarkable,” said Carlos Carrasco-Gonzalez of the Center of Radioastronomy and Astrophysics of the National Autonomous University of Mexico, leader of the research team. The 1996 image shows a compact region of a hot, ionized wind ejected from the young star. The 2014 image shows that ejected wind deformed into an 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 said.
The scientists believe the young star is forming in a dense, gaseous environment, and is surrounded by a doughnut-shaped, dusty torus. The star has episodes in which it ejects a hot, ionized wind for several years. At first, that wind can expand in all directions, and so forms a spherical shell around the star. Later, the wind hits the dusty torus, which slows it. Wind expanding outward along the poles of the torus, where there is less resistance, moves more quickly, resulting in an elongated shape for the outflow.
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