The National Science Foundation's Karl G. Jansky Very Large Array (VLA) was used to study a massive young star called W75N(B)-VLA 2, located 4200 light-years from Earth. Astronomers compared an image from 2014 with an image from 1996.
"The comparison is remarkable," said research team leader Carlos Carrasco-Gonzalez of the Center of Radioastronomy and Astrophysics of the National Autonomous University of Mexico, according to a press release from the National Radio Astronomy Observatory (NRAO). The earlier image shows hot, ionized wind being thrust out from the star. The newer image shows the ejected wind as an 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, according to the press release from NRAO.
"And we are seeing this dramatic change in real time, so this object is providing us an exciting opportunity to watch the developments over the next few years, as this very young star develops the characteristic bipolar outflow morphology," said director of the Joint Institute for VLBI in Europe (JIVE) and professor at Leiden University Huib van Langevelde, according to a press release from JIVE.
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.
"In the span of only 18 years, we've seen exactly what we predicted," Carrasco-Gonzalez said, according to the press release from NRAO. "Our understanding of how massive young stars develop is much less complete than our understanding of how Sun-like stars develop. 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 international team of astronomers that published their results in Science come from Mexico, the Netherlands, Sweden, Spain, Korea and Japan. The article is titled, "Observing the onset of outflow collimation in a massive protostar" and was written by C. Carrasco-González, J. M. Torrelles, J. Cantó, S. Curiel, G. Surcis, W. H. T. Vlemmings, H. J. van Langevelde, C. Goddi, G. Anglada, S.-W. Kim, J.-S. Kim and J. F. Gómez.
