The Most Massive and Brightest Star in the Milky Way?
This past spring, astronomers were able to detect a star in formation–a protostar–that appears to be one of the brightest and massive found in our galaxy thanks to data detected with the ALMA radio telescope, the Atacama Large Millimeter/submillimeter Array in Chile’s Andes Range. The study focused on the observation of a giant molecular cloud known as G331.5-0.1, which is located in the Norma spiral arm, in the Milky Way, some 24,000 light years from Earth. “In the center of the molecular cloud we had discovered carbon emissions of speeds up to 100 km/s (360,000 km/h), but we didn’t know how it was created” said Guido Garay, with the University of Chile and member of the research team.
"They are the main source of heavy elements and ultraviolet radiation, affecting the formation process of stars and planets, as well as the physical, chemical and morphological structure of galaxies," said the principal author of the study, Manuel Merello, a doctoral student at theUniversity of Texas who holds a master’s degree from the University of Chile. However, Merello added, “It’s difficult to observe the ‘birth’ and early phases of this type of star, so being able to do this with ALMA helps us better understand the interaction between the radiation and wind generated by these kinds of objects with the interstellar medium that surrounds them in the very early stages.”
Using a tracer (to track the emission of silicon monoxide, SiO), the astronomers were able to observe collisions between the jet of gas ejected between the object and its environment, revealing the existence of a very massive, bright star in formation, which ejected jets of gas that were highly collimated (that is, in a very narrow cone).
The astronomers also found a second, lower-speed molecular structure with spherical symmetry. “It’s like a shell,” said Garay. The results of this study show that two types of stellar wind appear in the formation process of this star: a highly collimated one that generates the jet and another spherically symmetrical one that produces the shell, which is something never been seen before.
"Thanks to the high sensitivity and angular resolution of ALMA, scientists are now able to study the characteristics of formation of high mass protostars in a detail that could never have been done before," said Lars Nyman, ALMA Head of Science Operations and member of the research team.
The research findings are presented in the article “ALMA observations of the massive molecular outflow G331.512−0.103,” published in the Astrophysical Journal, Vol. 774, of September 1, 2013.
The Daily Galaxy via ALMA Observatory