Over the past eighteen years, astronomers witnessed the unique phenomenon of the earliest stages of star formation in real time.
Image courtesy of Wikipedia (http://en.wikipedia.org/wiki/Star#/media/File:Witness_the_Birth_of_a_Star.jpg)
In 1996, scientists pointed radio telescopes at a star-forming region called W75N(B), noting that one of the objects inside of the region was a proto-star, VLA 2. At the time, VLA 2 lacked a coherent magnetic field and had an amorphous physical structure. As a result, the proto-star’s version of solar wind radiated roughly evenly in all directions. In 2014, eighteen years later, VLA 2’s solar wind was observed as focused into jets flowing from its poles (4). This change represents an important step in the proto-star’s journey to becoming a mature star.
Eighteen years may seem lengthy on a human time scale, but it is extremely brief when compared to the star’s approximately 100 million year life cycle—the equivalent of eighteen years on a star would be equivalent to roughly ten minutes when scaled to the length of a human lifetime. Carlos Carrasco-Gonzalez, one of the astronomers, explained the significance of his research: “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” (3).
The observations of VLA 2’s behavior give key insights into the early formation of massive stars—their rarity in the observable universe makes studying them difficult. In order for a star to become more massive, matter must be physically added to it. This is a problem because massive stars emit a lot of radiation, which pushes away nearby matter. The radiation pressure of a star does not scale linearly with mass, which means that the outward force of the radiation is stronger than the star’s inward-pulling gravity for sufficiently large young stars, preventing new matter from joining the star. This apparent contradiction is resolved by fact that instead of radiating in all directions evenly, stars like VLA 2 begin to radiate in jets, allowing matter to approach from other directions without being repelled (2).
In the future, several high-resolution telescopes can be aimed at VLA 2 and the surrounding star-forming region to gather even more information on the formation of this class of stars (4).
- Carrasco-González, C. (2015). Observing the onset of outflow collimation in a massive protostar. Science, 348(6230), 114-117. Retrieved April 5, 2015, from http://www.sciencemag.org/content/348/6230/114.full
- Hoare, M. (2015). How young stars grow and become focused. Science, 348(6230), 44-45. Retrieved April 5, 2015, from http://www.sciencemag.org/content/348/6230/44.full
- National Radio Astronomy Observatory. (2015, April 2). Astronomers watch unfolding saga of massive star formation. ScienceDaily. Retrieved April 6, 2015 from www.sciencedaily.com/releases/2015/04/150402161743.htm
- Perkins, S. (2015, April 2). Star formation caught in the act. Retrieved April 5, 2015.