How to Become a Star
Wednesday, April 8th, 2015April 8, 2015
In the astronomical blink of an eye, a protostar underwent a significant change in how energy flows from its core. A team from the Centre of Radio Astronomy and Astrophysics (Centro de Radioastronmía y Astrophysíca) in Michoacán, Mexico, led by Carlos Carrasco-González, discovered the event and published their findings in the journal Science.
A star develops from a giant cloud of gas and dust. Under the influence of its own gravity, the cloud begins to collapse inward, becoming smaller. The collapsing material becomes warmer, and its pressure increases. But the pressure tends to counteract the gravitational pull that is responsible for the collapse. Eventually, therefore, the collapse slows to a gradual contraction. The inner parts of the clump form a protostar, a ball-shaped object that is no longer a cloud but is not yet a star. Surrounding the protostar is an irregular sphere of gas and dust that had been the outer parts of the cloud.
Carrasco-González and colleagues studied the massive protostar W75N(B)-VLA 2, located 4,200 light-years from our solar system. (One light-year equals the distance light travels in a vacuum in a year, about 9.46 trillion kilometers.) When the protostar was first examined in 1996, it was releasing shockwaves in a spherical formation from its center. Astronomers could detect these shockwaves because they excited particles in the protostar’s surrounding cloud of gas, causing them to glow. When the team looked at the star in 2014, they noticed that the shockwave-containing region had changed from a sphere to an elongated oval. The scientists think this will be a short-lived event in the protostar’s formation, ending after 25 years or so.
Such a quick change is rarely detected when studying the stars. Stars live for millions or billions of years, so scientists piece together their life cycles by comparing and contrasting thousands of stars, rather than by directly observing transformations. Examining other such rapid changes in the future may help scientists better understand the nature of star and planet formation.
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