Astronomers spot reverse whirlpool jet flow that aids in star growth

December 27th, 2007 - 12:29 pm ICT by admin  

Washington, Dec 27 (ANI): Astronomers have discovered fountain-like gas jets spiraling outwards from a young star in a reverse whirlpool order, which is believed to aid in the growth of stars.

The international team of astronomers observed this bipolar jet called Herbig-Haro (HH) 211 using the Submillimeter Array (SMA).

According to astronomer Qizhou Zhang of the Harvard-Smithsonian Center for Astrophysics (CfA), HH 211 essentially is a ‘reverse whirlpool.’ Instead of water swirling around and down into a drain, we see gas swirling around and outward,” he explained.

Located about 1,000 light-years away in the constellation of Perseus, the jet is traveling through interstellar space at supersonic speeds.

Due to their spiral motion, the jets help the star to grow by drawing angular momentum from the surrounding accretion disk.

“Theorists knew that a star has to shed angular momentum as it forms,” said astronomer Qizhou Zhang of the Harvard-Smithsonian Center for Astrophysics (CfA). “Now, we see evidence to back up the theory,” he added.

Angular momentum is the tendency for a spinning object to continue spinning. It applies to star formation because a star forms at the center of a rotating disk of hydrogen gas. A star grows by gathering material from the disk. However, gas cannot fall inward toward the star until that gas sheds its excess angular momentum.

As hydrogen nears the star, a fraction of the gas is ejected outward perpendicular to the disk in opposite directions, like water from a fire hose, in a bipolar jet. If the gas spirals around the axis of the jet, then it will carry angular momentum with it away from the star.

The astronomers found clear evidence for rotation in the bipolar jet.

Gas within the jet swirls around at speeds of more than 3,000 miles per hour, while also blasting away from the star at a velocity greater than 200,000 miles per hour.

In the future, the team plans to take a closer, more detailed look at HH 211. They also hope to observe additional protostar-jet systems.

“These are intrinsically difficult measurements. We need narrow jets to be able to detect signs of rotation, and they have to be close enough for us to observe them with high resolution,” said CfA astronomer Tyler Bourke. “There are very few jets around that meet those criteria,” he added.

The central protostar from which the jet is spiraling outwards, is about 20,000 years old with a mass only six percent the mass of our Sun. It eventually will grow into a star like the Sun. (ANI)

Tags: , , , , , , , , , , , , , , , , , , ,

Posted in Health Science |