Wednesday, 28 June 2017

New-born star gorges on a 'space hamburger,' belching spinning jets

170420a_enAstronomers have observed the eating habits of a new-born star — and like any youngster, it has an affinity for fast food.

Using the powerful Atacama Large Millimeter/submillimetre Array (ALMA) in Chile, an international team of researchers has imaged the flow of material around a "young" 40,000-year-old protostar called Herbig-Haro 212 (or HH 212), located some 1,300 light-years away in the constellation Orion. A protostar is the earliest stage of star evolution, just before the star begins nuclear fusion in its core.

Protostars are known to generate powerful jets of gas that blast into interstellar space and this work reveals that HH 212’s jets are spinning, with the material blasting out from the protostar's poles like bullets.

The spinning bullets confirm the hypothesis that angular momentum is being removed from the protostar's accretion disk, or the orbiting gas and debris around the star, which the study's authors refer to as a "space hamburger." [Meet ALMA: Amazing Photos from Giant Radio Telescope]

HH 212's accretion disk is nearly edge-on from our perspective on Earth and has a radius of 60 astronomical units (AU), where 1 AU is the average distance at which the Earth orbits the sun — about 93 million miles. The disk has a "prominent equatorial dark lane sandwiched between two brighter features," the researchers said in a statement, giving it a resemblance to a hamburger.

The discovery of HH 212's rotating jets was made around the same time as another team was using ALMA to clock the angular momentum of rotating jets blasting from Orion KL Source I in the Orion Nebula, another protostar.

"We see jets coming out from most baby stars, like a train of bullets speeding down along the rotational axis of the accretion disks. We always wonder what their role is," lead astronomer Chin-Fei Lee, of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan, said in a statement. "Are they spinning, as expected in current models of jet launching? However, since the jets are very narrow and their spinning motion is very small, we had not been able to confirm their spinning motion.

"Now, using the ALMA, with its unprecedented combination of spatial and velocity resolutions, we not only resolve a jet near a protostar down to 10 astronomical units (AU) but also detect its spinning motion," Lee added. "It looks like a baby star spits a spinning bullet each time it takes a bite of a space hamburg

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