An international team of astronomers has taken some pretty incredible observations of a very young star, uncovering some important clues that explain how baby stars throw so much gas out of their metaphorical prams.
As yet, we still do not understand fully how massive stars form, but astronomers suspect that gas rotation is key. The group, led by Japanese researchers, looked at Orion KL Source I, a baby star located in one of the most active regions of the famous Orion Nebula. They looked at the gas outflow, in particular, the motion and shape of this outflow and were able to establish how rotation and magnetic fields come into play.
In their paper published in Nature Astronomy, the team stated that the outflow is being launched at 10 kilometers (6.2 miles) per second. The precise measurement might be able to solve a particularly thorny issue. Astronomers weren’t sure why most stars don’t spin very quickly and the gas outflow was believed to be the best candidate to take away some of the rotational momentum.
“We have clearly imaged the rotation of the outflow,” Professor Tomoya Hirota, from the National Astronomical Observatory of Japan, said in a statement. “In addition, the result gives us important insight into the launching mechanism of the outflow.”
The observations were taken by the Atacama Large Millimeter/submillimeter Array (ALMA), and were possible because Source I is relatively close, being 1,400 light-years away, and ALMA itself has incredible sensitivity. The observations show that the outflow is not launched by the star but is instead launched by the edge of the disk of material that is orbiting around the star.
This is something that is predicted in the so-called magnetocentrifugal disk wind (MDW) model. Some of the gas of the disk moves outwards and when it reaches the edge of the disk, it moves upwards along the magnetic field lines. In the case of Source I, the outflow begins at about 10 AU from the star, where 1 AU is the Earth-Sun distance.
Star formation is messy and there’s a lot we don’t know about it. But according to the team, thanks to ALMA, we will be able to learn so much more in the next few years. They are hoping to study more objects like Source I.
But this is not the only new discovery in stellar formation. Another paper published in Nature Astronomy today looked at stellar jets. While the outflows happen far from the young star, the jets take place within 10 million kilometers (6.2 million miles). In the study, which also uses ALMA observations, the researchers were able to find even more supporting evidence for the MDW model, so both the outflows and the jets are responsible for taking away angular momentum, and now we know a tiny bit more about star formation.