One of the big questions for the astrophysicists is how stars form from collapsing molecular clouds. It is know as the angular momentum problem.
In this cloud there is some rotation, which gives each gas some angular momentum. When it collapses inward, the pull is balanced by the centrifugal force until it can reach a certain radius where more angular momentum must be shed to continue collapsing.
Group led by Nami Sakai of the RIKEN Star and Planet Formation Laboratory, used measurements to find out how the gas can reach the surface of the new star. To find out why this process happens, Sakai and her group turned to the ALMA observatory, that has 66 radio dishes in the Atacama desert. They are in a careful configuration so they can provide data from many protostellar regions in the sky.
The protostar observed named L1527 in the Taurus Molecular cloud, 450 light years away. It has a spinning protodisk that looks edge on against us, in a big cloud of gas and dust.
The lead author Sakai found out that unlike the commonly known hypothesis, the transition from the envelope to the disk is far more complex that they’ve though.
“As we looked at the observational data,” says Sakai, “we realized that the region near the centrifugal barrier — where particles can no longer infall — is quite complex, and we realized that analyzing the movements in this transition zone could be crucial for understanding how the envelope collapses.”
“Our observations showed that there is a broadening of the envelope at that place, indicating something like a “traffic jam” in the region just outside the centrifugal barrier, where the gas heats up as the result of a shock wave. ”
“It became clear from the observations that a significant part of the angular momentum is lost by gas being cast in the vertical direction from the flattened protoplanetary disk that formed around the protostar.”
The behavior was pretty much the same as the ballistic model used, that has particles to behave like simple projectiles that are not influenced by other forces.
According to Sakai, “We plan to continue to use observations from the powerful ALMA array to further refine our understanding of the dynamics of stellar formation and fully explain how matter collapses onto the forming star. This work could also help us to better understand the evolution of our own solar system.”