The growth of two protostars observed by the ALMA radio telescope

The Serpens Main star-forming cluster with SMM4A and SMM4B in the inset (Image ESO/ALMA(ESO/NAOJ/NRAO)/Aso et al.)
The Serpens Main star-forming cluster with SMM4A and SMM4B in the inset (Image ESO/ALMA(ESO/NAOJ/NRAO)/Aso et al.)

An article published in the “Astrophysical Journal” describes the observation of the growth of two class 0 protostars. A team led by Dr. Yusuke Aso of the Academy Sinica Institute of Astronomy and Astrophysics (ASIAA, Taiwan) used the ALMA radio telescope to study their different evolutionary states obtaining a series of details on the protostars cataloged as SMM4A and SMM4B. Class 0 protostats have their peak emissions at submillimetric wavelengths making ALMA ideal to get to know star gestation better.

The processes that lead to the birth of stars are under study thanks to the examination of various protostars, objects that are still growing in mass absorbing it from the molecular cloud they are being born from. Protostars are classified according to the peak radiation they emit and in the case of the class 0 ones they appear surrounded by gas and dust that obscure a part of the electromagnetic spectrum such as infrareds, causing a peak at submillimetric wavelengths.

In the region cataloged as SMM4 a star formation process is taking place and using the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope, inaugurated in March 2013, with its high spatial resolution and its sensitivity to molecular signatures in cold regions it was possible to accurately detect the growth of two protostars with details that are consistent with the theoretical predictions:

  1. dusty disk growth on 100 astronomical-unit scales
  2. widening of outflow opening angles
  3. carbon monoxide (CO) desorption from icy grains due to temperature rising
  4. weakening of accretion shock

The observations indicate that the distance between SMM4A and SMM4B is about 2,100 times that between the Earth and the Sun. SMM4A is surrounded by a disk with a radius about 240 times the distance between the Earth and the Sun. SMM4B is surrounded by a structure that seems more compact, with a radius about 56 times the distance between the Earth and the Sun. It’s possible that in these disks planets are forming .

The researchers analyzed the presence of molecules such as carbon monoxide but also sulfur monoxide (SO) and gas and dust movements to try to understand the processes underway. They also compared two protostars’ evolutionary phases with those of a third protostar in that region cataloged as SMM11. The conclusion is that they’re at development stages a little different: SMM4A is the most advanced, followed by SMM4B and SMM11.

This is just one of the research concerning protostars. It adds new information about the processes underway in these objects and demonstrates the importance of observations at millimetric and submillimetric wavelengths in the study of class 0 protostars. Dr. Yusuke Aso stated that from now on the growth of baby stars will be recorded with greater precision at those wavelengths.

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