They discover evidence of the existence of a natural hydrogen maser in the center of NGC 253

A scientific team composed of researchers from the Center for Astrobiology (CAB, CSIC-INTA) has presented evidence of the existence of a natural hydrogen maser more than ten million light years , in the center of NGC 253, known as the Sculptor's Galaxy. & nbsp;

Previously, only this type of emission in six existing gas clouds at distances a thousand times closer, in stellar regions of the Milky Way. Therefore, this is probably the first detection in a galaxy external to ours.

This finding, whose result is published in The Astrophysical Journal Letters , has taken place at the moment in which the researchers responsible for the study were exhaustively analyzing the radiation coming from an ionized cloud by hundreds of massive stars, which constitutes a supercluster of stars, and whose existence was unknown.

The discovery of this cloud was possible thanks to the use of the great sensitivity and spatial resolution of the enormous set of radio telescopes that form the ALMA interferometer, located at 5,000 meters of altitude, in the Atacama desert (Chile). Their receivers tuned to wavelengths close to 1 millimeter allowed the authors to detect the weak emission lines of ionized hydrogen from that stellar supercluster and from others located near the center of the galaxy.

As commented by Alejandro Báez-Rubio, researcher at the Astrobiology Center and main author of the publication, "It is true that there were probably a few clouds of ionized gas with this type of maser emission in galaxies where hundreds of thousands of stars are forming in very small regions, such as NGC 253". However, "it was not easy to imagine that they would be detected since clouds of ionized gas with this type of emission are very scarce when requiring very specific physical conditions, with relatively high electronic densities", explains Báez-Rubio. Therefore, it was expected that the maser amplification produced in a few clouds with maser emission would be imperceptible in front of the emission from the rest of the clouds. Thus, the key to detecting them and "this is the truly surprising thing", says the CAB researcher, "is that in this case there are hundreds of massive stars that seem to be producing ionized clouds with broadcast maser". < div style = "text-align: justify;">
This finding provides scientists with a new natural laboratory to study the processes that occur under conditions extremes that generate hydrogen masers. In addition, it becomes a very useful technique to find out what types of stellar populations may be forming the stellar superclusters in which these masers are detected. In the specific case of the cloud in which it was detected, the intensity of the maser could be due to some 700 stars similar to MWC349A, a massive star formed by some 38 solar masses and that has been very studied for having been the first known with hydrogen maser emission and for being the brightest star at radio wavelengths.



Figure: representation of NGC 253, the Sculptor's Galaxy. © AngusLau

 

Fuente: UCC-CAB

 

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