Astronomers from the National Autonomous University of Mexico (UNAM) unveiled the discovery of more than 4,000 massive stars in a pair of colliding galaxies known as Las Antenas or NGC 4038/39.
The discovery was made by a group from the University’s Institute of Radio Astronomy and Astrophysics (IRyA), which highlighted that the name of the stars is Wolf-Rayet (WR).
The owner of the project, Mauricio Gómez González, explained that these are at least 25 times the mass of the sun . Even in their last stage they become 50 to 100 times larger than the size of this , in other words, it is the time when they are massive.
However, he detailed its life span is very short compared to that of other stars , just two to four million years. What happens is that the fusion processes in their cores are more efficient than those of low-mass stars.
According to the IRyA researcher, the detection process had to do with the fact that the WRs throw their outermost layers into the interstellar medium , in the same way in which the layers of an onion are separated. As it gets closer to the core, they get hotter and its components are more identifiable. “That was how we detected them,” he said.
However, they are not all the same. The researcher explained that hydrogen dominates in some and carbon in others. The stars evolved and little by little they shed their outer layers of oxygen and revealed their inner elements.
According to Gómez, when separating the light from very hot stars into colors or wavelengths , a spectrum is obtained and it is possible to denote its components.
“We find them in the range of the optical spectrum, in the visible, using spectra obtained from the VLT telescope, which is located in Chile,” he added.
On the other hand, the researcher pointed out that this type of stars has a very characteristic fingerprint , which is formed by a spectrum of helium, carbon, nitrogen and oxygen.
We look for these fingerprints in the spectrum of a pair of merging galaxies called the Antennas. In 38 regions, which are complexes of star clusters, we located these fingerprints, which together gave us a total of four thousand stars, two thousand rich in nitrogen and two thousand in carbon
The main difficulty the researchers encountered was the short life span of the WR stars, especially since being massive they represent only 10% of the four million years they live.
Gómez’s team is made up of Divakara Mayya, from the National Institute of Astrophysics, Optics and Electronics (INAOE); Jesús Toalá and Jane Arthur from IRyA; Javier Zaragoza-Cardiel, from the INAOE; and Martín Guerrero, from the Institute of Astrophysics of Andalusia, Spain.
The research results were published in Oxford’s Monthly Notices of the Royal Astronomical Society.
The group of astronomers managed to identify these more than four thousand stars, whose first discovery was made in 1867, when 600 of them were detected.