It is called cow but its full name is AT2018cow, a star of the Hercules constellation whose explosion was detected on June 16 this year. The nickname derives from the last three letters of the name with which the star has been classified, which in turn depend on the moment in which the observed phenomenon takes place, in this case the explosion of the star.
The cow since then, perhaps thanks also to the fame due to the nickname, was followed by many observers and by different research groups. And although months have passed since observations, astronomers have not yet been able to define precisely what happened.
At the beginning they thought that it was a supernova, but, the peak brightness of the explosion occurred after a few days, while for most supernovae this happens after a few weeks or more, moreover the brightness developed is much larger , from 10 to 100 times higher than that typical of the classic supernovae.
According to some researchers at Northwestern University in Illinois, none of the observations made makes it possible to say that we are facing a normal supernova, also the color of the light that comes from that star is different from that of the other supernovae, it is more tending to blue, this means that the temperature is much higher, and the fact that the light has remained blue even after some time, suggests that a phenomenon is underway that keeps the object exploded warm. The researchers also detected irregularities in X-ray emissions, which suggest that the cow is asymmetric and that there may be a ring of dust and gas around the main object.
Anna Ho from the California Institute of Technology also came to the same conclusion. She discovered how the radio waves emitted by the cow suggest that the explosion is spreading through a very dense medium, which recalls the clouds of gas emitted by certain stars before become supernovae.
According to Brian Metzger, astrophysicist of the Columbia University in the city of New York, something similar was observed in very distant galaxies but, because of the distance, it was not possible to study the phenomenon well. In this case, however, the object is located within a relatively close galaxy, so if we have patience we will be able to understand what happened and perhaps to discover a new kind of stellar explosion.