VIDEO. In the coming days, a particularly bright star will appear in the sky

In a few days, a new star will appear in the sky… Well, new, not quite! “There is a particular star, which bears the letter “T” in the constellation Corona Borealis that is going to explode and become much more “brilliant,” explains Philippe Zarka, research director at the CNRS, attached to the Laboratory for Space Studies and Instrumentation in Astrophysics at the Paris Observatory..

This explosion is superficial, which means the star will not be destroyed. On the other hand, it will become during this event a thousand times brighter than usual, and will become visible to the naked eye, as much as the North Star, according to some specialists.

T Coronae Borealis, abbreviated to T CrB, is the “near suburbs” of Earth: 2,600 light years all the same. “This star is special in that it is a binary, so it is formed of two stars. A white dwarf, very small, very compact and a red giant, very large, very low density. They both revolve around each other. And gravity deforms the red giant and actually makes it project mass onto the dwarf. This accumulation of mass after a while leads to an explosion of the upper layers of the dwarf.”explains Philippe Zarka.

This explosion is expected very soon, a few days to a few weeks, without it being possible to be more precise. And this for two reasons: such a phenomenon is observed approximately every 80 years, and the last time that T CrB could be observed with the naked eye was in 1946. The second explanation is that before its explosion, the luminosity decreases. However, observers have noted a decrease in its luminosity since March 2023.

“Previous observation of this nova showed that the increase in brightness which makes it become a thousand times brighter happens in less than a day, and the subsequent decrease which makes it return to the previous state in a few weeks.”warns Philippe Zarka. We must therefore not miss the moment of this explosion. However, for cost reasons, we cannot keep professional optical telescopes trained on T CrB. On the other hand, Philippe Zarka uses NenuFAR, the radio telescope of the Paris observatory, installed in Nançay (Cher) which captures the electrical radiation of the stars to observe this rare event.

“It has never been observed at low radio frequencies. So if we detect it with NenuFAR, it will be a first!”rejoices Philippe Zarka. “If I can explain to you today that a nova is made of a dwarf star, a red giant star that transfers mass, it is because we have studied it beforehand. Now, we will obtain other knowledge. What is the energy produced by this phenomenon? To what extent is it little or not destructive? What is produced at frequencies, wavelengths that we did not observe 80 years ago? What is produced in radio? By what mechanisms?”

All that remains is to wait for this explosion, scrutinized and awaited by amateur astronomers all around the globe.