It is a spectacle as rare as spectacular: two novas, these dazzling stellar explosions, appeared almost blow in the night sky, and they are fairly brilliant to be observed with the naked eye from earth. An unprecedented astronomical coincidence that enthuses scientists from around the world.
Since mid-June, amateurs of astronomy can indeed witness an exceptional phenomenon. On June 12, a first Nova called V462 Lupi was detected in the wolf constellation, in the southern hemisphere. Barely two weeks later, on June 25, a second Nova, V572 VELORUM, appeared in the neighboring constellation of the sails. Seeing a Nova with the naked eye is already a rare event – observing two simultaneously is simply historic.
What exactly is Nova?
Contrary to what its name could suggest, a Nova is not a freshly born star, but a temporary explosion caused by a dying star. More specifically, it is a white dwarf, an extremely dense stellar corpse, which is part of a binary system. This star gradually siphoning the material of a more massive neighboring star. When a critical mass is reached on its surface, an explosive nuclear reaction occurs, projecting light material into space.
The result? A flambé of light so intense that it can transform, for a few days or weeks, a star normally invisible from the earth at a brilliant point visible to the naked eye.
Not to be confused with supernovas, which mark the complete destruction of a star, classic Novas like V462 LUPI and V572 VELORUM only fall asleep the external layers of white dwarf. These stars can therefore, in theory, explode several times during their life.
A extremely rare phenomenon in the history of astronomy
Novas visible without telescope are already infrequent: there are approximately one per year, and sometimes none. See two in such a short period of time, visible at the same time, is exceptional. Stephen O’Meara, a recognized astronomer, says he has found no documented precedent of such a phenomenon, despite extensive research in astronomical archives.
The last comparable case dates back to 1936, with the Novas V630 SGR and V368 AQL. But at the time, the two objects were not at their peak of brightness simultaneously, which makes the current event even more striking.
Stars
During their peak of brightness, the two Novas reached impressive magnitudes:
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V462 LUPI culminated in an apparent magnitude of +5.5 on June 20.
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V572 VELORUM, even brighter, reached +4.8 on June 27.
For comparison, the more a celestial object has a weak magnitude, the more it is brilliant. For reference, the human eye can generally distinguish objects up to +6 in clear weather, far from the extreme performance of the moon (at -12,7), but more than enough to identify these two novas without instrument from a clear place.
V572 VELORUM (left) and V462 LUPI (right). It is perhaps the first time that several novas have been visible simultaneously with the naked eye. Image credit: Eliot Herman
Where to observe them?
The two novas are in the southern sky, which means that they are easily visible from the southern hemisphere. That said, V462 LUPI can also be observed from certain regions of southern North America, notably in Texas, Mexico or California. For V572 VELORUM, observation from these regions remains more difficult, but not completely excluded.
In any case, a good dark sky, clear and without light pollution, as well as twins or a telescope, will clearly improve the chances of identifying these stellar visitors.
Soon extinguished … but maybe not forever
Like all Novas, V462 LUPI and V572 VELORUM will not shine forever. They are already declining and could disappear from our field of vision in the coming weeks.
Nothing allows us to know if they will reappear one day. Certain novas, such as T Coronae Borealis – nicknamed “The Star of Fire” – are recurrent, exploding at regular intervals. T Coronae, for example, illuminates the sky about every 80 years and has been expected from one day to the next for more than a year. But for V462 LUPI and V572 VELORUM, it is the first explosion never recorded.