Mysterious radio signal received from dying star system

The object is designated SN 2020eyj and is located in a galaxy 400 million light-years away. Unfortunately, they do not write in the direction of which constellation it was seen. There is, however, object imagebut it is quite difficult for a person who is not an astronomer to understand its location.

SN means supernova, supernova. That is, scientists consider what they see to be a supernova explosion. Recall what kind of phenomenon this is: it can be said to be the “death” of a star, that is, the completion of its main life cycle. The core of the star runs out of fuel for thermonuclear reactions, and it begins to collapse under the influence of its own gravity. From this, it is incredibly hot and heats up its entire outer shell. Surprisingly, before “death” the star is much hotter than during life. This heated mantle naturally begins to expand, the star temporarily transforms into a red giant, swallows its own nearby planets along the way, and finally the mantle is superbly thrown into the surrounding space. This moment of reset is the flash of a supernova.

Supernova explosion. © Giphy

But, as modern astronomy has long since found out, this is not the only possible scenario for such a spectacular event. It turns out that the star can “die” a second time. For example, our Sun is too low-mass to put on such a show, and yet, after about 5 billion years, it will also swell and shed its shell relatively imperceptibly. And there will be one shrinking core. It will become a white dwarf. It will have a diameter of about 4 thousand kilometers or a little more. For comparison, now the diameter of the Sun is 1 million and almost 400 thousand kilometers.

So, in a normal situation, this white dwarf simply cools down a little and eventually turns into a black dwarf, that is, it ceases to emit light. And in the case of our Sun, this will be the case. But there are also unusual situations: when a star wanders around the galaxy not alone, but in gravitational union with another star. Then a very interesting scenario can unfold. For example, if the partner stars “died”, as they say, on the same day, that is, they simultaneously became white dwarfs, then these two can merge together after the “death”, and then there will be a real supernova explosion. That is, one by one, they ended their days quietly and calmly without any outbreaks, and then the reunion of two connected “hearts” adorned the Universe at parting.

Supernova explosion due to the merger of two stars. © Giphy

And even more peculiar stories happen: when one star has already shone and became a white dwarf, and its partner is still alive. Then the orphaned partner, as it were, sacrifices himself to the deceased friend: he gradually gives him his substance. The white dwarf is gradually gaining mass, and when it reaches 1.4 solar masses, the “obsolete heart” flares up. AND, how scientists understoodSN 2020eyj is just such an unusual event.

Supernova explosion animation SN 2020eyj. Video © Youtube / The Conversation

Until now, the problem was that in this case, powerful radio waves of a certain nature should come from the flash, but they could not be caught in any way. The SN 2020eyj object is the first such case. It is reported that after being discovered in 2020, it has been successfully observed for almost two years using several radio telescopes located in the UK at once. As astronomers write, the nature of the radio signals suggests that its source contains a lot of helium. It is believed that this is helium just from that still living partner – its upper layers were blown away by an explosive wave. Now scientists are thinking that, perhaps, in such cases, the substance of the neighboring star does not always blow away in such a way, and therefore radio signals were not heard.

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