January 20, 2021

Two stars about to touch

Two stars about to touch


An international team of astronomers, led by the researcher of the Institute of Astrophysics of the Canary Islands (IAC) and the University of La Laguna (ULL) David Jones, has discovered two stars that are very close to joining and that, if they did, could cause a "nova explosion" before the nebula in which they are found dissipates and, with it, unleash a process not predicted to date by the theory surrounding these phenomena.

As explained by the IAC, these stars have an orbital period of just over three hours. This finding, the result of several years of research, "is surprising because it is binary stars with one of the shortest orbital periods within a planetary nebula ever observed, and also reveals the possibility that, due to its proximity, the system can experience a nova explosion before the nebula dissipates. "

The results of the research have just been published in the prestigious scientific journal Monthly Notices of the Royal Astronomical Society (MNRAS).

The planetary nebulae are, remember the IAC, gas and dust envelopes that stars similar to our Sun expel at the end of their lives. "In many cases we see that this expulsion originates from an interaction between the progenitor star and a close companion, and that is why they form nebulae with such elaborate structures," explains Jones.

The planetary nebula M3-1 has been studied in the investigation. The observations immediately confirmed the suspicions. "When we started observing it, we immediately saw that it was a binary system and that its brightness changed rapidly, so it could mean that it had a very short orbital period," says Henri Boffin, researcher at the European Southern Observatory (ESO). ) in Germany. In fact, the calculated separation between the two stars is approximately 160,000 kilometers, that is, less than half the distance between Earth and the Moon.

After several campaigns of observations in Chile with the Very Large Telescope (VLT) and New Technology Telescope (NTT) telescopes, the researchers managed to Collect enough data to begin to understand the properties of stars, such as their mass, temperature and size.

The result of the observations contradicts the current theories of evolution of binaries that maintain that, once formed the planetary nebula, the stars remain separated during a long time before getting to interact again. When this happens, the nebula should have already dispersed so that it would not be observed.

However, an explosion of nova observed in 2007, known as Nova Vul 2007, inside another planetary nebula, questioned the model, according to researchers from the Canarian institute. "In the case of M3-1, we see another candidate who may experience a similar evolution; as the stars are almost touching, it should not take long to interact again and, perhaps, to produce a nova in a planetary nebula »concludes Jones.

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