2023-10-02 15:15:32
Astronomy faces an enigma that is difficult to explain. There exists about 530 light-years away a planet that was not swallowed or even orbitally disturbed by its star in a phase of destructive expansion, despite being within the radius of annihilation. It was saved from being swallowed and also maintains a stable, almost perfectly circular orbit around its star. Perhaps something prevented the destruction and orbital disruption of this planet. Or maybe what happened here was much more exotic than a star’s red giant phase.
When stars like our Sun approach the end of their lives, they begin to exhaust their nuclear fuel. They become red giants and reach their maximum size, swallowing nearby planets, then shrink again and finally cease their activity as a star.
The dying star around which the described enigmatic planet revolves had to expand up to 0.7 astronomical units. On the other hand, the planet is only 0.5 astronomical units away. (An astronomical unit is the distance that separates the Earth from the Sun).
The mystery has been investigated by Marc Hon’s team, from the University of Hawaii, United States.
The anomalous situation of 8 Ursae Minoris b has been observed by NASA’s TESS (Transiting Exoplanet Survey Satellite) astronomical satellite. The WM Keck Astronomical Observatory in Hawaii has also participated in the research.
That something protected that planet from annihilation is a difficult possibility to accept. As are, although perhaps less so, the two alternative explanations that Hon and his colleagues have put forward: the planet is the survivor of a merger between two stars, or it was formed from the debris left by that merger between stars.
The first of those two alternative scenarios begins with two stars the size of our Sun orbiting each other closely and with the planet in orbit. As time passes, one of the stars evolves a little faster than the other, entering its red giant phase, shedding its outer layers and finally becoming a white dwarf, a star that has ceased to be a star for a long time. cease in it the nuclear reactions that define the stars. In the white dwarf phase, the star shrinks to the diameter of a modest planet but still retains a lot of mass. In this first alternative scenario, when the other star begins its red giant phase, a situation is caused that leads to both stars colliding and merging into one. The product of that collision is the red giant we see today. This merger between stars stops the expansion of the red giant and prevents the destruction of the planet in orbit.
In the second scenario, the violent merger of the two stars expels abundant dust and gas, which forms a disk around the remaining red giant. This “protoplanetary” disk provides the raw material for the formation of a new planet. This is a kind of late second life for a planetary system, although the star is already close to its end.
Artistic recreation of planet 8 Ursae Minoris b in the middle of a ring of debris formed as a result of the violent fusion between two stars, one of the hypotheses proposed to explain why this planet exists in a place where this is apparently impossible. (Image: WM Keck Observatory / Adam Makarenko)
The study is titled “A close-in giant planet escapes engulfment by its star.” And it has been published in the academic journal Nature. (Source: NCYT from Amazings)
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