A Columbia University article makes an assumption that quite convincingly explains the very strange behavior (unusual decrease in luminosity) of the star Tabby (aka KIC 8462852), an object located at a distance of 1488 light years from us. The reason for this behavior, according to scientists, is the destruction of one of its planets by the star. In this case, the effect of strange flickering is explained by the fact that the planet left behind itself large debris, which from time to time reduce the level of brightness of the star. To be honest, this is perhaps the best theory available at the moment, and below we will consider why we think so.
A small team of three astronomers from the Department of Physics and Astronomy at Columbia University came to the conclusion about a cosmic collision. The researchers believe that the explanation for the slow, as well as short-term, sharp and very strong (up to 22 percent) decrease in the brightness of Tabby's star may be the result of a cosmic collision, the participants of which are the star itself and one of the planets that previously orbited it. A new article by Brian Metzger, Ken Schen and Nicholas Stone is currently undergoing peer review by the astrophysical journal Monthly Notices of the Royal Astronomical Society.
Object KIC 8462852, or Tabby's star, according to the observations, is the most ordinary and unremarkable star, but its strange behavior in recent years has caused real controversy among the astronomical community. Data from NASA's Kepler Space Telescope suggests that noticeable changes in the star's brightness began in 2015, but third-party studies show that the brightness of the star Tabby from 1890 to 1989 decreased by a total of 14 percent, as well as by another three percent only within the framework of a four-year observation by the Kepler telescope. This behavior is extremely unusual for such objects and, as it turns out, is very difficult to explain. On this occasion, several theories have been put forward, one more beautiful than the other, trying to explain the reasons for this phenomenon. Comets fell under suspicion, the star itself,changing its structure, planetary collision and, of course, alien cosmic megastructures.
According to one theory, the strange behavior of Tabby's star can be explained by the collision of two protoplanets (as in the image above), which created a huge amount of space debris. The new theory says that the collision could really have happened, but it happened between a huge planet and the star itself
The crux of the problem is that none of these early assumptions can clearly explain the double anomalous behavior of the star, that is, a short and sharp decrease in brightness, as well as a long-term decrease in luminosity. As for the theory of Metzger and his colleagues, it is just quite capable of explaining such behavior.
Scientists have suggested that one of its planets crashed into the star KIC 8462852. The gravitational energy created as a result of this collision could accelerate the rate at which the star produces thermonuclear energy, which, in turn, would manifest itself in the form of a sharp increase in its brightness and its subsequent long-term decrease. If this idea is correct, then most likely we are only watching Tabby's star return to its original normal brightness level. In addition, the new theory is also able to help us explain the short-term and sharp decrease in brightness. After the collision between the star and the planet, parts of the latter (and, possibly, part of its satellites, if any) took up eccentric orbits. And now, every time the remains of the planet and satellites move in front of the star (from our point of view), it flickers.
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As for the size of the planet that fell on the star, then, according to scientists, everything here will depend on when exactly the collision occurred.
“If the planet was the size of Jupiter, then the collision most likely occurred about 1000 years ago. At least this would explain the level of brightness decline that we are seeing now. If the object was the size of the moon, then a sharp rise and then a gradual decrease in brightness most likely occurred about a decade ago,”says Metzger.
At the same time, the scientist adds that a collision with a moon-like object in this case cannot explain the decrease in brightness observed over a century, but it is quite capable of explaining the change in brightness that occurred during four years of observation by the Kepler telescope. In addition, the researchers explain that they cannot yet confidently tell about the nature of the object itself or objects that could collide with Tabby's star.
“For now, we can only imagine many small or one large object with which this could happen. However, at this stage it is too difficult to give a definite answer. It is quite possible that the remnants in orbit in this case may provide us with some clues in solving this issue,”explains Metzger.
Stone, in turn, believes that the collision could not have happened overnight.
“Perhaps the entire collision process took several million years, during which the planet at first very slowly approached the star, and then eventually collapsed on it, which first caused a sharp increase in the brightness of Tabby's star, followed by a process of a slow decrease in its luminosity level, which we are watching now,”Stone comments.
“By the end of this slow process, any satellites near the planet would also be pulled by the field of Tabby's star. And if the planet was the size of our Jupiter or Saturn, with dozens of rather large icy moons, then potentially in this case, a huge cloud of space debris of varying degrees of density could accumulate in the orbit of the star,”Stone continues.
“Moreover, these satellites could now have a periapsis - the closest point of the orbit in relation to the central body (in this case, a star), which in this case turned out to be smaller than the size of the orbit of our Mercury around the Sun. In short, if these were ice worlds, then, it is quite possible that they evaporated very quickly, creating vast clouds of gas, vapor and dust, which now move after the larger remnants of satellites (or planets) and are able to significantly reduce the luminosity of the star. which was observed by "Kepler".
The supposed fact that we have witnessed the final stage of this collision suggests that such events are not rare in the universe. The Kepler space telescope has managed to study more than 100,000 stars to date, but it should be understood that there are about 100 billion of them inside the Milky Way alone.
"If we were able to observe such a star that engulfed the planet, which came into the field of view of Kepler, then this may well mean that only in our galaxy there can be millions of such stars that have created the same thing that did Tabby's star," explains Metzger.
According to the researchers, objects like the Tabby star are theoretically capable of "sucking dry" about 10 Jupiter-like planets, or about 10,000 moon-like satellites (not necessarily satellites, but objects with a similar mass) over the entire period of their life. And if so, then it is simply amazing.
Another important aspect of the theory proposed by Metzger and his team is that it is quite testable. Metzger says that the next time we witness a sharp decrease in the brightness of the star Tabby, we should expect to see the presence of a significant volume of gas and dust produced by the remains of an object colliding with the star.
“All this should lead to a short burst of infrared radiation (which will indicate the heating of the dust), which should last from a couple of days to a couple of weeks,” explains Metzger.
Another way to test the theory of Metzger and his colleagues would be to actually observe the collision of another planet or its satellite with a star. Such an event would be accompanied by a short and sharp increase in the brightness of the star with a smooth transition to the process of "fading".
The proposed theory really even now looks quite convincing and is not devoid of logical chains. Of course, she does not answer all the questions that exist, but thanks to such research, we will eventually be able to get closer to solving the mystery of the star Tabby.
NIKOLAY KHIZHNYAK
