Observing the displacement of Mercury's orbit helped scientists calculate the exact rate at which the Sun is "losing weight" due to thermonuclear reactions and solar wind, astronomers say in an article published in the journal Nature Communications.
“We have managed to solve one of the most fundamental and important problems in the physics of the Sun by applying the methods of planetary science. Looking at the problems of interest to us from a completely different angle, we were able to obtain more accurate estimates and get closer to a new understanding of how the sun and planets interact with each other, said Erwin Mazarico of the NASA Goddard Space Flight Center (USA).
The sun, like other stars, is a giant natural thermonuclear reactor that converts the energy released during the fusion of hydrogen nuclei and other light elements into light and heat. In addition, the Sun continuously throws out huge amounts of incandescent plasma into space in the form of the so-called "solar wind" - a stream of protons, electrons and other particles accelerated to very high speeds.
For more than 50 years, since the discovery of this phenomenon by the Soviet probe "Luna-1", scientists have been trying to understand how the solar wind arises and how it affects the behavior of the star itself and the eight planets of the solar system.
Its most obvious consequence, as noted by Mazariko, is that the Sun is constantly "losing weight." The ejected matter is not replenished by anything; as a result, the mass of the star gradually decreases. Theoretical estimates show that over the entire time of its life, it should lose about 0.1% of its mass and this should significantly affect the orbits of the planets.
For example, by the time the Sun runs out of supplies of "stellar fuel" and turns into a red giant, the Earth will move away from it by about 150 thousand kilometers, and the orbits of Mars, Jupiter and more distant planets will shift even more. This will affect their possible habitability and how they interact with asteroids and comets.
However, these estimates are extremely inaccurate - until now astronomers did not know how fast the Sun was “losing weight” and how quickly the planets were “running away” from it. This riddle, as Mazariko notes, was helped by Mercury.
Mercury, the scientist explains, is located about three times closer to the Sun than the Earth, so a decrease in the mass of the star will have a much stronger effect on the position of its orbit and the distance between the points of maximum approach to the star and and maximum distance from it. In particular, the most rough calculations show that in two years the orbit of Mercury should be displaced by about two meters.
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Such shifts would have been impossible to notice from Earth, but the MESSENGER probe has worked for a long time in orbit of Mercury, capable of accurately measuring how much time radio waves spend on traveling to and from Earth and how much they stretch.
These data allowed Mazariko and his colleagues not only to calculate the exact rate at which the sun is losing mass, but also to test the theory of relativity and find out how much our star differs in shape from an ideal ball.
Calculations have shown that each year the Sun "loses weight" by about 179 trillion tons, which is equivalent to about 3.5% of the total mass of the earth's atmosphere. Such values, astronomers note, are slightly lower than theoretical estimates, but in principle they correspond.
The remaining measurements, according to Mazariko, show that the behavior of the star is fully consistent with the theory of relativity, which makes it possible to use such observations to predict the fate of the solar system and study the history of its formation.
