The sun has lost weight: Dimensions of the native luminary

How to measure the radius of the sun? The question is quite interesting, especially when you consider that the star does not have a solid surface, and therefore it is rather difficult to determine where it actually begins.

As you move from the center of the star, its outer layer, which is commonly called the atmosphere, becomes less dense and, accordingly, more and more transparent. It is agreed to consider the zone in which the solar atmosphere ceases to be transparent to its own rays to be the zero mark corresponding to the hypothetical “beginning” of the Sun. As a result, the process of measuring its radius takes on a fairly simple form: we look at the star through a powerful telescope and fix the distance between the center of the solar disk and the zone where the brightness of the disk decreases sharply. According to the results of such measurements, the radius of the Sun is 695, 990 km (about 109 times more than the Earth).

A more sophisticated technique is proposed, based on the phenomenon of seismic waves, due to which the surface of the sun pulsates like a gigantic ocean. The theory claims that powerful acoustic waves can exist only in the opaque zone of the Sun and are unable to rise above its conditional surface, while their amplitude is related to the distance from the center of the star to its outer boundary. Thus, seismographic studies also allow us to calculate the radius of the Sun with a higher degree of accuracy. The wave method gave a value of 695, 700 km - 300 km less than the optical method.

Although the results of the two types of measurements differ by only 0.04%, this difference is quite enough to significantly complicate the construction of an integral model of solar physics.

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Swiss scientists managed to find a way to resolve this contradiction. A team led by Margit Haberreiter found that previous estimates of the radius of the Sun obtained by the optical method were somewhat overestimated due to an inaccurate determination of the zone where the star's atmosphere loses its transparency.

The result was obtained during experiments with a specially developed computer model that describes the process of light propagation in the outer layers of a star. The model showed that the zone where the atmosphere loses its transparency and the zone of a sharp decrease in the luminosity of the solar disk are not completely identical to each other. Luminosity sharply decreases already in the atmosphere, about 333 km above the surface of the Sun - that is, the zone where it becomes opaque and where seismic vibrations can already propagate. The result obtained very well explains the difference of 300 km, which is provided by two different methods for measuring the radius of the sun.

Models of the Sun, based on a larger estimate of its radius, must either be corrected or completely marked - the authors of the discovery summarize. We offer an article “Closer to the Sun”, which details the study of our luminary.

Published by The New Scientist Space

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