2 Scientists Claim That The Sun Is Fractionally Smaller Than We Thought

In a significant development that could change scientists' understanding of the Universe, the Sun, the star at the center of our Solar System might not be quite as big as we thought. According to a report by Science Alert, two astronomers have now found evidence that the radius of our Sun is a few hundredths of a percent slimmer than previous analyses indicated.

The new findings, which are currently under peer review, are based on sound waves generated and trapped inside the Sun's hot plasma interior, known as 'pressure' or p-modes. The paper detailing these findings was published on arXiv.

Astrophysicists Masao Takata from the University of Tokyo and Douglas Gough from Cambridge University explained that p-mode oscillations offer a "dynamically more robust" view of the Sun's interior compared to other oscillating sound waves. To understand this better, we can imagine the Sun as a ringing bell being hit by tiny sand grains. Millions of oscillating sound waves such as p-waves, g-modes, and f-modes are produced by that seismic commotion.

F-modes are the ones traditionally that have been used for measuring the Sun's seismic radius. However, scientists found that they not might be completely reliable as they do not extend right to the edge of the Sun's photosphere. Instead, p-modes are more useful as they reach further and are less susceptible to magnetic fields and turbulence in the upper boundary layer of the Sun's convection zone.

An introduction to the paper read, ''Analysis of f-mode frequencies has provided a measure of the radius of the Sun which is lower, by a few hundredths percent, than the photospheric radius determined by direct optical measurement. Part of this difference can be understood by recognizing that it is primarily the variation of density well beneath the photosphere of the star that determines the structure of these essentially adiabatic oscillation modes, not some aspect of radiative intensity.''

Both scientists now argue that p-modes should be used to measure the Sun's radius. Their calculations using only p-mode frequencies suggest the solar photospheric radius is very, very slightly smaller than the standard solar model.

''In this paper, we attempt to shed further light on the matter, by considering a differently defined, and dynamically more robust, seismic radius, namely one determined from p-mode frequencies. This radius is calibrated by the distance from the center of the Sun to the position in the subphotospheric layers where the first derivative of the density scale height changes essentially discontinuously. We find that that radius is more or less consistent with what is suggested by the f modes.

In addition, the interpretation of the radius inferred from p modes leads us to understand more deeply the role of the total mass constraint in the structure inversions. This enables us to reinterpret the sound-speed inversion, suggesting that the positions of the photosphere and the adiabatically stratified layers in the convective envelope differ non-homologously from those of the standard solar model,'' the research states.