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Curated by RSF Research Staff

Missing matter in the Sun’s interior

It is often assumed that a structure’s surface can be appropriately represented as a two-dimensional area, completely flat and devoid of any depth. However, in reality, two-dimensional surfaces do not exist in nature, if zoomed in sufficiently even the most seemingly flat surface has 3-dimensional structure. This can pose a problem when physics that have been formulated with two-dimensions are re-examined using a more realistic 3D model.

Just such a situation arose when astronomer Martin Asplund forewent the usual 2D model of the Sun’s surface, and instead used a supercomputer to model it as 3-dimensional surface. Asplund was hoping to formulate a more accurate model for analyzing spectral and seismological data to better understand the Sun’s interior.

Since the interior cannot be directly observed, sound and light emissions emanating from the Sun's surface are a window into the interior. Asplund’s new model brought to light a fascinating, if not controversial revelation, the seismological and spectrophotometric data indicated that the Sun had significantly less heavy elements than was previously calculated (using the defunct 2D model).

Because light and sound pass through heavy elements (most every element past hydrogen is referred to as a metal by astronomers) differently than light elements like hydrogen and helium, the Asplund’s updated calculations suggested a highly different chemical composition for the Sun---essentially the now absentee heavy elements account for several billion megatonnes of missing matter (the equivalent of around 1500 Earths).

The solution to the seeming conundrum is to posit that there is some form of matter at the center of the Sun---about 1027 kilograms of it---that does not behave like ordinary states of matter. Perhaps under the extreme temperatures and pressures of the interior region matter takes on different quantum properties, and has altered opacity or acoustic resonances.

Jim Bailey, at Sandia National Laboratories in New Mexico, seemed to confirm that this is indeed possible when he used the Z Pulsed Power Facility, or Z machine, to expose matter to temperatures and pressures equivalent to those found at certain locations within the Sun’s interior. Bailey found that his opacity measurements under these conditions indicated that matter may absorb and transmit light, and perhaps sound as well, differently when under conditions that deviate far from “normal” laboratory environments.

Another potential explanation is that some form of dark matter is at the center of the Sun, accounting for the mass yet only weakly interacting with the propagating phononic and photonic emissions. The exact nature of dark matter remains a mystery, several proposals have ranged from new sources of matter like weakly interacting massive particles (WIMPS), axions, to primordial black holes and superfluid dynamics of spacetime. Further analysis and supercomputer modeling may begin to reveal what lies in the Sun’s interior, but for now all that is certain is that the conventional model is not offering explanations that match observations.

Article: Hiding in plain sight: the mystery of the Sun's missing matter

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