The sun used to have rings like Saturn

Reports like this can be compared with the 1977 MMSN model disk. Here is the 1977 report on the MMSN. The Distribution of Mass in the Planetary System and Solar Nebula,, September 1977. The arXiv paper,, 19-Feb-1977.

The protoplanetary disk model for the origin of our solar system undergoes extensive revision over the years. When it comes to new models using multiple rings for the protoplanetary disk, consider systems like TRAPPIST-1. The well studied TRAPPIST-1 has 7 exoplanets, all move around the 0.08 solar mass red giant from about 0.01 to 0.06 au distance with total exoplanet mass < 6 earth masses. Just how the ring(s) and pressure bump(s) model can be applied to TRAPPIST-1 and form the 7 exoplanets, all moving in orbits very close to the host star and apparently in a very flat plane, should be interesting to demonstrate. Other examples of rings found by ALMA are at HL Tauri, very massive system with disk and rings compared to the MMSN and GM Aurigae.

Ref - Multiple Rings in the Transitional Disk of GM Aurigae Revealed by VLA and ALMA,, Sep-2018. "Our understanding of protoplanetary disks is rapidly departing from the classical view of a smooth, axisymmetric disk. This is in part thanks to the high angular resolution that (sub)millimeter observations can provide. Here, we present the combined results of Atacama Large Millimeter/submillimeter Array (ALMA) (0.9 mm) and Very Large Array (VLA) (7 mm) dust continuum observations toward the protoplanetary disk around the solar analog GM Aur. Both images clearly resolve the ∼35 au inner cavity. The ALMA observations also reveal a fainter disk that extends up to ∼250 au..."

Ref - the 18-page arXiv paper 06-Aug-2018, states GM Aurigae contains 2 rings but also notes clear evidence for evaporation of the disk too. "Recently, VLA observations at cm wavelengths revealed that GM Aur contains a substantial amount of ionized gas, suggesting that the disk could be undergoing some degree of photoevaporation (Mac´ıas et al. 2016). Some studies have shown that photoevaporation can explain the presence of small, significantly depleted cavities (Alexander et al. 2014; Owen 2016). However, the size of GM Aur’s cavity, combined with the presence of gas and small dust grains inside the cavity, points toward a dynamical clearing origin (Espaillat et al. 2014), indicating that planetary formation is probably taking place in GM Aur."

My note. The paper shows GM Aur is 1.1 Msun and about 160 pc. I also note the disk mass reported. “The dust mass (Mdust disk) in our disk model is 2.0 MJ . Using the dust-to-gas mass ratio of 0.01 assumed in our model, this implies a total disk mass of 200 MJ. Our model is able to constrain very accurately the dust mass of the disk, but since we are only fitting the dust emission, slightly different gas masses could be found by modifying the dust-to-gas mass ratio in the model. We note, however, that since we use a physical model that enforces hydrostatic equilibrium, the temperature structure of the disk, set mainly by the vertical dust distribution, is not entirely independent from the gas density in the disk. Therefore, our model is able to obtain a close estimate of the gas density structure of the disk and, hence, of the total disk mass. Our estimated value is consistent with previous measurements from the literature. In particular, McClure et al. (2016) constrained the gas mass of GM Aur to be between 25 and 204 MJ by fitting its HD (J=1−0) molecular emission with a similar model.”

My note. This is a massive disk for a 1.1 Msun star compared to the 1977 MMSN and later revisions. The canonical MMSN disk for 1.1 Msun star about 3.662370E+03 earth masses (dust and gas total). 25 Mjup = 7.945500E+03 earth masses. 204 Mjup disk mass = 6.483528E+04 earth masses. The estimate of 2 Mjup for dust = 6.356400E+02 earth masses of dust. When it comes to modifying the MMSN disk to explain the origin of our solar system using 3 rings as recently reported in (end of December 2021), this needs more study. HL Tauri disk cited in the report as an example, well studied disk with rings but also likely very massive with HL Tauri star mass estimates as high as 2 Msun. This 2018 report on GM Aurigae indicates 2 rings, possibly 3 rings with an apparent massive disk, likely out to 250 au and inner regions closer in to 35-80 au or so and likely photoevaporation taking place too.

Issues like this I feel should be clearly documented concerning new simulation models for the MMSN and creation of our solar system from the postulated protoplanetary disk around the Sun, some 4.5 billion years ago. It would be good one day to see a complete list of ALMA disk observations with properties shown like we have for the exoplanets confirmed now.

Another interesting report on this newer approach to the MMSN with rings was published, Cosmic history can explain the properties of Mercury, Venus, Earth and Mars,

This report mentioned the HL Tauri analog ALMA observations.

"Astronomers have managed to link the properties of the inner planets of our solar system with our cosmic history: with the emergence of ring structures in the swirling disk of gas and dust in which these planets were formed. The rings are associated with basic physical properties such as the transition from an outer region where ice can form where water can only exist as water vapor. The astronomers made use of a spread of simulation to explore different possibilities of inner planet evolution. Our solar system's inner regions are a rare, but possible outcome of that evolution. The results have been published in Nature Astronomy."...The most striking change was triggered by a literal picture: The first image taken by the ALMA observation after its completion in 2014. The image showed the protoplanetary disk around the young star HL Tauri in unprecedented detail, and the most stunning details amounted to a nested structure of clearly visible rings and gaps in that disk..."
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