Why do the planets in the solar system orbit on the same plane?


Oct 22, 2019
The article says, "Eventually, the cloud became a flat structure called a protoplanetary disk, orbiting the young star. The disk stretched hundreds of AU across and was just one-tenth of that distance thick, Haghighipour said.

What was the mass of this early protoplanetary disk said to be spinning around the early Sun, some 4.5 billion years ago?

According to Allen's Astrophysical Quantities, Fourth Edition, the current mass in the ecliptic from Mercury out to Pluto or a bit beyond is about 447 earth masses. According to the minimum mass solar nebula model (MMSN), the planets of our solar system were in a spinning accretion disk around the early Sun and contained at a minimum, some 3300 earth masses or so. Some models could be 10x that amount or more. Ref, Protoplanetary disks throw out more material than gets turned into planets, https://phys.org/news/2021-09-protoplanetary-disks-material-planets.html, Reference paper, Preliminary Evidence That Protoplanetary Disks Eject More Mass Than They Retain, https://arxiv.org/abs/2108.13429, 30-August-2021. "If interstellar objects originate in protoplanetary disks, they can be used to calibrate the fraction of mass that such disks eject..."

Other reports are out now and see *young* stars with disk that could range with enormous mass variations. Scientists chip away at secrets of planet formation, origin of life in bevy of new research, https://www.space.com/planet-formation-organics-alma-research-protoplanetary-disks

My observation. I dug into this. NASA ADS Abstract, many reports out. "Molecules with ALMA at Planet-forming Scales (MAPS)", easy to search the NASA ADS Abstract for these papers. Very detailed for the arxiv papers. The protoplanetary disk model allows disk mass for HD 163296 to range 5527 earth masses up to 386214 earth masses. Apply this range to the Sun as a one solar mass star and we have upper mass limit for the proto-sun and early solar system accretion disk model, 193107 earth masses, and the lower value 2763 earth masses. This is a very large disk mass range reported and consider what space.com report stated. "Overall, the research shows that there's plenty more to learn about what surrounds young stars, how planets form and what that means for the universe and life's prospects in it."
May 14, 2021
If such a huge percentage of the mass of each system is ejected during the formation period, and a small percentage is ‘retained’ by the system, that means there must be an enormous amount of mass in interstellar space in the form of gas, dust, small bodies, unused protoplanets, and rogue planets of all sizes. It’s a wonder that we don’t see more occultations of stars by the larger of these objects.
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