Many aspects of the solar system are explained by ‘pressure bumps’ in the protoplanetary disk of the sun.
According to a recent research, before the solar system had planets, the sun had rings, which were bands of dust and gas comparable to Saturn’s rings and likely had a role in Earth’s birth.
“Something occurred in the solar system to prevent the Earth from developing to become a much bigger form of terrestrial planet dubbed a super-Earth,” said André Izidoro of Rice University, alluding to the giant rocky planets observed orbiting at least 30% of sun-like stars in our galaxy.
Izidoro and his colleagues ran hundreds of simulations of the solar system’s development on a supercomputer. Their model, which was published online in Nature Astronomy, created rings that resembled those found around many distant, young stars. It also properly recreated some aspects of the solar system that many prior models had overlooked, such as:
Between Mars and Jupiter is an asteroid belt that contains objects from both the inner and outer solar systems.
The positions of Earth, Mars, Venus, and Mercury, as well as their steady, almost circular orbits.
Many solar system models overestimate the masses of the inner planets, including Mars.
The difference in chemical composition between objects in the inner and outer solar systems.
A area of comets, asteroids, and tiny things beyond Neptune’s orbit known as the Kuiper belt.
Astronomers, astrophysicists, and planetary scientists from Rice, the University of Bordeaux, the Southwest Research Institute in Boulder, Colorado, and the Max Planck Institute for Astronomy in Heidelberg, Germany collaborated on the research, which is based on the most recent astronomical research on infant star systems.
Three bands of high pressure emerged inside the young sun’s disk of gas and dust, according to their hypothesis. According to lead author Izidoro, a Rice postdoctoral researcher who received his Ph.D. at Sao Paulo State University in Brazil, such “pressure bumps” have been observed in ringed stellar disks around distant stars, and the study explains how pressure bumps and rings could account for the solar system’s architecture.
“Why don’t we have a super-Earth in our solar system if super-Earths are so common?” Izidoro remarked. “We hypothesize that pressure bumps in the inner and outer solar systems created separate pools of disk material and restricted how much material was accessible to build planets in the inner solar system.”
Bumps in the road
For decades, astronomers assumed that gas and dust in protoplanetary disks progressively got less dense as distance from the star increased. Planets are unlikely to originate in smooth-disk settings, according to computer models.
“In a smooth disk, any solid objects — dust grains or boulders — should be dragged inside extremely rapidly and lost in the star,” said Andrea Isella, an associate professor of physics and astronomy at Rice and one of the study’s co-authors. “Something must be done to halt them so that they can develop into planets.”
Izidoro noted that when particles travel faster than the gas surrounding them, they “experience a headwind and drift extremely swiftly toward the star.” Gas pressure rises at pressure bumps, gas molecules travel faster, and solid particles are no longer affected by the headwind. “That’s why dust particles collect around pressure bumps,” he said.
With the Atacama Large Millimeter/submillimeter Array, or ALMA, a massive 66-dish radio telescope that came online in Chile in 2013, astronomers have seen pressure bumps and protoplanetary disk rings, according to Isella.
“We’ve observed that a number of the protoplanetary disks in these systems are marked by rings,” Isella said. “ALMA is capable of getting extremely crisp photos of young planetary systems that are still developing.” “The pressure bump has the effect of collecting dust particles, which is why we see rings. There are more dust particles in these rings than in the spaces between the rings.”
Formation of a ring
Pressure bumps created in the early solar system in three locations where sunward-falling particles would have released substantial volumes of evaporated gas, according to Izidoro and colleagues’ model.
“It’s simply a function of distance from the star, since temperature rises as you move closer to the star,” said Rajdeep Dasgupta, the Maurice Ewing Professor of Earth Systems Science at Rice, who was a co-author on the paper. “A sublimation line we call the snow line is when the temperature is high enough for ice to be vaporized, for example.”
Pressure bumps along the sublimation lines of silicate, water, and carbon monoxide formed three unique rings in the Rice simulations. The essential element of sand and glass, silicon dioxide, became vapor at the silicate line. This created the sun’s closest ring, which would eventually give birth to Mercury, Venus, Earth, and Mars. The snow line appeared in the middle ring, and the carbon monoxide line appeared in the furthest ring.
Planetesimals and planets are born in rings
Sublimation lines would have moved toward the sun as protoplanetary disks cooled with age. This mechanism, according to the scientists, might enable dust to collect into asteroid-sized particles known as planetesimals, which could eventually collide to create planets. Previous research had believed that planetesimals may develop if dust concentrations were high enough, but no model presented a plausible theoretical explanation for how dust could accumulate, according to Izidoro.
“Our model demonstrates that moving pressure bumps may operate as planetesimal factories, and pressure bumps can concentrate dust,” Izidoro added. “We start with dust grains and work our way up through the phases of planet formation, from minuscule millimeter-sized grains to planetesimals, and finally planets.”
When cosmochemical signals, Mars’ bulk, and the asteroid belt are taken into account
Many prior models of the solar system created versions of Mars that were up to ten times more massive than Earth. Because “Mars was formed in a low-mass part of the disk,” the model properly anticipates Mars having around 10% of Earth’s mass, according to Izidoro.
The model, according to Dasgupta, also explains two cosmochemical mysteries in the solar system: the notable variation in chemical compositions of inner- and outer-solar system objects, as well as the existence of each of those items in the asteroid belt between Mars and Jupiter.
The center ring, according to Izidoro’s calculations, might account for the chemical dichotomy by blocking material from the outside system from accessing the inner system. The simulations also indicated that the asteroid belt was fed objects from both the inner and outer areas, and that it was in the proper position.
Dasgupta said, “The most prevalent sort of meteorites we obtain from the asteroid belt are isotopically similar to Mars.” “Andre demonstrates why the composition of Mars and common meteorites should be comparable. He’s given a thoughtful response to this subject.”
Super-accurate pressure-bump timing
In certain models, the delayed arrival of the sun’s middle ring resulted in the production of super-Earths, according to Izidoro, emphasizing the significance of pressure-bump timing.
“A lot of material had already entered the inner system and was accessible to build super-Earths by the time the pressure spike developed in those circumstances,” he added. “As a result, the moment when this intermediate pressure hump originated might be an important feature of the solar system.”
Izidoro works at Rice’s Department of Earth, Environment, and Planetary Sciences as a postdoctoral research associate. Sean Raymond of the University of Bordeaux, Rogerio Deienno of the Southwest Research Institute, and Bertram Bitsch of the Max Planck Institute for Astronomy are among the other co-authors. NASA (80NSSC18K0828, 80NSSC21K0387), the European Research Council (757448-PAMDORA), the Brazilian Federal Agency for Support and Evaluation of Graduate Education (88887.310463/2018-00), the Welch Foundation (C-2035), and the National Planetology Program of the French National Centre for Scientific Research funded the research.