An array of images of protoplanetary disks with bright suns at the centers surrounded by rings, arcs, filaments and spirals.]

The theory of how planets are made is being changed by the observations of newborn star systems.


The center is where the sun shines. The middle-aged star is unremarkable even though it is more placid than most. It's planets are a different story.

Mercury is more charred than a planet and probably lost its outer layers in a crash. Only one of Venus and Earth is fertile. Mars, like Mercury, never lost layers, but it just stopped growing. We have a large ring of leftover rocks after Mars. The vast majority of the material left over from our star is contained in Jupiter. The planets are made of gas and ice. The rocky planets and gas giants are almost 888-609- 888-609- 888-609- 888-609- 888-609- There is a puzzle about the solar system's eight planets.

Look far beyond the sun. The stars have planets of their own. Thousands of distant star-and-planet systems have been spotted byAstronomers. They have yet to find any that look like ours. The puzzle has become more complex: why these and why those.

The catalog of extrasolar planets, along with observations of distant, dusty planet nurseries and even new data from our own solar system, no longer matches classic theories about how planets are made Planetary scientists, forced to abandon decades-old models, now realize there may not be a grand unified theory of world-making The process of building planets is so complex that it becomes chaotic, according to a leading figure in planetary formation and migration theories.

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New research is being stimulated by the findings. The chaos of world-building has led to the emergence of patterns. Dust and pebble assembly rules are being worked out by teams of researchers. There is fierce debate over the timing of each step and the factors that determine a planet's fate. The oldest questions humans have asked ourselves are how we got here. Is there another place like this?

A Star and Its Acolytes Are Born

The basic outlines of the solar system have been understood for over 300 years. There is a theory that remains correct that was published in 1755 by the German philosopher. He wrote that the spheres belonging to our solar system, all the planets and comets, at the origin of all things were broken down into their basic basic material.

There is a cloud of gas and dust around us. Four and a half billion years ago, the cloud collapsed under its own weight and formed a new star. We don't know how things went down after that.

Surplus gas swirled around the sun after it started to light. There were planets there eventually. A basic planetary disk filled with hydrogen, helium and heavier elements was envisioned by the classical model. The model assumed that planets were formed where we see them today, beginning as small planets and incorporating all the material in their area.

The model assumed that the solar disk was filled with planetesimals, according to a recent review chapter on the field by an astronomer. People didn't consider any small objects.

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Drkowska uses computer simulations to explore the formation of planetesimals and planets out of dust grains.

The way wind sculpts sand dunes was thought to have caused planetesimals to arise. Physicists call it a power law because there are more small ones than large ones. "Just a few years ago, everyone assumed the planetesimals were distributed in a power law throughout the nebula," said Morbidelli, "but now we know it's not the case."

The change was made thanks to a few silver parabolas in the desert. Dust grains around newborn stars are some of the objects that the ALMA is designed to detect. ALMA captured stunning images of neatly sculpted infant star systems with planets embedded in the hazy disks.

The disks were thought to be smooth halos that grew as they moved away from the star. There were disks with deep, dark gaps, like the rings ofSaturn, and others with arcs and spirals. David Nesvorny is an astronomer at the Southwest Research Institute.

The ALMA is located in the desert of Chile.

There is a person named Sergio Otarola who works for the ESO/NAOJ/NARAO.

The classical model of planetary formation was found to be false by ALMA. We have to think about completely different models after rejecting it. The observations show that the earliest planet embryos are made when the dust collects in certain places. The snow line is far away from the star where water freezes. According to Morbidelli and Batygin, dust clumps at a condensation line where silicates form droplets instead of vapor. The rate at which dust falls toward the star is curbed by the condensation lines.

Morbidelli described it as a new paradigm.

From Dust to Planets

Astronomers were trying to understand how dust could accumulate quickly enough to form a giant planet, even before ALMA showed where dust likes to accumulate. Jupiter would have had to collect most of the gas around the sun within 10 million years. Jupiter's core must have formed very quickly after the sun set. The giant planet probably has a fluffy core according to the findings of the mission to Jupiter. How?

Astronomers have known for a long time that turbulence, gas pressure, heat, magnetic fields and other factors would prevent dust from drifting into large piles on the sun. The sun is likely to be drawn into the clumps by gravity.

A new theory for dust clumps was written by Andrew Youdin and Jeremy Goodman in 2005. They argued that after the sun set, gas flowed around the star, causing dust to gather in clumps, and keeping clumps from falling into the star. As they grew bigger, the primordial dust bunnies collapsed under their own weight. Streaming instability is a model for how millimeter-size dust grains can turn into large rocks. The mechanism can form planets about 100 kilometers across.

Astronomers still don't know why Jupiter is so big.

There is a variation on planet growth called pebble accretion. The dwarf planet Ceres that arises through the streaming instability quickly grows larger according to their idea. The dust grains and pebbles would spiral onto each other, like a snowball, because of the gravity and drag in the disk.

Merrill Sherman is a writer for the magazine.

The ALMA images may allow giant planets to form in the first million years after a star is born, according to a theory called pebble accretion. The theory is relevant to the small planets near the sun. The growth of Venus, Earth, Mars and Theia could be traced back to pebbles that weredrifting inward. Problems are still unresolved. The Earth-Theia crash is one of the vital processes that shaped the planets. She said that pebble accretion is very efficient and is a great way to avoid issues with the classical model.

Morbidelli doesn't believe in pebbles forming rocky worlds because of the idea that Earth formed over a long period of time. He stated that it was a matter of location. There are different processes for different environments. Isn't that why not? I think that's a good idea.

Astronomers argue about the precise condensation points in the solar nebula, whether planetesimals start out with rings that fall onto the planets, and when pebble accretion does, and where in a research paper every week. People can't agree on how the world was built.

Planets on the Move

For most of human history, the five wanderers of the night sky were the only known worlds. After 26 years, William Herschel found another wanderer and named him Uranus. Neptune was spotted by a man in the year 1847. The number of known planets suddenly went up.

In 1995 a telescope was pointed at a sunlike star called 51 pegasi, which was wobbling. It is being tugged at by a giant planet closer to it than Mercury is to us. More hot Jupiters were seen around other stars.

The search for exoplanets began after the telescope opened its lens. Most stars have at least one planet, and probably more. We don't have hot Jupiters or a class of worlds that are larger than Neptune but smaller than Earth. There are no star systems that look like ours, with only four rocky planets and four gas giants. It seems to be something that is unique to our solar system.

The Nice model might be able to unify the vastly different planetary architectures. The analysis of the rocks collected by Apollo astronauts suggested that the moon was hit by asteroids 3.8 billion years ago. In 2005, inspired by this evidence, Morbidelli and colleagues in Nice argued that Jupiter, Saturn, Uranus and Neptune did not form in their present locations, but instead moved around 3.8 billion years ago. The theory of the Nice model states that the giant planets changed their orbits so much that asteroids bombarded the inner planets.

The Nice model has stuck despite the fact that the evidence for the Late Heavy Bombardment isn't convincing anymore. According to Morbidelli, Nesvorny and others, the giants probably migrated even earlier in their history, and that Jupiter probably couldn't move all the way to the sun because of the gravity of the planet.

It's possible that we got lucky in our solar system, with multiple giant planets keeping each other in check so that no one swung sunward and destroyed the rocky planets.

Jonathan Lunine is an astronomer at Cornell University. Is it necessary for inward migration to happen when a giant planet is growing? There are combinations of giant planets that could stop that migration. It's a big problem.

According to Morbidelli, there is a debate about the timing of the giant-planet migration, and a possibility that it helped grow the rocky planets rather than threatening to destroy them. Morbidelli launched a five-year project to study whether an unstable orbital configuration after the sun's formation helped stir up rocky remains.

Many researchers think that giant planets and their migrations may affect the fates of their rocky brethren. Jupiter-size worlds can help move asteroids or limit the number of worlds that form. The small stature of Mars could be explained by the fact that Jupiter cut off the supply of material. Many stars studied by the telescope have super-Earths in close proximity, but scientists are not sure if they are more likely to be accompanied by giant planets farther out. A graduate student at the University of Arizona said that teams have shown correlations and anti-correlations between the two exoplanet types. She said that it is fun at conferences. You want to yell at each other, but which science is superior? You aren't sure.

Rebounding Planets

The timing of the Nice model migration has been dramatically changed by a new model. The giant planets may have migrated 100 times earlier than in the original Nice because of gas flow dynamics, according to a paper published in April.

A blond man in a gingham shirt smiles at the camera. Behind him is a framed illustration of a planet undergoing an epic collision.

A rebound mechanism by which giant planets that have moved close to their stars might then move back out has been identified by a planetary scientist.

The Michigan State University has a communications department.

As the sun warmed up the gas in the disk it blew it off into oblivion. When a baby giant planet is bathed in a warm disk of gas, it feels an inward pull towards dense gas closer to the star. The baby planet is moving closer to its star because of the inward pull. The balance changes after a few million years after the star is born. There is more gas on the far side of the planet compared to the star.

The rebound is a big deal. The arrangement can be disrupted by it. This does a good job of explaining the features of the giant planets. Evidence shows that hot Jupiters in other star systems are bound for a rebound.

A complex story is taking shape. Some answers may be hidden for now. The majority of the planet- finding observatories use search methods to find planets that are close to their stars. Astrometry, or the measurement of stars' movements through space, is something Lunine wants to see used by planet hunters. The Nancy Grace Roman Space Telescope is the one that he and others are most looking forward to. The light from a background star is warped by the gravity of a foreground star and its planets. Lunine said that the telescope will be able to capture planets with close proximity to Earth.

Nesvorny said modelers will continue to tinker with code and try to understand the chemistry that may play a role in where planetesimals coalesce. It will take a long time to understand that.

The problem is determined by the time it takes. Our lives are short and the birth of planets lasts for millions of years. We have snapshots from different points.

Batygin compared the effort to reverse engineer planets to trying to model an animal. An ant is more complex than a star. In planet formation, we are somewhere between an ant and a star.