protoplanet hypothesis means

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How Are Planets Formed?

How did the Solar System’s planets come to be? The leading theory is something known as the “protoplanet hypothesis”, which essentially says that very small objects stuck to each other and grew bigger and bigger — big enough to even form the gas giants, such as Jupiter.

But how the heck did that happen? More details below.

Birthing the Sun

About 4.6 billion years ago, as the theory goes, the location of today’s Solar System was nothing more than a loose collection of gas and dust — what we call a nebula. (Orion’s Nebula is one of the most famous examples you can see in the night sky.)

Then something happened that triggered a pressure change in the center of the cloud, scientists say. Perhaps it was a supernova exploding nearby, or a passing star changing the gravity. Whatever the change, however, the cloud collapsed and created a disc of material, according to NASA .

The center of this disc saw a great increase in pressure that eventually was so powerful that hydrogen atoms loosely floating in the cloud began to come into contact. Eventually, they fused and produced helium, kickstarting the formation of the Sun.

The Sun was a hungry youngster — it ate up 99% of what was swirling around, NASA says — but this still left 1% of the disc available for other things. And this is where planet formation began.

Time of chaos

The Solar System was a really messy place at this time, with gas and dust and debris floating around. But planet formation appears to have happened relatively rapidly. Small bits of dust and gas began to clump together. The young Sun pushed much of the gas out to the outer Solar System and its heat evaporated any ice that was nearby.

Over time, this left rockier planets closer to the Sun and gas giants that were further away. But about four billion or so years ago, an event called the “late heavy bombardment” resulted in small bodies pelting the bigger members of the Solar System. We almost lost the Earth when a Mars-sized object crashed into it, as the theory goes.

What caused this is still under investigation, but some scientists believe it was because the gas giants were moving around and perturbing smaller bodies at the fringe of the Solar System. At any rate, in simple terms, the clumping together of protoplanets (planets in formation) eventually formed the planets.

We can still see leftovers of this process everywhere in the Solar System. There is an asteroid belt between Mars and Jupiter that perhaps would have coalesced into a planet had Jupiter’s gravity not been so strong. And we also have comets and asteroids that are sometimes considered referred to as “building blocks” of our Solar System.

We’ve described in detail what happened in our own Solar System, but the important takeaway is that many of these processes are at work in other places. So when we speak about exoplanet systems — planets beyond our Solar System — it is believed that a similar sequence of events took place. But how similar is still being learned.

Making the case

One major challenge to this theory, of course, is no one (that we know of!) was recording the early history of the Solar System. That’s because the Earth wasn’t even formed yet, so it was impossible for any life — let alone intelligent life — to keep track of what was happening to the planets around us.

There are two major ways astronomers get around this problem. The first is simple observation. Using powerful telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers can actually observe dusty discs around young planets. So we have numerous examples of stars with planets being born around them.

The second is using modelling. To test their observational hypotheses, astronomers run computer modelling to see if (mathematically speaking) the ideas work out. Often they will try to use different conditions during the simulation, such as perhaps a passing star triggering changes in the dust cloud. If the model holds after many runs and under several conditions, it’s more likely to be true.

That said, there still are some complications. We can’t use modelling yet to exactly predict how the planets of the Solar System ended up where they were. Also, in fine detail our Solar System is kind of a messy place, with phenomena such as asteroids with moons.

And we need to have a better understanding of external factors that could affect planet formation, such as supernovae (explosions of old, massive stars.) But the protoplanet hypothesis is the best we’ve got — at least for now.

We have written many articles about the protoplanet hypothesis for Universe Today. Here’s an article about how the Solar System was formed , and here’s an article about protoplanets . We’ve also recorded a series of episodes of Astronomy Cast about every planet in the Solar System. Start here, Episode 49: Mercury .

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One Reply to “How Are Planets Formed?”

If the “asteroid” between Mars and Jupiter you’re referring to is Ceres, many planetary scientists argue it did coalesce into a planet, albeit a small one, smaller than it would have been if not for the influence of Jupiter. Ceres is in hydrostatic equilibrium, meaning rounded by its own gravity, is geologically layered into core, mantle, and crust, and may even have cryovolcanism and a subsurface ocean. These all are features of planets.

How many exoplanet system discoveries send planetary scientists back to the drawing board when it comes to understanding planet formation? Very likely, there is more than one way to form a planetary system. We still do not know how hot Jupiters ended up in close orbits around their stars or how giant planets ended up in very distant orbits from their stars. Once we are able to study exoplanet systems as a whole rather than just seeing one planet orbiting a star, a whole new range of possibilities regarding planet formation is likely to be considered.

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What is the Protoplanet theory?

How did the Solar System’s planets come to be? The leading theory is something known as the “protoplanet hypothesis”, which essentially says that very small objects stuck to each other and grew bigger and bigger — big enough to even form the gas giants, such as Jupiter.

Who proposed the protoplanet theory?

W. H. McCrea

In 1960, 1963, and 1978, W. H. McCrea proposed the protoplanet hypothesis, in which the Sun and planets individually coalesced from matter within the same cloud, with the smaller planets later captured by the Sun’s larger gravity.

How does the protoplanet theory explain the origin of the solar system?

The Protoplanet theory

The planets are smaller blobs captured by the star. The small blobs would have higher rotation than is seen in the planets of the Solar System, but the theory accounts for this by having the ‘planetary blobs’ split into planets and satellites .

What are the contributions of protoplanet hypothesis?

Migrating Planets: The protoplanet hypothesis explains most of the features of the Solar System ; however, the outer solar system is still strange, especially the properties of Pluto/Charon. One explanation is that the Solar System was not born in the configuration that we see today.

When was the protoplanet theory proposed?

The floccule/protoplanet theory. In 1960 , McCrea suggested a theory that linked planetary formation with the production of a stellar cluster and also explained the slow rotation of the Sun.

Is Mercury a protoplanet?

Basically, Mercury is pretty much a planet-scale cannonball and not much else . An artist’s impression of the collision between two massive protoplanets early in solar-system history. Such a “big splat” might have left Mercury with a thin silicate mantle overlying a huge, iron-rich core.

What are the 4 theories of the universe?

It’s thought that at such an incomprehensibly dense, energetic state, the four fundamental forces— gravity, electromagnetism, and the strong and weak nuclear forces —were forged into a single force, but our current theories haven’t yet figured out how a single, unified force would work.

What are examples of theories?

Examples include: Physics: the big bang theory, atomic theory, theory of relativity, quantum field theory . Biology: the theory of evolution, cell theory, dual inheritance theory.

Can time be defined?

Physicists define time as the progression of events from the past to the present into the future . Basically, if a system is unchanging, it is timeless. Time can be considered to be the fourth dimension of reality, used to describe events in three-dimensional space.

What are the types of theories?

Different Types of Psychological Theories

• Grand Theories. Grand theories are those comprehensive ideas often proposed by major thinkers such as Sigmund Freud, Erik Erikson,4 and Jean Piaget. …
• Emergent Theories. …
• Behavioral Theories. …
• Humanistic Theories. …
• Personality Theories. …
• Social Psychology Theories.

What are the 3 types of theory?

Although there are many different approaches to learning, there are three basic types of learning theory: behaviorist, cognitive constructivist, and social constructivist .

What is a simple definition of theory?

A theory is a carefully thought-out explanation for observations of the natural world that has been constructed using the scientific method, and which brings together many facts and hypotheses .

What are the five types of theory?

Over the years, academics have proposed a number of theories to describe and explain the learning process – these can be grouped into five broad categories:

• Behaviourist.
• Cognitivist.
• Constructivist.
• Experiential.
• Social and contextual.

What makes a theory a theory?

In everyday use, the word “theory” often means an untested hunch, or a guess without supporting evidence. But for scientists, a theory has nearly the opposite meaning. A theory is a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts .

What are the 6 major psychological theories?

The six Grand Theories in Psychology are: Psychoanalysis, Behaviorism, Cognitivism, Ecological, Humanism, and Evolutionary . The theorists of the well-known theories are (Freud, Erickson), (Watson, Skinner), (Piaget, Vygotsky), (Bronfenbrenner), (Rogers, Maslow), (Lorenz).

What are the two components of theory?

The components of theory are concepts (ideally well defined) and principles . A concept is a symbolic representation of an actual thing – tree, chair, table, computer, distance, etc.

What is the main purpose of theory?

Definition. Theories are formulated to explain, predict, and understand phenomena and, in many cases, to challenge and extend existing knowledge within the limits of critical bounding assumptions.

What are key characteristics of a theory?

A scientific theory should be:

• Testable: Theories can be supported through a series of scientific research projects or experiments. …
• Replicable: In other words, theories must also be able to be repeated by others. …
• Stable: Another characteristic of theories is that they must be stable. …
• Simple: A theory should be simple.

What is theory according to authors?

McQuail (1983) writes that a theory consists of a set of ideas of varying status and origin which seek to explain or interpret some phenomenon . Kurt Lewin (1958), a theory is a way of explaining the ordering and recurrence of various events in the ecosphere.

What is theory according to philosophers?

From Wikipedia, the free encyclopedia. A philosophical theory or philosophical position is a view that attempts to explain or account for a particular problem in philosophy . The use of the term “theory” is a statement of colloquial English and not reflective of the term theory.

What is the purpose of theory in research?

Theories are usually used to help design a research question, guide the selection of relevant data, interpret the data, and propose explanations of the underlying causes or influences of observed phenomena .

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Birth of a New World: Astronomers Confirm Protoplanet 374 Light Years From Earth

By University of Liege June 28, 2023

Image of the HD 169142 system showing the signal of the forming planet HD 169142 b (around 11 o’clock), as well as a bright spiral arm resulting from the dynamic interaction between the planet and the disc in which it is located. The signal from the star, 100,000 times brighter than the planet, was subtracted by a combination of optical components and image processing (mask in the center of the image). Observations at different times show the planet advancing in its orbit over time. Image obtained with ESO’s VLT/SPHERE instrument. Credit: V. Chrisitaens / ULiège

Located 374 light years away from Earth, HD169142 b has been confirmed as a protoplanet by a team of researchers from the University of Liège and Monash University.

An international team of researchers — including Valentin Christiaens from the University of Liège — has just published the results of the analysis of data from the SPHERE instrument of the European Southern Observatory ( ESO ), which confirms a new protoplanet. This result was made possible thanks to advanced image processing tools developed by the PSILab of the University of Liège. The study is published in the Monthly Notices of the Royal Astronomical Society (MNRAS).

Planets form from clumps of material in discs surrounding newborn stars. When the planet is still forming, i.e. when it is still gathering material, it is called a protoplanet . To date, only two protoplanets had been unambiguously identified as such, PDS 70 b and c, both orbiting the star PDS 70. This number has now been increased to three with the discovery and confirmation of a protoplanet in the disk of gas and dust surrounding HD 169142, a star 374 light years from our solar system.

A protoplanet is an embryonic planet, a large body that is in the process of becoming a planet. It forms from a concentration of gas and dust within a protoplanetary disc, a ring of material that orbits a newly formed star. As this material begins to coalesce, it creates a protoplanet that gradually grows by attracting more of the surrounding material through its increasing gravitational pull.

“We used observations from the SPHERE instrument of the European Southern Observatory’s ( ESO ) Very Large Telescope ( VLT ) obtained on the star HD 169142, which was observed several times between 2015 and 2019,” explains Iain Hammond, a researcher at Monash University (Australia) who stayed at ULiège as part of his doctoral thesis. “As we expect planets to be hot when they form, the telescope took infrared images of HD 169142 to look for the thermal signature of their formation. With these data, we were able to confirm the presence of a planet, HD 169142 b, about 37 AU (37 astronomical units, or 37 times the distance from the Earth to the Sun) from its star — slightly further than the orbit of Neptune .”

Back in 2020, a team of researchers led by R. Gratton had previously hypothesized that a compact source seen in their images could trace a protoplanet. Our new study confirms this hypothesis through both a re-analysis of the data used in their study as well as the inclusion of new observations of better quality.

The different images, obtained with VLT’s SPHERE instrument between 2015 and 2019, reveal a compact source that is moving over time as expected for a planet orbiting at 37 astronomical units from its star. All data sets obtained with the SPHERE instrument were analyzed with state-of-the-art image processing tools developed by the PSILab team at the University of Liège .

The last data set considered in our study, obtained in 2019, is crucial for the confirmation of the planet’s motion,” explains Valentin Christiaens, F.R.S.-FNRS research fellow at the PSILab ( STAR Institute / Faculty of Science ) of the ULiège. “This data set had not been published until now.”

A protoplanetary disc is a flat, rotating disc of dense gas and dust that surrounds a newly formed star. It forms from the original molecular cloud that collapsed to form the star and contains the leftover material that didn’t end up in the star itself. These discs play a crucial role in planetary system formation, as they are the environment in which protoplanets form and grow.

The new images also confirm that the planet must have carved an annular gap in the disc — as predicted by the models. This gap is clearly visible in polarized light observations of the disc.

“In the infrared, we can also see a spiral arm in the disc, caused by the planet and visible in its wake, suggesting that other protoplanetary discs containing spirals may also harbor yet undiscovered planets,” says Hammond.

The polarized light images, as well as the infrared spectrum measured by the research team, further indicate that the planet is buried in a significant amount of dust that it has accreted from the protoplanetary disc. This dust could be in the form of a circumplanetary disc, a small disc that forms around the planet itself, which in turn could form moons. This important discovery demonstrates that the detection of planets by direct imaging is possible even at a very early stage of their formation.

“There have been many false positives among the detections of planets in formation over the last ten years,” says Valentin Christiaens. “Apart from the protoplanets of the PDS 70 system, the status of the other candidates is still hotly debated in the scientific community. The protoplanet HD 169142 b seems to have different properties to the protoplanets of the PDS 70 system, which is very interesting. It seems that we have captured it at a younger stage of its formation and evolution, as it is still completely buried in or surrounded by a lot of dust.”

Given the very small number of confirmed forming planets to date, the discovery of this source and its follow-up should give us a better understanding of how planets, and in particular giant planets such as Jupiter , are formed.

Further characterization of the protoplanet and independent confirmation could be obtained through future observations with the James Webb Space Telescope ( JWST ). The high sensitivity of JWST to infrared light should indeed allow researchers to detect thermal emissions from the hot dust around the planet.

Reference: “Confirmation and Keplerian motion of the gap-carving protoplanet HD 169142 b” by Iain Hammond, Valentin Christiaens, Daniel J Price, Claudia Toci, Christophe Pinte, Sandrine Juillard and Himanshi Garg, 4 April 2023, Monthly Notices of the Royal Astronomical Society: Letters . DOI: 10.1093/mnrasl/slad027

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1 comment on "birth of a new world: astronomers confirm protoplanet 374 light years from earth".

“Given the very small number of confirmed forming planets to date, the discovery of this source and its follow-up should give us a better understanding of how planets, and in particular giant planets such as Jupiter, are formed.”

The paper discussion confirms that a (super)Jupiter massed candidate protoplanet is most likely.

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Protoplanet Theory and Earth’s Formation

No one really knows for sure how the Solar System began. It would be like ask­ing a child to give an account of his birth or a descrip­tion of his conception. Religious scriptures explain the creation of the Earth in compelling ways, but no two accounts agree exactly. Some of them, however, do come quite close to the scientist's idea of creation-or, at least, to the readings of the evidence lodged in the Earth's ancient rocks.

In exploring the origin of the Earth we must at the same time try to explain the beginning of the Solar Sys­tem, for the Earth's past is intimately tied to the history of our nearest neighbors in space.

In 1755 the German philosopher Immanuel Kant published his theory of the heavens, postulating that in the beginning there was an immense, cold whirling cloud of dust and gas. This suggestion is accepted readily by astronomers today. Their extremely powerful modern telescopes show re­mote, dark clouds of dust floating between distant stars -clouds that must even now be similar to the local, swirling cloud that Kant had in mind.

In 1796 Kant's contemporary, the French mathemati­cian Pierre Simon Laplace, took his idea a step further by suggesting how the Solar System might have formed from such a cloud.

The immense mass was set spinning by cosmic forces, Laplace hypothesized. At the same time it began to shrink in size under the gravitational pull of its own matter. At intervals, the contracting cloud shed veils of particles into space, which eventualy condensed into the planets. Shrinking under the force of its own gravity, meanwhile, the central mass became the Sun.

As potent as Laplace's concept was, it fell victim to fundamental physical laws of more recent discovery. Calculations based on these laws show that a shrinking Sun would spin faster and faster as it grew smaller and smaller, until today it would be rotating at a far greater speed than it actually is.

After Laplace's brilliantly imaginative picture was shown to contain flaws, several other seemingly plausi­ble suggestions were put forward by astronomers. One theory assumed the formation of the Sun first, with no planets. Then, a second star passing close by in space tore out a long stream of material. The planets, it was suggested, might then have condensed around the Sun, with the passing star continuing on its way. Unfortu­nately, calculations show that such hot material from the Sun would disperse, rather than form planets. Even if by some unknown process planets were to condense, their orbits would be much more irregular than those found in the Solar System today.

Another theory held that in the distant past of the cosmos, or universe, the Sun had a twin companion, and a passing star collided with its twin. Out of the debris resulting from such a collision, planets might possibly form in orbits around the single remaining sun. But the great distances at which the stars are scattered in space make collisions of this type most unlikely. If such a catastrophe did occur, it seems impossible that planets could form directly from the intensely hot and volatile material of the exploding stars. Both the "close encoun­ter" theory and the "collision" theory fail on one fur­ther count; neither explains how most of the planets have obtained moons.

More recently, cosmologists went back to the sugges­tion of Kant, careful to avoid the pitfall of Laplace. A theory took shape from the combined efforts of astronomers, mathematicians, chemists and geolo­gists. This hypothesis is called the "nebular" or "proto-planet" theory. It gives unity to so many seemingly disparate details of material reality that a majority of cosmologists have become convinced that it cor­rectly accounts for at least the broad features of cosmic evolution.

In the cold depths of the cloud surrounding the proto-Sun, certain atoms of gas combined to form com­pounds, such as water and ammonia. Slowly, solid dust crystals began to grow as did metallic crystals, includ­ing iron and stony silicates. And, gradually, gravita­tional and centrifugal forces at work in the spinning cloud flattened it into the shape of an enormous protoplanetary disc.

If we could have viewed the events at a great distance, our eyes would have beheld something like a gigantic, re­volving vinyl record, with the proto-Sun in the hole at the center.

Within the huge whirling disk, local eddies continued to appear. Some of the swirls were doubtless torn apart in collisions, while others were broken up by the in­creasingly strong gravitational pull of the proto-Sun. In a sense, each small eddy was carrying on a fight for survival. To hold itself together in the face of such dis­ruptive forces, an eddy had somehow to collect a cer­tain critical amount of substance to provide its own center of gravity.

In a kind of cosmic battle within the wheeling system, some local swirls gained material as others lost it. Ultimately a series of large whirling disks developed in the region around the Sun. Each was a proto-planet.

These proto-planets were sufficiently large to hold together under the strength of their own gravitational fields. As each moved through space around the Sun, it acted as a sort of scavenger, sweeping up leftover mate­rial from the original cloud.

At this stage thermonuclear fusion began in the core of the proto-Sun releasing large amounts of energy, and the proto-Sun began to shine. It "burned" fitfully at first, a dull red. In time it was to become the golden yellow star that we see today. Remember that the proto-Sun was about one hundred times larger in diam­eter than the proto-planets. It was this immense differ­ence in size, of course, that caused it to become a star rather than a planet. Its strong gravitational pull was sufficient to trap light hydrogen atoms in its interior, triggering thermonuclear fusion. Such was not the case with the smaller proto-planets.

Somewhere in the region of the proto-Sun, then, proto-Earth was born as a whirling cloud of icy parti­cles and solid fragments-a cosmic dust storm. Only later did this material collect into a ball, sticking to­gether because of the cohesive attraction of water and ice molecules. As proto-Earth orbited around the Sun, it swept up more material by gravitational attraction. Thus the Earth and the other planets formed by the process of accumulation of cold dusts from the region of space near the Sun.

Gradually radioactive elements within the cold ball of dust that was Earth began to give off heat. After mil­lions of years the Earth's temperature became high enough to melt the material at its center. At that time, the heavy metals-iron and nickel-that were spread throughout the ball began to sink to form the molten core of the planet. Afterward, molten rock frequently broke through fissures to the surface. And slowly, molecules of hydrogen, water vapor and other gases escaped from within to create an atmosphere above the planet's surface. But these light gases did not stay with the Earth for long. A second major source of heat was already in action-the rays of the Sun.

The Sun's radiation was now striking the Earth with full intensity, breaking up the molecular compounds in its primitive atmosphere and scattering them into space. Thus most of the atmospheric hydrogen and other light elements escaped from the Earth. This process eventu­ally left behind a high concentration of the heavier, rarer elements of the universe-elements essential for the formation of rocks, plants and our own bodies.

Be­cause of the escape into space over billions of years of such light atoms as hydrogen, the Earth now contains about one thousand times less mass than was present in proto-Earth when it condensed from the dust cloud. The origin of the Moon remains an enigma to scien­tists. Did it form at the edge of proto-Earth? Or did it form elsewhere in space as a separate planet that was later captured by the Earth's gravitational field? Or another theory is that the Moon was the result of a massive asteroid impact with the Earth. Cosmologists favor these last two possibilities rather than the older theory that the Moon was ripped out of that part of the Earth that is now the Pacific Ocean basin. And with the advent of manned exploration of the Moon like to be restarted very soon, it seems likely that the scientific enigma of the Moon will one day be solved.

The story of the Earth has almost reached the point where it can be taken up by a geologist. After the Earth stopped collecting debris from its path in space, its sur­face gradually cooled and became solid. A crust of rock formed; land masses appeared. But the Earth was not yet ready to support life as we know it today; its sur­face was still too hot for living organisms and the atmosphere was heavy with poisonous methane and ammonia. Molten lava flowed from fissures in the crust, allowing the escape of steam that had been trapped in the Earth's molten interior. In fact, many geologists think that this early volcanic activity brought to the surface most of the water that forms the present-day oceans-water originally trapped in icy dust.

As volcanic activity decreased on the Earth, intense ultraviolet radiation from the Sun broke up a portion of the atmospheric water molecules into separate atoms of hydrogen and oxygen. The Earth's gravitational pull wasn't strong enough to retain the lighter hydrogen atoms, and most of them drifted off into space. The heavier oxygen atoms would have remained. Although some free oxygen was thus liberated in the Earth's evolv­ing atmosphere, the gases methane and ammonia must have remained preponderant for a long time, since most of the free oxygen in today's atmosphere is known to exist as the byproduct of photosynthesis in plants, in­cluding the algae of lakes and oceans.

Year by year the Earth became cooler as it radiated heat and proto-Sun faded to the intensity of brightness we know now.

Soon the Earth's atmosphere had cooled enough to cause water vapor in the air to condense and fall back to the surface as rain. At first, the raindrops spattering on the hot surface boiled back in a hiss of steam. Eventually, though, the Earth cooled sufficiently to permit pools of water to collect over the surface. Soon the cooling atmosphere must have begun to yield tremendous amounts of rain.

All the water in the seven seas may have descended in one long continuous deluge. Gradually the shallow areas in the wrinkled crust filled, and oceans appeared on the face of the Earth.

Although scientists are generally convinced that the Earth on which we live has passed through the stages of development outlined in the previous paragraphs, no one, of course, can vouch for the exact chronology. Probably, proto-Earth reached its present size and shape some four and a half billion years ago.

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Planets Still Forming Detected in a Protoplanetary Disk

Just as the number of planets discovered outside our solar system is large and growing — more than 3,700 confirmed at last count — so too is the number of ingenious ways to find exoplanets ever on the rise.

The first exoplanets were found by measuring the “wobble” in their host stars caused by the gravitational pull of the planets, then came the transit technique that measured dips in the light from stars as planets passed in front of them, followed by the direct imaging of moving objects deemed to be planets, and numerous more.

A new technique can now be added to the toolkit, one that is useful only in specific galactic circumstances but is nonetheless ingenious and intriguing.

By detecting unusual patterns in the flow of gas within the protoplanetary disk of a young star, two teams of astronomers have confirmed the distinct, telltale hallmarks of newly formed planets orbiting the infant star.

In other words, the astronomers found planets in the process of being formed, circling a star very early in its life cycle.

These results came thanks to the Atacama Large Millimeter/submillimeter Array ( ALMA ), and are presented in a pair of papers appearing in the Astrophysical Journal Letters.

Richard Teague, an astronomer at the University of Michigan and principal author on one of the papers , said that his team looked at “the localized, small-scale motion of gas in a star’s protoplanetary disk. This entirely new approach could uncover some of the youngest planets in our galaxy, all thanks to the high-resolution images coming from ALMA .”

To make their respective discoveries, each team analyzed the data from various ALMA observations of the young star HD 163296, which is about 4 million years old and located about 330 light-years from Earth in the direction of the constellation Sagittarius.

Rather than focusing on the dust within the disk, which was clearly imaged in an earlier ALMA observation, the astronomers instead studied the distribution and motion of carbon monoxide (CO) gas throughout the disk.

As explained in a release from the National Radio Astronomy Observatory, which manages the American operations of the multi-national ALMA , molecules of carbon monoxide naturally emit a very distinctive millimeter-wavelength light that ALMA can observe. Subtle changes in the wavelength of this light due to the Doppler effect provide a glimpse into the motion of the gas in the disk.

If there were no planets, gas would move around a star in a very simple, predictable pattern known as Keplerian rotation.

“It would take a relatively massive object, like a planet, to create localized disturbances in this otherwise orderly motion,” said Christophe Pinte of Monash University in Australia and lead author on the other of the two papers.

And that’s what both teams found.

Detecting planets within a protoplanetary disk — or finding theorized planets within those disks — is a big deal.

That’s because information about the characteristics of very young planets orbiting young stars can potentially add substantially to one of the long-debated questions of planetary science: How exactly did those billions upon billions of planets out there form?

The leading theory of planet formation, the “core accretion model,” has planets forming slowly — with dust, small objects and then planetesimals smashing into a rocky core and leaving matter behind. In this model, the planet building takes place in a region close to the protoplanet’s stars.

Another theory looks to gravitational instabilities in the disk, arguing that giant planets can form quickly and far from their host stars.

The distribution of current solar system planets and beyond can give some clues based on the size, type and distribution of those planets. But planets migrate and evolve, and they have never been studied before they had a chance to do much of either.

The techniques currently used for finding exoplanets in fully formed planetary systems — such as measuring the wobble of a star or how a transiting planet dims starlight — don’t lend themselves to detecting protoplanets.

With this new method for looking into those early protoplanetary disks, the hunt for infant planets becomes possible. And the results in terms of understanding planet formation look to be very promising.

“Though thousands of exoplanets have been discovered in the last few decades, detecting protoplanets is at the frontier of science,” said Pinte.

This is not the first time that ALMA images of protoplanetary disks have been used to identify what seem to be protoplanets.

In 2016, a team led by Andrea Isella of Rice University reported the possible detection of two planets, each the size of Saturn, orbiting the same star that is the subject of this week’s report, HD 163296.

These possible planets, which are not yet fully formed, revealed themselves by the dual imprint they left in both the dust and the gas portions of the star’s protoplanetary disk.

But at the time that paper was published, in Physical Review Letters , Isella said the team was focused primarily on the dust in the disks and the gaps they created, and as a result they could not be certain that the features they found were created by a protoplanet.

Teague’s team also studied the dust gaps in the disk of HD 163296, and concluded they provided only circumstantial evidence of the presence of protoplanets. What’s more, that kind of detection could not be used to accurately estimate the masses of the planets.

“Since other mechanisms can also produce ringed gaps in a protoplanetary disk,” he said, “it is impossible to say conclusively that planets are there by merely looking at the overall structure of the disk.”

But studying the behavior of the gas allowed for a much greater degree of confidence.

The team led by Teague identified two distinctive planet-like patterns in the disk, one at approximately 80 astronomical units (AU) from the star and the other at 140 AU. (An astronomical unit is the average distance from the Earth to the sun.) The other team, led by Pinte, identified the third at about 260 AU from the star. The astronomers calculate that all three planets are similar in mass to Jupiter.

The two teams used variations on the same technique, which looked at anomalies in the flow of the gas – as seen in the shifting wavelengths of the CO emission — that would indicate it was interacting with a massive object.

Teague and his team measured variations in the gas’s velocity. This revealed the impact of several planets on the gas motion nearer to the star.

Pinte and his team more directly measured the gas’s actual velocity, which is better precise method when studying the outer portion of the disk and can more accurately pinpoint the location of a potential planet.

“Although dust plays an important role in planet formation and provides invaluable information, gas accounts for 99 percent of a protoplanetary disks’ mass,” said coauthor Jaehan Bae of the Carnegie Institute for Science.

So while those images of patterns within the concentric rings of a protoplanetary disk are compelling and seem to be telling an important story, it’s actually the gas that is the key.

This is all an important coup for ALMA , which saw its first light in 2013. The observatory was not designed with protoplanet detection and characterization as a primary goal, but it is now front and center.

Coauthor Til Birnstiel of the University Observatory of Munich said the precision provided by ALMA is “mind boggling.” In a system where gas rotates at about 5 kilometers per second, he said, ALMA detected velocity changes as small as a few meters per second.

“Oftentimes in science, ideas turn out not to work or assumptions turn out to be wrong,” he said. “This is one of the cases where the results are much more exciting than what I had imagined.

Observed features any origin model of the solar system/planets must explain

Atoms in your body, collapsing clouds of gas and dust in nebular hypothesis, the spinning nebula flattens, condensation of protosun and protoplanets, the composition of the sun, the two classes of planets, etc. explained by the nebula hypothesis:, evidence for the nebular hypothesis.

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• Published: 30 December 2021

Planetesimal rings as the cause of the Solar System’s planetary architecture

• Andre Izidoro   ORCID: orcid.org/0000-0003-1878-0634 1 ,
• Rajdeep Dasgupta   ORCID: orcid.org/0000-0001-5392-415X 1 ,
• Sean N. Raymond   ORCID: orcid.org/0000-0001-8974-0758 2 ,
• Rogerio Deienno   ORCID: orcid.org/0000-0001-6730-7857 3 ,
• Bertram Bitsch   ORCID: orcid.org/0000-0002-8868-7649 4 &
• Andrea Isella 5  

Nature Astronomy volume  6 ,  pages 357–366 ( 2022 ) Cite this article

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• Astrophysical disks
• Computational astrophysics
• Early solar system
• Inner planets

Astronomical observations reveal that protoplanetary disks around young stars commonly have ring- and gap-like structures in their dust distributions. These features are associated with pressure bumps trapping dust particles at specific locations, which simulations show are ideal sites for planetesimal formation. Here we show that our Solar System may have formed from rings of planetesimals—created by pressure bumps—rather than a continuous disk. We model the gaseous disk phase assuming the existence of pressure bumps near the silicate sublimation line (at T  ~ 1,400 K), water snowline (at T  ~ 170 K) and CO snowline (at T  ~ 30 K). Our simulations show that dust piles up at the bumps and forms up to three rings of planetesimals: a narrow ring near 1 au, a wide ring between ~3–4 au and ~10–20 au and a distant ring between ~20 au and ~45 au. We use a series of simulations to follow the evolution of the innermost ring and show how it can explain the orbital structure of the inner Solar System and provides a framework to explain the origins of isotopic signatures of Earth, Mars and different classes of meteorites. The central ring contains enough mass to explain the rapid growth of the giant planets’ cores. The outermost ring is consistent with dynamical models of Solar System evolution proposing that the early Solar System had a primordial planetesimal disk beyond the current orbit of Uranus.

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Data availability

Simulation data that support the findings of this study or were used to make the plots are available from the corresponding author upon reasonable request. Source data associated with the main figures of the manuscript are available at https://andreizidoro.com/simulation-data .

Code availability

Dust evolution simulations were performed using a modified version of the code Two-pop-py 5 , publicly available at https://github.com/birnstiel/two-pop-py , with modifications described in ref. 20 . N -body simulations modelling the growth of planetesimals to planetary embryos were performed using LIPAD 93 . This is a proprietary software product funded by the Southwest Research Institute that is not publicly available. It is based on the N -body integrator SyMBA, which is publicly available at https://www.boulder.swri.edu/swifter/ . Simulations of the late stage of accretion of terrestrial planets were performed using the Mercury N -body integrator 94 , publicly available at https://github.com/4xxi/mercury .

DeMeo, F. E. & Carry, B. Solar System evolution from compositional mapping of the asteroid belt. Nature 505 , 629–634 (2014).

Article   ADS   Google Scholar  

Kruijer, T. S., Kleine, T. & Borg, L. E. The great isotopic dichotomy of the early Solar System. Nat. Astron. 4 , 32–40 (2020).

Grewal, D. S., Dasgupta, R. & Marty, B. A very early origin of isotopically distinct nitrogen in inner Solar System protoplanets. Nat. Astron. 5 , 356–364 (2021).

Brasser, R. & Mojzsis, S. J. The partitioning of the inner and outer Solar System by a structured protoplanetary disk. Nat. Astron. 4 , 492–499 (2020).

Birnstiel, T., Klahr, H. & Ercolano, B. A simple model for the evolution of the dust population in protoplanetary disks. Astron. Astrophys. 539 , A148 (2012).

Article   ADS   MATH   Google Scholar  

Walsh, K. J., Morbidelli, A., Raymond, S. N., O’Brien, D. P. & Mandell, A. M. A low mass for Mars from Jupiter’s early gas-driven migration. Nature 475 , 206–209 (2011).

Raymond, S. N. & Izidoro, A. Origin of water in the inner Solar System: planetesimals scattered inward during Jupiter and Saturn’s rapid gas accretion. Icarus 297 , 134–148 (2017).

Huang, J. et al. The Disk Substructures at High Angular Resolution Project (DSHARP). II. Characteristics of annular substructures. Astrophys. J. Lett. 869 , L42 (2018).

Dullemond, C. P. et al. The Disk Substructures at High Angular Resolution Project (DSHARP). VI. Dust trapping in thin-ringed protoplanetary disks. Astrophys. J. Lett. 869 , L46 (2018).

Johansen, A. et al. Rapid planetesimal formation in turbulent circumstellar disks. Nature 448 , 1022–1025 (2007).

Müller, J., Savvidou, S. & Bitsch, B. The water-ice line as a birthplace of planets: implications of a species-dependent dust fragmentation threshold. Astron. Astrophys. 650 , A185 (2021).

Charnoz, S., Avice, G., Hyodo, R., Pignatale, F. C. & Chaussidon, M. Forming pressure traps at the snow line to isolate isotopic reservoirs in the absence of a planet. Astron. Astrophys. 652 , A35 (2021).

Gundlach, B. & Blum, J. The stickiness of micrometer-sized water-ice particles. Astrophys. J. 798 , 34 (2015).

Desch, S. J. & Turner, N. J. High-temperature ionization in protoplanetary disks. Astrophys. J. 811 , 156 (2015).

Flock, M., Fromang, S., Turner, N. J. & Benisty, M. 3D radiation nonideal magnetohydrodynamical simulations of the inner rim in protoplanetary disks. Astrophys. J. 835 , 230 (2017).

Qi, C. et al. Imaging of the CO snow line in a solar nebula analog. Science 341 , 630–632 (2013).

van ’t Hoff, M. L. R., Walsh, C., Kama, M., Facchini, S. & van Dishoeck, E. F. Robustness of N 2 H + as tracer of the CO snowline. Astron. Astrophys. 599 , A101 (2017).

Article   Google Scholar  

Pinilla, P. et al. Trapping dust particles in the outer regions of protoplanetary disks. Astron. Astrophys. 538 , A114 (2012).

Dittrich, K., Klahr, H. & Johansen, A. Gravoturbulent planetesimal formation: the positive effect of long-lived zonal flows. Astrophys. J. 763 , 117 (2013).

Izidoro, A., Bitsch, B. & Dasgupta, R. The effect of a strong pressure bump in the Sun’s natal disk: terrestrial planet formation via planetesimal accretion rather than pebble accretion. Astrophys. J. 915 , 62 (2021).

Dra̧żkowska, J. & Alibert, Y. Planetesimal formation starts at the snow line. Astron. Astrophys. 608 , A92 (2017).

Simon, J. B., Armitage, P. J., Li, R. & Youdin, A. N. The mass and size distribution of planetesimals formed by the streaming instability. I. The role of self-gravity. Astrophys. J. 822 , 55 (2016).

Chambers, J. A semi-analytic model for oligarchic growth. Icarus 180 , 496–513 (2006).

Tanaka, H., Takeuchi, T. & Ward, W. R. Three-dimensional interaction between a planet and an isothermal gaseous disk. I. Corotation and Lindblad torques and planet migration. Astrophys. J. 565 , 1257–1274 (2002).

Lambrechts, M. et al. Formation of planetary systems by pebble accretion and migration. How the radial pebble flux determines a terrestrial-planet or super-Earth growth mode. Astron. Astrophys. 627 , A83 (2019).

Hansen, B. M. S. Formation of the terrestrial planets from a narrow annulus. Astrophys. J. 703 , 1131–1140 (2009).

Izidoro, A., Haghighipour, N., Winter, O. ~C. & Tsuchida, M. Terrestrial planet formation in a protoplanetary disk with a local mass depletion: a successful scenario for the formation of Mars. Astrophys. J. 782 , 31 (2014).

Izidoro, A., Raymond, S. N., Morbidelli, A. & Winter, O. C. Terrestrial planet formation constrained by Mars and the structure of the asteroid belt. Mon. Not. R. Astron. Soc. 453 , 3619–3634 (2015).

Levison, H. F., Kretke, K. A. & Duncan, M. J. Growing the gas-giant planets by the gradual accumulation of pebbles. Nature 524 , 322–324 (2015).

Raymond, S. N. & Izidoro, A. The empty primordial asteroid belt. Sci. Adv. 3 , e1701138 (2017).

Morbidelli, A. et al. Fossilized condensation lines in the Solar System protoplanetary disk. Icarus 267 , 368–376 (2016).

Warren, P. H. Stable-isotopic anomalies and the accretionary assemblage of the Earth and Mars: a subordinate role for carbonaceous chondrites. Earth Planet. Sci. Lett. 311 , 93–100 (2011).

Dauphas, N. et al. Calcium-48 isotopic anomalies in bulk chondrites and achondrites: evidence for a uniform isotopic reservoir in the inner protoplanetary disk. Earth Planet. Sci. Lett. 407 , 96–108 (2014).

Wittmann, A. et al. Petrography and composition of Martian regolith breccia meteorite Northwest Africa 7475. Meteorit. Planet. Sci. 50 , 326–352 (2015).

Lodders, K. An oxygen isotope mixing model for the accretion and composition of rocky planets. Space Sci. Rev. 92 , 341–354 (2000).

Dauphas, N. The isotopic nature of the Earth’s accreting material through time. Nature 541 , 521–524 (2017).

Brasser, R., Mojzsis, S. J., Matsumura, S. & Ida, S. The cool and distant formation of Mars. Earth Planet. Sci. Lett. 468 , 85–93 (2017).

Bottke, W. F., Nesvorný, D., Grimm, R. E., Morbidelli, A. & O’Brien, D. P. Iron meteorites as remnants of planetesimals formed in the terrestrial planet region. Nature 439 , 821–824 (2006).

Chambers, J. E. Making more terrestrial planets. Icarus 152 , 205–224 (2001).

Kokubo, E. & Ida, S. Formation of protoplanet systems and diversity of planetary systems. Astrophys. J. 581 , 666–680 (2002).

Bus, S. J. & Binzel, R. P. Phase II of the Small Main-Belt Asteroid Spectroscopic Survey. A feature-based taxonomy. Icarus 158 , 146–177 (2002).

Urey, H. C. The cosmic abundances of potassium, uranium, and thorium and the heat balances of the Earth, the Moon, and Mars. Proc. Natl Acad. Sci. USA 41 , 127–144 (1955).

Vernazza, P., Zanda, B., Nakamura, T., Scott, E. R. D. & Russell, S. In The Formation and Evolution of Ordinary Chondrite Parent Bodies (eds Bottke, W. F., DeMeo, F. E. & Michel, P.) 617–634 (University of Arizona Press, 2015).

Weiss, B. P. & Elkins-Tanton, L. T. Differentiated planetesimals and the parent bodies of chondrites. Annu. Rev. Earth Planet. Sci. 41 , 529–560 (2013).

Neumann, W., Kruijer, T. S., Breuer, D. & Kleine, T. Multistage core formation in planetesimals revealed by numerical modeling and Hf–W chronometry of iron meteorites. J. Geophys. Res. Planets 123 , 421–444 (2018).

Sanders, I. S. & Scott, E. R. D. The origin of chondrules and chondrites: debris from low-velocity impacts between molten planetesimals? Meteorit. Planet. Sci. 47 , 2170–2192 (2012).

Moskovitz, N. & Gaidos, E. Differentiation of planetesimals and the thermal consequences of melt migration. Meteorit. Planet. Sci. 46 , 903–918 (2011).

Asphaug, E., Jutzi, M. & Movshovitz, N. Chondrule formation during planetesimal accretion. Earth Planet. Sci. Lett. 308 , 369–379 (2011).

Desch, S. J. & Connolly, J. H. C. A model of the thermal processing of particles in solar nebula shocks: application to the cooling rates of chondrules. Meteorit. Planet. Sci. 37 , 183–207 (2002).

Yang, C. C., Johansen, A. & Carrera, D. Concentrating small particles in protoplanetary disks through the streaming instability. Astron. Astrophys. 606 , A80 (2017).

Kunitomo, M., Guillot, T., Ida, S. & Takeuchi, T. Revisiting the pre-main-sequence evolution of stars. II. Consequences of planet formation on stellar surface composition. Astron. Astrophys. 618 , A132 (2018).

Izidoro, A., Morbidelli, A., Raymond, S. N., Hersant, F. & Pierens, A. Accretion of Uranus and Neptune from inward-migrating planetary embryos blocked by Jupiter and Saturn. Astron. Astrophys. 582 , A99 (2015).

Tsiganis, K., Gomes, R., Morbidelli, A. & Levison, H. F. Origin of the orbital architecture of the giant planets of the Solar System. Nature 435 , 459–461 (2005).

Nesvorný, D. Dynamical evolution of the early Solar System. Annu. Rev. Astron. Astrophys. 56 , 137–174 (2018).

Deienno, R., Morbidelli, A., Gomes, R. S. & Nesvorný, D. Constraining the giant planets’ initial configuration from their evolution: implications for the timing of the planetary instability. Astron. J. 153 , 153 (2017).

Nesvorný, D. et al. OSSOS XX: the meaning of Kuiper Belt colors. Astron. J. 160 , 46 (2020).

Gladman, B., Marsden, B. G. & Vanlaerhoven, C. In The Solar System Beyond Neptune (eds Barucci, M. A., Boehnhardt, H., Cruikshank, D. P. & Morbidelli, A.) 43–57 (University of Arizona Press, 2008).

Fressin, F. et al. The false positive rate of Kepler and the occurrence of planets. Astrophys. J. 766 , 81 (2013).

Mayor, M. et al. The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets. Preprint at https://arxiv.org/abs/1109.2497 (2011).

Izidoro, A. et al. Formation of planetary systems by pebble accretion and migration. Hot super-Earth systems from breaking compact resonant chains. Astron. Astrophys. 650 , A152 (2021).

Morbidelli, A. Planet formation by pebble accretion in ringed disks. Astron. Astrophys. 638 , A1 (2020).

Lambrechts, M., Johansen, A. & Morbidelli, A. Separating gas-giant and ice-giant planets by halting pebble accretion. Astron. Astrophys. 572 , A35 (2014).

Raymond, S. N., Izidoro, A. & Morbidelli, A. In Solar System Formation in the Context of Extra-Solar Planets inPlanetary Astrobiology (eds Meadows, V. S., Arney, G. N., Schmidt, B. E. & Des Marais, D. J.) (University of Arizona Press, 2020).

Pinilla, P., Pohl, A., Stammler, S. M. & Birnstiel, T. Dust density distribution and imaging analysis of different ice lines in protoplanetary disks. Astrophys. J. 845 , 68 (2017).

Dra̧żkowska, J. & Dullemond, C. P. Planetesimal formation during protoplanetary disk buildup. Astron. Astrophys. 614 , A62 (2018).

Ueda, T., Flock, M. & Okuzumi, S. Dust pileup at the dead-zone inner edge and implications for the disk shadow. Astrophys. J. 871 , 10 (2019).

Ida, S., Guillot, T. & Morbidelli, A. The radial dependence of pebble accretion rates: a source of diversity in planetary systems. I. Analytical formulation. Astron. Astrophys. 591 , A72 (2016).

Zhang, Y. & Jin, L. The evolution of the snow line in a protoplanetary disk. Astrophys. J. 802 , 58 (2015).

Zhang, K., Blake, G. A. & Bergin, E. A. Evidence of fast pebble growth near condensation fronts in the HL Tau protoplanetary disk. Astrophys. J. Lett. 806 , L7 (2015).

Baillié, K., Marques, J. & Piau, L. Building protoplanetary disks from the molecular cloud: redefining the disk timeline. Astron. Astrophys. 624 , A93 (2019).

Bitsch, B., Morbidelli, A., Lega, E. & Crida, A. Stellar irradiated discs and implications on migration of embedded planets. II. Accreting-discs. Astron. Astrophys. 564 , A135 (2014).

Ziampras, A., Ataiee, S., Kley, W., Dullemond, C. P. & Baruteau, C. The impact of planet wakes on the location and shape of the water ice line in a protoplanetary disk. Astron. Astrophys. 633 , A29 (2020).

Birnstiel, T., Andrews, S. M., Pinilla, P. & Kama, M. Dust evolution can produce scattered light gaps in protoplanetary disks. Astrophys. J. Lett. 813 , L14 (2015).

Drążkowska, J., Alibert, Y. & Moore, B. Close-in planetesimal formation by pile-up of drifting pebbles. Astron. Astrophys. 594 , A105 (2016).

Asplund, M., Grevesse, N., Sauval, A. J. & Scott, P. The chemical composition of the Sun. Annu. Rev. Astron. Astrophys. 47 , 481–522 (2009).

Desch, S. J., Kalyaan, A. & O’D. Alexander, C. M. The effect of Jupiter’s formation on the distribution of refractory elements and inclusions in meteorites. Astrophys. J. Suppl. Ser. 238 , 11 (2018).

Pinilla, P., Lenz, C. T. & Stammler, S. M. Growing and trapping pebbles with fragile collisions of particles in protoplanetary disks. Astron. Astrophys. 645 , A70 (2021).

Schneider, A. D. & Bitsch, B. How drifting and evaporating pebbles shape giant planets. I. Heavy element content and atmospheric C/O. Astron. Astrophys. 654 , A71 (2021).

Lenz, C. T., Klahr, H., Birnstiel, T., Kretke, K. & Stammler, S. Constraining the parameter space for the solar nebula. The effect of disk properties on planetesimal formation. Astron. Astrophys. 640 , A61 (2020).

Lenz, C. T., Klahr, H. & Birnstiel, T. Planetesimal population synthesis: pebble flux-regulated planetesimal formation. Astrophys. J. 874 , 36 (2019).

Okuzumi, S. & Hirose, S. Planetesimal formation in magnetorotationally dead zones: critical dependence on the net vertical magnetic flux. Astrophys. J. Lett. 753 , L8 (2012).

Lynden-Bell, D. & Pringle, J. E. The evolution of viscous discs and the origin of the nebular variables. Mon. Not. R. Astron. Soc. 168 , 603–637 (1974).

Shakura, N. I. & Sunyaev, R. A. Black holes in binary systems. Observational appearance. Astron. Astrophys. 24 , 337–355 (1973).

Bai, X.-N. & Stone, J. M. Magnetic flux concentration and zonal flows in magnetorotational instability turbulence. Astrophys. J. 796 , 31 (2014).

Gerbig, K., Lenz, C. T. & Klahr, H. Linking planetesimal and dust content in protoplanetary disks via a local toy model. Astron. Astrophys. 629 , A116 (2019).

Ormel, C. W. & Klahr, H. H. The effect of gas drag on the growth of protoplanets. Analytical expressions for the accretion of small bodies in laminar disks. Astron. Astrophys. 520 , A43 (2010).

Johansen, A. & Lambrechts, M. Forming planets via pebble accretion. Annu. Rev. Earth Planet. Sci. 45 , 359–387 (2017).

Walsh, K. J. & Levison, H. F. Planetesimals to terrestrial planets: collisional evolution amidst a dissipating gas disk. Icarus 329 , 88–100 (2019).

Deienno, R., Walsh, K. J., Kretke, K. A. & Levison, H. F. Energy dissipation in large collisions—no change in planet formation outcomes. Astrophys. J. 876 , 103 (2019).

Morbidelli, A. & Crida, A. The dynamics of Jupiter and Saturn in the gaseous protoplanetary disk. Icarus 191 , 158–171 (2007).

Raymond, S. N., Quinn, T. & Lunine, J. I. Making other earths: dynamical simulations of terrestrial planet formation and water delivery. Icarus 168 , 1–17 (2004).

O’Brien, D. P., Morbidelli, A. & Levison, H. F. Terrestrial planet formation with strong dynamical friction. Icarus 184 , 39–58 (2006).

Levison, H. F., Duncan, M. J. & Thommes, E. A Lagrangian Integrator for Planetary Accretion and Dynamics (LIPAD). Astron. J. 144 , 119 (2012).

Chambers, J. E. A hybrid symplectic integrator that permits close encounters between massive bodies. Mon. Not. R. Astron. Soc. 304 , 793–799 (1999).

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Acknowledgements

A. Izidoro, R. Dasgupta and A. Isella acknowledge NASA grant 80NSSC18K0828 for financial support during preparation and submission of the work. A. Isella and A. Izidoro acknowledge support from the Welch Foundation grant No. C-2035-20200401. B.B. thanks the European Research Council (ERC Starting Grant 757448-PAMDORA) for financial support. R. Deienno acknowledges support from the NASA Emerging Worlds program, grant 80NSSC21K0387. S.N.R. thanks the CNRS’s PNP programme for support. A. Izidoro thanks M. Maurice for numerous inspirational discussions, and the Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES), in the scope of the Programme CAPES-PrInt, process number 88887.310463/2018-00, International Cooperation Project number 3266.

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Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA

Andre Izidoro & Rajdeep Dasgupta

Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, Pessac, France

Sean N. Raymond

Southwest Research Institute, Boulder, CO, USA

Rogerio Deienno

Max-Planck-Institut für Astronomie, Heidelberg, Germany

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Contributions

A. Izidoro conceived the project in discussions with R. Dasgupta and B.B. A. Izidoro performed numerical simulations modelling dust evolution and planetesimal formation. S.N.R., R. Deienno and A. Izidoro conducted N -body numerical simulations. A. Izidoro analysed the results of numerical simulations and led the writing of the manuscript. R. Dasgupta helped with the cosmochemical implications of the model and constructed Fig. 5 . All authors discussed the results and commented on the manuscript.

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Correspondence to Andre Izidoro .

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Peer review information Nature Astronomy thanks Eiichiro Kokubo and Bradley Hansen for their contribution to the peer review of this work.

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Extended data

Extended data fig. 1 final distribution of planetesimals in a simulation with three pressure bumps..

a) Including the effects of planetesimal formation via zonal flows 80 , see Eq. ( 8 ). b) Neglecting the effects of planetesimal formation via zonal flows 21 , 65 . Final distribution of planetesimals in a simulation with three pressure bumps. Top and middle panels show the evolution of the gas and pebble surface densities, respectively. The initial dust-to-gas ratio is Z 0  = 1.3%, ϵ  = 1 × 10 −4 , α t  =  α ν /27. The final rings contain 2.5 M ⊕ (inner), 85 M ⊕ (central), and 18 M ⊕ (outer) in planetesimals. In both simulations r c  = 25 au.

Extended Data Fig. 2 Final distribution of planetesimals in a simulation with two pressure bumps ( β  = 0.7).

Final distribution of planetesimals in a simulation with two pressure bumps ( β  = 0.7). Top and middle panels show the evolution of the gas and pebble surface densities, respectively. The planetesimal formation efficiency in this simulation is ϵ  = 7.5 × 10 −7 . The initial dust-to-gas ratio is Z 0  = 0.01, α t  =  α ν /40, α M R I  = 3 α ν , and r c  =  ∞ .

Extended Data Fig. 3 Cumulative mass fraction distributions representing the feeding zones of terrestrial planets in simulations with Jupiter and Saturn in their current orbits.

a) Inner planetesimal ring with surface density profile given by Σ pla   ∝   r −1 . Curves are computed from 6 solar system analogues. b) Inner planetesimal ring with surface density profile given by Σ pla   ∝   r −5.5 . Curves are computed from 12 solar system analogues. Cumulative mass fraction distributions representing the feeding zones of terrestrial planets in simulations with Jupiter and Saturn in their current orbits. Thin green, blue and red curves represent Venus, Earth, and Mars analogues. Shaded regions encompassing each thin line represent 95% confidence bands derived from the Kolmogorov–Smirnov statistic. Each selected planetary system contains one single Venus, Earth, and Mars-analogue.

Extended Data Fig. 4 Simulation using the same parameters of simulation shown in Extended Data Figure 2 , but considering that the bump at the snowline forms later, at ~ 0.1 Myr after the beginning of the simulation.

Planetesimal formation efficiency is set at ϵ  = 7.5 × 10 −7 .

Supplementary information

Supplementary information.

Supplementary Figs. 1–10, effects of different parameters of the model, additional methods and comparison with other Solar System models.

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Protoplanetary Disk

This visualization shows the evolution of a young, isolated protoplanetary disk over 16,000 years, including the start of planetary formation. Credit: NASA’s Goddard Space Flight Center, the Advanced Visualization Laboratory at the National Center for Supercomputing Applications, A. Boley, A. Kritsuk and M. Norman

protoplanetary-disk

Oct 30, 2023

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How Planets are Formed: Everything You Need to Know

The Universe, as we know it today, is littered with stars, planets, and innumerable celestial objects that have been floating through space for billions of years. And somehow, we all ended up on a planet that supports the miracle of life as we know it, the Earth. But how are planets formed? Here’s everything that you need to know

The most widely accepted theory on how planets are formed, the protoplanet hypothesis , posits that solar systems around the universe originate from rotating discs of space dust, covered in frozen gasses, which have collided and stuck together over millennia and slowly transformed into planets.

The nature of the universe is something that scientists have been debating for decades, and figuring out exactly how the universe came to be is an endeavor as old as humankind itself.

And, while the Big Bang Theory on how our universe is widely known and, to a lesser extent, understood among us everyday people, most won’t have heard of the protoplanet hypothesis (also known as the nebular hypothesis).

In this article we’ll learn exactly how plan ets are formed, along with all the main theories surrounding their formation…

Note: This post may contain affiliate links which will take you to online retailers that sell products and services. If you click on one and buy something, I may earn from qualifying purchases. See my Affiliate Disclosure for more details.

The Protoplanet Hypothesis

It simply isn’t possible for us to truly understand the conception of our planet, the Sun, and the Universe, because the Earth is at least four billion years old , and the Sun is several million older, and they are only a fraction of the Universe’s age .

But throughout hundreds of years of hypotheses, dating back to ​​Galileo Galilei’s controversial theory, proposed more than 400 years ago, that the Earth revolves around the Sun and not the other way around .

Thanks to the incredible developments in science and technology, we have been able to observe our skies with far greater accuracy than Galileo, and we can see far further into the depths of the Universe. And, with countless Astronomers spending their careers patiently observing the heavens, we have managed to piece together as many parts of the puzzle as possible.

And, without getting into a time machine and going back to when the Earth and other planets originally formed, we have been able to use the instruments like super telescopes at our disposal to stitch together a hypothesis that provides a fairly compelling explanation about the origins of planets.

Evidence suggests that stars and their planets condensed from vast clouds of cosmic gasses. And the protoplanets hypothesis is the leading theory that outlines the birth of stars, planetary systems, and moons from the gaseous nebula.

The theory suggests that the cloudy nebula condensed after pressure changed in the nebula. It is unknown what may have caused this; it could have been an exploding supernova or passing star.

The nebula’s cloud then collapsed to form a disc or halo of material, which would rotate around the gravitational center. So strong was the pressure in the gravitational center that loose hydrogen atoms came into contact with other floating molecules to form helium – which led to the birth of a star, in the case of the solar system, The Sun.

Want to learn more about stars? Check out my other articles: “ How are Stars Formed? “, “ Are Stars Considered Planets? “, and “ What Are Stars? Everything You Need to Know “

As the Sun matured and got larger, it devoured almost everything in space around it, except for about 1% of what remained of the matter in the halo/disc. That remaining matter would kickstart the formation of our planets.

In this tumultuous period, the solar system’s infancy, large bodies of gas, dust, and debris were violently floating around and colliding with one another, eventually sticking together and combining to form larger pieces of dust and gas, becoming what resembles a meteor.

As these new, bigger rocks grew, so did their gravitational pull, which attracted smaller rocks that collided and stuck to the rapidly expanding celestial bodies that formed our rocky planets. The sun pushed gasses to the outer orbits (which is why gas giants like Jupiter/Saturn/Neptune are further out, and more rocky planets like Earth, Mars, and Mercury are closer to the sun).

The smaller, undeveloped, young “protoplanets” collided to form bigger bodies of rocks or “planets” as we know them today. There is evidence of this theory to be found all over our solar system, with debris scattered all over the show, albeit to a far lesser extent than the solar system’s early days.

For example, an asteroid belt between Mars and Jupiter exists, which would have led to the formation of more planets, if not for the fact that Jupiter is so large and its gravity kept these “leftovers” from the infancy of our solar systems under lock and key.

How The Earth Was Formed

Even if we can explain how planets came into existence, the simple fact of the matter is that we live on a giant chunk of rock that is so incredibly unique – it’s the only planet that supports life as we know it. So what was it about the formation of our life-giving utopia that has given it the unique ability to be a haven for living organisms? To understand this, we need to take a closer look at what happened here on Earth.

Planet Earth has a “squashed” spherical shape (an oblate spheroid), with a heavy metal core and a lighter surface crust, with a thin outer atmosphere that provides breathable air. These attributes make it truly unique, and the theory behind how the Earth acquired its unique features is well documented. This is how our planet was able to form vast oceans, arable land, forests, mountains, freshwater rivers, and so on:

In the Earth’s infancy, it probably would have more closely resembled Saturn and Jupiter and was a mere gigantic volume of gas and dust. As the density of the planetary body grew through particle collisions, it would take on a solid state, leading to the creation of the Earth’s crust and inner layers.

The Earth’s core is made up of iron and molten metals, and these molten metals would eventually lead to the formation of massive volcanoes all over the planet. All of this volcanic activity was relentless, and all of the emissions that resulted from these global volcanic eruptions formed what we know today as Earth’s atmosphere.

Furthermore, these volcanoes played a key role in forming the Earth’s crust and creating planetary anomalies like islands.

The volcano emissions that formed the earliest iterations of the Earth’s atmosphere, made up of hydrogen and helium, were accelerated by a meteor shower that hit the Earth, which led to emissions of carbon dioxide and water vapor.

However, the presence of sulphuric gasses from the volcanic eruptions would have made the Earth uninhabitable at the time. Once all of the gasses within our atmosphere condensed, it rained for the first time.

Gradually, the Earth cooled down, and the surface formed a thin crust, but under the crust, hot rock continued to react, which moved the crust below, breaking it apart (plate tectonics) – a process that continues to this day. These subterranean plates shift around, meet each other, collide, crumble and create mountains or deep underwater trenches.

Over time, thanks to the presence of water on our planet (which could take liquid form due to the composition of our atmosphere), photosynthetic bacteria would release oxygen into the Earth’s atmosphere.

Once oxygen entered our atmosphere, it found its way into our oceans, giving rise to marine life forms , which would eventually evolve into all the species of animals that we know today.

The final change to the Earth’s atmosphere’s composition resulted in what we know today, comprised of roughly 21% oxygen and 78% nitrogen.

There is one final piece to the puzzle that makes it possible for life to thrive on Earth – Our magnetic field. This is an invisible phenomenon, diverting high-energy particles from the sun, such as solar winds (a stream of plasma and other particles), among other potentially damaging forces that make other parts of the universe uninhabitable, away from the Earth.

This means there’s relatively little radiation that makes its way from the sun through to the Earth. Scientists are still learning more about the purpose and origins of Earth’s magnetic field, but the standing belief is that it’s the iron and heavy metals that make up the Earth’s core that has led to this phenomenon.

How Do We Verify The Protoplanet Hypothesis?

We are talking about a moment in history where there were no humans around to observe what was happening, so the difficult question for everyone is, “ how do we prove the protoplanet hypothesis? ” There are two methods that Astronomers are using to test the hypothesis: Observation and modeling.

Observation

By using powerful super telescopes, such as the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the South African Large Telescope (SALT) in South Africa, or the ​​Multi-Mirror Telescope (MMT) in Arizona, astronomers can observe dusty disks/halos from other parts of the universe, where young planets are being formed everywhere.

These planets outside the Solar System (exoplanets) can be seen from billions of lightyears away by the Hubble Space Telescope (which operates from space).

We can observe primitive solar systems and planets forming around the vast expanses of the known universe, how things have changed over time, and whether the way things play out is consistent with the theory.

But the problem with this, of course, is that the events in the protoplanet hypothesis occurred over a period of billions of years, meaning we’d be waiting for a very, very long time to verify this theory. This is why astronomers have turned to modeling to arrive at an answer faster.

To test their hypotheses, astronomers use computers to calculate whether their theories are viable. By accounting for various conditions, they can run a simulation, adding variables to the equation to see if it is consistent with their theory.

The simulation can recreate the conditions of the young Earth, speed things up over time, and add variables such as a passing star and see what kind of changes that would make to the composition. If the model remains robust after several runs, accounting for additional variables, the theory carries some weight.

However, modeling isn’t necessarily accurate. There are countless complications, variables, and stumbling blocks that we simply don’t know about, which could easily throw off some of the most widely accepted theories. Accounting for every moon, every asteroid, rock, particle, and an infinite range of external factors is simply impossible. There’s a lot about our Universe that is and may always be shrouded in mystery.

How Were The Gas Giants Formed?

We may know how rocky planets like ours were formed, but the process was very different for the gas planets like Jupiter, Saturn, Uranus, or Neptune.

Check out my article “ 7 Planets that are Made Out of Gas “

In the Solar System’s infancy, in the early stages of the accretion disk (the flat, condensed structure that surrounded the young Sun), the Sun wasn’t large enough to be considered a star, but eventually, as it gained mass, would become a protostar which gave off solar flares that would push gasses further from its orbits than the rocky protoplanets.

The Sun pushed particles, especially the lighter particles like hydrogen, helium, etc., to the solar system’s outer limits, along with “ices” like water, methane, and so forth. This meant that the heavier, rockier elements, like iron, stayed in the middle of this young Solar System. These would collide and grow and turn into dwarf planets. From there, many theories have emerged about how the gas giants were formed.

As these terrestrial objects began to enter orbits, collapse into one another, and create bigger and bigger planets, a few of them (four) possibly moved to the outskirts or could potentially have formed a lot further away from the sun. We aren’t certain about exactly where the earliest iterations of the gas giants originated, but we do know what came after.

As these terrestrial bodies blew through the gasses that were pushed to the outskirts of the solar system, they would start to gain mass, accumulating a massive body of various gasses at a far greater rate than the rockier planets closer to the sun (which is why they became “giants”). Think about the gas giants’ accumulation of mass as something akin to a snowball effect.

One such example was a rocky protoplanet that was roughly one and a half times the size of earth, which accumulated all of these gases, primarily helium, turned into Jupiter. A little further out, similar elements came together to form Saturn, while, further out from there, where very light elements such as ammonia, methane, and water were present is where Uranus and Neptune were formed.

However, a lot of this theory is grounded in speculation because we don’t know what the surfaces of the gas giants actually look like, and we don’t know that they even necessarily have cores. Getting close enough to inspect what’s underneath all of the tumultuous storms that we can observe on Jupiter, Saturn, Uranus, and Neptune is not possible right now

What About The Moons?

Starting with our own moon, it is believed that the brightest object in our sky was born out of a catastrophic collision between the Earth and a Mars-sized protoplanet in the earliest stages of our planet’s formation.

The remaining debris orbited the Earth, much like the accretion disk that formed around the Sun, with smaller fragments of rock and debris from the impact colliding and clumping together to form what is now the moon that appears in our skies every night.

While the definition of what constitutes a moon can be somewhat arbitrary and inconsistent, let’s consider them to be the same as a natural satellite. A satellite is any body of mass that follows a distinct orbit around a planet. Natural satellites are always much smaller than the planets they’re orbiting, but our moon (the Moon) is distinctly large. It is 0.273 times the diameter of the earth.

One of Neptune’s moons, Triton, for example, is 0.055 times its diameter, while Saturn’s Titan is 0.044 times its diameter, Jupiter’s Ganymede 0.038 its diameter, and Uranus’ Titania is 0.031 times its diameter. 

The only planet with a Moon that’s larger in comparison to ours is Pluto, with Charon being 0.52 of the tiny planet’s diameter. Charon is believed to have also have been born out of a celestial impact involving Pluto and another protoplanet.

Where Do Saturn’s Rings Come From?

It is commonly believed that Saturn’s rings are a consequence of the gas giant’s massive gravitational pull but resulted in a completely different phenomenon to what was observed with the accretion disk. Saturn’s rings were likely formed when asteroids, comets, or even small moons were broken up while orbiting around the planet.

After continued collisions, they broke up into smaller pieces rather than being clumped together. When the pieces gradually spread around, they formed the rings that we observe today.

However, did you know that Jupiter, Uranus, and Neptune also have rings that are just a lot smaller and harder to see? We only learned about Jupiter’s rings in 1979 when the Voyager 1 Spacecraft flew past our solar system’s largest planet.

Are There Any Earth-Like Planets Out There?

So now that you know how a planet is formed let’s take a look at some of the other planets that we’ve discovered outside of our Solar System that have the potential to support life as we know it on Earth.

Planet Gliese 581 d

One such planet is Gliese 581 d , a planetary body that’s six times the size of the Earth that falls within the “Goldilocks zone” (a position close enough to the planet’s sun not to be too cold, but far enough not to be too hot) and located 20.2 light-years away from us.

But we may not be so keen to go because, even though it could support life, theoretically, because water can exist there and it has at least one ocean, it has an average surface temperature of -18ºC (-0.4ºF). Another is ​​ HD 85512 b , a planet 3.6 times bigger than the Earth, which is covered in clouds.

However, the problem with this planet is that it’s tidally locked, meaning one side of the planet is perpetually facing the sun while the other remains plunged in a state of perpetual darkness. 

Planet Kepler-69c

Kepler-69c is perhaps the most famous planet that falls into the habitable zone of its solar system. However, as Earth-like as it may seem, the planet appears to have properties far more similar to Venus’, which makes it a far from favorable environment for life to thrive in.

Planet Tau Ceti e

Tau Ceti e , a planet that has temperatures in a similar range to ours (70ºC/158ºF), which is 1.8 times Earth’s size and supports a strong atmosphere, has a rocky surface similar to our and is relatively nearby (relatively being the operative word) at just 11.9 million lightyears away from us.

Planet Gliese 667 Cf

Gliese 667 Cf , a planet with three suns (although it only orbits one of them), also falls within the “Goldilocks zone” due to its unique features, but it only receives about 60% of the amount of sunlight that the Earth does.

Planet Kepler-62f

Kepler-62f – 1.4 times the size of the Earth – is very similar to our planet but has a much smaller, cooler sun, and there’s a very high probability that water can exist there.

However, at 1200 lightyears away, it’s hard to think that getting there will be an easy job, regardless of how much our technology could improve in the future.

Planet Gliese 667 Cc

Gliese 667 Cc is a planet that’s roughly 3.8 times the size of earth, which probably looks more like Mars.

However, it is 85% similar to the Earth , with its rocky surface, but ventures very close to the limits of the “Goldilocks zone”, resulting in -18.85ºC (-1.93ºF) temperatures. Nonetheless, it receives roughly 90% as much light as we do on Earth, making it a promising candidate for a habitable planet.

Planet Keppler-2e

Keppler-62e , which is also a bit far out at 1200 lightyears away, has a high probability of water, is about 1.6 times larger than Earth, and has similar characteristics, such as a cloudy sky, meaning that it will likely have similar warmth and humidity to what we experience here.

Planet Gliese 581 g

Gliese 581 g is one of the closest examples we have to an Earth-like planet , however, because it has distinct oceans and continents that look almost just like our own.

It’s also “only” 20.3 lightyears away. It is rocky and supports a strong atmosphere similar to ours, but the temperatures are rather off-putting, at -37 to -12ºC (-34.6ºF to 10.4ºF).

There is an incredibly high probability of life on this planet , but it is still up for debate, which is why it will always live in the shadow of our “Future Home”, the planet Kepler-22b …

Planet Kepler-22b

The Kepler-22b is 2.4 times the size of Earth, which lives in the sweet spot of the “Goldilocks zone”, with temperatures estimated to be between -11ºC (12.2ºF) and 22ºC (71.6ºF), and it doesn’t even have its own atmosphere!

However, the planet does appear to be covered with oceans and lacks the rocky surface that we’d ideally like. It is located approximately 620 light-years from Earth. The jury is still out on Kepler-22b , however, and some suggest that it may even be a gas planet, and we have to do a lot more research to find out about its true nature.

How The Origins Of Our Universe Can Shape Our Future

Studying the origins of the Universe and how planets are formed can often seem like a very academic exercise. However, this isn’t just about formulating abstract theories that have no relevance to our current reality – the protoplanet hypothesis tells us a lot about our environment and what makes the miracle of life such a miracle. It tells us about how the climate changes and how our atmosphere’s composition makes a massive difference to its conditions.

By using modeling to figure out how our planet came into being, we maya also be able to predict how the effects of climate change can change our environment and affect how habitable our planet is. And, if we reach a point where intergalactic space travel is possible, understanding how our planet was created and how it has changed over time allows us to search the heavens for candidates that could serve as a new miraculous, live-giving host to humankind.

It is only with the help of astronomers that we can unlock the secrets to the recipe that allows life to exist on earth. 

More About Stars and Planets…

Check out more of my articles about stars and planets:

• Can a Planet Becomes a Star?
• Are Stars Considered Planets?
• How are Stars Formed?
• 7 Planets the are Made Out of Gas

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Protoplanet Imaged During Formation

AB Aurigae b was directly imaged in joint operations between the Subaru and Hubble telescopes and provides evidence for the disk instability theory of planet formation.

In joint observations between the  Subaru Telescope  and the  Hubble Space Telescope , a protoplanet called AB Aurigae b has been directly imaged during its formation. AB Aurigae is only a two-million-year-old star, and this baby planet is actually nine times the mass of Jupiter and orbiting 13.9 billion kilometers away. That’s three times the distance between the Sun and Neptune. And finding this protoplanet where it is definitely breaks a bit more of our theories on planetary formation. Or as lead author Thayne Currie said:  AB Aur b sheds new light on our understanding of the different ways that planets form.

You see, while we know that planets migrate, we didn’t think that planetary cores could form this far away from the star. This would mean that a gas giant’s core would form closer in and then migrate out to collect the gases. In our previous story, models show that Jupiter migrated inward at some point to collect all the heavier elements in its atmosphere, and now this baby world shows us that gas giants  can  form out the great distance Jupiter would have needed before migrating inward.

And that means instead of the “standard” core accretion method we’ve talked about before, where rocky worlds spin and spin and crash and collect up material and then migrate outward for their gases, we now have to seriously consider the disk instability hypothesis. That’s where the massive protoplanetary disk, full of gases, cools down over time and then breaks into one or more collapsing clumps of planetary mass. Sort of similar to how stars form, but only if you don’t look too closely at the process.

Honestly, this discovery is huge, and not just in the size of the exoplanet kind of way. Planetary scientists have been debating the core accretion versus disk instability methods for decades now. And it took the combined power of Subaru’s extreme adaptive optics system, infrared spectrograph, visible light camera, and 13 years of observations plus the ability of Hubble to separate the planet from its star and provide a baseline for the system.

The results of this discovery were published in  Nature Astronomy .

More Information Hubblesite  press release Subaru Telescope  press release “ Images of embedded Jovian planet formation at a wide separation around AB Aurigae ,” Thayne Currie et al., 2022 April 4, Nature Astronomy

This story was written for the Daily Space podcast/YouTube series. Want more news from myself,  Dr. Pamela Gay , and  Erik Madaus ? Check out  DailySpace.org .

If you enjoy reading stories like these and would like to support me as a writer,  please consider signing up to become a Medium member . It’s $5 a month and gives you unlimited access to stories on Medium. Thank you for reading!

This article was originally published by Beth Johnson on  medium.com .

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protoplanet

Definition of protoplanet

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1949, in the meaning defined above

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