The creation of the inner planets

[Arctic Frost]

Original comment 6-26-20 Edit 6-30-20: I am exploring the inner planets creation theory as it puzzles me how dust became enough mass to create planets. Just the dust, I understand once material starts collecting together. However, Gas Giant moons getting into the inner system somehow strikes me as more plausible. I need to educate myself on this subject because I may be leading myself down a rabbit hole with my hypothesis.

Which is: Doesn’t it make more sense that a GAS GIANT was formed or found itself within the original inner system of the sun just as we are observing in other systems?

As the sun aged and grew the dynamics of gravity between the two forces ripped apart the gas giant allowing the sun to captivate it’s moons and create the inner system. I’m uneducated so I don’t know.

 

[Helio]

I guess Nova is a crack pot organization.

Perhaps they feel entitled to be more explosive than others. [hope you like puns. ]

Here it is: Doesn’t it make more sense that a GAS GIANT was formed in the original inner system of the sun just as we are observing in other systems?

Well, you might enjoy a little planet formation theoretical history to help give some perspective on this.

The first big idea regarding our star's formation came from folks like Kant and others who thought that a gas cloud in space could collapse. But the problem with it was that, like and ice skater spinning faster by pulling her arms in, the angular momentum would cause unimaginable rotation speeds -- self-destruction speeds. So it was debunked... at least for a while.

It was then thought that our Sun encountered a fly-by of another star that pulled off some solar material which produced the planets. So your idea for larger ones close to the Sun would make reasonable sense.

When magnetohydrodynamics were applied to the disk formation due to a cloud collapse, and confirmed with things like bi-polar flows from protostars, then the collapse idea gained ground, which is the modern view.

The planets form from the accretion disk but the giants form where the disk temperatures are low enough for ices to hold together. The hot Sun would push outward the lighter elements and vapors that came from melting the inner ices. So, the problem boils down to boiling, so to speak.

Worse, the inner planet atmospheres would be much warmer than the outer planets so the lighter elements (e.g. hydrogen) would be bouncing around at speeds beyond any of our inner planet's escape velocities. So, for the terrestrial planets, it was only the heavier elements that stuck.

The colder temperatures gave another advantage to the giants by having extra mass early on they formed very quickly giving little time for competitive protoplanets to form near them.

Remember that about 75% of the mass of giant clouds is hydrogen. Since hydrogen is so light, then any planet that could hold onto hydrogen had a huge advantage. Jupiter happened to be located beyond the frost line when it formed.

The ability to find large exoplanets vs. smaller ones is to be expected. It's easier to find an elephant in the backyard than a squirrel. But better scopes will help find the tougher (more squirrely) smaller planets.

A great book new book on formation is When the Earth had Two Moons (Erik Asphaug).

As the sun aged and grew the dynamics of gravity between the two forces ripped apart the gas giant allowing the sun to captivate it’s moons and create the inner system. Now tell me am I a crack pot for this idea or is it valid? I’m uneducated so I don’t know.

There is great evidence of some very dynamic events that allowed us to get what we got. Uranus had to have taken quite a blow of some kind to knock more than 90 deg. from the ecliptic. It's a little strange that our inner region seems a bit tame by comparison.

There are pros and cons to every model that has been introduced, AFAIK. Some are more popular than others, of course.

 

[Arctic Frost]

Perhaps they feel entitled to be more explosive than others. [hope you like puns. ]

Well, you might enjoy a little planet formation theoretical history to help give some perspective on this.

Worse, the inner planet atmospheres would be much warmer than the outer planets so the lighter elements (e.g. hydrogen) would be bouncing around at speeds beyond any of our inner planet's escape velocities. So, for the terrestrial planets, it was only the heavier elements that stuck.

The colder temperatures gave another advantage to the giants by having extra mass early on they formed very quickly giving little time for competitive protoplanets to form near them.

Remember that about 75% of the mass of giant clouds is hydrogen. Since hydrogen is so light, then any planet that could hold onto hydrogen had a huge advantage. Jupiter happened to be located beyond the frost line when it formed.

A great book new book on formation is When the Earth had Two Moons (Erik Asphaug).

EXCELLENT! Thank you so much! I’ve always envisioned a gas giant forming as normal, moons and all, and somehow finding itself too close to the sun as a means to bring its moons into the inner system. But I knew I had a ton to learn and I just wasn’t certain what direction to go to educate myself further. By yours and others‘ guidance I am so excited to run off and dig into exoplanets, gas giants formations vs small planet formation. Having someone point out specific references and suggesting books is like finding a gold mine to someone like me that gets a little overwhelmed due to my lacking knowledge.

 

[Catastrophe]

EXCELLENT! Thank you so much! I’ve always envisioned a gas giant forming as normal, moons and all, and somehow finding itself too close to the sun as a means to bring its moons into the inner system. But I knew I had a ton to learn and I just wasn’t certain what direction to go to educate myself further. By yours and others‘ guidance I am so excited to run off and dig into exoplanets, gas giants formations vs small planet formation. Having someone point out specific references and suggesting books is like finding a gold mine to someone like me that gets a little overwhelmed due to my lacking knowledge.

You might like the closing remarks of
"Migrating Multis" Astronomy Now Feb 20 2014 Dr Becky Enoch
"We are just beginning to understand the range of planetary systems out there. The rich variety of new multi-planet discoveries will continually provide challenges for our developing theories of planetary formation."

 

[Arctic Frost]

You might like the closing remarks of
"Migrating Multis" Astronomy Now Feb 20 2014 Dr Becky Enoch
"We are just beginning to understand the range of planetary systems out there. The rich variety of new multi-planet discoveries will continually provide challenges for our developing theories of planetary formation."

Wonderful quote! Thank you. I feel so encouraged to learn more. I have quite a bit of research to do but I'm feeling much more confident now in which direction to take my time.

 

[dfjchem721]

I have quite a bit of research to do but I'm feeling much more confident now in which direction to take my time.

Some people consider Jupiter to be a sub-brown dwarf*. By extension, they would also consider our solar system a "binary" : a yellow dwarf and a sub-brown dwarf. Looking at all the moons of Jupiter and its enormous magnetic field makes it all seem like two "nearly" independent systems. But size is everything in this biz! While a binary is quite a stretch, it does present the notion of what might make our system a true "binary".

Others discount Jupiter as a "sub-brown dwarf" as they are usually defined as a "free-floating planet" (aka rogue planets). But since some distant exoplanets have been observed orbiting distant stars and called sub-brown dwarfs, it is open to some debate regarding Jupiter.

You might also wish to consider researching brown dwarfs**. They are essentially super gas giants that also lack sufficient hydrogen for star formation, and so have some relationship to Jupiter.


* https://en.wikipedia.org/wiki/Sub-brown_dwarf


** https://en.wikipedia.org/wiki/Brown_dwarfs


Of course a good review of Jupiter might help tie all these sub-stellar gas giants together for those interested in such objects:

Jupiter - Wikipedia

en.wikipedia.org

(Never let anyone tell you that Wikipedia is not a good source of information. It is an excellent source. Its biggest issue is that it frequently does not give enough information. Most of it is well reviewed and accurate, and easy to understand.)

 

[Catastrophe]

Just for the record, I have simplified the Wiki explanation somewhat:

Planet formation in the Solar System (Wiki)

The planets are thought to have formed from the solar nebula, the disc-shaped cloud of gas and dust left over from the Sun's formation. The currently accepted method by which the planets formed is accretion, in which the planets began as dust grains in orbit around the central protostar. Through mutual attraction, these grains formed into clumps up to 200 metres in diameter, which in turn collided to form larger bodies (planetesimals) of ~10 kilometres (km) in size. These gradually increased through further collisions, growing at the rate of centimetres per year over the course of the next few million years.

The inner Solar System, the region inside 4 AU, was too warm for volatile molecules to condense, so the planetesimals that formed there could only form from compounds with high melting points, such as metals (like iron, nickel, and aluminium) and rocky silicates. These rocky bodies would become the terrestrial planets (Mercury, Venus, Earth, and Mars).

While the terrestrial planets were forming, they remained in a disk of gas and dust. The gas did not orbit the Sun as rapidly as the planets. The resulting drag and, more importantly, gravitational interactions with the surrounding material caused the planets gradually to migrate. inward as the disk dissipated.

The giant planets (Jupiter, Saturn, Uranus, and Neptune) formed further out, beyond the frost line, which is the point between the orbits of Mars and Jupiter where the material is cool enough for volatile icy compounds to remain solid. The ices that formed the Jovian planets were more abundant than the metals and silicates that formed the terrestrial planets, allowing the giant planets to grow massive enough to capture hydrogen and helium, the lightest and most abundant elements.

After between three and ten million years, the young Sun's solar wind would have cleared away all the gas and dust in the protoplanetary disc, blowing it into interstellar space, thus ending the growth of the planets

FOLLOWING ON FROM THERE:
" Doesn’t it make more sense that a GAS GIANT was formed or found itself within the original inner system of the sun just as we are observing in other systems?"

Certainly there are reports of exoplanets close to their stars.

I have certainly seen reports of gas giants being in close proximity to the Sun, and have wondered at (been surprised at) the length of time stated for which such planets could survive that close! But that seems to be the claim.

 

[Helio]

Migration of planets likely plays a key roll regardless of the star. It's very unlikely large, gasesous, planets formed originally near their host star due to higher gas temperatures.

While the terrestrial planets were forming, they remained in a disk of gas and dust. The gas did not orbit the Sun as rapidly as the planets. The resulting drag and, more importantly, gravitational interactions with the surrounding material caused the planets gradually to migrate. inward as the disk dissipated.

Yes, the solar pressure (radiation and wind) on the light gas allowed it to have a slower orbital rate.

As I see it, when gas and dust grow in size then they must begin to fall toward the star. If you increase the size of any particle, say, by 10 fold (diameter), then you will have increased the cross sectional area by 100x which, by itself, would allow the star's radiation and wind to move it outward. But the mass of the object increases as the cube of diameter, so it is now 1000x more massive, so the net effect is that it will fall toward the star. This would be even greater as the gas and dust grow even larger, of course. Eventually, Keplerian motion is where the larger objects will have, and this means inward migration.

There is also the Yarkovsky Effect where solar heating causes larger objects (e.g. meteoroids), with their non-uniform re-radiation, to change their orbit.

But the inward motions aren't all the same, so as one large object migrates inward, then odd results are likely when it nears another large body. It's a heck of a dance and it's one no one has solved yet for the Solar system.

 

[Arctic Frost]

Just for the record, I have simplified the Wiki explanation somewhat:

Planet formation in the Solar System (Wiki)

The planets are thought to have formed from the solar nebula, the disc-shaped cloud of gas and dust left over from the Sun's formation. The currently accepted method by which the planets formed is accretion, in which the planets began as dust grains in orbit around the central protostar. Through mutual attraction, these grains formed into clumps up to 200 metres in diameter, which in turn collided to form larger bodies (planetesimals) of ~10 kilometres (km) in size. These gradually increased through further collisions, growing at the rate of centimetres per year over the course of the next few million years.

The inner Solar System, the region inside 4 AU, was too warm for volatile molecules to condense, so the planetesimals that formed there could only form from compounds with high melting points, such as metals (like iron, nickel, and aluminium) and rocky silicates. These rocky bodies would become the terrestrial planets (Mercury, Venus, Earth, and Mars).

While the terrestrial planets were forming, they remained in a disk of gas and dust. The gas did not orbit the Sun as rapidly as the planets. The resulting drag and, more importantly, gravitational interactions with the surrounding material caused the planets gradually to migrate. inward as the disk dissipated.

The giant planets (Jupiter, Saturn, Uranus, and Neptune) formed further out, beyond the frost line, which is the point between the orbits of Mars and Jupiter where the material is cool enough for volatile icy compounds to remain solid. The ices that formed the Jovian planets were more abundant than the metals and silicates that formed the terrestrial planets, allowing the giant planets to grow massive enough to capture hydrogen and helium, the lightest and most abundant elements.

After between three and ten million years, the young Sun's solar wind would have cleared away all the gas and dust in the protoplanetary disc, blowing it into interstellar space, thus ending the growth of the planets

FOLLOWING ON FROM THERE:
" Doesn’t it make more sense that a GAS GIANT was formed or found itself within the original inner system of the sun just as we are observing in other systems?"

Certainly there are reports of exoplanets close to their stars.

I have certainly seen reports of gas giants being in close proximity to the Sun, and have wondered at (been surprised at) the length of time stated for which such planets could survive that close! But that seems to be the claim.

Thank you, Cat! This helps tremendously. I like how this analogy of my gas giant being the harbor of life bearing planets is bringing me to actual knowledge. As I learn, my analogy becomes more frayed but my mind becomes more sound, so to speak. I still feel the thrill that my analogy might; have credit in other solar systems, needs to be completely revamped or perhaps disposed off, while having the true satisfaction that my mind is expanding properly. It is a joyous ride Thanks!

 

[Arctic Frost]

Migration of planets likely plays a key roll regardless of the star. It's very unlikely large, gasesous, planets formed originally near their host star due to higher gas temperatures.
Yes, the solar pressure (radiation and wind) on the light gas allowed it to have a slower orbital rate.

As I see it, when gas and dust grow in size then they must begin to fall toward the star. If you increase the size of any particle, say, by 10 fold (diameter), then you will have increased the cross sectional area by 100x which, by itself, would allow the star's radiation and wind to move it outward. But the mass of the object increases as the cube of diameter, so it is now 1000x more massive, so the net effect is that it will fall toward the star. This would be even greater as the gas and dust grow even larger, of course. Eventually, Keplerian motion is where the larger objects will have, and this means inward migration.

There is also the Yarkovsky Effect where solar heating causes larger objects (e.g. meteoroids), with their non-uniform re-radiation, to change their orbit.

But the inward motions aren't all the same, so as one large object migrates inward, then odd results are likely when it nears another large body. It's a heck of a dance and it's one no one has solved yet for the Solar system.

I think I actually understand what you’re explaining here, but just barely grasping it. I have weaned away from thinking a gas giant formed inside the 4AU (hope I got that right, basically the inner area of the sun.) Now my imagination has it forming as normal then moving. I imagine a dance between my gas giant and a weak sun fighting for domination over the ice moons. I imagine these moons clashing together to create protoplanet type (is that the right term) structures. It is the ice moons that intoxicate me as water based planets forming by the sun perplexes me. However, I'm realizing I must learn the basics in order to actually hypothesize. It’s incredibly fun!

 

[Catastrophe]

I have just come across this, which seems relevant!

Core of a gas planet seen for the first time
By Paul Rincon Science editor, BBC News website

• 1 July 2020

 

[Catastrophe]

Core of a gas planet seen for the first time - BBC News
www.bbc.co.uk › news › science-environment-53250819

Sorry I had to add this separately. I obtained it from a search and then the edit wouldn't let me add it.

 

[Helio]

I think I actually understand what you’re explaining here, but just barely grasping it. I have weaned away from thinking a gas giant formed inside the 4AU (hope I got that right, basically the inner area of the sun.)

Yes, each star, or protostar, will have a frost line where volitales stay frozen. But it's actually multiple frost lines because it requires colder temperatures for, say, methanes verus water. Closer to the Sun these ices become a gas and the solar wind and radiation will gently push them out. Guess where they go -- they go past the frost line and Jaws (Jupiter) is waiting there to gobble them in their now frozen state. The colder temperatures, btw, allows these ices to become larger as they stick to one another.

 

[Arctic Frost]

Core of a gas planet seen for the first time - BBC News
www.bbc.co.uk › news › science-environment-53250819

Sorry I had to add this separately. I obtained it from a search and then the edit wouldn't let me add it.

Oh my goodness, how exciting! I couldn’t help but latch onto this:

“ . . . where the planet is ripped apart from orbiting too close to its star, or even a collision with another planet late in its formation. . .”

This is exactly what I envision. The question being; what if our new found gas giant with it’s gasses stripped away also came with a set of moons? Wouldn’t that star grab them and start them anew? Now, let us think of Venus, the planet that seems to have a history before the history of which we are aware. Venus is my muse, but I fear the dear girl leads me astray. Hahahaha, back to the basics. This is wonderful information, thank you so much for sharing it!

 

[Arctic Frost]

Yes, each star, or protostar, will have a frost line where volitales stay frozen. But it's actually multiple frost lines because it requires colder temperatures for, say, methanes verus water. Closer to the Sun these ices become a gas and the solar wind and radiation will gently push them out. Guess where they go -- they go past the frost line and Jaws (Jupiter) is waiting there to gobble them in their now frozen state. The colder temperatures, btw, allows these ices to become larger as they stick to one another.

The gases, they are my culprit to accepting the common theory though acceptance grows with understanding. In reading the wonderful book you suggested I found that I have an aversion to terminology. I am gifted with an advanced understanding of imagery, but can’t seem to get those terms down quickly. A friend recently caused me a belly laugh when he stated, “. . . Now what is that scientific term I’m looking for? Ah yes, blobs . . .”

I often wonder if other poor souls are like me. Terminology has plagued my understanding in all the disciplines I explore, so it is a common occurrence for me. I do know this, watch out, for once I understand the terms I become fierce in my understanding and my mind takes flight. Your book is invaluable to me, I am so grateful you suggested it!

 

[Catastrophe]

" I am gifted with an advanced understanding of imagery, but can’t seem to get those terms down quickly."

I really relate to this. I am doing a lot of studying at the moment on chemical composition of nebulae (but it is relevant to planet formation from gaseous disc) and I am finding (this is not new to me) that simple sketches can encapsulate reams of words. Some H's dotted around, arrow showing ionising radiation, duplicate with differing photon energies, results. All there held together in the mind's eye.

 

[Helio]

The gases, they are my culprit to accepting the common theory though acceptance grows with understanding.

What is it about gases that you find confusing?

I have an aversion to terminology. I am gifted with an advanced understanding of imagery, but can’t seem to get those terms down quickly.

Yep, it's never old to state that a picture is worth a thousand words, though a thousand pictures is much better still when it comes to astronomy.

I think half the battle for any scientific field is learning the terms. I wish I would have spent more time making sure I understood each new term that came my way, but I sometimes just stayed satisfied with all those pictures. If you see a term, this forum will help. Sometimes Wiki is unclear, or too verbose, in its presentation on certain, more complex, terms.

I often wonder if other poor souls are like me.

I would bet a vast majority would qualify, so take heart. Understanding the terms means you capture their purpose. Their there for a reason, so if you "get it" then you're essentially there already.

Your book is invaluable to me, I am so grateful you suggested it!

The author is unusually gifted in presenting all those key ideas. I usually take notes when I read a book so I can review what I learned. I must have 30 or 40 pages of notes for this book; a new record. Even though he has a few mistakes, usually in historical accounts, it is very helpful in understanding the likely early dynamics in the Solar System.

 

[Arctic Frost]

What is it about gases that you find confusing?

I’m starting to understand the view now but originally I felt gases too light to gather with heavier elements so close to the sun and couldn’t understand why they believed that. The mathematical “push and pull” you describe was unknown to me. The exciting happenstance is I am now discovering I have a LOT more to think about. I still love my gas giant idea but in a different way.

Notes! Oh my goodness, why didn’t I think of that. The glossary and I are on intimate terms but it makes my reading excruciatingly slow.