How do planets form?

[BDanielMayfield]

Now that literally thousands of exo-planets have been discovered it is safe to assume that most stars are or once were orbited by planets. Planets are known to be a natural byproduct of star formation, but how, to the best of current theory, does vacuum thin interstellar gas and dust come together to form planets?

Bruce

[bystander]

An interesting theory presented here.

[neufer]

An interesting theory presented here.

---

<<Hail forms in strong thunderstorm clouds, particularly those with intense updrafts, high liquid water content, great vertical extent, large water droplets, and where a good portion of the cloud layer is below freezing 0 °C (32 °F). The growth rate is maximized where air is near a temperature of −13 °C (9 °F).>>

[BDanielMayfield]

Thanks Art. Perhaps this inspired your post?

This is a very interesting model. It reminds me somewhat of how hail stones grow in thunderstorms here on Earth. In the case of hail, gravity is pulling ice pellets down while strong up-drafts blow the pellets repeatedly up into freezing temp regions of the cloud. In the case of young red dwarf stars, there might be considerable back and forth migration of the ice line due to all the flaring of the star.

Presumably, such a process could be at work around any young star, no matter its mass, as all young stars are very active at first. I also wonder if other chemicals or elements besides H2O might play similar roles at their respective ice lines.

I've always wondered how pebbles with negligible gravitational attraction manage to stick together and grow into a protoplanet massive enough to start gravitational growth. This model provides a very logical explanation. Nice

Bruce

A key factor with water acting as a growth catalyst is how sticky water is as liquid droplets freeze onto objects below zero C as objects move across the "ice line", causing the growth of ice crystals. I wondered about other molecules playing similar roles. Methane (CH4, melting point -182.5 C) and ammonia (NH3, melting point -77.7 C) come to mind. Are these and others sticky enough to cause growth as particles move across these ice lines too?

Bruce

[warmingwarmingwarming]

http://news.nationalgeographic.com/2017 ... e-science/

And Black Holes shooting out blobs that eventually turn into planets.

[BDanielMayfield]

http://news.nationalgeographic.com/2017 ... e-science/

And Black Holes shooting out blobs that eventually turn into planets.

There are likely some odd and rare modes of planet formation from the debris of stellar destruction, but the main method is undoubtedly accretion of the leftovers from star birth, not death. This main pathway to planet formation, the one that can produce Earth-like planets orbiting normal stars is what I was asking about. Since evidence is piling up that nearly all stars have planets the formation pathway must be robust, that is, it must be an automatic byproduct of star formation that doesn't require an odd or rare set of conditions.

What processes allow dust motes to grow into pebbles, stones, boulders, rubble piles, and then planetesemals large enough to begin gravitational attraction, all while surviving potentially destructive collisions? I was intrigued by the idea that ice might play a very critical role here.

Bruce

[Chris Peterson]

http://news.nationalgeographic.com/2017 ... e-science/

And Black Holes shooting out blobs that eventually turn into planets.

There are likely some odd and rare modes of planet formation from the debris of stellar destruction, but the main method is undoubtedly accretion of the leftovers from star birth, not death. This main pathway to planet formation, the one that can produce Earth-like planets orbiting normal stars is what I was asking about. Since evidence is piling up that nearly all stars have planets the formation pathway must be robust, that is, it must be an automatic byproduct of star formation that doesn't require an odd or rare set of conditions.

What processes allow dust motes to grow into pebbles, stones, boulders, rubble piles, and then planetesemals large enough to begin gravitational attraction, all while surviving potentially destructive collisions? I was intrigued by the idea that ice might play a very critical role here.

I think this is the correct way of looking at things.

How do planets form? This we know with a high degree of certainty, but a low degree of precision: the vast majority of planets form just as you suggest, by the accretion of material in a disc around newly forming stars. That view is well supported by theory and a lot of observational evidence. It's what we might call the "big picture", and we almost certainly have it correct.

Beyond that, there remain other interesting questions yet to be answered (or answered well). Are there other mechanisms for planet formation? Yes, probably. Things like stars being shredded by interactions with black holes. Not a significant contributor to planet formation (especially planets in orbit around stars), but very plausible. And as you allude to at the end, what are the actual mechanisms of accretion? We're pretty sure that there are electromagnetic mechanisms- particles acquiring static charge which enhance accretion before gravity becomes the driving force. And now, this ice boundary theory you bring up.

We're not going to find many researchers who doubt accretion is the primary factor in planet formation. But there's a lot of interesting work being done to explore all the possible mechanisms present in presolar discs that can actually produce planets.

[warmingwarmingwarming]

http://news.nationalgeographic.com/2017 ... e-science/

And Black Holes shooting out blobs that eventually turn into planets.

There are likely some odd and rare modes of planet formation from the debris of stellar destruction, but the main method is undoubtedly accretion of the leftovers from star birth, not death. This main pathway to planet formation, the one that can produce Earth-like planets orbiting normal stars is what I was asking about. Since evidence is piling up that nearly all stars have planets the formation pathway must be robust, that is, it must be an automatic byproduct of star formation that doesn't require an odd or rare set of conditions.

What processes allow dust motes to grow into pebbles, stones, boulders, rubble piles, and then planetesemals large enough to begin gravitational attraction, all while surviving potentially destructive collisions? I was intrigued by the idea that ice might play a very critical role here.

Bruce

"Undoubtedly" is a word that should be used sparingly, for instance, after solid proof, like when sipping a glass of water, "This water is undoubtedly wet." Theories on planetary formation do not fit that test. There is simply TOO MUCH to learn, to speculate on, to ponder, to examine, to observe.

[Chris Peterson]

http://news.nationalgeographic.com/2017 ... e-science/

And Black Holes shooting out blobs that eventually turn into planets.

There are likely some odd and rare modes of planet formation from the debris of stellar destruction, but the main method is undoubtedly accretion of the leftovers from star birth, not death. This main pathway to planet formation, the one that can produce Earth-like planets orbiting normal stars is what I was asking about. Since evidence is piling up that nearly all stars have planets the formation pathway must be robust, that is, it must be an automatic byproduct of star formation that doesn't require an odd or rare set of conditions.

What processes allow dust motes to grow into pebbles, stones, boulders, rubble piles, and then planetesemals large enough to begin gravitational attraction, all while surviving potentially destructive collisions? I was intrigued by the idea that ice might play a very critical role here.

Bruce

"Undoubtedly" is a word that should be used sparingly, for instance, after solid proof, like when sipping a glass of water, "This water is undoubtedly wet." Theories on planetary formation do not fit that test. There is simply TOO MUCH to learn, to speculate on, to ponder, to examine, to observe.

Undoubtedly is being used correctly here. We know beyond reasonable doubt that the planets around stars are formed locally around those stars, and we observe that process directly around other stars.

[warmingwarmingwarming]

There are likely some odd and rare modes of planet formation from the debris of stellar destruction, but the main method is undoubtedly accretion of the leftovers from star birth, not death. This main pathway to planet formation, the one that can produce Earth-like planets orbiting normal stars is what I was asking about. Since evidence is piling up that nearly all stars have planets the formation pathway must be robust, that is, it must be an automatic byproduct of star formation that doesn't require an odd or rare set of conditions.

What processes allow dust motes to grow into pebbles, stones, boulders, rubble piles, and then planetesemals large enough to begin gravitational attraction, all while surviving potentially destructive collisions? I was intrigued by the idea that ice might play a very critical role here.

Bruce

"Undoubtedly" is a word that should be used sparingly, for instance, after solid proof, like when sipping a glass of water, "This water is undoubtedly wet." Theories on planetary formation do not fit that test. There is simply TOO MUCH to learn, to speculate on, to ponder, to examine, to observe.

Undoubtedly is being used correctly here. We know beyond reasonable doubt that the planets around stars are formed locally around those stars, and we observe that process directly around other stars.

How many of the potentially 200 Billion galaxies/10 to the 24th power planets have you looked at? Undoubtedly very, very few.https://www.google.ca/search?q=how+many ... e&ie=UTF-8

But even without those numbers .. there is solid speculation that stars capture planets that did not originate near them. However .. we have had that discussion before.

[warmingwarmingwarming]

There are likely some odd and rare modes of planet formation from the debris of stellar destruction, but the main method is undoubtedly accretion of the leftovers from star birth, not death. This main pathway to planet formation, the one that can produce Earth-like planets orbiting normal stars is what I was asking about. Since evidence is piling up that nearly all stars have planets the formation pathway must be robust, that is, it must be an automatic byproduct of star formation that doesn't require an odd or rare set of conditions.

What processes allow dust motes to grow into pebbles, stones, boulders, rubble piles, and then planetesemals large enough to begin gravitational attraction, all while surviving potentially destructive collisions? I was intrigued by the idea that ice might play a very critical role here.

Bruce

"Undoubtedly" is a word that should be used sparingly, for instance, after solid proof, like when sipping a glass of water, "This water is undoubtedly wet." Theories on planetary formation do not fit that test. There is simply TOO MUCH to learn, to speculate on, to ponder, to examine, to observe.

Undoubtedly is being used correctly here. We know beyond reasonable doubt that the planets around stars are formed locally around those stars, and we observe that process directly around other stars.

Is Harvard Smithsonian not a credible source about rogue planets being capture by stars?
https://www.cfa.harvard.edu/news/2012-12

Blobs of material ejected from black holes are said to become planets roaming space beyond their original galaxies .. so they can be captured by other stars in other galaxies.

[warmingwarmingwarming]

There are likely some odd and rare modes of planet formation from the debris of stellar destruction, but the main method is undoubtedly accretion of the leftovers from star birth, not death. This main pathway to planet formation, the one that can produce Earth-like planets orbiting normal stars is what I was asking about. Since evidence is piling up that nearly all stars have planets the formation pathway must be robust, that is, it must be an automatic byproduct of star formation that doesn't require an odd or rare set of conditions.

What processes allow dust motes to grow into pebbles, stones, boulders, rubble piles, and then planetesemals large enough to begin gravitational attraction, all while surviving potentially destructive collisions? I was intrigued by the idea that ice might play a very critical role here.

Bruce

"Undoubtedly" is a word that should be used sparingly, for instance, after solid proof, like when sipping a glass of water, "This water is undoubtedly wet." Theories on planetary formation do not fit that test. There is simply TOO MUCH to learn, to speculate on, to ponder, to examine, to observe.

Undoubtedly is being used correctly here. We know beyond reasonable doubt that the planets around stars are formed locally around those stars, and we observe that process directly around other stars.

From Harvard:

https://www.forbes.com/sites/startswith ... 8a654c1591

Those planets form quickly, and not from accretion discs.

[Chris Peterson]

Undoubtedly is being used correctly here. We know beyond reasonable doubt that the planets around stars are formed locally around those stars, and we observe that process directly around other stars.

How many of the potentially 200 Billion galaxies/10 to the 24th power planets have you looked at?

We don't need to look at billions. All we need is a sampling. And we have that (with a growing population).

[Chris Peterson]

"Undoubtedly" is a word that should be used sparingly, for instance, after solid proof, like when sipping a glass of water, "This water is undoubtedly wet." Theories on planetary formation do not fit that test. There is simply TOO MUCH to learn, to speculate on, to ponder, to examine, to observe.

Undoubtedly is being used correctly here. We know beyond reasonable doubt that the planets around stars are formed locally around those stars, and we observe that process directly around other stars.

From Harvard:

https://www.forbes.com/sites/startswith ... 8a654c1591

Those planets form quickly, and not from accretion discs.

So? As I noted, it's likely that there are other mechanisms of planet formation. What is certain beyond reasonable doubt is that the vast majority of planets which are in orbit around stars formed locally from accretion discs. Interactions between stars and black holes are rare viewed against the total population of stars. Captures of bodies formed outside of stellar systems are also statistically rare. Every new stellar system we observe has a dust disc of some sort around it.

[warmingwarmingwarming]

Undoubtedly is being used correctly here. We know beyond reasonable doubt that the planets around stars are formed locally around those stars, and we observe that process directly around other stars.

From Harvard:

https://www.forbes.com/sites/startswith ... 8a654c1591

Those planets form quickly, and not from accretion discs.

So? As I noted, it's likely that there are other mechanisms of planet formation. What is certain beyond reasonable doubt is that the vast majority of planets which are in orbit around stars formed locally from accretion discs. Interactions between stars and black holes are rare viewed against the total population of stars. Captures of bodies formed outside of stellar systems are also statistically rare. Every new stellar system we observe has a dust disc of some sort around it.

Hold on to what you have.

[BDanielMayfield]

http://news.nationalgeographic.com/2017 ... e-science/

And Black Holes shooting out blobs that eventually turn into planets.

There are likely some odd and rare modes of planet formation from the debris of stellar destruction, but the main method is undoubtedly accretion of the leftovers from star birth, not death. This main pathway to planet formation, the one that can produce Earth-like planets orbiting normal stars is what I was asking about. Since evidence is piling up that nearly all stars have planets the formation pathway must be robust, that is, it must be an automatic byproduct of star formation that doesn't require an odd or rare set of conditions.

What processes allow dust motes to grow into pebbles, stones, boulders, rubble piles, and then planetesemals large enough to begin gravitational attraction, all while surviving potentially destructive collisions? I was intrigued by the idea that ice might play a very critical role here.

Bruce

"Undoubtedly" is a word that should be used sparingly, for instance, after solid proof, like when sipping a glass of water, "This water is undoubtedly wet." Theories on planetary formation do not fit that test. There is simply TOO MUCH to learn, to speculate on, to ponder, to examine, to observe.

If the word "undoubtedly" can only be used for things as patently obvious as the wetness of water the word would be restricted to only the absurdly obvious.

Undoubtedly is being used correctly here. We know beyond reasonable doubt that the planets around stars are formed locally around those stars, and we observe that process directly around other stars.

http://news.nationalgeographic.com/2017 ... e-science/

And Black Holes shooting out blobs that eventually turn into planets.

There are likely some odd and rare modes of planet formation from the debris of stellar destruction, but the main method is undoubtedly accretion of the leftovers from star birth, not death. This main pathway to planet formation, the one that can produce Earth-like planets orbiting normal stars is what I was asking about. Since evidence is piling up that nearly all stars have planets the formation pathway must be robust, that is, it must be an automatic byproduct of star formation that doesn't require an odd or rare set of conditions.

What processes allow dust motes to grow into pebbles, stones, boulders, rubble piles, and then planetesemals large enough to begin gravitational attraction, all while surviving potentially destructive collisions? I was intrigued by the idea that ice might play a very critical role here.

I think this is the correct way of looking at things.

How do planets form? This we know with a high degree of certainty, but a low degree of precision: the vast majority of planets form just as you suggest, by the accretion of material in a disc around newly forming stars. That view is well supported by theory and a lot of observational evidence. It's what we might call the "big picture", and we almost certainly have it correct.

Beyond that, there remain other interesting questions yet to be answered (or answered well). Are there other mechanisms for planet formation? Yes, probably. Things like stars being shredded by interactions with black holes. Not a significant contributor to planet formation (especially planets in orbit around stars), but very plausible. And as you allude to at the end, what are the actual mechanisms of accretion? We're pretty sure that there are electromagnetic mechanisms- particles acquiring static charge which enhance accretion before gravity becomes the driving force. And now, this ice boundary theory you bring up.

We're not going to find many researchers who doubt accretion is the primary factor in planet formation. But there's a lot of interesting work being done to explore all the possible mechanisms present in presolar discs that can actually produce planets.

Thank you Chris for this defense of our (in this instance) shared viewpoints.

Warming, are you suggesting that the Earth or any other planets in this system were formed elsewhere, apart from the Sun? Just spitballing a question here, to see if it sticks.

Bruce

[warmingwarmingwarming]

"Undoubtedly" is a word that should be used sparingly, for instance, after solid proof, like when sipping a glass of water, "This water is undoubtedly wet." Theories on planetary formation do not fit that test. There is simply TOO MUCH to learn, to speculate on, to ponder, to examine, to observe.

If the word "undoubtedly" can only be used for things as patently obvious as the wetness of water the word would be restricted to only the absurdly obvious.

Undoubtedly is being used correctly here. We know beyond reasonable doubt that the planets around stars are formed locally around those stars, and we observe that process directly around other stars.

I think this is the correct way of looking at things.

How do planets form? This we know with a high degree of certainty, but a low degree of precision: the vast majority of planets form just as you suggest, by the accretion of material in a disc around newly forming stars. That view is well supported by theory and a lot of observational evidence. It's what we might call the "big picture", and we almost certainly have it correct.

Beyond that, there remain other interesting questions yet to be answered (or answered well). Are there other mechanisms for planet formation? Yes, probably. Things like stars being shredded by interactions with black holes. Not a significant contributor to planet formation (especially planets in orbit around stars), but very plausible. And as you allude to at the end, what are the actual mechanisms of accretion? We're pretty sure that there are electromagnetic mechanisms- particles acquiring static charge which enhance accretion before gravity becomes the driving force. And now, this ice boundary theory you bring up.

We're not going to find many researchers who doubt accretion is the primary factor in planet formation. But there's a lot of interesting work being done to explore all the possible mechanisms present in presolar discs that can actually produce planets.

Thank you Chris for this defense of our (in this instance) shared viewpoints.

Warming, are you suggesting that the Earth or any other planets in this system were formed elsewhere, apart from the Sun? Just spitballing a question here, to see if it sticks.

Bruce

It's possible, Daniel, according to what some of us NOW think we know .. and my substantiations are in the conversation.

And yes, I think the word undoudtedly should only be used where the reality is absolutely easily seen and absolutely easily confirmed with no trace of doubt whatsoever. Otherwise, lots of innocent people are hanged because they are undoubtedly guilty .. and as you probably know, LOTS of INNOCENT people have been hanged, or electrocuted, or gassed, or injected with death drugs .. often based on witnesses saying "It was undoubtedly him."


And you know, with the number of galaxies in the universe, and the number of planets, our teeny tiny knowledge of planet formation touches on what, .00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001 percent or something undoubtedly ridiculously even smaller.
Yet .. some of us think we know a LOT despite these many, many pages of highly scientific discussion. https://scholar.google.ca/scholar?q=alt ... UQgQMIIDAA

[warmingwarmingwarming]

And just to show that we are merely beginning to learn there is this from this forum: http://asterisk.apod.com/viewtopic.php?f=31&t=37314

[BDanielMayfield]

Warming, are you suggesting that the Earth or any other planets in this system were formed elsewhere, apart from the Sun? Just spitballing a question here, to see if it sticks.

Bruce

It's possible, Daniel, according to what some of us NOW think we know .. and my substantiations are in the conversation.

I can't agree. Personally, I believe that several lines of well reasoned evidence, a preponderance of evidence, supports the conclusion that basically the whole solar system formed together over 4 billion years ago.

And yes, I think the word undoudtedly should only be used where the reality is absolutely easily seen and absolutely easily confirmed with no trace of doubt whatsoever.

Ok, I can see your point that 'undoubtedly' means without a trace of doubt. Even with this tight definition I still think that the vast, overwhelming majority of planets found orbiting a star or a group of stars were formed in orbit of that same star or same group of stars, with only very rare exceptions. Since we can now see accretion disks around young stars there is in fact now reasonable and ample confirmation that planets do indeed form around young stars, undoubtedly even.

And you know, with the number of galaxies in the universe, and the number of planets, our teeny tiny knowledge of planet formation touches on what, .00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001 percent or something undoubtedly ridiculously even smaller.
Yet .. some of us think we know a LOT despite these many, many pages of highly scientific discussion. https://scholar.google.ca/scholar?q=alt ... UQgQMIIDAA

Very true that we have much more to learn, but we can see where the great bulk of planet formation is taking place; around new formed stars. The details of exactly how planets are formed is uncertain, but is becoming less so each year.

Bruce

[warmingwarmingwarming]

Warming, are you suggesting that the Earth or any other planets in this system were formed elsewhere, apart from the Sun? Just spitballing a question here, to see if it sticks.

Bruce

Very true that we have much more to learn, but we can see where the great bulk of planet formation is taking place; around new formed stars. The details of exactly how planets are formed is uncertain, but is becoming less so each year.

Bruce

"the great bulk of planet formation" Regarding the Black Hole Spitball formation .. “Our galaxy could be populated by hundreds of millions of these cold fragments that are the direct remnants of stars,” Girma says. From the National Geographic article. Those cold fragments are said to form into planets in a very short time.

There is yet another remarkable way planets are formed by the hundreds of millions, again having nothing to do with acretion discs, but that theory is not allowed discussion on this forum, but I have discussed it privately with you.

And as we are in infancy in exploring our own solar system, yet alone Galaxy and its neighbours, there will almost certainly be more ways planets are formed.

[geckzilla]

See, you say they "are formed" as if you've witnessed it first-hand. Come on, we have observational evidence for one way, and none at all for your way. This is the same thing that got you banned last time. You think your facts are better than everyone else's. We're done, here.

[Chris Peterson]

"the great bulk of planet formation" Regarding the Black Hole Spitball formation .. “Our galaxy could be populated by hundreds of millions of these cold fragments that are the direct remnants of stars,” Girma says. From the National Geographic article. Those cold fragments are said to form into planets in a very short time.

That's a high extreme. But let's take it. Hundreds of millions of rogue planets, of which only a tiny fraction could ever be captured by stars. So at most a few million outsider planets in orbit, in a galaxy with a hundred billion stars, most of which appear to have produced their own planets. (And there are probably a lot more rogue planets that originated in protostellar discs and were ejected- more than there are stars by some estimates.)

And as we are in infancy in exploring our own solar system, yet alone Galaxy and its neighbours, there will almost certainly be more ways planets are formed.

I don't think anybody is arguing otherwise. The point, however, is that it's nearly certain that nothing is going to alter our understanding that the primary mechanism for planet formation is accretion in protostellar discs, a mechanism that accounts for 99.99% or more of all the planets. All the mechanisms are interesting, but we have an excellent sampling of what's going on, based on actual observation. We don't need to observe so much more of the Universe, because we've already observed enough to know that the rules appear the same everywhere.

[BDanielMayfield]

I may have lost somewhat of a friend over this, but I feel strongly that the laws of physics work together to automatically produce planets around most stars, as well as rogue planets by various means. I'm a contrarian as to the root cause of the laws of physics, but not as to the rule of physical law. So it was useful to learn that rogue, hyper velocity planets might form from stars shredded by close encounters with black holes. Cool. It would be a nice discovery and confirmation of the theory if someday examples of such rogue planets are found heading at high speed straight out from the core of our galaxy. But, is this a viable, reasonable, or even logically possible explanation for any of the planets in our system? No way.

Bruce

[Chris Peterson]

I may have lost somewhat of a friend over this, but I feel strongly that the laws of physics work together to automatically produce planets around most stars, as well as rogue planets by various means. I'm a contrarian as to the root cause of the laws of physics, but not as to the rule of physical law. So it was useful to learn that rogue, hyper velocity planets might form from stars shredded by close encounters with black holes. Cool. It would be a nice discovery and confirmation of the theory if someday examples of such rogue planets are found heading at high speed straight out from the core of our galaxy. But, is this a viable, reasonable, or even logically possible explanation for any of the planets in our system? No way.

Well, I think we'd have to accept that it's logically (and even physically) possible. But given how easy it is to demonstrate the statistical rarity of such a capture, it most certainly isn't reasonable.

[BDanielMayfield]

I may have lost somewhat of a friend over this, but I feel strongly that the laws of physics work together to automatically produce planets around most stars, as well as rogue planets by various means. I'm a contrarian as to the root cause of the laws of physics, but not as to the rule of physical law. So it was useful to learn that rogue, hyper velocity planets might form from stars shredded by close encounters with black holes. Cool. It would be a nice discovery and confirmation of the theory if someday examples of such rogue planets are found heading at high speed straight out from the core of our galaxy. But, is this a viable, reasonable, or even logically possible explanation for any of the planets in our system? No way.

Well, I think we'd have to accept that it's logically (and even physically) possible. But given how easy it is to demonstrate the statistical rarity of such a capture, it most certainly isn't reasonable.

I was looking at this as not just an orbital mechanics problem (which could only be possible if the speed of the rogue was low enough), but also from the planet's composition issue. Such a planet would most likely be quite unusual. Also, if it came from the core of our galaxy it wouldn't be orbiting in our ecliptic plain.

Bruce