Do Planets Drift?

[hazelm]

Before I let my imagination wander any further, a question.  Do planets drift either away from or toward the sun?  Thank you. 

[A-wal]

Yes they do. It's known as planetary migration. The planets in the solar system might have been in a different order in the past, I think it's generally accepted that Uranus and Neptune have switched places at least.

[hazelm]

Yes they do. It's known as planetary migration. The planets in the solar system might have been in a different order in the past, I think it's generally accepted that Uranus and Neptune have switched places at least.

I'd forgotten about Uranus and Neptune.  Right.  So, I need to reword my question.  The reason is an article I read this morning about Venus.  No sense in posting it unless I can make sense.  So --- what I meant is are all the planets moving toward the sun or away from it over the billions of years? Or, maybe on the whole, not moving either way?  This would be different from what Uranus and Neptune did independently of the rest.

 

Thank you. 

[A-wal]

Most systems have 'hot Jupiters' that couldn't have formed that close to the star so in general planets tend to gradually fall into their star. I'm not 100% on this but I think the Solar System is one of the less common ones where the planets seem to be slowly moving away.

[hazelm]

Most systems have 'hot Jupiters' that couldn't have formed that close to the star so in general planets tend to gradually fall into their star. I'm not 100% on this but I think the Solar System is one of the less common ones where the planets seem to be slowly moving away.

Thank you.  Let me go find that story again and comment what I was thinking.  It's been a few hours.  I shall return.

[A-wal]

I should have said most planets fall towards their star, not into their star, or there wouldn't be so many observable hot Jupiters. I suppose an increase in repulsion force from the star must overpower the increase in gravity (or at least greatly slow down the approach) when planets get close enough.

Edited March 31, 2018 by A-wal

[hazelm]

Thank you.  Let me go find that story again and comment what I was thinking.  It's been a few hours.  I shall return.

All right.  Possible life on Venus:  https://www.sciencedaily.com/releases/2018/03/180330171302.htm?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+sciencedaily%2Ftop_news%2Ftop_science+%28ScienceDaily%3A+Top+Science+News%29

 

Near the end is this:  (Quote)  Lemaye notes, however, that the part of the equation that isn't known is when Venus' liquid water evaporated.  Extensive lava flows in the last billion years likely have either destroyed or covered up the planet's earlier terrestrial history.  (Unquote)

 

My issue stems from my belief that the planets are generally drifting away from the sun.  If this is true, then Venus would not have lost its liquid water but would be only now developing liquid water.  My thought has always been that Earth would some day be as dry as Mars is today and Venus would be the next  "green" planet.

 

I know and admit that there are a lot of flaws in my thinking but it's my thinking.  Scientists who have been studying Venus much more thoroughly than I might knock my theory into a cocked hat fast.  We shall see.  Maybe the rocky planets are headed toward a gaseous form.  Or, take a look at what orbits between Mars and Jupiter. 

[hazelm]

I should have said most planets fall towards their star, not into their star, or they wouldn't be so many observable hot Jupiters. I suppose an increase in repulsion force from the star must overpower the increase in gravity (or at least greatly slow down the approach) when planets get close enough.

 

 

Gravity might say so but forgive me for not buying it.   Is there something called "repulsion force"?  Of course.  I think I just know it by another term.  All right.

Edited March 31, 2018 by hazelm

[A-wal]

Well if there's a possibility of life having existed on Mars (apparently) then why not Venus?

 

I think Venus is supposed to have had a runaway greenhouse effect but I don't know if (or know if it's generally accepted that) it's anything to do with it getting closer to the sun. It seems the most likely explanation so maybe it's not generally thought that the planets are moving away from the sun, like I said I'm not sure about that.

 

Gravity might say so but forgive me for not buying it.   Is there something called "repulsion force"?  Of course.  I think I just know it by another term.  All right.

I don't really get what you're trying to say in that post. I just meant that I know most (or at least a lot more than expected) systems have a hot Jupiter that couldn't have formed that close to their star so they must have migrated inwards and there must be a force from the star repelling them to at least slow down their fall or there wouldn't be so many observed hot Jupiters.

 

I have come across the idea that stars might eject matter that moves away from the star and becomes a gas giant but it's definitely not an accepted model, I'm not sure if it's even considered credible.

[hazelm]

Well if there's a possibility of life having existed on Mars (apparently) then why not Venus?

 

I think Venus is supposed to have had a runaway greenhouse effect but I don't know if (or know if it's generally accepted that) it's anything to do with it getting closer to the sun. It seems the most likely explanation so maybe it's not generally thought that the planets are moving away from the sun, like I said I'm not sure about that.

 

I don't really get what you're trying to say in that post. I just meant that I know most (or at least a lot more than expected) systems have a hot Jupiter that couldn't have formed that close to their star so they must have migrated inwards and there must be a force from the star repelling them to at least slow down their fall or there wouldn't be so many observed hot Jupiters.

 

I have come across the idea that stars might eject matter that moves away from the star and becomes a gas giant but it's definitely not an accepted model, I'm not sure if it's even considered credible.

All right.  I misunderstood.  My mind is fixed on looking at the entire lineup of planets.  Thanks for clarifying.

[hazelm]

Do you mean, are planets capable of leaving a star system like our own?

 

Yes, planets can go drifting through space, usually either knocked out of orbit by a larger astronomical bodies or literally thrown out by a strong gravitational source. Many supermassive black hole get ejected from the center of their galaxies.

No, I am looking at one solar system and asking if the planets within that solar system will drift either toward or  -----  hmmmm "the opposite" of ---- the sun.  They would still be part of that solar system but drifting either toward or back from that sun.  In this case, I am looking at our solar system.

 

Surely is hard not to say "away from".  :-)

Edited March 31, 2018 by hazelm

[DaveC426913]

No, I am looking at one solar system and asking if the planets within that solar system will drift either toward or  -----  hmmmm "the opposite" of ---- the sun.  They would still be part of that solar system but drifting either toward or back from that sun.  In this case, I am looking at our solar system.

 

Surely is hard not to say "away from".  :-)

 

The position of planets often evolves over astronomical time frames (hundreds of millions of years or more) through interaction. They don't drift away and just keep on drifting. They may move in for a while, then out again, even occasionally switching positions depending on their interactions. It is very rare - and catastrophic - for a planet to actually get ejected from a system.

[hazelm]

The position of planets often evolves over astronomical time frames (hundreds of millions of years or more) through interaction. They don't drift away and just keep on drifting. They may move in for a while, then out again, even occasionally switching positions depending on their interactions. It is very rare - and catastrophic - for a planet to actually get ejected from a system.

Thank you.  That's exactly what I wanted to know.  Now to recall why I asked.  It was a story about Venus but I'll have to think a while.  Either that or find it in whichever magazine it was.

 

Thanks again. 

[JMJones0424]

Just to reiterate, there is no physical reason that a planet in a star system would drift towards or away from the star at the center other than normal gravitational interactions.  Most people have a very poor innate understanding of orbital mechanics as this is not at all descriptive of how objects that we encounter on a daily basis move.  The apparent absurdity is similar to viewing the motion of gyroscopes.

 

There is no known repulsive force in a solar system that could cause a planet to drift outwards.  There is a very slight force imparted by radiation pressure and by events like solar flares, but this force is negligible compared to the inertia of a planet.  An interesting exercise would be to compare the radiation pressure of the sun on the Earth with the force of blowing on the Eiffel tower.  I don't know, but I'd bet that blowing on the Eiffel tower is more effective at changing its position.  Newtonian mechanics is very good at describing the position of planets orbiting a star, and when it isn't, it is usually because the gravitational field or the relative speed is significantly greater than anything we normally experience.