Planets in Deep Space: Can They Escape Orbit?

[binbots]

Can planets escape there orbit? If so does that mean there are planets in deep space?

 

[Drakkith]

Sure, it's possible. A passing object with a high enough mass can disrupt the orbits of planets and possibly cause them to be ejected.

 

[binbots]

Do we have any idea how many planets could actually be out there?

 

[Drakkith]

Do we have any idea how many planets could actually be out there?

Nope. No idea. I don't think there's anyway to know for sure or to make a very close guess.

 

[binbots]

So there could be billions upon billions? If that is the case how do we know how much mass is in each galaxy?

 

[russ_watters]

Well, we just became aware that there are likely thousands of planet sized objects in wide orbits around the sun. There could be thousands more planet sized objects ejected from orbit.

We can measure the mass of the galaxy by the orbital speed of the objects in it. Not easy because they are so big, but doable for many.

 

[mjacobsca]

There are many ways planets can end up in deep space. Interactions with other planets (especially early in the solar system's life-cycle when there are dozens of large objects forming, colliding, and affecting each other), gravitational interactions from passing stars and black holes in which a planet gets caught in the crossfire and expelled from its solar system (more common in star clusters and closer in towards the center of the galaxy), being "released" from a solar system due reduced gravity of a parent sun when it goes through the red giant phase and expels most of its mass in fierce solar winds (a future possibility for Earth), or even due to supernovae. All of these are possible and even likely throughout the galaxy. Raw guesses on numbers are not really possible, but billions of interstellar wanderers may be plausible from what I have read. And over the vast eons of time, almost any interaction that can occur, will occur, throughout the galaxy and universe. Not only that, many of these wandering "dark" planets may have internal sources of heat, sub-glacial oceans, and primitive life. So the answer to your question is most definitely "yes", but actual data is hard to come by because we can't see these objects at all.

As for your question relating to overall mass of the galaxy, I would guess the contribution from a few billion interstellar planets would be negligible in a galaxy with hundreds of billions of stars, considering that stars can be millions of times the mass of a single planet, and super-massive black holes billions of times more massive than the stars.

 

[Drakkith]

Well, we just became aware that there are likely thousands of planet sized objects in wide orbits around the sun. There could be thousands more planet sized objects ejected from orbit.

We can measure the mass of the galaxy by the orbital speed of the objects in it. Not easy because they are so big, but doable for many.

Planet sized, or dwarf planet sized, or what? Just want to make sure I'm not missing some newly discovered planets around the sun lol.

 

[russ_watters]

Planet sized, or dwarf planet sized, or what? Just want to make sure I'm not missing some newly discovered planets around the sun lol.

Well, you're highlighted the main the logical inconsistency in the new definitions. "Planet sized" and "dwarf planet sized" are the same size. The size requirement is that they be massive enough to be able to pull themself into a spheroid. The only difference between the two definitions is that a "planet" has swept its orbit of debris. The way I understand it, what makes Pluto a non-planet, then, is that it it has an orbit eccentric enough to cross with Neptune's and thus hasn't cleared its orbit of debris.

Anyway, here's what the wiki on the subject says about how many:

It is suspected that at least another 40 known objects in the Solar System are dwarf planets, and estimates are that up to 200 dwarf planets may be found when the entire region known as the Kuiper belt is explored, and that the number might be as high as 2,000 when objects scattered outside the Kuiper belt are considered.

http://en.wikipedia.org/wiki/Dwarf_planet

 

[Drakkith]

Ah ok. Thanks russ.

 

[DaveC426913]

The way I understand it, what makes Pluto a non-planet, then, is that it it has an orbit eccentric enough to cross with Neptune's and thus hasn't cleared its orbit of debris.

Never quite understood this definition...

So, Neptune is not a planet either, since it has not cleared its orbit of debris...

 

[russ_watters]

Dunno - maybe I'm wrong and there is more debris.

 

[DaveC426913]

Dunno - maybe I'm wrong and there is more debris.

No. I'm not refuting you.

Assuming the definition of a non-planet is 'has not cleared its orbit of debris', then Neptune is not a planet.

I never understood why they made a change in the definitions when their definitions were inadequate the moment they were uttered. They haven't gained any ground except causing the rewrite of HS textbooks.

 

[Drakkith]

The definition of a planet according to the 2006 IAU's General Assembly:

A celestial body that is (a) in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

Definition of Clearing the Neighborhood:

Clearing the neighbourhood of its orbit" is a criterion for a celestial body to be considered a planet in the Solar System. This was one of the three criteria adopted by the International Astronomical Union (IAU) in its 2006 definition of planet.[1]

In the end stages of planet formation, a planet will have "cleared the neighbourhood" of its own orbital zone, meaning it has become gravitationally dominant, and there are no other bodies of comparable size other than its own satellites or those otherwise under its gravitational influence.

I never understood why they made a change in the definitions when their definitions were inadequate the moment they were uttered. They haven't gained any ground except causing the rewrite of HS textbooks.

What would you do instead? We have to have reasonable definitions in order to classify objects. I think the current definition fits nicely. Especially considering we were going to be forced to add possibly tens to hundreds of new planets if we hadn't changed it. And then what would we do in school and everday conversation?

 

[DaveC426913]

OK so the operative phrase is "of comparable size".

 

[FtlIsAwesome]

Can planets escape there orbit? If so does that mean there are planets in deep space?

Yes, not only that but there was a dicussion of such planets possibly being habitable Europa-like worlds due to internal heat: https://www.physicsforums.com/showthread.php?t=470790