How Fast Do Rogue Planets Move?

[Curufea]

Re: How Fast Do Rogue Planets Move?

 

One way to move a planet is to change its orbit from elliptical to a slingshot - slow the planet enough such that it falls towards its sun in a slingshot.

 

It would mean you'd only be able to move it in the plane of the ecliptic, though - and it may take half a year (of that planet) or so before the planet is on its way.

 

On a side note - the Puppeteers of Known Space by Larry Niven, have "The Rosette" - 5 planets and a sun they have moving away from the galactic core (to escape the explosion).

[Sundog]

Re: How Fast Do Rogue Planets Move?

 

One method of getting a rogue planet is to have a system change from a sigular to a close binary. If this were to happen to Sol, Mercury would be slingshotted, Venus would have a seriously perturbed orbit, and Earth would have a slightly disturbed orbit.

 

Of course, this would necessitate a close encounter with another star at just the right angles and velocities for mutual capture, which isn't exactly likely.

[Choldath]

Re: How Fast Do Rogue Planets Move?

 

There was a PC game some time ago that allowed you to set up your own solar system. I can't remember what it is, but it looks a bit like this.

 

http://dan-ball.jp/en/javagame/planet/

[BobGreenwade]

Re: How Fast Do Rogue Planets Move?

 

There was a PC game some time ago that allowed you to set up your own solar system. I can't remember what it is, but it looks a bit like this.

 

http://dan-ball.jp/en/javagame/planet/

 

Thanks for reviving that link.

 

Funny thing... I set one up just for giggles, put as many satellites in as I could just to see how many would survive, and just checked back after five minutes. Two of the bodies I put in have become moons.

 

I never had that happen the first time the link made the rounds....

[SteveZilla]

Re: How Fast Do Rogue Planets Move?

 

One method of getting a rogue planet is to have a system change from a sigular to a close binary. If this were to happen to Sol, Mercury would be slingshotted, Venus would have a seriously perturbed orbit, and Earth would have a slightly disturbed orbit.

 

Of course, this would necessitate a close encounter with another star at just the right angles and velocities for mutual capture, which isn't exactly likely.

 

Not to mention what the extra solar radiation would do to us and our climate. Think we have Global Warming now? Just wait until the solar energy (Optical, Radio, Thermal, UV, Gamma...) received by the Earth gets increased 25% from the capture of a small second star (a second G-type would roughly double our received radiaion).

 

But on the up side, the Northern (& Southern) Lights would be spectacular!

[Nyrath]

Re: How Fast Do Rogue Planets Move?

 

Not to mention what the extra solar radiation would do to us and our climate. Think we have Global Warming now? Just wait until the solar energy (Optical' date=' Radio, Thermal, UV, Gamma...) received by the Earth gets increased 25% from the capture of a small second star (a second G-type would roughly double our received radiaion).[/quote']

It depends upon how close the second star is.

 

In the Alpha Centauri system, the distance between Alpha Centauri A and Alpha Centauri B varies from 11 AU to 35 AU (i.e., between the distance betwix Sol and Saturn, and the distance betwix Sol and Pluto).

 

This means that from the viewpoint of a person on a hypothetical planet at 1 AU from either star, the other star will appear as a brilliant star, but will not contribute anything detectable for solar heat.

 

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

[SteveZilla]

Re: How Fast Do Rogue Planets Move?

 

Anthing close enough to slingshot Mercury out of the system (per Sundog's post) would be (I would think) close enough to make a noticable difference in received solar energy.

[Captain Obvious]

Re: How Fast Do Rogue Planets Move?

 

There was a PC game some time ago that allowed you to set up your own solar system. I can't remember what it is, but it looks a bit like this.

 

http://dan-ball.jp/en/javagame/planet/

 

Heh...awesome...I set up a binary star and got a planet going in a figure 8 loop around them.

[Michael Hopcroft]

Re: How Fast Do Rogue Planets Move?

 

This is actually key to the motives for moving the planet. The rogue planet was home to a race of "benevolent" aliens who found it bombarded by a race of "malevolent" aliens with asteroids containing virulent spores and microbes that needed the nearby sun to reproduce quickly (terraforming bio-bombs). Their navy didn't have sufficient numbers to interdict the assault' date=' and the planet was too far from her sister worlds to receive timely aid. The resident aliens took a gamble.... space billiards.[/quote']

 

But wouldn't that have eliminated them as well? Conditions that eliminate photosynthesis should, sooner or later, eliminate all other life as well for several reasons -- most notably that without photosynthesis the oxygen in what atmosphere is retained gets replaced with carbon dioxide and animals that haven't already starved or frozen suffocate.

 

This of course assumes that the planet in its new condition can retain an atmosphere at all. If it strays too close to the sun, the gases boil away. If it strays too far, they freeze. Either way makes life impossible.

 

The only way for anything to survive would be in massive temperature-controlled shelters under the planet's surface, and to hope you can provide enough food and oxygen for a long enough period. It becomes a matter of trying to hold out until rescue comes, and hoping it comes at all.

 

Such shelters defy physics, but then so does jolting a life-bearing planet out of orbit without killing everything.

[Basil]

Re: How Fast Do Rogue Planets Move?

 

There was a PC game some time ago that allowed you to set up your own solar system. I can't remember what it is, but it looks a bit like this.

 

http://dan-ball.jp/en/javagame/planet/

OK, that instantly became my favorite webtoy.

[Sundog]

Re: How Fast Do Rogue Planets Move?

 

Anthing close enough to slingshot Mercury out of the system (per Sundog's post) would be (I would think) close enough to make a noticable difference in received solar energy.

 

 

Actually, the information I posted was based on the conditions in the Alpha Centauri system.

 

Gravitational perturbations apparently have a worse effect the closer you are to one of the primaries.

[tkdguy]

Re: How Fast Do Rogue Planets Move?

 

Heh...awesome...I set up a binary star and got a planet going in a figure 8 loop around them.

Most of my planets collided with one another!

 

Edit: I even managed to destroy the main planet (the earth?)

[SteveZilla]

Re: How Fast Do Rogue Planets Move?

 

Actually, the information I posted was based on the conditions in the Alpha Centauri system.

 

Gravitational perturbations apparently have a worse effect the closer you are to one of the primaries.

 

I never would have figured that. I would have thought that for any planet orbiting "between" the stars (i.e., around one of the two binaries), the closer the orbit is to the Binaries' Center Of Mass, the more perturbed it would be. Case in point would be the 'figure 8' orbit, IMO.

[Maur]

Re: How Fast Do Rogue Planets Move?

 

But wouldn't that have eliminated them as well? Conditions that eliminate photosynthesis should' date=' sooner or later, eliminate all other life as well for several reasons -- most notably that without photosynthesis the oxygen in what atmosphere is retained gets replaced with carbon dioxide and animals that haven't already starved or frozen suffocate.[/quote']

 

Killing photosynthesis does not kill all life. We have thermophiles living in the oceans that do not appear to get any of their energy from the sun. They get it from the sulphides ejected by the black smokers.

 

This of course assumes that the planet in its new condition can retain an atmosphere at all. If it strays too close to the sun, the gases boil away. If it strays too far, they freeze. Either way makes life impossible.

 

I'd be careful about using the word impossible when it comes to life. We've used it many times only to find our assumptions were incorrect. While life as we know it might not survive in such conditions, some might survive. Case in point, we've found bacteria frozen in ice for 25,000 years that came back to functioning life as soon as it was warmed up.

 

The only way for anything to survive would be in massive temperature-controlled shelters under the planet's surface, and to hope you can provide enough food and oxygen for a long enough period. It becomes a matter of trying to hold out until rescue comes, and hoping it comes at all.

 

Such shelters defy physics, but then so does jolting a life-bearing planet out of orbit without killing everything.

 

No, it doesn't defy physics. It just defies our current level of technology.

[keithcurtis]

Re: How Fast Do Rogue Planets Move?

 

Cancer, have you ever tried to work out the feasibility of the Bronson Bodies from When Worlds Collide?

 

Keith "I must have read that book a dozen times" Curtis

[Cancer]

Re: How Fast Do Rogue Planets Move?

 

Cancer, have you ever tried to work out the feasibility of the Bronson Bodies from When Worlds Collide?

 

Keith "I must have read that book a dozen times" Curtis

 

I must sheepishly admit I've never read that book, so I have only a vague idea of what those are. Never thought about them in a physical-reality sense.

[keithcurtis]

Re: How Fast Do Rogue Planets Move?

 

Spoilers ahead!

 

The book is far different from the movie. In the book, there are two planets, not a planet and star. Bronson Alpha is a gas giant, roughly the size of Neptune. Bronson Beta is a terrestrial planet/satellite. They were torn from their original orbit presumably by the close passage of another star. The original inhabitants of Bronson Beta saw their doom for centuries, but earth had no such luck. Putting aside the amazing coincidence of these planets coming to our solar system (the characters often ponder if it is divinely-directed, a la the Flood), the motions are fairly well described.

 

The planets arrive from the southern (and fairly unwatched, in the early 20th century) skies, roughly 90° from the ecliptic. They pass through the solar system on a parabolic(?) course, whipping around the sun. Thus they pass by the earth twice, at six month intervals. On the first passage, Bronson Alpha destroys the Moon. Whether this was a direct impact or if it is torn apart by tidal forces is unspecified. Earth is devastated, of course and civilization collapses. It is on the second pass that the end comes. A few hastily-constructed rockets brave the passage between Earth and Bronson Beta, which has been thawing all this time. Bronson Alpha impacts the earth with a glancing blow, which of course destroys it utterly. The gravitational forces of the masses in question cause Bronson Alpha to continue out into space, while Bronson Beta takes an eccentric orbit about the sun, canted 90° to the ecliptic while varying in distance from the sun somewhat between the distances described by Venus and Mars.

 

Unlikely premise in the extreme, but again, the characters note this in the book, some becoming extremely religious. It's a great read, and probably my first experience with an Apocalyptic novel.

 

Keith "Recommends the sequel, too" Curtis

[Nyrath]

Re: How Fast Do Rogue Planets Move?

 

Cancer' date=' have you ever tried to work out the feasibility of the Bronson Bodies from When Worlds Collide?[/quote']

My gut feeling is that it is believable as far as the initial scenario goes: Neptune sized body with Earth-sized moon whizzes past Earth causing earthquakes, loops around the Sun, then obliterates Earth.

 

The part about the Earth-sized moon magically escaping its primary's gravity and magically decelerating into a perfect circular orbit one AU from the Sun is more or less impossible, AFAIK

[Cancer]

Re: How Fast Do Rogue Planets Move?

 

... And you only get one encounter. Yes, the parabolic orbit could intersect Earth's orbit at two points, but it's utterly impossible to have the two bodies have close passes at both of those points in one orbit.

[Clonus]

Re: How Fast Do Rogue Planets Move?

 

If you actually have a species of people who decide to move their planet to deal with a biocontrol problem, then obviously they can move their planet as fast as you want them to.

[Cancer]

Re: How Fast Do Rogue Planets Move?

 

True, but at that point you depart from standard orbital mechanics, and you're magically moving the planet around to suit your plot. Also, those people are making a conscious, premeditated choice to destroy an inhabited planet and everything that lives on it, because there's no natural way to get two close passes in a single orbit. You can't have that happen by accident, only by willed action and use of trans-human tech.

[Maur]

Re: How Fast Do Rogue Planets Move?

 

If they can get a planet moving then they aren't using orbital mechanics that a normal star system operates under since they are applying a force that isn't normally there.

[Vondy]

Re: How Fast Do Rogue Planets Move?

 

But wouldn't that have eliminated them as well? Conditions that eliminate photosynthesis should, sooner or later, eliminate all other life as well for several reasons -- most notably that without photosynthesis the oxygen in what atmosphere is retained gets replaced with carbon dioxide and animals that haven't already starved or frozen suffocate.

 

This of course assumes that the planet in its new condition can retain an atmosphere at all. If it strays too close to the sun, the gases boil away. If it strays too far, they freeze. Either way makes life impossible.

 

The only way for anything to survive would be in massive temperature-controlled shelters under the planet's surface, and to hope you can provide enough food and oxygen for a long enough period. It becomes a matter of trying to hold out until rescue comes, and hoping it comes at all.

 

Such shelters defy physics, but then so does jolting a life-bearing planet out of orbit without killing everything.

 

Species survival: this is totally dependent on what assumptions are in play about the technology available to the inhabitants and whatever measures they took prior to playing space billiards. I didn't propose any yet, so I don't have a problem to deal with at this point. Presumably, however, if one plans to move a planet, let alone has the ability to do so, one has a plan to ensure one's survival (as that was the motive for moving the planet).

 

As for the atmosphere: current theories accept the possibility of rogue planets (ejected from systems) that have atmospheres and surface water, though those atmospheres aren't likely to be friendly to humans, and the planet is likely to have significant vulcanism. Also, atmospheres don't burn off overnight. A one-time pass close to a primary is very different from a close orbit (a long term situation). What's more, the survivability of surface water would be dependent on atmospheric density, albedo, and a host of other factors. Again, a question of which "assumptions" are in play.

 

At this point I'm only concerned with the feasibility of moving a planet from a system within 12 LY to the Sol system over a short period (100-300 years). After that I can work backwards and come up with a "believable" set of assumptions.

[SteveZilla]

Re: How Fast Do Rogue Planets Move?

 

If one is playing Billiards with one's world (as opposed to using the Gas Giant "Candle" method), then one has no way to do a midway course correction... Better get it 100% right on the first try, and that there are no unknown variables.