Tidal lock

[Spartan159]

If a planet in the habitable zone of an M class star had a decent sized moon, would that possibly keep the main world from being tidal locked to the star?

I'm looking at both Rhylanor and Porozlo in particular. "Thwacks Grandfather upside the head with a trout" I may just declare Ancients! IMTU for supposedly temperate worlds around M stars in the Spinward Marches.

 

[tjoneslo]

As I understand it, that moon would either be smashed into the planet or ejected from the whole system. The same tidal forces that stop the planet from rotating would also mangle the moon.

 

[aramis]

If a planet in the habitable zone of an M class star had a decent sized moon, would that possibly keep the main world from being tidal locked to the star?

I'm looking at both Rhylanor and Porozlo in particular. "Thwacks Grandfather upside the head with a trout" I may just declare Ancients! IMTU for supposedly temperate worlds around M stars in the Spinward Marches.

Several theorize that such a pair could last long enough to be life-bearing.

 

[Lycanorukke]

If a planet in the habitable zone of an M class star had a decent sized moon, would that possibly keep the main world from being tidal locked to the star?

I'm looking at both Rhylanor and Porozlo in particular. "Thwacks Grandfather upside the head with a trout" I may just declare Ancients! IMTU for supposedly temperate worlds around M stars in the Spinward Marches.

A few ways to dodge tidal locking apart from a moon.

Resonant spin/orbit - ie: Mercury where a day is 59 Earth days.

Big Impact - something hit the planet a few million years ago spinning it up. It will lock again in another million years, but for now you have day/night.

Recent arrival - The planet migrated in from the outer system or is a captured rogue. Again it will lock eventually but for now you're sweet.

Atmosphere - A very interesting one. A paper discusses how an atmosphere can counteract tidal locking in some circumstances. Brief overview here.

 

[whulorigan]

I'm looking at both Rhylanor and Porozlo in particular. "Thwacks Grandfather upside the head with a trout" I may just declare Ancients! IMTU for supposedly temperate worlds around M stars in the Spinward Marches.

GT: First In has a world-design example of Rhylanor scattered among the sidebars thru the book. It suggests that Rhylanor is currently in an orbital configuration in which it completes exactly 5 retrograde rotations on its axis per prograde revolution about its primary star.

 

[shaunhilburn]

A few ways to dodge tidal locking apart from a moon.

Resonant spin/orbit - ie: Mercury where a day is 59 Earth days.

Big Impact - something hit the planet a few million years ago spinning it up. It will lock again in another million years, but for now you have day/night.

Recent arrival - The planet migrated in from the outer system or is a captured rogue. Again it will lock eventually but for now you're sweet.

Atmosphere - A very interesting one. A paper discusses how an atmosphere can counteract tidal locking in some circumstances. Brief overview here.

Another scenario that I've given some thought to is ice accumulation on the night side causing enough imbalance that libration would eventually "tip the scales" and slowly flip the planet back around into a new lock position. It would mean lock-freeze-thaw-flood cycles lasting a several million years. During that interval continents (if any) could drift into the daylight or into the night.

It's just conjecture; I haven't actually worked it out. It would have to be a huge amount of ice, possible 5 points of the hydro digit.

 

[shaunhilburn]

"Thwacks Grandfather upside the head with a trout" I may just declare Ancients! IMTU for supposedly temperate worlds around M stars in the Spinward Marches.

The notion of flare sterilized M dwarf planets with a frozen atmosphere on the outer hemisphere started to fall into disfavor about 15 years ago.

The possibility of temperate, even hospitable M dwarf worlds is now taken seriously enough that funding is allocated to searching for them.

 

[Timerover51]

GT: First In has a world-design example of Rhylanor scattered among the sidebars thru the book. It suggests that Rhylanor is currently in an orbital configuration in which it completes exactly 5 retrograde rotations on its axis per prograde revolution about its primary star.

If that is the case, then how does the daylight side keep from frying, and the nighttime side keep from freezing?

 

[tjoneslo]

If that is the case, then how does the daylight side keep from frying, and the nighttime side keep from freezing?

Rhylanor has a 3 atmosphere (Very thin). So who's to say it hasn't already.

The general rule for these kind of worlds is if the atmosphere is thick enough it doesn't have time to freeze out. The slow rotation of the world with it's constant (if slow) shifting of the face toward the world

 

[Enoki]

Rhylanor has a 3 atmosphere (Very thin). So who's to say it hasn't already.

The general rule for these kind of worlds is if the atmosphere is thick enough it doesn't have time to freeze out. The slow rotation of the world with it's constant (if slow) shifting of the face toward the world

Slow rotation, like Venus, would be worse than a tidal lock. With a tidal lock you have a habitable zone between the "day" and "night" side. With a slow rotation, you have a wait on death row for your day in the sun...

 

[whulorigan]

Slow rotation, like Venus, would be worse than a tidal lock. With a tidal lock you have a habitable zone between the "day" and "night" side. With a slow rotation, you have a wait on death row for your day in the sun...

Except that as tjoneslo noted, it has a "3" (Very Thin) atmosphere - meaning that people are not living on the surface of the world without artificial life support anyway.

 

[Enoki]

Except that as tjoneslo noted, it has a "3" (Very Thin) atmosphere - meaning that people are not living on the surface of the world without artificial life support anyway.

Doesn't change that a slow rotation would require radically different construction than a tidal lock. Surface structures might not even be possible with slow rotation. Think something like a slow version of the Riddick prison hell world...

 

[Magnus von Thornwood]

Depends on your definition of people...

Except that as tjoneslo noted, it has a "3" (Very Thin) atmosphere - meaning that people are not living on the surface of the world without artificial life support anyway.

I think you meant to say human as last I checked the Dandies (can't spell their proper name) counted as people since they are Citizens of the Imperium and they live on Rhylanor's surface with a 3 (Very Thin) Atmo just fine.

So people can, just that humans aren't those people. :devil:

 

[whulorigan]

I think you meant to say human as last I checked the Dandies (can't spell their proper name) counted as people since they are Citizens of the Imperium and they live on Rhylanor's surface with a 3 (Very Thin) Atmo just fine.

So people can, just that humans aren't those people. :devil:

Good point. Yes, I meant Humaniti . . .

 

[SanDragon]

Llellewyloly, Herr Baron!