Tidally locked worlds

[Gruffty]

Orignially posted by Temp Mal:
Clear as mud now?

Yup!

Originally posted by TempMal:
Basically yes - but only if you're talking about a terrestrial world (remember gas giants take a LOT longer to slow down their rotation because of their fluid nature). Solid bodies tidelock so fast when they're close to their star that pretty much the only time you'll see freely-rotating bodies close to the star is less than a million years just after the system forms.

OK, so for a solid body, we automatically make the tidelocked world an old world.

Gas giants can rotate, if the Ref/GM decides to put one in the HZ. But presumably, still no satellites around a GG in the HZ of an M V?
(

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[Gruffty]

Just as an aside, I assume that asteroid/planetoid belts are OK to be orbiting an M V star? Perhaps an "old" world that fell apart (or was smashed apart by another body somehow) or just didn't accrete to form a world?

<Edit:> Thought: if an asteroid belt orbits an M V star within its HZ, would the belt still rotate round the star, or would it be tidally locked?

 

[TempMal]

OK, so for a solid body, we automatically make the tidelocked world an old world.

No, a million years old is YOUNG. Earth is 4.6 BILLION (ie 4,600 million) years old. If Earth was around an M V star then it would have been tidally locked pretty much while it was still cooling and accreting.

Gas giants can rotate, if the Ref/GM decides to put one in the HZ. But presumably, still no satellites around a GG in the HZ of an M V? (

)

I'd say no. The solar tides would probably disrupt the orbits of the satellites and cause them to spiral in and crash into the planet. However, I'm not 100% sure about that, but I'd say that it's better to assume it's not possible.

 

[Gruffty]

Orignially posted by TempMal:
No, a million years old is YOUNG.

Teh. That's why you're the scientist and I'm not

I'll just leave that bit out then.

Originally posted by TempMal:
The solar tides would probably disrupt the orbits of the satellites and cause them to spiral in and crash into the planet. However, I'm not 100% sure about that, but I'd say that it's better to assume it's not possible.

I'm happy with the no satellites concept. No satellites orbiting a GG in the HZ of an M V.

 

[Gruffty]

Gruffty's Tidally Locked Worlds Rules
(a.k.a. the "Gruffty is opting out of doing lots of really hard maths" rules ):

Solid Planets
"A solid planet orbiting an M V star (with a mass of less than 0.7 sol) will be tidally locked to its star if the planet's orbit is within the M V star's habital zone. Such a tidally locked world will not have any moons in orbit."

Gas Giants
"A gas giant orbiting an M V star (with a mass of less than 0.7 sol) within that star's habitable zone will rotate around its axis. However, such a gas giant will not have any moons in orbit."

 

[Border Reiver]

Looks good. Simple and concise, no room for prevarication. I like it.

 

[TempMal]

That's probably good enough

 

[Gruffty]

Thanks I like them, too.

That just leaves the asteroid belts to sort out

As TempMal said, the maths and physics involved in this sort of thing are horrendous - I didn't really fancy trying to work out how to plug a huge formula into Excel.

 

[Border Reiver]

Don't even think about it, I start an OU math program this year (for fun ) and am shitting myself. Still got time to change my mind and find something a bit less cerebral like history.

 

[Gruffty]

Teh. I start my BSc (Hons) Professional Practice (Mental Health) again at the end of the month. Time to revisit Festinger's Theory of Cognitive Dissonance. Anyhoo, back to good ol' Trav...

Asteroid belts.

Do they rotate round an M V star if they're within the HZ? I haven't actually seen asteroid belts mentioned in any of the articles I've read on M V stars and tidal lock. Only solid planets and GGs have been discussed so far.

I *feel* that an asteroid belt orbiting in the HZ of an M V star would either be stationary or extremely slow moving. BTW, I'm assuming that an asteroid belt (say for example, our own in our solar system) does actually orbit a star, i.e. all the individual pieces orbit together in the same direction, at approximately the same speed.

 

[TempMal]

Asteroid belts are just a swarm of small objects moving in roughly similar orbits.

if you have trouble visualising thing, downlaod the Celestia solar system viewer from http://www.shatters.net/celestia/download.html , you can see some (not all) of the main belt asteroids there.

Now you mention it, I'm not entirely sure what an asteroid belt close to an M V (or any star) would be like. I'd guess that it might act more like a ring system around a planet, with all the rocks in a thin disk around the star, all the orbits being pretty close to circular, and with gaps caused by other planets outside the belt.

It'd probably look rather different to our own somewhat chaotic asteroid belt with its eccentric and inclined orbits. Certainly you could get such asteroid belts and oort clouds/kuiper belts a lot further out (beyond 1 AU), but a belt that's really close (within an AU, certainly within 0.5 AU) would probably bear a closer resemblance to a very big planetary ring system in terms of its general layout. Though if it's warm then there'd be no ice, and so it'd be pretty dark in appearance (not like Saturn's, more like Jupiter's or Uranus').

 

[Border Reiver]

That could be a nice concept Mal, a ringed star. I think I may try to illustrate it.

 

[Gruffty]

Bodies Orbiting M V Stars Rules

Solid Planets
"A solid planet orbiting an M V star (with a mass of less than 0.7 sol) will be tidally locked to its star if the planet's orbit is within the M V star's habital zone. Such a tidally locked world will not have any moons in orbit."

Gas Giants
"A gas giant orbiting an M V star (with a mass of less than 0.7 sol) within that star's habitable zone will rotate around its axis. However, such a gas giant will not have any moons in orbit."

How about this?

Asteroid/Planetoid Belts
"An asteroid/planetoid belt orbiting an M V star (with a mass of less than 0.7 sol) within that star's habitable zone will rotate around the M V star. Such an asteroid/planetoid belt will appear as a ring system around the star, similiar to those that may orbit a gas giant."

 

[TempMal]

To be clear, it would probably look like a "ring system" only in the sense that it'd be a flattened disc. Don't be thinking of saturn's rings here though - it's still an asteroid belt, you wouldn't be able to see it as a ring system any more than you could see Sol's asteroid belt as a ring system if you were to look at it from outside. At best you'd probably see a dusty disc (since the orbits are smaller, material would be more densely packed), kinda like Jupiter's rings. It'd also be more hazardous for travellers since there'd be more material in the circumference of the orbit - you'd be much more likely to hit something.

Remember, planetary ring systems are caused by bodies torn apart by tidal stresses between about 1.5 and 3 planetary radii. Stellar asteroid belts are just leftovers from system formation though, usually due to the influence of giant planets outside the belt's orbit.

That raises another point - if there's a giant planet (a la Jupiter or Saturn) in the outer zone (say, about 1 AU from the star) then its gravitation influence would probably disrupt any planetary formation within its orbits. Jupiter does that to the asteroid belt in the Solar system - if Jupiter was where Mars was, then Earth and probably Venus would probably never have formed and there'd be an asteroid belt here instead. So the presence of giant planets near the habitable zone would severely preclude the formation of terrestrial planets there.

 

[Gruffty]

Originally posted by TempMal:
At best you'd probably see a dusty disc

Right, gotcha.

Originally posted by TempMal:
That raises another point - if there's a giant planet (a la Jupiter or Saturn) in the outer zone (say, about 1 AU from the star) then its gravitation influence would probably disrupt any planetary formation within its orbits. Jupiter does that to the asteroid belt in the Solar system - if Jupiter was where Mars was, then Earth and probably Venus would probably never have formed and there'd be an asteroid belt here instead. So the presence of giant planets near the habitable zone would severely preclude the formation of terrestrial planets there.

Now, that's odd, because I was just about to bring that up, as I know that Jupiter interferes with the asteroid belt. I think I read something quite in-depth about last week, alongside an article about gas giants "spiralling" in towards their primaries and causing chaos amongst planets and their satellites.

 

[Merxiless]

I also want to make the point that the orbital period / length of year of an asteroid belt will average that of a planet at the distance of the belt.

An asteroid belt rock at the orbit of Mars will take just as long to orbit the sun as Mars does, assuming same eccentricity, etc.

Tidal locking doesn't slow the movement of the orbit around the sun, it slows the rotational spin of the object.

 

[parmasson]

"Thanks Kurega, can you add some more. I need definitions for Nebulae, Galaxies, Dark Matter, Comets, Lasers, White hole?"

Hmmmm MTU seems to be lacking in many of those features.

I would say that comets might make good hiding places if they were close enough to form a tail. OK for fuel but kinda useless otherwise.

Nebuale are just durn pretty. Not enough gas to be useful and not dense enough to hide behind. Either the stars in them are too young for good stuff or too old.

The open market price on dark matter has been falling since the 26th century. Best not mentioned really.

Galaxy: With a Jump 6 limit I don’t have to be concerned with that.

White hole? Never seen one, if I did all that crap that got sucked in the black hole end might come shooting out near the speed of light. Best not to hang around that bit-o-space.

Lasers are what we use to blow up other spaceships!

 

[TempMal]

Nebuale are just durn pretty. Not enough gas to be useful and not dense enough to hide behind. Either the stars in them are too young for good stuff or too old.

Curious thing about nebulae: they look pretty from far off, but close up they're apparently damn near invisible! This seems to be because when you're far (ie a few thousand ly away) you're looking at all the light provided by the illumination of a few stars in the nebula, coming out of a small area of sky. But when you get up close, that same amount of light is spread out over a bigger area of sky, so the nebula actually dims and becomes harder to see as you approach it. If you were a few parsecs from the edge of one you probably wouldn't even be able to see it!

Kooky, huh.

 

[Pickles]

Originally posted by Border Reiver:
Don't even think about it, I start an OU math program this year (for fun ) and am shitting myself. Still got time to change my mind and find something a bit less cerebral like history.

Do it! OU maths is way too hard. I took it as a 'spare' module at the beginning of my BSc. I did so badly that had to work my butt off for the next 3 years to make up enough grades to get a first. And I used to be good at maths, too ...

 

[parmasson]

"but close up they're apparently damn near invisible!"
Never really though about it.
Yep kooky.