Cartography of M-star tidally locked planets

Quaoar · 2016-09-03 03:32:32

Considering that the habitable zone of a tidally locked planet is near the terminator, would it be better to chart them using a modified Mercator projection, putting the cylinder tangential at the terminator instead at the equator?
In this way we will have 90 stellar parallels in the day-side and 90 parallels in the night side, with the inhospitable sub-stellar and anti-stellar poles expanse, but the habitable zone near the terminator well represented.

I'm not an expert and I'm very interested in knowing your opinion.

Thanks to all
Quaoar

Last edited by Quaoar (2016-09-03 03:33:52)

Void · 2016-09-03 08:13:48

I really like that.

https://en.wikipedia.org/wiki/Tidal_locking
And for those who don't like tidal locked worlds, in this article which explains where the effect is weak, you can get different outcomes of a slow spinning world such as Mercury.

But I like tidal locked worlds to think about very much.

I have some models I like to keep in my head.
I have updated them as I encounter other peoples thinking. I usually don't bother to make them complex with the Coriolis Effect, but keep to a more simple model. I figure the Coriolis Effect can be added in later to get a more precise estimate of how the model would behave.

I typically morph two types of polarity to their extremes, for my play models.

Moisture, from it's bare minimum to allow for life somewhere on the planet, to a water world. (So, +/- on that).

Distance from the star, from a circumstance where just the furthest dark side, maybe even at elevation is cool enough, to the opposite, where just high noon, in a deep depression is warm enough. (So, +/- on that).

And it entertains me. Granted, at any of the extremes, you more often will have failures to support life, but I believe that with the apparent randomness of the planet creation process, in some cases even at the extremes, there could be cases of a life friendly planet.

While much discussion centers on the disabilities of tidal locked worlds, and also how they are overcome, I see great advantages to them for the potential to host life.

One of my favorite places to visit in my mind, is a water(Ice) world, where photo life can only happen in the raft of ice under the high noon. In small bubbles of salty water. In that case humans would have nice houses with stationary mirrors to warm them. But I am not sure that without rivers the atmosphere could be stable.

Another involves a dry planet with a tiny sea on the midnight side. I enjoy sailing a boat on that dark sea and seeing the stars reflected in the water, and the towns lights on the shoreline. Again, such a hot planet would have some trouble with atmosphere.

Last edited by Void (2016-09-03 08:33:58)

Tom Kalbfus · 2016-09-03 08:19:20

In Stephen Baxter's novel Proxima, he used the terms Substellar point for the point where the Sun is directly over head, and the opposite point was called the Antistellar point, on the dark side of the planet. Would you want to use those terms? Since on Earth the Sun rises in the East, why not call the Substellar point the East Pole, while the Antistellar point would be called the West Pole. When you are facing east, North is to your left, so in this case North if clockwise around the planet and South is counterclockwise. But Baxter used the conventional North, South, East, and West Directions. His planet still had a North Pole, the planet still rotated, it just rotated at the same speed that it orbited the star, but relative to other planets and stars, they still were seen to rise in the East and set in the West. The Proxima b planet will still need communications satellites, there are four possible places where they could be put, the most useful ones would be Proxima b L1 and L2. L3 is on the opposite side of Proxima, L4 is 60 degrees ahead of Proxima b in its orbit and L5 is 60 degrees behind., and they are each about 7,500,000 km away, not terribly useful if you want telephone like communications. Proxima power would be useful, just set up your solar panels on the ground and orient them towards Proxima, no need to tract the star, you could even use Solar concentrators if you like.

Last edited by Tom Kalbfus (2016-09-03 08:29:44)

GW Johnson · 2016-09-04 11:44:00

I checked Void's link to the Wikipedia article on tidal locking. It seems that, from what we know here in the Solar System, that locking is associated with very low orbital eccentricity, while resonance at other than 1:1 is associated with significant orbital eccentricity.

The exoplanet may be very close to Proxima Centauri, but I'd hazard the guess we know nothing about its eccentricity. That means we know nothing yet about it being tidally locked. But if eccentric and resonant, that means its days are only somewhat less long than its 11.2-day year.

My guess is that conditions could be quite harsh if locked, not so very much if resonant.

The "Goldilocks zone" calculation applies only if the planet has an Earthlike atmosphere. Otherwise, all bets are off.

GW

Last edited by GW Johnson (2016-09-04 11:45:26)

Tom Kalbfus · 2016-09-04 12:29:48

I think the Jupiter system is the best model we have for Proxima Proxima has the mass of 127 Jupiters if I recall correctly, what would be the masses of the Galliean satellites if we increased their masses 127 times?
Satellite Mass 127 times
Io 8.93×10^22 kg --> 1.134*10^25 kg
Europa 4.8×10^22 kg --> 6.096*10^24 kg
Ganymede 1.48×10^23 kg --> 1.88*10^25 kg
Callisto 1.08×10^23 kg --> 1.08*10^23 kg

Earth mass is M⊕ = (5.9722±0.0006)×10^24 kg
I guess Europa would come closest to Earth mass if scaled up to the same proportion as Proxima.

Seems the Galilean satellites are tidally locked, why wouldn't the planets around proxima be?

Distances could be multiplied by 11.269 times to get new orbits of
Io 421,800km -->4,753,264.2 km
Europa 671100km -->7,562,625.9 km
Ganymede 1,070,400km-->12,062,337.6 km
Callisto 1,882,700km-->21,216,146.3 km

Seems like Europa becomes an earthlike planet if you scale up its mass in proportion to Proxima, and you increase its distance by the square root of Proxima's mass in Jupiter masses. So maybe the Proxima system resembles Jupiter's.
https://en.m.wikipedia.org/wiki/Galilean_moons

GW Johnson · 2016-09-04 22:07:53

Scaling planet/moon systems by mass ratios seems unjustifiable to me.

All we really know is it's Proxima Centauri, for which we have an actual diameter measurement from an apparent disk size, and an actual distance measurement from parallax. Between these and the H-R diagram, we think we know the mass of the star.

But you must understand, this stellar mass is an inference, not a measurement. There is an enormous gulf between observation and inference. Far too few appreciate that fact.

Based on the inferred stellar mass, and the actual observation of gravitational wobble, we know (poorly) the mass of the exoplanet Proxima Centauri b. They say it's 1.3 Earth masses, but the error bars on that are least plus or minus a factor of 2 to 3.

This thing could be as small as a "typical" moon, or as big as Neptune. Its composition is merely inferred from its mass, there is no observation to support any contentions about that. None at all. Not that there might not be in the near future, it's just that we have no data yet.

We do know the period of its orbit about the star as 11.2 days, to within maybe 10% or so. We know absolutely nothing observationally about the eccentricity of that orbit. All we know is that it's a trinary system, for which our theories and models predict this exoplanet should not exist at all.

That speaks volumes about the reliability of our theories and models of such systems. They are thus demonstrable bullshit.

Dare trust observations. The rest (theories and calculations) is but rampant speculation, and mostly egregious bullshit.

All that being said, there is a planet there, and it deserves to be investigated. We are marginally/barely capable of actually doing that. So we ought to try. Simple as that.

No telling what we might find. The history up to now within our own system is that ground truth has always been at extreme variance with prior remote-sensed "claims". Things have not only been more different than we ever expected, they have been far more different than we ever could have imagined.

I see no reason not to expect that trend to continue with exoplanets.

There is a report in the latest issue of the journal "Science" that proposes a piecewise classification of radius versus mass, at variance with prior nomenclature. This report divides things into stars (thermonuclear fusion), Jovian-type worlds (not capable of fusion), Neptune-like worlds, and Terran-like worlds that include all the tiny moons and dwarf planets.

It is only a proposal, but does make a bit of sense, when you look at the actual data plotted on a radius vs mass plot, as a log-log plot. There do seem to be 4 different slopes on that log-log plot, corresponding to those four proposed classification labels. There thus does appear to be "something" to this notion. It is unidentified, and unexplained, as of yet. Only a proposal.

GW

Last edited by GW Johnson (2016-09-04 22:19:53)

Tom Kalbfus · 2016-09-04 22:33:10

As I said before on another thread, a while back, even before Proxima b was discovered, Alpha Centauri is the "New Mars", back in the late 19th century when we thought Mars might have had canals and there might have been life, perhaps even an ancient civilization of canal builders, Proxima Centauri b is that planet for us now, early in the 21st century, I'll bet there will be a whole bunch of science fiction novels written about it, now that we know it exists. And for a time, we can imagine all sorts of things about it, like we once did about Mars, and maybe Proxima b is just as unreachable as Mars was back in the late 1890s. I'm sure we can find a way to get there, that we can't even imagine now, probably by the 22nd or 23rd centuries, humans will make their first footsteps on that planet's surface.

Terraformer · 2016-09-06 07:30:39

If it's a warm Neptune, then it will likely have a super-rotating atmosphere, so whilst the planet may be tidal locked, floating habitats would experience a day-night cycle.

If such a world exists, and has an N2/CO2/H2/He atmosphere, as well as a large collection of moonlets that can be taken apart for construction materials, we could build some very large floating islands in the planets atmosphere.

JoshNH4H · 2016-10-01 11:51:50

The cool thing about tidally locked planets is that every tidally locked planet will probably have some zone at an earthlike temperature unless it has a thick atmosphere.

Tom Kalbfus · 2016-10-11 19:14:10

What about a "Wet Venus" Imagine there is a planet that is halfway between Earth and Venus, its oceans haven't boiled away, and its atmosphere is thick with water vapor, as we originally thought Venus would be like. A wet venus might be too hot for a human to live on its surface, but they can live in the upper atmosphere.

GW Johnson · 2016-10-12 16:39:08

The consensus of the on-line stories I saw ranged from a deep-ocean water-world to a completely-desert rocky planet. With a variation like that, in "considered opinions" among "qualified individuals", I submit that we know precisely ZERO (!!!) about what this planet might actually be like. Other than that it is not a gas giant.

So, big f***ing deal. We WILL NOT KNOW (!!!) until some probe actually reaches it.

Does that not render nearly 100% of the speculations in this thread worthless? If not, I'd really like to to know why not. Doesn't matter how much fun they might be.

GW

JoshNH4H · 2016-10-15 18:35:45

Speculation for its own sake, no? We mix science, engineering, and science fiction rather freely on this board

GW Johnson · 2016-10-16 16:31:54

Hi Josh:

You are quite right, we do mix science, engineering, and science fiction very freely on these forums.

I just think that we sometimes devolve into angels-on-the-head-of-a-pin arguments too easily.

My point here is that the Proxima Centauri planet is one of these things about which we still REALLY know next-to-nothing.

From a factual standpoint, we still know NOTHING, regardless of the various press releases, except that it seems unlikely to be a gas giant.

GW

JoshNH4H · 2016-10-17 19:59:23

I should add that there's nothing wrong with mixing the three here. We are an internet forum run by a small non-profit advocacy organization. We have virtually no power to set policy and no resources at our disposal, so as long as we clarify our assumptions there's no reason not to soften the cold, hard truth.

GW Johnson · 2016-10-20 14:22:18

Hi Josh:

I probably just over-react now and then. Sometimes the wilder and more-unreasonable flights of fancy really frustrate me. It's hell having been an engineer, because I tend to be such a compulsive realist.

Still working on the ramjet book. Nowhere near done, but I have written down pretty much everything I know about flameholding. Some science, at least as much art.

GW

JoshNH4H · 2016-10-20 20:35:49

I definitely appreciate the reality check now and again. It's really interesting sometimes to look at the underlying assumptions about the universe that are behind a lot of the discussions here. Turns out a whole lot of them can be traced back to Zubrin.

GW Johnson · 2016-10-21 12:28:13

Smart man, but he's not God.

GW

JoshNH4H · 2016-10-21 16:30:37

Zubrisis 1 wrote:

1:1 In the beginning Zubrin created the heaven and the earth.
1:2 And the heavens were without form, and void; and darkness was upon the face of the deep. And the Spirit of Zubrin moved upon the face of Mars.
1:3 And Zubrin said, Let there be nuclear reactors: and there were nuclear reactors.
1:4 And Zubrin saw the energy, that it was good: and Zubrin divided the bodies of the heavens into two groups.
1:5 And Zubrin called the one Mars, and the all the rest he called dragons and siren song. And the evening and the morning were the first day.
[...]

Void · 2016-10-21 19:31:39

Terraformer · 2016-10-22 07:15:09

JoshNH4H · 2016-10-22 09:53:36

I've become somewhat less of a Zubrinite with time.

GW Johnson · 2016-10-22 16:02:09

Some of us have been having a related discussion over in the Human Missions/Musk's Plans for Mars thread. It started getting into Zubrin's recent critique of Musk's concepts.

Zubrin is smart, but like so many, he sometimes forgets there is more than just one way to do a job. After championing his own approach for so long, he seems to have forgotten that there are others equally valid. I just put that down to human nature.

It gets down to what you assume when faced with an objective to accomplish. The objective does not dictate your assumptions. In fact, there is usually no one "right" set of assumptions to make. But if two people make different assumptions, the end results can look dramatically different, without making either solution "wrong".

To be "wrong", something about your assumptions must be not in accord with all of the known constraints on the problem. This gets complicated by changes in what we think we know as time goes by. This is one place NASA is still screwing up: what we know now about microgravity diseases and radiation risks is not what it was 20 years ago. Or 40 years ago. But they're still not very serious about addressing these.

Zubrin's critique assumes Musk should be making the same assumptions that Zubrin made. Musk did not. As near as I can tell, there's nothing wrong with what Musk/Spacex have done. But they were trying to create the interplanetary equivalent of a one-size-fits-all oceangoing container ship, to be used for all jobs, whether an exact fit or not.

Zubrin on the other hand assumes that he has to do an "exact fit" by means of some combination of stages, capsules, one- and two-way habs, to maximize the ratio of landed to thrown mass.

Neither is right, neither is wrong. Nor are those two concepts the only ones that would work. I posted one over at "exrocketman" recently that is a modernized update of the 1950's orbit-based mission with landers.

I used a big two-way, refuellable lander, so I needed no landed habs, the landing boat serves for that. But unlike both Zubrin and Musk, I planned on landing at multiple sites, basing from orbit, and I did not assume I could make enough propellant quickly enough to get my crew home. I took the whole kit and kaboodle needed to accomplish the minimum mission there to orbit. Any propellant my crew can make is just more landings at more sites.

Any of the 3 concepts could work just fine, and there's probably more.

What often happens with such things is that the ego gets bound up with the concept, so we spend more time arguing (emotionally-motivated) to defend the ego than need be. This readily trips over the tendency to assume at the outset of the argument the other guy's idea is completely wrong, just because it is different from yours.

But it is required to make the right assumptions. Otherwise, efforts are vain. That's what's wrong with Congress mandating a giant rocket design on NASA, instead of just setting a goal = Mars. Typical management incompetency. Seen it before. It's just a whale of a lot worse with politicians. It was bad enough in industry.

GW

Last edited by GW Johnson (2016-10-22 16:10:37)

JoshNH4H · 2016-10-22 20:22:05

The big issue with NASA right now is that it's not really going to Mars. The big issue with SpaceX (Admittedly, I haven't looked much into their plans) is that they haven't justified going to mars or demonstrated funding for it.

JoshNH4H · 2016-10-22 21:22:09

By the way, GW, take a look at this thread, I think it would interest you.

Cesaryxpob · 2017-09-28 17:43:03

Planets found so far include CoRoT - 7b, a rocky orb almost five times the size of Earth but with a molten side because it orbits its star extremely closely

New Mars Forums

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#1 2016-09-03 03:32:32

Cartography of M-star tidally locked planets

#2 2016-09-03 08:13:48

Re: Cartography of M-star tidally locked planets

#3 2016-09-03 08:19:20

Re: Cartography of M-star tidally locked planets

#4 2016-09-04 11:44:00

Re: Cartography of M-star tidally locked planets

#5 2016-09-04 12:29:48

Re: Cartography of M-star tidally locked planets

#6 2016-09-04 22:07:53

Re: Cartography of M-star tidally locked planets

#7 2016-09-04 22:33:10

Re: Cartography of M-star tidally locked planets

#8 2016-09-06 07:30:39

Re: Cartography of M-star tidally locked planets

#9 2016-10-01 11:51:50

Re: Cartography of M-star tidally locked planets

#10 2016-10-11 19:14:10

Re: Cartography of M-star tidally locked planets

#11 2016-10-12 16:39:08

Re: Cartography of M-star tidally locked planets

#12 2016-10-15 18:35:45

Re: Cartography of M-star tidally locked planets

#13 2016-10-16 16:31:54

Re: Cartography of M-star tidally locked planets

#14 2016-10-17 19:59:23

Re: Cartography of M-star tidally locked planets

#15 2016-10-20 14:22:18

Re: Cartography of M-star tidally locked planets

#16 2016-10-20 20:35:49

Re: Cartography of M-star tidally locked planets

#17 2016-10-21 12:28:13

Re: Cartography of M-star tidally locked planets

#18 2016-10-21 16:30:37

Re: Cartography of M-star tidally locked planets

#19 2016-10-21 19:31:39

Re: Cartography of M-star tidally locked planets

#20 2016-10-22 07:15:09

Re: Cartography of M-star tidally locked planets

#21 2016-10-22 09:53:36

Re: Cartography of M-star tidally locked planets

#22 2016-10-22 16:02:09

Re: Cartography of M-star tidally locked planets

#23 2016-10-22 20:22:05

Re: Cartography of M-star tidally locked planets

#24 2016-10-22 21:22:09

Re: Cartography of M-star tidally locked planets

#25 2017-09-28 17:43:03

Re: Cartography of M-star tidally locked planets

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