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Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

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Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#121

Post by moloch-hai »

mcv wrote: post #89
irq wrote: post #63

Earlier quoted context omitted.

> I don't think we know exactly what gives a body a magnetic field, or how it is maintained, but rotation seems to be important. The magnetic field on Earth is caused by electrical currents flowing in the rotating molten metal of the outer part of our planet’s core. You’re right, rotation is an important factor.

I've long suspected that tidal forces from our moon may be a big factor in keeping the outer core liquid, and thereby keeping our magnetic field active. I have no idea if that's actually true, but if it is, both rotation and a large moon might be requirements for advanced life.

Tidal forces from the sun are remarkably close in magnitude to those from our moon. Their chaotic interaction seems to me to interfere with any big, systematic effect on Earth's rotation.

It seems possible that during certain times in the past, the lengths of the day and month (and year?) were in close enough resonance to accelerate loss of rotation for a while, until the change drove them back out of it .

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#122

Post by moloch-hai »

exitb wrote: post #83
moloch-hai wrote: post #40

None of these "habitable" planets is really plausibly habitable. In particular, orbiting so close, they are all tidally locked 1:1 to their star, presenting always the same face. If they have any water, it is frozen on the dark side. But they might have no water anyway because they (might!) have no magnetic field to fend off the solar wind that would take away all their hydrogen, as happened to Venus. Earth has its b…

There's probably much more complexity to it, but I wonder if a tidally locked planet could have a habitable ring of mild weather along the terminator.

Anyway if the water is not all locked up in ice on the dark side. There could be so damn much water that enough sublimates to rain on the hot side or the terminator.

Still, not a place I would start looking for life.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#123

Post by floxy »

adastra22 wrote: post #113
loxias wrote: post #69

Earlier quoted context omitted.

Yeah. I found and read that before my above comment (and skimmed some of the associated paper[1]) but all that says is direct detection hasn't been attempted since Viking, and that most good signals require in situ or sample return. It still doesn't answer my question! "astrobiologists distinguish between direct detection of life and biosignatures". The highest methods in terms of strength of evidence obtainable with…

Direct observation means, well, observing it directly. Seeing living cells in a microscope. Growing it in a Petri dish. Genetic testing, if it turns out it has DNA or RNA like us. Within our own solar system that generally means sample return, or sending people with a full biology lab. For an extrasolar planet? I don't think the astrobiology community is of a single mind regarding what should count as direct observat…

> multi pixel imaging of the planet would be required to claim direct observation.

Here is an interesting proposal for direct imaging of an exoplanet with 1 km resolution:

https://arxiv.org/abs/1802.08421

...and an interesting youtube video about it:

https://www.youtube.com/watch?v=NQFqDKRAROI

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#124

Post by Dylan16807 »

moloch-hai wrote: post #120
Dylan16807 wrote: post #119

Earlier quoted context omitted.

> Only 1:1 locking is of any interest here. Agreed, what matters is what percentage of these planets are 1:1 locked. > All these exoplanets are certainly so locked. How do you know? Just citing moons in our system isn't enough.

Easy, 100%. Do you imagine that fusion occurring in the parent body makes any difference? Tidal locking involves nothing but gravity and friction.

Sizes of both objects, speeds, distributions of the chunks coming together, these things have effects. It's not just about being moons but the way you're extrapolating from a single system. And telling everyone to ignore Mercury because you're too right is not helpful.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#125

Post by floxy »

danw1979 wrote: post #48
BeefWellington wrote: post #32

Earlier quoted context omitted.

Kepler-452b has 2X Earth gravity. Eternal leg day. But seriously, these are all too far away for us to reach in any of our lifetimes, barring some insane discovery that breaks all the rules as we know them.

Fusion propulsion, clever shielding and general relativity gets you anywhere in the galaxy in your lifetime, or so I thought …

Roundtrip Interstellar Travel Using Laser-Pushed Lightsails:

https://web.archive.org/web/20220826053918/https://citeseerx...

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#126

Post by moloch-hai »

Dylan16807 wrote: post #124
moloch-hai wrote: post #120

Earlier quoted context omitted.

Easy, 100%. Do you imagine that fusion occurring in the parent body makes any difference? Tidal locking involves nothing but gravity and friction.

Sizes of both objects, speeds, distributions of the chunks coming together, these things have effects. It's not just about being moons but the way you're extrapolating from a single system. And telling everyone to ignore Mercury because you're too right is not helpful.

The point is that these planets orbit extremely close to their star: much closer than Mercury is to the sun, never mind Venus. That is what matters. It has literally nothing to do with any sort of magickal moonityness. Mercury is not special; it is just not locked 1:1. Yet.

Moons in our solar system orbit closer to planets than planets to the sun, so get locked much more quickly. Venus and even Mercury have not quite got there. Earth is in a more complicated arrangement, which helps us avoid it. That might even have been essential for life.

You may read up elsewhere on what determines the tidal forces, friction, and rotational momentum and energy that determine how long it takes to get into a locked state. That would be smarter than word games.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#127

Post by sammalloy »

causi wrote: post #87
sammalloy wrote: post #75

Earlier quoted context omitted.

I always go back to people like Drake and Shostak. They seem pretty convinced that "they" are out there, but the problem is that there’s no known way to communicate with them due to distance and time. If there’s a way to solve this problem, please let me know. Sagan and others seemed to think that if we could communicate (a very big if), then we could exchange our knowledge, but how exactly could you do that? The pro…

I think we'd better hope that we're alone. If creatures like us are common then that's bad new for us, because "life that behaves like humans and exists for millions of years" and "a galaxy that hasn't been completely filled long before now" are mutually-exclusive states. If we have any chance at all of conquering the stars we'll be doing it alone.

This is a reformulation of the Great Filter argument. Are there any good counterarguments?

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#128

Post by adastra22 »

floxy wrote: post #123
adastra22 wrote: post #113

Earlier quoted context omitted.

Direct observation means, well, observing it directly. Seeing living cells in a microscope. Growing it in a Petri dish. Genetic testing, if it turns out it has DNA or RNA like us. Within our own solar system that generally means sample return, or sending people with a full biology lab. For an extrasolar planet? I don't think the astrobiology community is of a single mind regarding what should count as direct observat…

> multi pixel imaging of the planet would be required to claim direct observation. Here is an interesting proposal for direct imaging of an exoplanet with 1 km resolution: https://arxiv.org/abs/1802.08421 ...and an interesting youtube video about it: https://www.youtube.com/watch?v=NQFqDKRAROI

It's a cool idea. Unfortunately getting something out to 550 AU and stopping there would take the better part of a century even with advanced technology. And once you're there, you're really stuck in terms of what you can look at. You can only see what's on the other side of the sun, and with an orbital period of 12800 years, it's not like you're going to sweep out much of the sky in a reasonable timeframe.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#129

Post by causi »

sammalloy wrote: post #127
causi wrote: post #87

Earlier quoted context omitted.

I think we'd better hope that we're alone. If creatures like us are common then that's bad new for us, because "life that behaves like humans and exists for millions of years" and "a galaxy that hasn't been completely filled long before now" are mutually-exclusive states. If we have any chance at all of conquering the stars we'll be doing it alone.

This is a reformulation of the Great Filter argument. Are there any good counterarguments?

Sure, plenty. They just mostly require us to change over time. Maybe sapient species mature and don't feel the need to ever expand, for millions of years. Maybe interstellar travel is so hard nobody ever does it nor do they make machines that do. What worries me, though, is it doesn't seem that impossible. It seems like if humans exist long enough one of us is going to make and launch a Von Neumann probe that eats the entire galaxy. The fact no alien species has makes me think we're far and away more likely to go extinct long before attaining that capability.

I remember a line from a sci-fi novel: "We only consider a species mature when you could put the power to destroy the world into the hands of every single individual with complete confidence that none of them will ever use it." I think we're, eventually, doomed.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#130

Post by moloch-hai »

rendall wrote: post #81
moloch-hai wrote: post #50

Earlier quoted context omitted.

All such planets orbiting so close to their star are certainly tidally locked. Even Venus is almost tidally locked, tens of millions of miles away from the sun. All moons in our solar system are locked. It is the norm.

Thanks. TIL. I have read a science fiction story or two set on tidally locked planets, and the humans occupy the slim twilight belt between the hemispheres facing towards and away from the sun, where the temperatures are less extreme. If it has an atmosphere, though, I imagine its expansion and compression cycle would make it quite stormy.

Given the negligible variation in energy input to various parts of the planet, over time, I would expect it to be fatally placid.
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