We found one!

[steuard]

Wow oh wow. Universe Today just posted an article about an Earth-like planet discovered around a nearby red dwarf star. (The original source appears to be a UC Santa Cruz press release.)

It's right in the star's "habitable zone" (which mostly means "right temperature for liquid water") and has a mass about 3-4 times Earth's, so a quick estimate is that gravity there might be about 40% stronger than here (it wouldn't be too different than standing in an elevator as it gets going). That's plenty to hold an atmosphere. The planet has its quirks, of course: it's close to its cool sun, so a full orbit only takes about a month. Also, like our Moon it always has the same side facing "in": a planet of eternal sunlight on one side and eternal shadow on the other. Naturally, the only comfortable places to live would be in the twilight region encircling the planet between the extremes of hot and cold, where the red sun burns forever on the horizon.

This is awesome. And it's sooner than most people expected to find something like this, which may mean that planets like ours really are pretty common after all!

Now if only we could find a way to get there.

Comments

[kirin]

Maybe I should put my comment here rather than facebook for better discussion possibilities. Which was: This is indeed pretty awesome, but on two seconds of thought, a glut of habitable planets in the galaxy could imply not so great things about the probability of higher life evolving spontaneously, given we haven't seen any of it.

[steuard.livejournal.com]

Yeah, it would certainly remove one popular way of resolving the Fermi paradox.

Personally, I'm very happy to have a lot of other places out there where we could live, even if there's nobody living there now. But it's not clear how we'd see them unless they actually came here: think about how our use of radio, etc. is dropping now that we're shifting to the internet for communication! And it would take them a long time to personally visit any appreciable fraction of the stars in the galaxy!

[kirin]

True on general radio chatter - you'd have to happen to intersect a relatively thin expanding shell from the "radio-heavy period" of a civilization. On the other hand, a civilization past that point that was still interested in being found could purposely send signals in the direction of identified habitable planets. But of course, that's exactly the sort of thing SETI's looking for, and they've still only covered small fractions of the sky in any detail. And it could be that they *don't* particularly want to go out of their way to be found.

And yeah, uninhabited habitable planets are peachy if we ever develop practical interstellar travel. Unless it turns out the practical way to do it is to leave most of our biological shells behind, in which case habitability might not matter so much...

[steuard.livejournal.com]

a civilization past that point that was still interested in being found could purposely send signals in the direction of identified habitable planets.

Another suggestion that I saw a few years back was that more advanced civilizations may have found more effective means of communicating over vast distances. I read a paper discussing the advantages of neutrino communications over EM waves. It sounds like some of our newest neutrino detectors might be sensitive enough to pick up neutrino beam communications (the awesome Ice Cube that's based on a cubic kilometer of Antarctic ice, for example), and the technology for creating such a beam wouldn't be that far out of reach if we were really determined to make one.

Unless it turns out the practical way to do it is to leave most of our biological shells behind, in which case habitability might not matter so much

I don't know: I wouldn't be surprised if we came up of ways to avoid carrying biology along on the trip before we came up with ways of avoiding the need for it on the other end. (I'm envisioning something like an automated robotic nursery and learning center to raise children from frozen embryos, for example. Don't ask me too much about the ethics of that, but I might still prefer that scenario to never "getting out" at all.)

[spoonless.livejournal.com]

Unfortunately, I think the more likely conclusion is that intelligent life just always blows itself up with nukes or bioweapons after reaching a certain stage of development, shortly after us.

[steuard.livejournal.com]

Oh, so pessimistic! At least give us the option of death by VR!

But also, I'm skeptical of this sort of argument in part because it seems to generalize so broadly from human psychology. It doesn't feel like we're that far from the "not blowing ourselves up" edge, culturally speaking, though I'll admit it's a risk. So given that aliens could be enormously different from us or anything we've imagined, it's hard for me to believe that they'd all self-destruct.

That's why the "slow exploration, lots of stars" argument starts to feel tempting to me. Maybe an advanced civilization is always forced to adopt a culture of linear population growth (rather than exponential) to survive until interstellar travel becomes available, and that limits the rate at which they spread.

[spoonless.livejournal.com]

A quick check reveals that the official "Doomsday Clock" is at 11:54, 6 minutes to midnight...

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

Of course, I don't take that particular clock all that seriously. They might as well have chosen a calibration where we are an hour from midnight, or a day from midnight, or anything. But the idea of countries like Pakistan having nukes, and soon countries like Iran and North Korea, does kinda scare the crap out of me. And that's just nukes, which are fairly hard to transport around. What happens when it gets a lot easier to engineer viruses like Ebola, and terrorists can carry them around in their underwear? As much as I love technology, I think the problem is that the more advanced the technology gets, the more it only takes a few bad apples to do a lot of damage.

I do think the VR thing is a possibility.

The main resolution I like for the fermi paradox is just that there aren't enough civilizations close enough to us... the ones far away are just too far away, and aren't directing anything at us. That one seems the most reasonable to me. But this gets less likely as we discover more earthlike planets.

I agree, it's hard to say how much we can generalize from human psychology. But if there's one thing I would count on being a pretty general consequence of any form of evolved life, it is some kind of competitive instinct, coming from the basic mechanism that drives evolution which is competition over natural resources.

[nasu-dengaku.livejournal.com]

Oh wow, that's great. Knowing that 1/501 known planets is Earthlike vs 0/500 means the galaxy is likely full of such planets.

[spoonless.livejournal.com]

I used to TA an intro astronomy course for the guy they quote in that article, Steve Vogt. I remember trying to convince him that we really *do* understand quantum mechanics, after he said he thought nobody really understood it and surely it had to be wrong on some level.

[spoonless.livejournal.com]

Oh, right, and I also remember explaining to him after one lecture he gave that muons were not mesons but leptons, after he kept referring to them as "mu mesons" through the whole lecture. (Historically, that's what they were called, apparently, before people realized they were different from other mesons and reclassified them.)

Astronomers are funny. He was a cool guy though, I liked him.

[lordhylas.livejournal.com]

Think of the winds generated by the temperature gradient.

[kirin]

I'm really not sure how that would work when the temperature distribution is relatively stable. Obviously you can't have continuous net wind from one pole towards the other...

[steuard.livejournal.com]

Yeah, and the worst case scenario is that the winds carry air to the frigid pole of the planet where it's cold enough that the atmospheric gasses condense and never return to the hot side: you'd wind up with no active atmosphere at all. Or even if the N_2 and O_2 didn't freeze out, all of the water would wind up frozen on the dark side and the planet as a whole would be bone dry.

But it's possible that the heat transport involved with those winds would prevent the worst of that from happening. It's remarkably hard to simulate such things!

[lordhylas.livejournal.com]

Why can't we model it? It seems like it would be a much simpler model than, oh, Earth, with our varying heat input.

For the model of this, we could start with a spherical mass of uniform temperature air. Insert an insulator in the middle of it (the planetary mass would serve as an insulator, no?). Introduce a single heat source on one side to serve as the solar input. And there we go. If we later want to account for vapor cooling (for liquid water that might exist in the twilight zone), we can add that in that region, but we at least have a start with this admittedly very simplistic model. Maybe volcanism would further complicate the model.

But I think that, with the heat input on the day side, and the very cold night side, if there is an atmosphere, then, thermodynamically, there *has* to be heat flow from the hot side to he cold side, which means wind. And the more extreme the temperature difference between the day and night sides, the higher the winds, no?

[steuard.livejournal.com]

My impression is that a fairly basic model isn't too hard, but that basic models by and large wind up with the atmosphere (or at least all its water) freezing out on the cold side, and that's the end of that. I haven't studied this much at all, but most of the ideas that I've heard of for avoiding that fate rely on nonlinear effects in the atmosphere (or in the oceans, if there are any) to make the heat redistribution work. (One model suggested that liquid water might be able to flow from the hot side to the cold side even underneath a thick ice layer, which might be enough to prevent the worst of the effects.)

Maybe it's not actually as complicated as it sounds, but it's certainly intimidating to me!

[lordhylas.livejournal.com]

Well, a tide-locked planet like this has been the stuff of many a science fiction story. Now perhaps with enough study we can answer those speculations. But we will need better resolution telescopes first. Heck, we don't even know if it even *has* an atmosphere yet. We need some spectroscopy for that. But that can give us a *lot* of info.

[akjdg.livejournal.com]

The propensity for a planet that is tidally locked to its star being conducive to the rise of life is an interesting question. The weather patterns in the atmosphere would be the first question. Assuming the atmosphere didn't all condense on the cold side (and perhaps some gas would remain bouncing around the terminator at least), the convective currents along the terminator would be something. Lots of dramatic thunderstorm-type events, perhaps.

If the planet was endowed with a lot of water, and that did transport to the dark side, you would expect liquid phase water at the base of glaciers (due to pressure and/or geothermal heat). Would such a planet tend to be tectonically dead or alive? If the gravitational lock is anything like the Earth-moon system, that will help drive tectonics and keep some heat about on the dark side.

Also, isn't the Earth's strong geomagnetic field important to the retention of our atmosphere? Perhaps the solar wind from a red dwarf is weaker than from our sun, but an actively circulating planetary core seems pretty important to a stable atmosphere. Especially if one side of the planet is extremely hot.

[ricevermicelli.livejournal.com]

I saw this article this morning, and it's been making me happy.

I mean, the conditions actually don't seem all *that* conducive to life - but it's interesting to imagine, and it's an optimistic sign for other planets.

I prefer to think that the fact that we haven't encountered other intelligent species yet is a sign either that they're leaving us alone to figure our stuff out, or that they're struggling with the same things that we are.