Tidal Heating Shrinks Goldilocks Zone Around Red Dwarfs 70
scibri writes "An overlooked factor could shrink the habitable zone for planets around M-class dwarf stars by as much as 50%. For these smaller, cooler stars, the habitable zone was thought to extend to relatively close orbits. But as you get closer to a star, the tidal force it exerts on a planet increases. Since planets do not have perfectly circular orbits, tidal forces cause the planet to flex and unflex each time it moves closer to or further from its star; kneading its interior to produce massive quantities of frictional heat — enough to scour the planet of any liquid water. Because M-class dwarf stars are the most numerous in the galaxy, and close-in planets are easier to spot than more distant ones, such stars have been a major target for planet hunters seeking Earth-like worlds. But now it seems we may have been looking in the wrong place for Earth's twin."
earths twin? (Score:1)
Earths twin would be a planet of the same size, orbiting a star of the same size and characteristics, in the same way.
I think you mean "planets that may have water".
Friction is hell (Score:4, Insightful)
In space or on face
Sudsy blade orbits
Don't leave a trace
Burma Shave
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You are weird.
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I like the Burma Shave send ups. This one is pretty good.
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Moons around large planets as well? (Score:1)
What about moons around large planets? Similar, no?
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Io would be a good example of that since it is the most geologically active object in the solar system. (thank you wikipedia)
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I'm a bit hazy on my stellar life cycles, but wouldn't red dwarfs have been larger stars in the past, and have stripped the atmospheres of any planet close enough to be in the habitable zone?
Re:Moons around large planets as well? (Score:4, Informative)
Goldilocks and the Red Dwarfs (Score:5, Funny)
Funny, I don't remember that one.
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Yea, I was surprised it got modded up, I was amazed someone modded it Interesting.
It does of course make sense that gravitational forces would warm up orbiting bodies, we even have plenty of examples of that happening here in our own solar system.
Time to modify another variable from the Drake Equation.
I blame Arnold J Rimmer (Score:3)
That smeghead makes everything around Red Dwarf uninhabitable.
Idiots! (Score:1)
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It is never explicitly stated that Goldilocks did not associate with Dwarfs.
Teach the Controversy!
arguement should cut both ways (Score:5, Insightful)
Could someone please explain this to me?
Re:arguement should cut both ways (Score:4, Informative)
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What about other small, bright, and dense objects?
A white dwarf, for instance?
You also discount the potential for exotic photosynthetic life around the brown dwarves. For instance, here on earth normal green photosynthetic plants can absorb multiple photons of red freq light and combine the energy from them with some clever quantum mechanics to have enough energy to push a high energy electron into a chemical bond site.
It doesn't seem inconcievable that there could be very slow respiration organisms that h
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A white dwarf, for instance?
A white dwarf doesn't last for long and is a relic of a previous red giant that has been thoroughly baking your planet for quite some time. If you look upon the sky and see a white dwarf as your sun, check your pulse, since you're most likely a ghost.
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Actually, a white dwarf lasts forever (i.e. significantly longer than the age of the universe), unless it's unlucky enough to have a companion dumping mass on it to exceed the Chandrasekhar limit. Of course, the preceding giant phase is problematic, but it does make for nice, sterile systems for an expansionist civilization -- might be the place to look for advanced ETI?
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. . .but a brown dwarf would have no (or little) emissions in the visible spectrum. Perhaps something besides terrestrial life could find it habitable, but I don't think we would be able to live there.
You also discount the potential for exotic photosynthetic life around the brown dwarves.
I only discount the possibility that such a planet would be sufficiently earth-like to be habitable to you and me, or even to the spruce trees outside my window. I chose to limit my comment because the topic of both the summary and the article is earth-like worlds. As you did, I can visualize some sort of life there, I just can't see ours living there.
I'm not an astrophysicists, but wouldn't the spectral emissions of a white dwarf be a little rough on terrestrial-like life? Again, I think that it would b
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The world would be "dark", or a deep wine red colored in terms of "daylight", but with oxygen producing photosynthesis, and tectonic warming, the planet would have a "habitable" biosphere, you would just need a flashlight everywhere you go.
Any animal forms would be either blind, or have very large, flat eyes, or just eye spots. (Red light is low energy, and is scattered easily. IR and nIR are absorbed by water, so the vitreous humors in these hypothetical creature's eyes would pose a hidrance to photon con
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It depends on the frequency of the NIR.
You are right that water absorbs NIR. It also absorbs red light quickly, which is why you don't see red scuba suits. We are assuming the planet is heated using both light emissions from the brown star, and heavy geological activity (geysers and what not) caused by the gravitational tug of war.
Brown stars are variable blackbody emitters. Some emit long wavelenth IR only. Some emit all the way into the visible red spectrum. In this case, we are looking at a star that
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Tidal effects fall off with the cube of the distance, not square. Radiant energy from the star fall off with the square. Since tidal effects fall off much faster, the inner boundary of the Goldilocks zone is pushed back farther than the outer edge would be.
Headline is wrong, looking in the wrong places (Score:3)
In TFA they say that people looking for Exo-planets are looking for ones with close orbits. They believe now that because of tidal forces those planets would have hotter temps and not be candidates for a Earth-like planet.
Looking for close orbit planets is a fine way to find exoplanets.
What they should say is that looking for close orbit planets is not a good way to find earthlike planets with liquid water.
Now take in your head the originally believed habitable zone, you are going to have to shorten that on
Re:arguement should cut both ways (Score:4, Interesting)
Would make for an interesting long-term strategy for an advanced race to survive past the life of stars, if you can heat from within via tidal forces around say, a super massive black hole. Just dont be the jerk to mess that one up.
"Sir! We forgot to exchange values between Metric and Imperial, the entire planet is about to get sucked into a black hole!"
"Well...alteast we dont need to worry about budget cuts next year."
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I was thinking that. Surely for smaller stars, there's still a "Goldilocks zone" where stellar input + tidal heating = just the right amount of heat. It may be considerably narrower than the Sun's, but there are so many more red dwarfs than there are Sun-like stars that I'd expect the numbers to even out. Add in the extremely long lifetimes of smaller stars, and it seems like red dwarfs are still good candidates for extra-Solar-System life.
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That makes sense, thanks.
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As such, once you get out to the right distance (for Sol, it's between the outside of Venus' orbit to the inside of Mars' orbit, right about where we are), tidal forces from the primary no longer have the same warming effect that could boil away the oceans.
Remember, our tides come from our satellite (luna), and it doesn't exert enough
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Actually I believe our moon is highly responsible for earth still having a molten core, and a good strong protective magnetic field with it.
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It probably does, but the effect would be minimal since at the outer edge of the Goldilocks zone the gravity gradient is going to be very small.
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It does work both ways, where did you get the idea it doesn't? The fact that planets closer to their star may be warmer then expected is more relevant though, since that's where astronomers tend to look for planets.
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As tidal forces depend on gravity, they push the inner boundary of the zone much further away than they push the outer one, thus the zone itself shrinks.
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If your planet is too cold, it is because it is too far from the star. If it is too far from the star, it isn't getting tidal heating either. This legitimately puts a cap only on one end of the range.
There are such places. (Score:2)
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This makes me think that most of these planets are tidally locked to their parent star. They are very hot on the side facing the star and cold on the other side.
If you put tidal heating on the formula, maybe those freezing dark sides are not so freezing after all.
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If they are tidally locked, there won't be any tidal heating.
Life like we need a planet at the habitable zone, with tick athmosphere (to hold water), and not tidally locked into its star.
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But what about tidal locking? (Score:2)
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Yes, but depending on atmosphere a tidally locked object will have 2 habitable zones, well I guess really one ring-like habitable zone.
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--The question is whether any higher life forms could adapt to such a change--
That is THE big question and you sure know how to ask it.
Does it matter? (Score:2)
Even if the environmental changes from tidal locking wiped out most advanced lifeforms plenty of microbes and extremophiles would almost certainly survive. Since dwarf stars have a MUCH longer lifespan than larger stars there would be likely be plenty of time for more advanced life to evolve multiple times over.
As for winds and weather, I imagine they would actually be (relatively) mild near the day/night poles, but strong and steady near the twilight ring, with cold,dry air flowing dayward at the surface
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"Looking in the wrong place" (Score:2)
"But now it seems we may have been looking in the wrong place for Earth's twin."
Why do people feel compelled to say things like this? There are multiple reasons why we will continue to be motivated to identify planets orbiting M-class stars. The most compelling is perhaps that we simply don't yet know the full range of potential planetary scenarios, both the types of orbits they might adopt and the material nature of the planets themselves. We can't yet even anticipate the full range of unique conditions that might make a planet habitable (for humans much less otherwise). The more
Researcher reads Niven's Neutron Star, 'Oh Crap' (Score:1)
Researcher was probably reading Neutron Star and went 'Oh, Crap!'
Smaller on one side, larger on the other (Score:1)
The article fails to mention that although the habitable zone would shrink closer to the sun, it would expand further from the sun. Tidal forces obey a power law, so this expansion on the far side would not be as great as the area lost on the near side, but it does open up some interesting possibilities, such as having a dark, warm planet.
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Mashup (Score:2)
Tidal heating is self-eliminating (Score:5, Interesting)
They compare to Jupiter's moon Io in the article, whose proximity causes tidal heating and makes it the most geologically active body in the solar system. However, all the energy that goes in to tidal heating is drawn from its orbital energy and would normally cause the orbit to circularize (tidal dissipation), thus eliminating the heating - the only reason that doesn't happen with Io is because it's locked in a 1:2:4 orbital resonance with Europa and Ganymede, both of which have much greater orbital energies.
Now I imagine this would take longer with a planetary-sized orbit than with a moon-sized orbit, but unless the planet migrated inwards considerably I would expect that it would have largely occurred while the proto-planetary cloud was still coalescing. It might contribute to a longer cooling period, but I don't see how that's really a problem, it's not like a lot of these dwarf stars aren't considerably older than Sol, even a few billion extra years years of cooling would still give life there a head start on us. In fact, considering that Earths volcanic phase is when life here got it's start, a mechanism that might have extended that period seems like it could make life even more likely.
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Also worth pointing out that even if a red dwarf planet's orbit were perturbed by other worlds, as is the case with Io, you won't get strong heating. The distances between a red dwarf's planets will be far larger than the distance between Jupiter's moons, so the orbital perturbations will be much *much* weaker.