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Tidal Heating Shrinks Goldilocks Zone Around Red Dwarfs

Soulskill posted more than 2 years ago | from the can-we-blame-newton-for-this dept.

Space 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."

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earths twin? (1)

Anonymous Coward | more than 2 years ago | (#39931587)

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 (4, Insightful)

smitty_one_each (243267) | more than 2 years ago | (#39931641)

Friction is hell
In space or on face
Sudsy blade orbits
Don't leave a trace
Burma Shave

Re:Friction is hell (2)

xevioso (598654) | more than 2 years ago | (#39932083)

You are weird.

Re:Friction is hell (1)

thesaintar (865954) | more than 2 years ago | (#39932511)

Pure awesome

Re:Friction is hell (0)

wcrowe (94389) | more than 2 years ago | (#39932523)

I like the Burma Shave send ups. This one is pretty good.

Re:Friction is hell (1)

smitty_one_each (243267) | more than 2 years ago | (#39937127)

Trying to get first post with an ad jingle for a long-dead product somehow does it for me.

Re:Friction is hell (0)

Anonymous Coward | more than 2 years ago | (#39933673)

Slashdot needs "+1: Awesome"

SOUNDS GAY !! (-1)

Anonymous Coward | more than 2 years ago | (#39931667)

Not that it should matter, ........ but it does !!

Moons around large planets as well? (1)

Anonymous Coward | more than 2 years ago | (#39931747)

What about moons around large planets? Similar, no?

Re:Moons around large planets as well? (2)

Jeng (926980) | more than 2 years ago | (#39932011)

Io would be a good example of that since it is the most geologically active object in the solar system. (thank you wikipedia)

Re:Moons around large planets as well? (2)

Intrepid imaginaut (1970940) | more than 2 years ago | (#39933687)

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? (3, Informative)

justin12345 (846440) | more than 2 years ago | (#39935683)

You're confusing red dwarves with white dwarves. Red dwarves form small, white dwarves are the stellar cores of G type stars after they have blown off most of their mass during their red giant phase.

Goldilocks and the Red Dwarfs (4, Funny)

Jeng (926980) | more than 2 years ago | (#39931763)

Funny, I don't remember that one.

Re:Goldilocks and the Red Dwarfs (0)

Anonymous Coward | more than 2 years ago | (#39931949)

I know it's a joke, but the 'Goldilocks' it refers to is the zone that's not too hot, nor too cold, but it's just right for us humans...
'

Re:Goldilocks and the Red Dwarfs (2)

Jeng (926980) | more than 2 years ago | (#39932061)

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.

Re:Goldilocks and the Red Dwarfs (0)

Anonymous Coward | more than 2 years ago | (#39932155)

I think it was the one where the Cat was looking for a new outfit, Lister was trying to find the best breakfast vindaloo, and Kryton was having trouble finding power crystals that were the right size.

Re:Goldilocks and the Red Dwarfs (0)

Anonymous Coward | more than 2 years ago | (#39938471)

Possibly only available in porn version.

Re:Goldilocks and the Red Dwarfs (0)

Anonymous Coward | more than 2 years ago | (#39938679)

Go to the adult shelf, down to the right.

I blame Arnold J Rimmer (2)

dkleinsc (563838) | more than 2 years ago | (#39931771)

That smeghead makes everything around Red Dwarf uninhabitable.

Idiots! (1)

bbbaldie (935205) | more than 2 years ago | (#39931773)

Goldilocks didn't have any dwarfs! Geez...

Re:Idiots! (2)

Jeng (926980) | more than 2 years ago | (#39932259)

It is never explicitly stated that Goldilocks did not associate with Dwarfs.

Teach the Controversy!

arguement should cut both ways (4, Insightful)

anwyn (266338) | more than 2 years ago | (#39931907)

Why does this arguement not show that there are places that should be to cold, but are not because of tidal heating?

Could someone please explain this to me?

Re:arguement should cut both ways (3, Informative)

bored_engineer (951004) | more than 2 years ago | (#39932033)

In the context of red dwarfs, it's about distance. Gravity falls off with the square of the distance from the source. So, as the distance increases, the influence of the primary would fall off, thereby reducing the tidal heating. I suppose that it could heat a planet orbiting a brown dwarf, 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.

Re:arguement should cut both ways (2)

wierd_w (1375923) | more than 2 years ago | (#39933347)

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 have very large "leaves", and which collect near IR photons en mass. If the photon flux overall is high enough, they would gather enough photonic energy from the brown star to make chemical energy sources. (Granted, this would have to be near IR, not true IR, because sufficiently high real IR flux would toast the surface like a heat lamp. Water is also strongly opaque to IR and nIR light, so a water rich atmosphere would scatter it pretty heavily.)

A large world, with a reasonably "bright" brown star emitting lots of red and nIR light, and just enough gravitational tug, and you have the potential for some interesting surface life.

Re:arguement should cut both ways (2)

K. S. Kyosuke (729550) | more than 2 years ago | (#39933675)

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.

Re:arguement should cut both ways (1)

Anonymous Coward | more than 2 years ago | (#39935615)

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?

Re:arguement should cut both ways (1)

bored_engineer (951004) | more than 2 years ago | (#39934269)

. . .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 be exotic, rather than "earth-like."

Re:arguement should cut both ways (1)

wierd_w (1375923) | more than 2 years ago | (#39934849)

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 conduction to the retina. The less humor in between the focusing lens and the retina, the more efficient they eye would be. Hence large and flat.)

Plants would probably be such a dark shade as to appear black. It would be a warm world that for us at least, is bathed in continual night. (Some people have limited ability to see IR light, so some people might see a dull red "day" on the planet.)

The planet would have other harvestable energy sources for artificial lighting, such as wind and hydro, (slow respiration of native life would limit coal and oil deposit formation), and since you don't have to blow as much energy on environmental control, its reasonable that with essentially some big stadium lights, we could grow earth flora there for food. (I'm thinking big sulfur lamps with a little orange neon added to push the yellow spectrum a little. Got plenty of red already.)

It wouldn't be anything like earth, but humans could potentially colonize it.

Would make a great setting for a scifi book.

Re:arguement should cut both ways (1)

bored_engineer (951004) | more than 2 years ago | (#39935079)

I'll defer, as you've clearly given it more thought than I'm willing to do. I did enjoy reading the setting that you've proposed, and you'll have to let me read your story, should you write it.

Re:arguement should cut both ways (0)

Anonymous Coward | more than 2 years ago | (#39935967)

The planet would have other harvestable energy sources for artificial lighting, such as wind and hydro,

You could also use PV -- we optimize for visual light because that's peak insolation, but silicon PV cells can be good well into NIR.

Not sure about hydro, though, since you don't get much NIR through a water-vapor atmosphere; I'm thinking, even if water-based life exists, surface water is pretty scarce, and the atmosphere remains unsaturated, else your exotic photosynthesis doesn't get the NIR it needs. (But I'm not even sure if that works -- if the atmosphere is unsaturated, there's no rain/dew, and vapor from plants builds up until some part of the atmosphere is saturated... Dammit, Jim, I'm an engineer, not a meteorologist.)

Re:arguement should cut both ways (1)

wierd_w (1375923) | more than 2 years ago | (#39937003)

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 emits at the far end of the visible spectrum, and the near IR spectrum. The star is a small star, and the planet is heated primarily by tectonic activity. This means water would be liquid even if the star was totally dark. The tidal forces keep it sloshing, and keeps the crust hot.

A planet this close to the star is likely to be tidelocked. This means one side of the atmosphere will be baked hard by intense IR and nIR light. The scattering of the water vapor in the atmosphere will create a strong "dusk" light dispersal through the atmosphere. This means a fairly wide terminator zone where life could thrive. It also means a hot, baked side of the planet, and a chill far side.

Atmospheric water will condense out and rain heavily on the far side of the planet. This also creates a strong atmospheric temperature gradient, so there are powerful storms and winds.

The oceans of this world will be turbulent and hostile near the surface. Deep ocean would probably be temperate because of deep seafloor heating, and strong prevailing currents from the tidelocked weather on the surface. I would expect a thriving chemoautotroph supported smoker ecology down there.

Given widespread ocean cover like earth's, water will steam away from the oceans under the unrelenting light. Heat tolerant organisms could thrive on the ocean surface at this side of the planet, which probably where most of the atmospheric carbon sequestration will occur. Water will convect here, driving deep ocean currents from the deep ocean on the far side, and up to the surface on the light side. Algeal photosynthesis occurs under the high brightness (water blocks a lot of the energy, but we are close enough to the star to be tidelocked, and to be heated by tectonic forces. This means the sun will be huge in the sky, and will be dumping epic shittons of IR on the bright side of the planet. More than the atmosphere can scatter, and the ocean would provide a needed filter role to protect the algea.) These oceans would be hot, steaming, and humid. Strong hurricanes would form here.

Over the terminator zone, organism laden surface ocean would flow out toward the chilled dark side of the planet. Hot air laden with water would ride under cold upper atmosphere air from the dark side. This would cause heavy rains and thunderstorm activity. This area would be drenched under repeated, and heavy rainfall. This is where the equivilent of broadleaf forests of dark colored surface flora would thrive. Mountain ranges would create temporary rainshadows and make areas of the surface climactically mild. On earth it creates a desert, such as found in western california. Here, it creates rainshadow that stops the endless barrage of hurricanes and typhoons from the lit side, and shelters lifeforms. The sea level of this region will rise and fall yearly as the planet completes its orbit due to the growth and shrinkage of the tidal bulge. Evolutionarily, this is where the pressure to adapt to surface life would occur, because organisms on the coastal shores would suffer seasonal habitat loss as the sea levels dropped in the summer.

The tectonic activity of the planet ensures plenty of rift zone in this area from repeated elongation and contraction of the crust as the tidelocked planet completes an eliptical orbit. This means rift valleys and mountain ranges to harbor surface life. It also means seasonal earthquakes, rockslides, mudslides, and the like.

The dark side of the planet is cold. Warm ocean water quickly chills, and water heavy air rains, then snows out its load. The heavy precipitation on this side of the planet drives the deep recirculatory current from the bright side. This current brings a constant flow of algae from the bright side to this side just past the terminal zone. This means there is a buildup of biomass in the ocean at this region just past the terminator. Ocean methane and oil is likely. Also likely are shoals of eyeless "fish", and filter feeders. Over the extreme cold far side, icepack like a polar icecap is probable. Glacial flow keeps things in balance.

At least, that's how I would envision lifeforms on such an exotic planet.

Adding a moon to the system makes it even crazier, but I doubt a moon would survive both the kneading from the parent star, and from its planetary partner. On such a small body the stresses would tear it apart most likely. A planetary ring from a destroyed moon casting seasonal shadows would make the weather even more interesting.

Re:arguement should cut both ways (0)

Anonymous Coward | more than 2 years ago | (#39933737)

Yawn.

Re:arguement should cut both ways (1)

Anonymous Coward | more than 2 years ago | (#39936023)

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.

Re:arguement should cut both ways (0)

Anonymous Coward | more than 2 years ago | (#39937167)

Gravity falls off with the square of the distance from the source.

Tidal effects are related to the rate of change of the gravitational field, so they fall off with the cube of the distance from the source.

Headline is wrong, looking in the wrong places (2)

Tekfactory (937086) | more than 2 years ago | (#39932079)

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 the side closer to the star. One would not necessarily extend that zone an equal distance away from the star as planets not in close orbits won't get the extra heating.

Re:arguement should cut both ways (3, Interesting)

Lithdren (605362) | more than 2 years ago | (#39932095)

I dont see anything that claims thats not possible, so I dont quite get where you get this from. It would be a strange place indeed, a planet warmed by tidal friction from within would have a very different biology of life. I'd imagine most life would be deep underwater near rifts in the oceans floor, there'd be no point in forming near the surface, depending on what caused the tidal forces.

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."

Re:arguement should cut both ways (1)

FriendlyPrimate (461389) | more than 2 years ago | (#39934451)

It wouldn't be that strange. Europa is theorized to have a liquid ocean due to tidal heating.

Re:arguement should cut both ways (1)

JTsyo (1338447) | more than 2 years ago | (#39943559)

What you fail to mention is that the liquid is not water.

Re:arguement should cut both ways (1)

Daniel Dvorkin (106857) | more than 2 years ago | (#39932107)

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.

Re:arguement should cut both ways (2)

K. S. Kyosuke (729550) | more than 2 years ago | (#39933595)

Once the tidal heating contribution to the total thermal budget is significant, you can be sure it won't last for long. It wouldn't last the 4,300 My that are the age of Earth, and the 10 Gy that are the lifetime of our Sun. The even longer lifespan of a dimmer star hardly compensates for it. Life needs time to emerge and to evolve, and rather stable conditions as well. We on Earth happen to be fortunate, the hypothetical Reddwarfeans wouldn't be.

Re:arguement should cut both ways (1)

Daniel Dvorkin (106857) | more than 2 years ago | (#39944539)

That makes sense, thanks.

Re:arguement should cut both ways (1)

damien_kane (519267) | more than 2 years ago | (#39933867)

Smaller stars (like Sol) generally output much more heat, so the habitable zone due is much farther away from the edge of the start than for a larger, cooler star (from TFA).
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 force on us to mess up the Earth's core (just move our oceans around a bit)

Re:arguement should cut both ways (1)

G00F (241765) | more than 2 years ago | (#39934623)

<quote>Remember, our tides come from our satellite (luna), and it doesn't exert enough force on us to mess up the Earth's core (just move our oceans around a bit)</quote>

Actually I believe our moon is highly responsible for earth still having a molten core, and a good strong protective magnetic field with it.

Re:arguement should cut both ways (0)

Anonymous Coward | more than 2 years ago | (#39936323)

Indeed, such thinking just demonstrates a mindset where people think there is some cutoff point where a force has no effect at all.

Q: What happens when an irresistible force meets an immovable object?
A: All forces are irresistible and no objects are immovable.

Even the article itself displays signs of willful blindness to this simple fact.

Re:arguement should cut both ways (1)

Chris Burke (6130) | more than 2 years ago | (#39932109)

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.

Re:arguement should cut both ways (0)

Anonymous Coward | more than 2 years ago | (#39932261)

because tidal forces are inversely proportionate to the square of a planet's orbital distance from the gravitational source, so the only planets that experience strong tidal forces are the ones that orbit very close to their respective suns. Normally this would place the planet too close to the star to be habitable, but dwarf stars have a very low ratio of light output versus mass, so the habitable zone is therefore closer to the star (where tidal forces are stronger, too).

Re:arguement should cut both ways (2)

amRadioHed (463061) | more than 2 years ago | (#39932331)

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.

Re:arguement should cut both ways (1)

Hentes (2461350) | more than 2 years ago | (#39932371)

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.

Re:arguement should cut both ways (1)

Surt (22457) | more than 2 years ago | (#39932483)

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. (1)

qwerty shrdlu (799408) | more than 2 years ago | (#39932561)

Io and Callisto are the same distance from the Sun, but Io is a _lot_ hotter. If you get far enough from a red dwarf sun to be too cold, the tides are a lot weaker.

Re:arguement should cut both ways (2)

ulzeraj (1009869) | more than 2 years ago | (#39932575)

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.

Re:arguement should cut both ways (1)

marcosdumay (620877) | more than 2 years ago | (#39933927)

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.

Re:arguement should cut both ways (0)

Anonymous Coward | more than 2 years ago | (#39934943)

I will grant you that a tidally locked planet isn't likely to possess atmospheric qualities we need .. but I don't see how the tidal lock itself is terribly important. We'd just want to live near the terminator, where the temperature isn't sun-side scorching or night-side chilly. Oh, and bring some black-out curtains.

Probably won't be a great place to live, so we'd be there for the resources more than anything. Although, who knows..places with moderate, relatively unchanging temperatures are pretty popular places on Earth ...

Re:arguement should cut both ways (1)

JTsyo (1338447) | more than 2 years ago | (#39943623)

What do you think happens when one side is 1,000F+ hotter than the other? We're talking gale force winds or higher all the time.

Re:arguement should cut both ways (0)

Anonymous Coward | more than 2 years ago | (#39934261)

Yeah, but it's easier to find planets with closer orbits.

But what about tidal locking? (1)

K. S. Kyosuke (729550) | more than 2 years ago | (#39932903)

I would have assumed that tidal locking would eventually cause more trouble for life than tidal heating does good.

Re:But what about tidal locking? (1)

Jeng (926980) | more than 2 years ago | (#39933137)

Yes, but depending on atmosphere a tidally locked object will have 2 habitable zones, well I guess really one ring-like habitable zone.

Re:But what about tidal locking? (1)

K. S. Kyosuke (729550) | more than 2 years ago | (#39933397)

The thing is that if the planet is made habitable and fit for life to spring into existence on it to a significant degree due to tidal heating, once the tidal heating stops due to tidal locking, the conditions on the planet will have been drastically altered by this (day length, averages of temperatures in various points on the surface, eccentricity and semi-major axis, year length...). The question is whether any higher life forms could adapt to such a change. This could really lead to extreme changes, and not even atmosphere will protect you from this. In fact, atmosphere could cause rather terrible wind conditions on a tidally locked body.

Re:But what about tidal locking? (1)

EvilBudMan (588716) | more than 2 years ago | (#39933891)

--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.

Re:But what about tidal locking? (-1)

Anonymous Coward | more than 2 years ago | (#39934585)

Tidal heating wouldn't stop when the planet becomes tidally locked. Tidal hearing is due to a change in distance between two objects (as exists with elliptical orbits) and not due to an objects rotation around its axis.

Does it matter? (1)

Immerman (2627577) | more than 2 years ago | (#39936265)

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 and hot, wet air flowing nightward at high altitude. Storms would likely be severe and virtually continuous, but since the system is in dynamic equilibrium less volatile than on Earth, which has Bernoulli forces and a daily heating cycle constantly churning things up.

Re:But what about tidal locking? (1)

grep_rocks (1182831) | more than 2 years ago | (#39940199)

I didn't think in general a tidally locked planet was habitable, in a tidally locked planet the dark side becomes a cold trap, freezing out the atmosphere - unless you get massive recirculation of heat due to oceans, even if you did have a favorable configuration of the contents plate techtonics would likely eventually push you into an unfavorable configuration, causing the atmosphere to freeze out, once that happens, its over.

"Looking in the wrong place" (1)

macraig (621737) | more than 2 years ago | (#39933307)

"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 planets we identify and characterize, the better we get at estimating those full ranges. So just because these M-class planets are less likely to be a home-away-from-home is not a very good reason to stop looking for them altogether.

Researcher reads Niven's Neutron Star, 'Oh Crap' (1)

BubbaDave (1352535) | more than 2 years ago | (#39933647)

Researcher was probably reading Neutron Star and went 'Oh, Crap!'

Smaller on one side, larger on the other (1)

Anonymous Coward | more than 2 years ago | (#39934323)

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.

Re:Smaller on one side, larger on the other (1)

JTsyo (1338447) | more than 2 years ago | (#39943661)

That would only work on a really weak star. If you're far enough from the star that you aren't receiving enough solar energy, then you're too far for tidal effects.

Mashup (1)

tompaulco (629533) | more than 2 years ago | (#39936013)

Worst Disney Mashup ever.

Tidal heating is self-eliminating (4, Interesting)

Immerman (2627577) | more than 2 years ago | (#39936611)

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.

Re:Tidal heating is self-eliminating (2)

goodmanj (234846) | more than 2 years ago | (#39936705)

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.

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