Habitable Worlds around White Dwarf Stars?

by Paul Gilster on August 1, 2012

Not all that long ago we assumed habitable planets needed a star like our Sun to thrive, but that view has continued to evolve. M-class red dwarfs may account for as many as 80 percent of the stars in our galaxy, making habitable worlds potentially more numerous around them than anywhere. And let’s extend our notion of habitability to what Luca Fossati (The Open University, UK) and colleagues call a Continuous Habitable Zone (CHZ). Now things really get interesting, for a red dwarf evolves slowly, so planets could have a CHZ with surface water for billions of years.

But what about white dwarfs? Stellar evolution seems to rule out habitable worlds around them because we normally think of stars entering their red giant phase and destroying their inner planets enroute to becoming a white dwarf. But can a new planetary system emerge from the wreckage? We’ve already found planets orbiting close to the exposed core of a red giant (KOI 55.01 and KOI 55.02), showing that the end of main sequence evolution isn’t necessarily the end of planetary survival. We’ve also found evidence in the metallic lines in the spectra of white dwarfs for rocky bodies close to such stars, a kind of ‘pollution’ thought to be caused by the accretion of small, rocky worlds or perhaps planetesimals (see Planetary Annihilation Around White Dwarfs for more).

Image: Almost all small and medium-size stars will end up as white dwarfs, after all the hydrogen they contain is fused into helium. Near the end of its nuclear burning stage, such a star goes through a red giant phase and then expels most of its outer material (creating a planetary nebula) until only the hot (T > 100,000 K) core remains, which then settles down to become a young white dwarf which shines from residual heat. Credit: Jonathan Saurine/Science Vault.

The conditions on planets orbiting close to a cool white dwarf might be relatively benign. What Fossati and team show is that the cooling process in these stars slows down as their effective temperature approaches 6000 K, producing a habitable zone that can endure up to eight billion years. And it turns out that white dwarfs offer advantages M-dwarfs do not, providing a stable luminosity source without the flare activity we associate with younger M-class stars. As you would expect, a cool white dwarf has a habitable zone close to the star, ten times closer than for M-dwarfs. One recent study has used this to argue that a Mars-sized planet in the white dwarf CHZ would be detectable with today’s ground-based observatories even for faint stars.

But there are other options including polarized light that may be used to detect a planet with an atmosphere around a white dwarf. Normally, starlight is unpolarized, but when light reflects off a planetary atmosphere, the interactions between the light waves and the molecules in the atmosphere cause the light to become polarized. The paper notes that the polarization due to a terrestrial planet in the CHZ of a cool white dwarf would be larger than the polarization signal of a comparable planet in the habitable zone of any other type of star except brown dwarfs. Analyzing polarization is thus a viable way to detect close-in rocky planets around white dwarfs.

Would the ultraviolet radiation put out by a white dwarf disrupt the formation of DNA molecules? Fossati and company created a computer model to study the DNA dose expected for an Earth-like planet in the white dwarf habitable zone using an Earth atmosphere model. The result:

The DNA-weighted UV dose encountered at the surface of an Earth-like planet in the white dwarf CHZ becomes comparable to that of an exoplanet in the habitable zone of a main sequence star at approximately 5000 K. Interestingly, present-day solar conditions produce an average dose on Earth a factor of only 1.65 less than that for a white dwarf with solar Teff [effective temperature]. Varying terrestrial atmospheric conditions at times produce DNA-weighted doses on Earth as high as that on a CWD planet… [T]he DNA-weighted dose for a hypothetical Earth-like planet around a CWD is remarkably benign from an astrobiological perspective, for an extremely long period of time.

So white dwarfs, the remnants of those stars not massive enough to become a neutron star, may provide us with interesting venues for life. We can even imagine a typical star going through its pre-red giant phase with a planetary system nurturing life and then, after the red giant phase is complete, beginning a post Main Sequence astrobiological phase with a planetary system in a new configuration. The notion is plausible on the strength of this paper, though the researchers point out that 10 percent of all white dwarfs host magnetic fields that could be problematic for life. This paper assumes the hosting white dwarf is a non- or only weakly magnetic star.

The paper is Fossati et al., “The habitability and detection of Earth-like planets orbiting cool white dwarfs,” accepted for publication in Astrophysical Journal Letters (abstract). Thanks to Adam Crowl for the pointer. For more on planets around red giants, see Planets Survive Red Giant Expansion.

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{ 33 comments }

Matt Burleigh August 1, 2012 at 13:58

The “elephant in the room” here is that we don’t yet know of a particularly plausible mechanism to get a terrestrial planet into a stable orbit close to the white dwarf. The planets KOI 55.01 and KOI 55.02 are probably the cores of Jovian planets that survived “common envelope” evolution with the host star. As such, they won’t be much like Earth. The asteroids and small terrestrial planets thought to create the dust disks around white dwarfs are flung in from much wider orbits, presumably perturbed by some large Jupiter-like body much farther out. They get destroyed very quickly – getting them, unharmed, into a stable orbit is dynamically extremely difficult. There may be ways: Kratter & Perets have recently proposed a novel mechanism for populating the white dwarf habitable zone in binary stellar systems through capturing planets ejected from the companion star. Of course, as an observer I would argue the best thing to do is to look. After all, theoreticians weren’t exactly falling over themselves to predict the existence of Hot Jupiters before 51 Peg was discovered. We have searched around 200 white dwarfs in the SuperWASP survey for terrestial planets in their habitable zones. We didn’t find anything, sadly, but it’s a start….. see Faedi et al. 2011, MNRAS, 410, 899.

Michael August 1, 2012 at 14:18

Any world in close orbit around the white dwarf will surely be tidally locked, but there should be sufficient thermal effects to keep the planet warm. However water may be be a big issue although comets/asteriods from the demise of the old star may be around to help out. Intellegent life may find it very difficult to escape from the orbit near the white dwarf though.

Dave Moore August 1, 2012 at 15:52

The very high magnetic field is interesting. If the white dwarf had a rotational period significantly different from the planets orbital period, and the planet had an iron core, then there would be an enormous amount of inductive heating. If the planet had a longer orbit than the stars rotation, then the magnetic forces would push it outwards. While, if the rotation period was less than the star’s rotational period, the planet would experience a breaking force and spiral in. (Think magnetic tethers orbiting Earth.)

Christopher Phoenix August 1, 2012 at 17:37

This is very interesting! If we find terrestrial planets in the habitable zone of cooling white dwarfs, it will be a big blow to the “Rare Earth Hypothesis”. It would be strange to live on such a planet- the color of the light from a CWD must be much bluer than the golden rays from our yellow sun. We have already found planets orbiting stellar remnants, so it may not be so long before we find a planet in the habitable zone of a CWD…

Phil August 1, 2012 at 20:08

Well, if the white dwarf is the same temperature as the sun, then it will have basically the same colour as the sun! Sure there will be lots of younger, hotter, bluer white dwarfs, but I get the impression that Fossati et al are less interested in those than the ones that have already cooled to a sun-like temperature.

P

Eniac August 1, 2012 at 23:18

As I understand, both color and apparent diameter of the sun on a CDW planet would be similar to that of ours. The most obvious difference would be the lack of day/night cycle, and on the night side, the stars would move dizzyingly fast. It would be nearly impossible to send probes to the outer system, or into an escape trajectory, not with chemical rockets, anyway. Strong, changing magnetic fields offer interesting possibilities, including the availability of abundant free energy for any lifeform that masters the production of metal conductors. The equivalent of fire on such a world could be heat generated by a closed loop of wire.

David August 2, 2012 at 3:11

Matt,

Hot Jupiters were predicted in 1952, as were the transit and radial velocity techniques that
could find them. See
http://articles.adsabs.harvard.edu/full/1952Obs….72..199S

Ronald August 2, 2012 at 5:23

The HZ of such a white dwarf must be very, very narrow. In combination with the need for a (newly formed or migrated) terrestrial planet to be right within in, such favorable situations are probably very rare.
Then there is tidal locking and the question whether such a planet will contain enough water.

stephen August 2, 2012 at 11:46

Life based on ammonia, methane or other substances might survive. As the planet heats up and the local chemistry changes, ammonia life might go by the wayside as water-carbon life becomes predominant.

How large a life form can be subject to panspermia?
Life might evolve with the need to undergo periodic hibernation, and they’d develop carapaces to protect themselves from very harsh winters and/or summers.
As the star becomes a red giant, catastrophic events propel life forms into space, where they go into hibernation and orbit the star for many years. As the star becomes a white dwarf and obtains a planet at the appropriate distance, the life forms end up on the planet surface….

Is that too contrived and unlikely?

Michael August 2, 2012 at 14:06

Just thinking about the enviroment close to the White dwarf, orbital mechanic dictate very high impact velocities from comets/asteriods.

andy August 2, 2012 at 15:21

It’s an interesting question as to what the KOI-55 planets actually are: are they each remnant gas giant cores, or the disrupted remains of a single gas giant? In any case they are receiving extreme levels of irradiation from the sdB star which would probably do a good job at removing volatiles and maybe also has a good chance of eroding the heavier stuff too. By the time the parent star ceases helium fusion and becomes a white dwarf they might well be too dry (if they still exist) for habitability.

Gerry August 2, 2012 at 16:43

What an image; ancient planets orbiting the glowing cinder of a dead sun through countless eons, perhaps harboring exotic alien organisms. That sounds like a great setting for an H.P. Lovecraft story.

Christopher Phoenix August 2, 2012 at 17:14

@Phil I got the impression that “white dwarfs” were just that, blue-white, but that is only true when the star is still new and very hot. Over time, the white dwarf cools down to more sun-like temperatures, as you noted- thanks for pointing this out. Perhaps they should change the name to something not quite as color-specific…

@Eniac

The authors of the paper on habitable planets orbiting CWDs assume a weakly magnetic white dwarf, not a white dwarf with strong magnetic fields. Such fields may be problematic for life.

If intelligent life could evolve on a planet orbiting a strongly magnetic white dwarf, the magnetic fields could be both an advantage an a problem. Moving conductors could harvest electrical energy, but induced currents might be a problem for electronic devices. Perhaps all electronics will need to be contained within a magnetically shielded shell.

As for space travel- perhaps the aliens could use magnetic sails and tethers instead of rocketry. A white dwarf’s strong magnetic fields could make magnetic “field drives” a practical means of space propulsion. Free power is also a possibility for any craft carrying a large conductive tether.

ethanol August 2, 2012 at 19:17

Michael:

Just thinking about the enviroment close to the White dwarf, orbital mechanic dictate very high impact velocities from comets/asteriods.

This is a good point, although I imagine that with such high orbital velocities and such a small volume of the inner solar system that following an extremely violent period of consolidation, everything would be pretty well cleared out. Unless the orbital energies were such that every impact generated a larger volume of ejected debris and everything went all to hell.

Along those lines, does anyone know whether there have been any studies on the viability of habitable gas toruses ala Larry Niven’s The Integral Trees? Although now i can’t remember if that was around a white dwarf of a neutron star.

Rob Henry August 2, 2012 at 19:26

Eniac’s statement that fire could be generated by a closed loop of wire on such a world has incredible biological implications to me. It implies that large (multicellular) creatures with electrically conductive material in their protoplasma, would have alternative sources of energy to photosynthesis. This would give evolution much more incentive to produce complex creatures than around Sol type stars.

Perhaps then SETI enthusiasts can exist in the delusion that all other advanced civilisations in the Milky Way evolve on such stars. Being trapped in these gravitational wells, it suddenly makes sense that they signal in the hope of finding others.

From our perspective it seems that building an interstellar spacecraft would only take a tiny fraction of the cost of a few centuries of continuous broadcasts that are powerful enough to be picked up by our closest neighbours. And the starship has way more chance of reward.

coolstar August 2, 2012 at 21:02

Eric Agol at the U. of Washington has simulated a search for planets in the HZs of WDs at http://tfa.cfht.hawaii.edu/papers/agol_tfa_paper.pdf. (sorry, haven’t bothered to see where this was published). His quite reasonable findings are not particularly optimistic:
” If 20 one meter telescopes were devoted to this survey, then the calendar
time would be about 15 years; any further reduction in time would require more telescopes, fewer target stars,
or a shorter observing duration per star (the latter two cases would cause a decrease in the number of detected
planets).”
He finds that with this system, and an eta earth of 1%, one earth sized planet in the HZ would be found, on average.

The eclipse depths are huge, since the planet and the WD are roughly the same size, which leads to a typical eclipse depth of 60%. But, because the HZ is so close in at around 0.01 AU, the total eclipse times are only a couple of minutes. So you need, essentially, continuous monitoring over the average (not a lot of variability here) period of around 32 hours.

Agol’s simulations using the LSST show that it will do better, by roughly a factor of 20. Realistically, I strongly suspect that a LSST survey will actually get accomplished first. A significant finding from his modelling is that
“The remarkable coincidence between the white dwarf habitable zone at the peak of the white dwarf luminosity function and twice the Roche limit means that a transit survey for planets around the nearest white dwarfs will
be biased towards detecting Earth-temperature planets. ”

My apologies if this paper has been discussed here before! (I remembered seeing the paper, but not WHERE….).

There’s also a pro-am search already underway for such planets: http://www.brucegary.net/WDE/. I think this was actually motivated by the Agol paper.

coolstar August 2, 2012 at 21:05

addendum: the pro-am search WAS motivated by the Agol paper which was published in the Ap. J. Letters (still too lazy to give you the ref, but it’s easily found by using the NASA ADS system) and discussed in a July 2011 issue of the New Scientist.

Eniac August 2, 2012 at 22:31

Christopher:

The authors of the paper on habitable planets orbiting CWDs assume a weakly magnetic white dwarf, not a white dwarf with strong magnetic fields. Such fields may be problematic for life.

I do not understand how they would be. Life as we know it is quite completely unperturbed even by strong magnetic fields.

If intelligent life could evolve on a planet orbiting a strongly magnetic white dwarf, the magnetic fields could be both an advantage an a problem. Moving conductors could harvest electrical energy, but induced currents might be a problem for electronic devices. Perhaps all electronics will need to be contained within a magnetically shielded shell.

Sure. However, you could say with the same justification:

If intelligent life could evolve on a planet with an oxygen atmosphere, the chemical potential could be both an advantage an a problem. Combining the oxygen with biomass could harvest chemical energy, but uncontrolled combustion might be a problem for dwellings. Perhaps all dwellings will need to be equipped with lightening rods, and careful watch will have to be held over them with mobile devices ready to produce large amounts of water on short notice.

-

The two situations areastoundingly analogous, even thought the physical principles are very different.

Eniac August 2, 2012 at 22:41

Two more simple corrections: 1) Moving conductors in a static field will not produce energy. What is required is static conductors and moving fields. 2) Induced current is not a problem unless there are fairly long wires. Miniaturized electronics would not be affected, but power lines and all other kinds of wires will. So there would be early incentive for wireless communications, and power would not be transmitted through wires. Instead, it would be produced locally by wire loops designed to capture it out of thin air.

By the way, I have heard it said that if you live in close proximity to a radio station, you can actually light up a bulb for free using a wire loop and rectifier.

Eniac August 2, 2012 at 22:44

Another correction: A rectifier is not required to light up a bulb

Rob Henry August 3, 2012 at 5:25

Ethanol, it has to be a neutron star, and the reason is simple – our universe is not old enough for it to be a white dwarf. Let me explain.

This living space in The Integral Tree is not a *dense* gas as in dense interstellar clouds – its trillions of times greater than that description. It is like Earth‘s atmosphere and there is only one way to produce that. Take a gas giant whose core has a density such as that its orbit is just outside a star’s Roche limit. Now since this limit depends on density, the whole planet would be outside this limit if its envelope was included. This smears the envelope in a torus around the orbit of that core. Thus the “smoke ring”. If the core is massive enough it can prevent this torus from dissipating over a sufficiently tight orbit (at least this is the theory).

The Roche Limit for an Earth density core around a solar mass WD is 600,000 km. A solar mass WD should be about 0.8% the suns radius, so a 6,000K one would be four times brighter than our sun at the smoke ring. Even worse, I suspect that the universe is not old enough for a WD that is that massive to even cool to 6,000 yet. Less massive WD’s may be cool enough now but would have a greater radius and smaller Roche limit so our inhabitants would fry.

Ron S August 3, 2012 at 11:29

Rob: “Eniac’s statement that fire could be generated by a closed loop of wire on such a world has incredible biological implications to me.”

Not to mention how useful it would be to start a campfire in the backcountry!

Eniac: “Moving conductors in a static field will not produce energy. What is required is static conductors and moving fields.”

Am I misunderstanding something here? All that matters is relative motion.

Eniac: “…I have heard it said that if you live in close proximity to a radio station, you can actually light up a bulb…”

You have to get very close to the antenna, typically within the near field of a strong power source at a frequency where the bulb is a moderately-effective resonator (try MF or HF). Do this with a long-tube fluorescent, not a compact or incandescent bulb.

andy August 3, 2012 at 11:59

One other way you might be able to get planets into the HZ of a white dwarf is via second-generation planet formation. If the white dwarf is able to capture material from a red giant companion star (as is apparently happening with Mira B), it may go on to form planets. I’d suggest WD+WD binary systems may be good candidates for trying to find these kind of close-in planets.

Eniac August 3, 2012 at 21:45

Eniac: “Moving conductors in a static field will not produce energy. What is required is static conductors and moving fields.”

Am I misunderstanding something here? All that matters is relative motion.

I should have clarified this. If you move a coil in a stationary field, you only get the energy out that you put in. You need a magnetic field that changes due to an external energy source, such as the star’s rotation or the planet’s orbit.

Eniac August 3, 2012 at 21:52

You have to get very close to the antenna, typically within the near field of a strong power source at a frequency where the bulb is a moderately-effective resonator (try MF or HF). Do this with a long-tube fluorescent, not a compact or incandescent bulb.

I don’t think the near field is required. The far field also carries energy, indeed most of the energy goes into the far field, this is what antennas are designed for.

You are right, though, that you probably need a resonant circuit, so you might need to include a capacitor of some sort and carefully tune the resonant frequency of the loop+capacitor circuit to the transmitted frequency.

Ron S August 4, 2012 at 11:28

Eniac: “I don’t think the near field is required. The far field also carries energy, indeed most of the energy goes into the far field, this is what antennas are designed for.”

All the energy in the far field traverses the near field, and the flux is generally quite a bit higher (lots of ground-effect complications, though). MF vertical radiators (such as used for AM band broadcast) work best since the E field connects strongly to ground. The thing is that within the near field (say, under 1 wavelength) the E & H fields can be exceptionally strong since these fall off with the cube of the distance (again, with a variety of real-world complications). That is, think E & H, not EM, in the near field, and what they can do.

Eniac: “…so you might need to include a capacitor of some sort and carefully tune the resonant frequency of the loop+capacitor circuit…”

No, not necessary but it can help. I should have been clearer. In the near field of an MF vertical radiator, the E field lines are generally vertical due to ground interaction. So, hold a fluorescent tube upright (or stick it in the ground) and the V/m differential between the tube ends can be enough to light the tube, if only dimly.

I knew a couple of people years back who did this when they worked in broadcast engineering. Just don’t get caught by your supervisor since they tend to frown on this nonsense (although they probably did the same when they too were young).

JFGH August 6, 2012 at 18:38

Life can exist in ways we can not imagine yet…So, why not? It is only the human arrogance what make us tell we should search for similar worlds to ours.
Today, Curiosity has landed…If it finds some type of microbial martian life there…Likely, our biases on the search for life/habitable worlds will change a bit. We should be more flexible in our definition of “life beings”.

Torbjörn Larsson, OM August 7, 2012 at 12:31

2nd gen planetary systems, sometimes including 2nd gen protoplanetary disks. I love it when the “Rare Earth” idea gets a kick in the pants. (Idea, since you can’t really formulate a reasonable, testable bayesian model akin to Drake’s equation up to and including inhabited planets.)

@ Ronald:

“The HZ of such a white dwarf must be very, very narrow.”

Surface habitable zones are by definition relatively narrow. But you have also the ice moon/planet habitats, whether bound to stars or not. Such a 2nd gen planet would always contribute.

If we have a WD with a 2nd gen protoplanetary disk, fractured or recaptured material from binary companions et cetera, the probabilities for settling any HZ goes up.

Other than that, we can play the number game. ~ 97 % of stars will end up WDs. Most of them will be binaries @ ~ 50 %, who has a greater chance for 2nd gen planet captures/protoplanetary disk formation.

“Then there is tidal locking”.

Which slightly constrains habitables to a dense enough atmosphere. Not a problem.

“and the question whether such a planet will contain enough water.”

Too much water is a problem for habitability as we know it. We are lucky terrestrials in protoplanetary disks have a fair chance of being precisely as dry as Earth-Moon, Mars and likely Venus. An order of magnitude less water and we would have no oceans, an oom more water and we would have no land.

2nd gen terrestrial would have as much water in their mantle as ours, whether they were recycled or born out of a new protoplanetary disk with fresh volatiles snagged from a companion. That would result in pretty much the same surface/crust/ice locked ocean habitabilities, depending on which habitability zone/type they end up in/with.

@ Michael:

Fair point, but we don’t know the mass distributions for such systems. Also, in Abramov et al models, life survives any reasonable impact flow rate, certainly the LHB since cells proliferate and spread faster than any impactors can keep up sterilizing.

In later works cells (and now nematodes!) survive even crust busters in a Goldilocks zone ~ 1 km down. Life is a plague on a planet.

Torbjörn Larsson, OM August 7, 2012 at 12:53

@ Rob Henry:

“creatures with electrically conductive material in their protoplasma, would have alternative sources of energy to photosynthesis.”

The cytoplasma is an electrolyte in the sense that hydrogen ions are necessary for many metabolic processes, such as hydrolysis, phosphorylation and the bulk of ATP generation through the chemiosmotic chain.

It is the double membrane of cells that shield them from inductive effects. Note that no life on Earth has evolved magnetic systems for energy capture, only sensing, despite a relatively steady source. It implies cellular life forms can’t easily use this. If you could grow cellular macrostructures without membranes … but you can not.

“Perhaps then SETI enthusiasts can exist in the delusion that all other advanced civilisations in the Milky Way evolve on such stars. Being trapped in these gravitational wells, it suddenly makes sense that they signal in the hope of finding others.

From our perspective it seems that building an interstellar spacecraft would only take a tiny fraction of the cost of a few centuries of continuous broadcasts that are powerful enough to be picked up by our closest neighbours. And the starship has way more chance of reward.”

You can do costly near space exploration, but due to lightspeed constraints there is only two feasible economies in space, information barter and colonization. The former would be narrowcast, the latter would most cheaply be a natural extension of interplanetary colonization out into the Oort clouds between stars.

I think we can see that such divergent alternatives means the Fermi question is too loosely constrained to be useful. The galaxy may be colonized and we will never see it as dispersing Oort cloud migrations will be radio silent, or be an information barter market and we will eventually find out by the necessary pr drives.

SETI is then not necessarily deluded as much as marginally useful.

amphiox August 7, 2012 at 16:06

It is only the human arrogance what make us tell we should search for similar worlds to ours.

Not arrogance. Simple practicality. It makes perfect sense that when you are just starting out looking as we are, and are thus naive and inexperienced at the task, you should start with the “low-hanging fruit”, and look in the places you know and understand best, where you would have the greatest chance of recognizing what you find. Particularly when you have only so much resources available to devote to the search.

That is why we look for worlds like our own, because we know what life on worlds like our own looks like, or at least what one type of life on a world like our own can look like, so we know what to look for. There may well be types of life vastly alien to our own with vastly different requirements. But we don’t know what those requirements are or what their constraints are, and we don’t know what kinds of signatures such lifeforms might leave behind. And you cannot conduct a reasonable search on such ignorance.

It makes sense to first start looking for things similar to ourselves, that we would have a better chance of recognizing. On finding it, and recognizing the similarity, we can then compare it to ourselves, and learn how it is different. And thus we expand the totality of the sphere of what we can recognize as life. Our next search can then be for life that is like our own AND/OR like the first example of life we find. And when we find that next example, our horizons on what life can be will expand yet further, allowing us to search even further.

But to search for life so utterly alien to ourselves that we can only make random guesses as to what it is like right now would be an exercise in which success or failure would be determined by pure luck.

Rob Henry August 7, 2012 at 17:29

Torbjörn Larsson, there is not that much potential energy for capture on Earth since our magnetic field moves slowly.

I liked your point on the supposed requirement of both aquatic and terrestrial environments for the advancement of life. I also think that tidal lock might eventually be shown to be an advantage here. I note that it could modulate the release of water from the dark side ice cap according to geological heating, and irrespective of whether that cap is 10km deep or several hundred. The dayside might typically resemble a well watered continental interior.

Eniac August 7, 2012 at 22:38

Torbjörn Larsson:

Note that no life on Earth has evolved magnetic systems for energy capture, only sensing, despite a relatively steady source.

There is no significant electromagnetic energy to be harvested anywhere on Earth, except for visible light. So, there is no steady source, and your observation shows nothing. However, you are right that even if there were sufficiently strong and changing magnetic fields, microorganisms would be in no position to harvest energy from them. It will take macroscopic structures, and most likely metal, too.

Alien experimenters might notice that rings made of gold or silver turn warm in certain situations, and they may figure out how to use them to power electrical arcs, which can be used for lighting, warmth, and process heat. The latter could open up more advanced metallurgy, leading to plowshares and swords, and all the rest we know….

Chris Phoenix August 8, 2012 at 3:05

@Christopher – Might we be related? Your writing sounds like mine, and I know I have a cousin also named Chris Phoenix (father Vern, uncle Ray – my father). I’m surprised I haven’t seen you on the web before. Please email me at cphoenix at gmail.com.

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