Category Archives: exoplanets

Life in the Year 100 billion trillion – Part I

If our Universe is open, either flat or hyperbolic in geometry, then it will expand forever… or at least until space-time’s warranty expires and a new vacuum is born from some quantum flip. Prior to that, most likely immensely distant, event the regular stars will go out and different sources of energy will be needed by Life in the Universe. A possible source is from the annihilation of dark matter, which might be its own anti-particle, thus self-annihilating when it collides. One possibility is that neutrinos will turn out to be dark matter and at a sufficiently low neutrino temperature, neutrinos will add energy to the electrons of atoms of iron and nickel by their annihilation. This is the energy source theorised by Robin Spivey (A Biotic Cosmos Demystified) to allow ice-covered Ocean Planets to remain hospitable for 10 billion trillion (1023) years.

Presently planets are relatively rare, just a few per star. In about 10 trillion years, or so, according to Spivey’s research, Type Ia supernova will scatter into space sufficient heavy elements to make about ~0.5 million Ocean Planets per supernova, eventually quite efficiently converting most of the baryon matter of the Galaxies into Ocean Planets. A typical Ocean Planet will mass about 5×1024 kg, be 12,200 km in diameter with 100 km deep Ocean, capped in ice, but heated by ~0.1 W/m2 of neutrino annihilation energy, for a planet total of ~50 trillion watts. Enough for an efficient ecosystem to live comfortably – our own biosphere traps a tiny 0.1% of the sunlight falling upon it, by comparison. In the Milky Way alone some 3,000 trillion (3×1015) Ocean Planets will ultimately be available for colonization. Such a cornucopia of worlds will be unavailable for trillions of years. The patience of would-be Galactic Colonists is incomprehensible to a young, barely evolved species like ours.

We’ll discuss the implications further in Part II.

Orlando is Awesome!

Too much to tell on the very aggressive schedule here, so a detailed report will need to wait, but I met a FAN! You know who you are. Thanks for the encouragement and I promise more content – I have some actual journal paper ideas gestating and I will need input from my audience, I suspect. One is a paper on Virga-style mega-habitats and Dysonian SETI, to use a new idea from Milan Cirkovic. The other looks at exoplanets and Earth-like versus the astrobiology term of “habitable” – the two are not the same and the consequences are sobering. The recent paper by Traub (go look on the arXiv) which estimates 1/3 of FGK stars has a terrestrial planet in the habitable zone does NOT mean there’s Earths everywhere. What it does mean and how HZ can be improved as a concept is what I want to discuss.

More later. I have my talk to review and get straight in my head – no hand notes, though I have practiced it – plus I want something helpful to say to Gerald Nordley, mass-beam Guru, on the paper he graciously added me as a co-author. Also I will summarize my talk and direct interested readers to the new web-site from John Hunt, MD, on the interstellar ESCAPE plan.

Hydrogen Greenhouse Worlds…

The first planets to form probably attracted a primary atmosphere of H/He from the solar Nebula. In our Solar System these were driven off from the four Inner Planets and retained by the Outer Giants, but in theory smaller planets can retain such a mixture. I’ve speculated about such worlds on these blog pages before and now there’s a new arXiv piece discussing the greenhouse abilities of H/He…

Hydrogen Greenhouse Planets Beyond the Habitable Zone

…the summary conclusion being that 40 bars of H2 can keep the surface at 280 K out to 10 AU around a G type star and 1.5 AU around an M star. Thus planets with oceans of water can exist at Saturn-like orbital distances given enough primary atmosphere. Super-Earths are the most likely to retain their H/He primary atmospheres due to their higher gravity, as young stars put out a LOT of EUV light which energizes the hydrogen and strips it away in a billion years or so, if the planet is too close. Out past ~2 AU for a G-star and that effect isn’t so dramatic, thus a Super-Earth where the Asteroid Belt is today would’ve retained its primary atmosphere and probably be warm & wet.

Such a “habitable planet” is only barely defineable as habitable because it has liquid water, but is unlikely to remain warm/wet habitable if the hydrogen is exploited/depleted by methanogens making methane out of it with carbon dioxide, nor oxygenic photosynthesisers making O2, via CO2+H2O->CH2O+O2, which then reacts rapidly with hydrogen. Could another kind of photosynthesis evolve to restore the hydrogen lost? Hydrogen makers exist on Earth, so it’s not unknown in biochemical terms, but I wonder what other compound they need to release net hydrogen from methane/sugars/water?

Strange Habitats

Some recent news pieces have expanded possible locales for Life. We’ve looked at…

Supernova made Earths warmed via Dark Matter

…and we’ll look at…

White Dwarf Habitable Zones

…but a new(ish) idea is “failed stars” – brown dwarfs, but smaller than the 13 Jupiter-mass deuterium-burning limit – might be suitable for life based on other solvents like ammonia and ethane, not just water…Failed Stars for Life

Another idea, which Frederick Pohl imagined in his last Heechee novel, is Life existing inside super-massive Black Holes…

Is There Life inside Black Holes?

…a Kerr-Newmann Black Hole (i.e. A spinning one) has a region between its inner and outer event horizons which permits stable orbits, thus providing a locale for adventurous Lifeforms to exist. Just how they would get power for living and avoid in-falling matter from beyond the outer horizon is speculative, at best, but truly advanced entities might want direct access to the singularity that might exist within.

But does General Relativity give us a sure guide to the interior of Black Holes? Theo M. Nieuwenhuizen has applied some alternative gravity theories to black holes, with the interesting result that instead of infinite blue-shift at the event horizon, and even more bizarre phantasmagoric phenomena within, instead the mass of the collapsed star might form a giant Bose-Einstein Condensate, without any of the singularities and weird horizons of regular GR. Of course whether the particular gravity theory is correct requires experimental confirmation, but it does suggest that plain-old GR, as Einstein gave it to us, might be incomplete.

Fermions & the Fermi Paradox

R.J.Spivey writes a provocative essay for the arXiv…

From Fermions to the Fermi Paradox: A Fertile Cosmos Fit for Life?

…basically Spivey suggests we’re jumping to conclusions too soon about Life in the Cosmos, that the real party is after our current Stelliferous Era, when Life exists in a multitude of planets formed from supernova remnants, powered by neutrino annihilation in pressurized iron. Spivey is also disinclined to include us as that “Life” – we might yet attain that level of advancement, but for now our Future fate is for us to create. We might fail to advance to the level of Galactic Colonists, able to adapt to Ocean planets under ice, living off the thin trickle of energy from neutrinos (via the reverse photo-neutrino effect) for 100 billion trillion years. He suggests that the efforts to make artificial life will fail and that we’ll need to hone our bioengineering skills to remodel an ecosystem fit for the Ocean planets of the distant future.

News from Zarmina!

It’s all over the news! Earth-like Planet Found (for real)!

Of course we don’t know much about Zarmina (Gliese 581 g) other than some very bare basics, but her discoverer, Steve Vogt, has expressed his near 100% certainty there’ll be Life on Zarmina of some kind. While I agree with his sentiment I think we should stay skeptical of all claims of inhabitants on that distant world. But that hasn’t stopped some from going further. For example, this “Daily Mail” piece…

Does ET live on Goldilocks planet? How scientists spotted ‘mysterious pulse of light’ from direction of newly-discovered ‘2nd Earth’ two years ago

…covering the 2008 claim of signal detection by Dr Ragbir Bhathal (University of Western Sydney) who is an active member of SETI, particularly OSETI – the Optical Search for Extra-Terrestrial Life. At the time he didn’t let out a lot of information, but now it seems his positive signal came from Gliese 581, the star, or close to it. Or did it? I’m not entirely impressed by the article because it’s both vague and inaccurate. At the time of Dr. Bhathal’s initial claim the constellation of Tucanae was quoted as the region in question. Now the story has changed. Until Dr. Bhathal releases more information or someone else makes another positive detection the claim can only be “under investigation”.

Yet what if it was true? Zarmina is being called a “ribbon world” – a planet tidally locked to face its star forever with the same face, thus endless day on one side and endless night on the other. The ribbon refers to the border between night and day, the Terminator, which is in a state of never-ending twilight. Duncan Lunan’s discussion of the Green Children of Wolfpit, who were mentioned by Francis Bacon [erratum: Robert Burton, in his “Anatomy of Melancholy” (1651)] as possible extraterrestrials, suggests such a world. Their story comes from the 12th Century and Lunan did a write-up for “Analog” some years ago. The children were found disoriented and speaking a foreign language in the town of Wolfpitt/Wolpitt. The strangest thing about them, aside from their curious story, was their bright green skin, which eventually returned to normal. They claimed to have come from “St Martin’s Land”, but gave a description of their homeland as always being in twilight. This fits the concept of a ribbon world, but their undeniable humanity caused Lunan to make the SF leap that they were from a human colony on a ribbon world accidentally time-space transported to Medieval Earth. Of course there’s an alternative mundane explanation, but their twilit homeland is terribly evocative and hard to explain as an earthly locale.

We’ll only ever know the truth if we go looking for it… Part II.

E-Eyes on the Cosmos

New Horizons, the fastest launched probe, is shooting towards a close encounter with Pluto and its three moons on July 14, 2015. As NH will get ~50 metre resolution we can work out the baseline for an interferometer to achieve the same. In visible light, say 0.5 micrometers, the limit of distinguishable detail 50 metres apart needs an aperture of 61,000 metres for Pluto’s distance of ~5 trillion metres. So a near-term interferometer won’t see Pluto better than the probe, not unless the scopes are really, really far apart and their optical signal can be combined as a virtual interference pattern to analyze. A challenge, and though there’s nothing unphysical in the idea it’s not happening soon enough to beat New Horizons.

The planned European Extremely Large Telescope, a massive telescope with a 42 metre wide mirror, will show an image of Pluto about 32 pixels wide, if the pixels are packed to the optical limit. That’s pretty good for a planet so far away. Two E-ELTs 200 metres apart would increase that to ~160 pixels or so.

What’s the extreme of performance possible?

Since 1995 there’s been some NASA discussion of a Exosolar Planet Mapper able to produce ~100 pixel images of Earth-like planets up to ~10 pc away. At that extreme, some 300 quadrillion metres away, an Earth-like planet with a ~130 km resolution needs a telescope some 1,400 km wide. While it’s tempting to say an interferometer that big is doable since radiotelescopes have been combined in bigger interferometers there’s a major problem. The photons reflected off the planet have spread themselves far and wide across an immense spherical wavefront. At 10 pc 1 square metre of reflecting surface of the planet has had its rays spread over ~2.1E+21 square metres. Each photon now has ~2 square metres to itself. To get a decent signal we’d have to catch a lot of photons with a lot of telescopes and keep extraneous noise out. Tricky.

Primordial Dramas and Present Easy-Breathing

Our Solar System has changed dramatically over the aeons since the planets accreted/collapsed out of the initial nebula. The Sun both got brighter in overall output, but has dimmed in its extreme UV brightness (EUV) and solar-wind levels, with dramatic consequences for the atmospheres of the terrestrial planets & giant planet-sized moons. A good review article:

Atmospheric Escape and Evolution of Terrestrial Planets
and Satellites
Space Sci Rev (2008) 139: 399–436, DOI 10.1007/s11214-008-9413-5

…available at one of the co-authors, R.E.Johnson’s, webpage. EUV absorption in the very uppermost atmosphere, the exosphere, can drive the temperatures there to extremely high levels. This is due to the nature of EUV interactions with the very widely separated atoms and ions of the exosphere. Most of the atmosphere is well mixed, due to interparticle collisions, but in the exosphere the atoms rarely collide. Instead they can be struck by highly energetic photons, like EUV, and retain that energy, equivalent to thousands of degrees. This puffs the exosphere up even further and makes it easier for the atmosphere to escape into space, causing potentially several times the present day atmospheric masses to be driven off.

Another suite of processes produce what’s called non-thermal escape basically via energy transfer from the solar-wind to the upper atmosphere. Such processes can be very complicated to model and simulate, and can often only be properly understood by direct measurement thanks to long-term space-probe missions. Finally another possible atmospheric escape process is via direct blow-off via impacts. This isn’t happening in the present day at appreciable levels – fortunately – but is believed to have been important on smaller bodies like Mars and the large Gas Giant moons. Volatiles can also be accreted via this mechanism – the difference lies in the speed of the incoming impactor. Too fast and the incoming material blows away into space, taking some of the surface with it.

Some surprising masses of primordial atmosphere can be lost via these mechanisms, reshaping the body in question irrevocably. Some plausible changes – Venus lost an ocean, Earth lost excess hydrogen, Mars lost its primordial warming blanket of CO2, the Galileans lost Titan-like atmospheres and Titan lost several times its present day nitrogen atmosphere. And, just possibly, Earth owes its ocean to accretion via comets. At least some of it, almost certainly.

The implications for exoplanetary systems are worth considering. A smaller planet in a red-dwarf habitable zone will experience a much higher impactor speed, due to its higher orbital velocity. But, contrariwise, will it experience more impactors? Our own impact flux depended heavily on the movements of the Gas Giants – a primordial Titanomachy, if you will, which pummelled the planets with gravitationally tossed proto-comets & asteroids. Red dwarf stars seem to produce fewer Gas Giants, at least of Jupiter/Saturn class sizes, and may well produce a less severe impact flux. Could that mean their terrestrial planets are deprived of cometary volatiles and thus desert planets?

That’s one possible example and no doubt more will be conceived as our understanding improves.