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(10) Bringing It All Together In Astrobiology and Astrophysics: The Problems With Cosmic Rays (In Space), Muons (On Planets), Homelessness and Extinction [and Some House Music]

2023.02.03 11:24 Chas-- (10) Bringing It All Together In Astrobiology and Astrophysics: The Problems With Cosmic Rays (In Space), Muons (On Planets), Homelessness and Extinction [and Some House Music]

The wonderful Christian astronomer-mathematician mentor I mentioned previously from the research lab I worked in when I was young? He also pointed out to me the most difficult fact that we learned during the Apollo program. Any trip to Mars in any space ship that we can construct anytime soon, will be a death sentence.
Let me elaborate just how difficult this problem is, in summary form.

The Bright Side of Galactic Cosmic Rays

Cosmic rays in space are nuclei of the various elements, ejected from a kaleidoscope of stellar events, starting from the early largest stars and proceeding as metals began to become prevalent and changed the nature of stars as the products of early supernovae became second and third generation stars and exotics. When those primary cosmic ray nuclei moving at relativistic speeds (>= 0.1 c : the speed of light) and impact the high atmosphere of earth, they break up into pieces in a shower, producing a shower of muons that penetrate down to the ground level and even kilometers into the earth.
I'll light the fire you place the flowers
Life in the universe is all about the stellar evolution of a menagerie of stars, metallicity and where the periodic table of the elements comes from. The kind of advanced life forms that are found on Earth require about 23-25 of the elements, ranked 5 (essential for life) and 4 (essential for some species) in that list, and where those elements come from is a number of different kinds of stellar events (in the menagerie above) that need to be fairly local in the region of the galaxy where life starts. Not only that, the elements need to be widely abundant enough on the planet itself that life can flourish without traveling all the time to consume them. Plants, for instance, are not good travelers and you need their photosynthesis to breath oxygen. It is our immense and extremely rare fortune that the abundances of the elements are present in the solar system, and that furthermore, they are all abundantly and widely present on earth. We could be here and alive, but without any kind of advanced technology and thus trapped on this world, earthbound. Also, with just a few percent more planetary mass, it would be prohibitive to launch a vehicle into orbit.
I believe in my heart, that this is no accident, and that belief is based in faith in the Lotus Sutra and our common destiny to spread it. The abundances of the elements in our solar system are completely perfect for what we need: to do anything that we want to do. Most of the elements for advanced technology arise from merging neutron stars and that excellent chemical cornucopia and all the other fortunate coincidences we will discuss below, having occurred here on this planet where Buddhism, the Lotus Sutra and Nichiren Daishonin's practice of the Lotus Sutra has arisen seems extremely unlikely due to random chance. That great fortune bestows upon us earthlings unimaginable power compared to other intelligent life forms that may not have been so profoundly fortunate. We will explore more in terms of just how unlikely our fortune is. For now, as Spidey learned from his Dad, "With great power comes great responsibility."
In the vase that you bought today
The widespread deposits of most the advanced periodic table on Earth have been hypothesized to have landed here during the late heavy bombardment caused by Jupiter encroaching near enough to Mars to break up planet five and divert those pieces and various leftovers from the coalescing of the solar system, which created the asteroid belts, and also dropping a large number of those rocks on earth, between 4 .1 and 3.8 billion years ago. That advanced treasure allows us to create the technology to become space-faring. The resonance between Jupiter and Saturn that pulled Jupiter back before it destroyed Earth like it did planet five, is why we are here to enjoy that treasure. That metallicity required enough passage of time since the big bang for the evolution of that menagerie of stars to populate our galaxy with enough metals beyond the hydrogen and helium we inherited from the big bang. All of the elements originate as cosmic rays out of violent events in the history of the universe. [As seen on the Discovery Channel show: How the Universe Works episode: "How the Universe Built Your Car"]
A large number of elder civilizations and those to come in the cosmos will be impoverished in comparison to ours.

The Dark Side of Galactic Cosmic Rays (GCRs)

Cosmic ray (CR) metal nuclei primaries and their secondaries, called daughters, slow down when they interact with matter, by virtue of their nuclear positive charge. You might think that because they mostly emanate from the galactic center, that there would be a variation in distribution from the direction of the milky way, but in fact the magnetic field of the galaxy itself has made that distribution of CR impacts extremely even from all directions (called isotropic across the four pi of solid angle) except when you are in low earth orbit, with the earth blocking two pi of the solid angle flux of particles.
Staring at the fire for hours and hours
There is a chart called the Bethe-Bloch dE/dX (Stopping Power of matter), which shows the kinetic energy of the cosmic rays on the x axis and the energy deposited per unit of travel (damage trail of the particle or dE/dx) in the y axis. Notice that, like a tumbling bullet slowing down and causing more damage, as the cosmic ray primary nucleus slows down it spends more time in a region and rips more electrons from the local matter as it stops. In the middle part of the curve it causes much less damage, but as the particle is traveling closer to the speed of light on the right end of the curve the damage increases from the intense electric field. This is due to the relativistic Lorentz contraction in the direction of travel: the spherical positive electric field of the nuclear particle becomes as flat and wide as a pancake slamming into the target. That flatness condenses the electric field and its damaging power increases profoundly the closer you get to the speed of light. [Here is a set of slides with the details of this, and another copy of that chart on slide 14 of 28, in case the other chart URL gets broken. And here is a whole course on Astroparticle Physics from U. Wisconsin]
Lawrence Berkeley Laboratory (the folks who made elements like Lawrencium and Berkelium) have a Chapter 24 of some government review on cosmic rays, which has all the data presented nicely. In figure 24.1 (not table 24.1) on page 3, you can see the abundance curves for cosmic ray primaries Fe-iron, C-carbon, He-helium and H-hydrogen on the y-axis, versus the kinetic energies (KE) on the x-axis: as they were measured in space. Note the high end for all of those dipping down in abundance on the right. I have used a very handy web calculator for relativistic kinetic energy to calculate some velocities of those four elements at the high end of KE:
Element Atomic Mass (nucleons) Full Nuclear Kinetic Energy (electron volts) Fractional Velocity of Light Speed (c)
Fe (iron) 55.85u 1.3963TeV 0.9994c
C (carbon) 12.011u 4.804TeV ~1c
He (helium) 4.0026u 3.6023TeV ~1c
H (hydrogen) 1.008u 2.218TeV ~1c
[There are many other cool calculators there as well, physics, etc.]
While I listen to you play
However, those four particle curves are mostly showing their abundances in the low dE/dx range in the middle of the Bethe-Bloch chart and not (1) in the dangerous stopping realm in the left, or (2) the dangerous relativistic realm on the right. So adding shielding to your spacecraft would make the middle realm particles stopping in your passengers, and would cause the low abundance relativistic particles to fragment and produce daughter nuclei and muon showers to bathe your passengers in. Nevertheless, by the time you get to Mars and back in your wisely unprotected space vehicle, you will have received a deadly dose of radiation, although the shielded part of the space craft will protect you from the low energy particle storms from the sun. Just don't stay in there, when the solar wind isn't blowing. And the effective 10 feet of lead that earth's atmosphere and magnetosphere provide you in terms of radiation protection in the skyward (orthogonal) direction (and even better in other angles)? That's not there on Mars, it's more like millimeters of lead.

The Even Darker Side of Extra-Galactic Cosmic Rays (EGCRs)

Now, those are the friendly cosmic rays from our galaxy. They are made isotropic, and evenly directed in all angles in space by the galactic magnetic field. They also serve to create that magnetic field by their charged nature, and that field protects us from cosmic rays from outside our galaxy, which are much, much worse. The University of Utah has been measuring those for some time in a project called HiRes, here's their cool poster. They use widely spread fluorescent light mirrors focused on photo-multiplier tubes high on a mountain top to detect the muon showers coming from secondaries, emanating out of cosmic ray primaries impacting the top of the atmosphere, and put those showers back together electronically and digitally collating the coincidence data into a pancake snapshot of the shower of muons. [Interestingly, from the cosmic rays' frame of reference, its electric field is spherical and it is flying smack into an immensely dense pancake earth coming at it at ~1c. That's why Einstein called it relative.]
If you go back to the Chapter 24 document from LBL and look at figure 24.10 on page 17, you will see the results of the HiRes experiment in that orange line at the right end, which shows a 1020.5 eV particle, and that's 300 Exa eV or 300,000,000 TeV of kinetic energy. That extra-galactic cosmic ray particle has the kinetic energy of a baseball thrown at 57.6 MPH, but with a diameter smaller than the point of the tiniest needle. You really, really don't want to fragment that particle with shielding, just as the Marines say, "Embrace the suck!" Those particles have been observed in creating a visible lesion in the eye of an astronaut.
Your love song all night long for me only for me
This would appear to make space travel impossible, or like my astronomer-mentor said, a death sentence.
In the short run, NASA's solution to this problem for the current Artemis Mars Project, when I outlined the issue pretty extensively in a fairly large meeting (the most recent time that I worked there): was to send older astronauts, (1) since they had already been exposed in space and knew all the consequences of that and still wanted to be the ones going, (2) they were closer to the end of their lives and would thus not suffer much of a reduced life span, and (3) they had already reproduced if they were going to, so deadly mutations would not be passed on to their descendants.
In the long run, I have no doubt that this and all other related "impossible" problems preventing the fulfillment of our joint mission are just technological and will be solved by engineering: because (1) all of the "impossible" problems I have worked on were solved by a competent team (and daimoku), (2) human beings are just getting more competent by computer and other high technology aided methods, and (3) my total faith that humanity are all Buddhas and essentially following Nichiren Daishonin's plan and the Buddha's intent, irregardless of "evidence" to the contrary.

The Impacts of Various Radiation Sources on Habitability

In the paper Big-Bang to Big Brains - Paul A. Mason, New Mexico State University, frames the discussion of habitability in reference to the including presence and persistence of the basic requirements for life:
The emergence of life awaited the development of habitable environments. Life famously requires energy, water, and nutrients present in sufficient quantities to allow efficient chemical reactions, a key to organic chemistry and metabolism. The existence of a region surrounding a star, usually called the habitable zone, was introduced by Strughold, to define a range of distances for which liquid water on an Earth-like planet’s surface is possible. The formation of a habitable planet is life’s prerequisite. A potentially habitable planet might lose its water, like Mars and Venus, never have water in the first place, or even have too much water.
He also summarizes the things that habitability must persistently preclude:
Now we must consider that the planetary environment must survive the effects of its host star(s)’ development. Low mass stars, M-types, have prolonged magnetic activity and thus they have habitable zones subject to bursts of XUV radiation and high particle fluxes. On the other hand, stars with only a bit more mass than the Sun have lifetimes that are far shorter. If complex life generally needs billions of years to develop as on Earth, then complex life cannot be supported by main sequence stars that are about 20% more massive that the Sun. Solar type stars and lower mass K-types both have extended lifetimes and activity levels suitable for complex life. Because of the dangers in the central regions of galaxies and low metallicities in the outskirts, the galactic habitable zone and super-galactic habitable zone concepts were introduced.
Come to me now and rest your head
There is a superbly designed graph presenting Professor Mason's inclusions and preclusions on page 6 of that paper above and also on a poster he presented to a conference on Habitable Worlds in 2017. On the x axis, he shows the age of the universe in billions of years on the bottom, and also using the red-shift of the stellar systems being observed on the top (a handy gauge!) On the y-axis, he shows the local density of stars on the right, and how those lines converge to unity in the present day on the bottom right corner and 100x density on the upper right corner. Not enough density, no metallicity, too much, a stiff radiation field and too many muons for life on the surface. The green dotted line labeled AGN activity means the active galactic nucleus (where the SMBH, the super massive black hole lives in our galaxy), which has calmed down mightily since the early days of our spiral galaxy (no more quasars in this end of cosmic history.) Note that the star formation rate has dropped by a factor of ten since its peak when the galaxy was 3 to 4 billion years old. We are almost at the end of that everywhere in the cosmos. When that ends, we have eight or so billion years of life left for main sequence stars like ours to create new life. Here's the legend underneath that graphic:
Figure 5: The universe becomes habitable for life in stages. Simple life became possible roughly 9 billion years ago and complex life emerged about 5 billion years ago and then only within the moderate density, Super-Galactic Habitable Zone
I mostly agree, although even in the hot zone closer into the denser galactic nucleus, at the upper end of the density scale, it is possible that there are oceans and complex life in the depths, shielding life from muonic hurricanes by miles of water. And that would hold for the enhanced radiation field inside merging galaxies as well. Muons have a short half life of 1.56μs (~15 hundred feet at ~one foot per nanosecond), which is extended by a factor of 70, due to relativistic time dilation in their early path at 0.9999c at the top of the atmosphere, but death comes quickly for them as they slow down. Remembering the flat pancake thing from Lorentz contraction, the 10km of our thick atmosphere (and the earth itself) appears 70 times thinner to a 0.9999c muon. In the center of all spiral galaxies and in all other large galaxies, those living advanced civilizations will be trapped by that stiff radiation field in those oceans, until their main sequence G2 star ends its life as our sun will, by heating up and expanding into a red giant, encompassing the orbits where life is possible and consuming those planets, like earth will be consumed, before shedding that outer atmosphere as a planetary nebula and becoming a white dwarf.
The emergence of life as we know it relies on several factors. Over time, galactic disks not only allowed for the concentration of elements, but the magnetized galactic wind of disk galaxies also provided protection.
Nothing like a strong magnetic field, produced by pesky GCRs, preventing the deadly EGCRs from penetrating our defenses: "They may be bastards, but they're our bastards." - Dwight Eisenhowe5-star General and 34th POTUS.
For just five minutes everything is done
In another paper by Paul A, Mason, and Peter L. Biermann of the Max Planck Institute for Radio Astronomy at Bonn, Germany, Astrophysical and Cosmological Constraints on Life, The professors go into much more detail regarding the sources of radiation, condensed below:
SEPs: [Solar Energy Particles, the wind from the sun] are responsible for mass loss of planetary atmospheres. However, planets may be magnetically protected. For example, the magnetic field of the Earth detects or traps SEPs, enhancing the habitability of Earth. Mars currently does not have a significant global magnetic field, and its mass is about 10% of the mass of the Earth. Mars still experiences significant atmospheric mass loss due to solar activity as measured by instruments aboard the MAVEN spacecraft. In the early life of the Sun it was less luminous than it is now, however it was also much more active.
GCRs: SNe [Supernova explosions] are probably not the source of all GCRs, but this detection [the Fermi gamma-ray telescope] suggests that shocks within SN remnants do accelerate particles. [Benyamin] considered the spiral arms of galaxies as the main location of GCR sources. [Aartsen] found a large-scale anisotropy in PeV emission and suggested that this result is consistent with a superposition of flux from a just few nearby sources, likely SN remnants. SN explosions of the most massive stars (above 25M [M: solar masses]) are more important in many aspects, but the standard SNe (stars between 8 and 25M) are the major contributors to CR-protons, and dominate the overall energetics.
EGCRs: Taken at face value, UHECRs from M82 [starburst galaxy] suggest that planets in galaxies with rapid star formation are subject to high fluxes of UHECRs from local sources, like GRBs [gamma ray bursters], microquasars, and relativistic SNe remnants. ... An AGN [active galactic nucleus] likely inhibits life or even eliminates habitability within its host galaxy. AGN might even adversely affect other nearby galaxies as UHECRs are able to break free from the magnetic confines of the host galaxy. ... Radio galaxies are effective particle accelerators.
SFR: [star formation rate] The SFR history plays an important role in the habitability of galaxies. The most massive stars do not last long and explode as SN-Type Ib/c, followed by the chemical enrichment of the ISM [interstellar medium]. However, nearby SNe and GRBs probably have quite adverse effects on life (Gehrels; Thomas), causing mass extinctions, temporary sterilization, and even atmosphere removal if they happen very close.
GRBs: Gamma-ray bursts are stellar explosions that generate enormous radiation beamed in two opposing directions. Local GRBs may occasionally sterilize large portions of the land-based life in the Galaxy. (Annis) argues that GRBs are so critical to astrobiology that the Universe is currently undergoing a phase transition from no intelligent life to intelligence as a result of the reduction of GRBs. While we generally agree that the reduction of the number and luminosity of GRBs is critical to habitability, the timing of this transition is likely not universal. Galaxies with active SMBHs, especially those resulting from mergers, will remain uninhabitable for many Gyr into the future.
SMBHs: Nearby super-massive black holes. As we observe SMBHs in the local Universe, it is clear that many of them remain quiet for a long time, but these inactive SMBH have been active in the past and the right kind of accretion event will turn an inactive SMBH into an active one. AGN [active galactic nuclei] activity as a function of redshift is shown in Figure 4 [also, the poster]. The peak around z = 2 indicates that AGN were most active 10 Gyr years ago. AGN activity dropped by an order of magnitude by the time the Earth formed, about 4.6 Gyr ago, corresponding to z = 0.45, and it has fallen by another order of magnitude since then. The density of EGCRs was dramatically higher in the past not only because the density of CRs sources was orders of magnitude higher, but also due to an important cosmological effect. The co-moving volume of the Universe was smaller by a factor of (1 + z)3 in the past, exposing planets to more direct UHECRs from SMBHs as well as from extragalactic SNe. ... In our cosmic neighborhood we have several SMBH. These are in M31, M32, M81, M94, NGC5128 (Cen A), and in our own Galaxy [Sagittarius A*], all within about 5 Mpc today.
SMBH Mergers from Galaxy Mergers: Galaxy mergers amplify the SN and GRB rates and SMBH activity. During a merger, giant molecular clouds collide, resulting in a considerable increase in the SFR [star formation rate] and its associated SNType II rate. Considering the starburst galaxy M82 ... The SFR in that region is about 10 times that of a normal star forming galaxy like the Milky Way. ... When two big galaxies merge and both contain SMBHs, then their SMBHs also merge. Gergely and Biermann (2009) showed that the spin of the final merged black hole will be aligned with the direction of the angular momentum of the SMBH binary orbit, and so it is in a totally different direction than the original spins of the two SMBHs. This means that while this happens the two jets sweep through the sky [of the new galaxy], cleaning out [killing life across] a large conical solid angle (Gopal-Krishna).
Such a cozy room the windows
This is what will happen to our galaxy, the Milky Way, when the larger Andromeda galaxy (M31) and the nearby spiral galaxy (M33) collide and begin to merge in 4 billion years. For a long, long while, life in the new galaxy will be impossible on land, only deep underground or under the oceans. Of course the earth will be consumed as our sun swells and becomes a red giant some time around then.
The Galactic center SMBH: The nucleus of the Milky Way emits high energy radiation and particles, potentially harmful to life. Extremely high energy gamma-rays have been detected using Cherenkov telescopes ... UHECRs [ultra-high energy cosmic rays] detected at Earth are probably from accreting SMBHs at the centers of galaxies. The Galactic magnetic field helps to protect us from these EGCRs. ... we see that the Galactic SMBH poses the greatest threat to global sterilization of planetary surfaces in the Galaxy. By analogy, the greatest threat to planets in external galaxies might arise from the presence of local SMBHs. Many if not most galaxies do not harbor SMBHs, so these may be more suitable galaxies for complex life.

Location, Location, Location

The danger posed by individual objects is a strong function of distance and depends on the direction of beamed radiation source. Planetary habitability is especially inhibited when high local SFRs [star formation rates] are coupled with the growth of SMBHs [galactic center super massive black holes].
The worst threats are those that cause complete planetary sterilization; these are most often local threats as a planet's location is a key to habitability. Life on Earth has avoided the worst catastrophes, since evidence shows the continuous presence of life for 3.5 Gyr. As discussed in the introduction, mass extinctions were quite common on Earth, yet there is no evidence of a complete planetary sterilization. [Actually, the likely collision with Theia (Mars-sized) that created the moon was sterilizing 4.5 Gyr ago.] Mass extinction events on Earth, have paved the way for an increase of evolutionary diversity as new niches became open. A key factor of habitability is the severity and frequency of sterilization and mass extinction events and how readily life is able to recover from them. The expansion of the Universe and the local reduction in the SFR improves the habitability of planets protected by magnetic fields and thick atmospheres.
Life depends on water, and therefore, a catastrophic or gradual loss of atmospheric water can result in a loss of habitability. Here we propose that a planet sufficiently supplied with a protective atmosphere and magnetic field in the mid-disk of the Milky Way is currently more habitable than similar planets in many other galaxies in the contemporary Universe. We argue this because, first, the Sun stays relatively far away from the SMBH in the center of the Milky Way, a major threat. Second, the Galactic SMBH has a relatively low mass and has been unusually inactive for some time, since only minor mergers have taken place in the Milky Way over the last 10-12 Gyr (Gilmore). Third, the galactic disk currently forms new stars at a rate which sustains a global magnetic disk wind, providing an efficient shield against EGCRs without supplying too many GCRs. It is difficult to evaluate the danger of radiation and particle dosage as we do not know what complex life is capable of withstanding. However, we speculate that life, and especially metazoan life on the surface, can be harmed by large doses of particles and radiation. Within this context, we conclude that life as we know it was rare or impossible in the disk of the Milky Way earlier than about 5-6 Gyr ago. An earlier limit, at about 8 Gyr ago, also exists for only microbial life. These temporal limits are illustrated in Figure 4 [also, in the poster]. Habitable conditions probably exist somewhat earlier in some disk galaxies, i.e. those without recent mergers or SMBH activity, like the Milky Way, compared to other more recently active galaxies.
Are illuminated by the evening

The Impact of Various Protective Elements On Habitability

... many additional factors also affect so called habitable zone planets. Planetary system dynamics, host star activity, asteroid and comet impacts are important habitability factors. A planet's geomagnetic, atmospheric, hydrological, and biological history shapes its ability to support life. ... Life on planets have several lines of protection from high energy particles. First, planets in the disk of a star forming galaxy are protected from all but the highest energy EGCRs because of shielding by the galactic magnetic field. Lower energy CRs accelerated from galactic sources, especially SN remnants, become deflected by magnetic fields to be contained in the Galactic magnetosphere. Those, mostly very high energy, EGCRs penetrate the galactic magnetosphere. Both magnetically confined GCRs and the dangerous high energy GCRs with direct trajectories impact the astrosphere [volume of lower density gas around a solar system created by the solar wind]... The astrosphere protects planets from the lower energy (E < 300 MeV) GCRs. A global planetary magnetic field provides the next layer of protection, not only from GCRs but also from the SEPs emitted by the host star(s). The last line of protection is the planetary atmosphere.
Elements: Atmospheric ozone O3 provides a significant UV shield against CRs. It is thought that the complexity and diversity of life on Earth increased as a result of the increase of oxygen in the atmosphere produced by photosynthetic life. This increase of oxygen coincided with the Cambrian explosion in the geological record, 541 million years ago. CRs indirectly cause harm to potentially habitable planets by removing ozone. With the removal of ozone, XUV radiation from the host star may desiccate the planet's atmosphere even if it is in the traditional habitable zone by definition. ... The high abundance of Fe is necessary to establish the planetary magnetic field. Planets without a sufficient Fe core probably cannot maintain a dynamo of sufficient strength to supply magnetic protection against CRs from a variety of sources over biologically relevant timescales. Planets with weak magnetic moments subject to high and intermittently intense fluxes of CRs are not expected to support life on the surface.
Galactic Magnetic Fields: life on planets in the disks of star forming galaxies are protected from EGCRs by a magnetic galactopause generated by the galactic wind. This wind is analogous to the solar wind generating the heliosphere surrounding the solar system. This protective effect of the magnetic field in galaxies is closely connected to the spiral structure. It is driven by SNe explosions within the disk as well the shearing effect from differential rotation of the disk ... Later after CNO abundances increased locally, the SFR slowed, and the associated threats to life decreased. ... Locally, we are just barely above the protective threshold of a strong galactic wind, and thus it is conceivable that potential life in a region not too far from the Galactic plane might not have enough protection from CRs, or suffer from a temporary weakening of that Galactic wind. The same holds true for a planet that is farther out in the disk [towards the edge], than about 10 kpc; out there the conditions to drive a galactic wind may no longer hold.
Astrospheres: The circumstellar environment is dominated by electromagnetic radiation from the host star(s) and stellar winds launched by magnetic fields in the hot corona of cool main sequence stars. ... As the wind escapes it fills an astrosphere - a bubble of outflowing plasma originating as a stellar wind and terminating at a dense hydrogen wall just outside the astropause. In the case of our Sun, the heliopause is about 120 au from the Sun. Protection from host star winds is a prerequisite to planetary habitability, however these winds also protect life on planets from GCRs. ... A strong stellar wind significantly reduces the flux of GCRs, but the higher energy CRs penetrate the astrosphere. ... The Voyager spacecrafts provided the first opportunity to directly measure the interstellar GCR flux. ... The interstellar proton number flux per kinetic energy is 15 times higher than it is at 1 au from the Sun. ... low-mass star winds are weaker and corresponding astrospheres are smaller and less effective at stopping GCRs than winds from higher mass stars. ... On the other hand, a planet in the circumbinary HZ (habitability zone) of a pair of solar like stars and with a binary period of say 25 days, will be exposed to reduced X-ray and UV radiation due to tidal deceleration of stellar rotation in binaries. In addition, a circumbinary astrosphere is produced from a combined wind, thereby reducing GCRs compared to the single star case.
Sunshine through them fiery gems for you, only for you
Planetary magnetic fields: ... Venus is too close to the Sun to have surface water, but may have previously been in the HZ when the Sun was younger and fainter. However, Venus rotates very slowly, once every 243 days, and as a result it does not have a global magnetic field. Venus lost its habitability as the result of its proximity to the Sun and it suffered a runaway greenhouse effect. Mars previously had surface water, but its low gravity is unable to prevent atmospheric mass loss. Mars lost its habitability for complex life once it cooled, lost its dynamo, and its atmosphere lost its protection capacity from SEPs [solar energy particles].
... Larger planets of similar composition will generate stronger magnetic fields.
The Atmosphere: ... A team modeled atmospheric effects of the UV and SEP flux from a large flare of the active M dwarf AD Leonis. These effects on an Earth-like planet without a magnetic field in the HZ were simulated. They found that the UV emission from such a flare should not have a significant impact on the atmospheric ozone, however, NO2 produced by ionization from SEP protons may result in a greater than 90% ozone depletion about two years after the flare, with a predicted recovery time of 50 years.
... High energy CRs, especially UHECRs, hit the atmosphere and create an air-shower, as the enormous energy is converted into potentially millions of secondary particles, including muons, neutrinos, electrons, positrons, neutrons, and protons, with muons having the greatest penetration capacity. If the secondary particles are energetic enough, and their flux is sufficiently high, muons can impact even subsurface life. If the radiation dose is too high, the chances of sustaining life as we know it on the planet are very low. A team examined the dependence of the GCR-induced radiation dose on the strength of the planetary magnetic field and its atmospheric depth, and found that the latter is the decisive factor for the protection of a planetary biosphere. Thicker atmospheres provide longer path lengths for both primary and secondary CRs, especially lowering the flux of secondary particles at the surface. An atmosphere should be thick enough to provide surface pressure that is sufficient to maintain liquid water (or other solvent), which is required for surface life.
SGHZ: [super-galactic habitable zone] ... complex life is severely compromised on the surface of planets within the central region of large clusters of galaxies and superclusters: ... [Also,] 1) the ubiquity of galaxy mergers, 2) periods of intense star formation experienced by many galaxies either during natural spiral arm formation or as the result of a merger, and 3) activity associated with SMBH accretion and CR acceleration, especially as the result of a SMBH merger. The merger and star formation history is an important factor in the habitability of a galaxy. .We may find, that only relatively small galaxies are able to maintain habitable environments over long times.
... Our own galaxy is probably on the borderline. On the other hand, the metal abundance is correlated with galaxy size, and thus oxygen (e.g., in water) and other life-required elements may not be available in sufficient quantities in small galaxies. So between these two requirements, a) no central SMBH and no extreme central star density (prone to make GRBs), and b) sufficient amount of heavy elements, there may be only limited time in the Universe, and only a few galaxies, to allow life, especially complex life to develop. ... These scenarios are illustrated schematically on the right side of Figure 4 [also, in the poster]. The limit estimated for minimal or microbial life depends greatly on local conditions, but is estimated here to be about 8 Gyr ago or when the Universe was about 6 Gyr old. ... About 5-6 Gyr ago, when the Universe was 8-9 Gyr old, metal abundances were comparable to present day in some locations and AGN and the SFR had decreased to about 10 times present day levels. Where habitable conditions were met, life probably transitioned from simple to complex about that time.
And 5 Gyr ago was when the Dark Energy acceleration kicked into high gear and the life of the cosmos was extended by earlier cosmic life than ours. But, go ahead, pat yourself on the back, nice work. ;)
Many planets in the densest regions of the local Universe may remain uninhabitable due to intense particle fluxes and sterilizing events. We introduce the concept of a Super-Galactic Habitable Zone to address this possibility. For the future, all this means that if humanity survives long enough, then our descendants may need to keep moving, First into space or to another planet with a different star (as the Sun dies), and then certainly to another galaxy.
That last paragraph says move it, for survival or I say, with a mission.
Our house is a very very very fine house With two cats in the yard Life used to be so hard Now everything is easy 'cause of you and I'll
Our house is a very very very fine house With two cats in the yard Life used to be so hard Now everything is easy 'cause of you and I'll
I'll light the fire while you place the flowers In the vase that you bought today - Graham Nash of Crosby, Stills and Nash
Nash wrote this song after the afternoon described in the song, when he was living with Joni Mitchell. She is an example of the miracle of the brain to possess exquisite talent for singing while playing the piano with two hands, not just a left beating out a rhythm while the right picks out a melody. Here is an example of her sublimely low entropy -- causing the cosmos to expand just to make sure the balance is kept and the Second Law of Thermodynamics is not violated.
The cosmos is "our house", with a lot of uninhabitable rooms. We appeared here for the one great reason (in 4 parts) and with the intent of the last 4 lines of the Jiga-Ge. Our problem is that the house is burning, many guests are trapped, and who will we save? I have a version 0.1 of a rescue plan.
submitted by Chas-- to SGIWhistleblowersMITA [link] [comments]