Aren't there any rock or similar firm material on/in the gas giant planets?

Aren't there any rock or similar firm material on/in the gas giant planets?

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Aren't there any rock or similar firm material on/in the gas giant planets? What happens if a rock asteroid hits one of these planets? Shouldn't the rock accumulate in the center of the planet due to its high density?

The inside of a giant planet is not like regular gas.

First of all, it is hot. You are away of how it gets hot inside the Earth (causing volcanos). It is also hot inside Jupiter, but since Jupiter is bigger, it is hotter. It would be hot enough to vaporise rock under "normal conditions".

The pressure is immense, and things stop behaving as you are used to when the pressure is very high. For example, all the atoms in a gas are pushed so close together that they are touching (like they would be in a liquid). This means that there is no boiling point and no real difference between the gas and liquid phases. At extreme pressures, hydrogen atoms are pushed so close together that their electrons can start to flow from atom to atom, forming a fluid metal.

Pressure that can push atoms so close that they can turn hydrogen to a metal mean that you can't send a probe to this region. You can't swim in a metallic hydrogen sea.

Nevertheless, heavier atoms like iron, silicon, carbon, oxygen, will tend to fall towards the centre of the planet, and so there may be a since rocks are made mostly of atoms like iron, silicon, carbon, oxygen, you could describe this as a "rocky" core. But don't think this is a kind of solid surface that you could stand on.

The Longest Year

I don’t usually write about newly discovered record-breaking objects found by astronomers, because in general it’s not long before that record falls. But in this case, I’ll make an exception for Kepler-421b. It has the longest year—that is, it has the longest orbital period around its star—for any exoplanet yet seen crossing in front of its star.*

That by itself is enough to make this an interesting object, but even cooler (literally) is where that puts this planet: Far enough from its star that it may have formed in a different way from the other planets we’ve detected around other stars. It may very well be an ice giant, like Uranus or Neptune, and not a gas giant or rocky planet.

First, let’s go through the basics: The host star is Kepler-421, a star much like the Sun but a bit smaller and cooler. It’s located about 1,000 light years away, which is a fair ways (the Milky Way galaxy is 100,000 light years across). From Earth, that makes the star pretty faint.

The planet, Kepler-421b, was discovered by the Kepler observatory, a space-based telescope that has found so many of the recently-discovered exoplanets. It uses the transit method to find planets if we see the planet’s orbit around its star edge-on then every time the planet passes between us and the star it blocks a bit of the star’s light. It’s tricky for example Kepler-421b only blocks about 0.3 percent of the star’s light. But with modern detectors, that sort of dip in light is detectable.

Generally speaking, you need three transits to be sure you’ve got something. If you see just one it could be a starspot, or some other nonplanetary object interfering with your observations. A second transit tells you the orbital period (the year) of the planet, but it could still be a coincidental starspot. If you get a third transit at the right time interval after the second, then you can be more confident.

Adapted from a diagram by Greg Loughlin

For Kepler-421b, the astronomers only saw two transits, which made me suspicious, but after reading their paper I’m more inclined to think they got it. The shape of the “light curve” and the incredible match between the two transits make it very likely they did find a planet. For the rest of this article I’ll just assume it exists, but remember that it has yet to be confirmed independently.

Kepler-421b is about four times the diameter of Earth (judging from how much of the starlight it blocked), and has a year that’s 704 Earth days long. That’s amazing most exoplanets found have much shorter periods, like days or weeks. That orbit puts it about 180 million kilometers (110 million miles) out from the star. Since the star is cooler than the Sun, the planet actually receives about one-fourth the light from its star as Earth does from the Sun. That’s even less than Mars gets, so the planet is pretty chilly.

And that brings us to the second cool thing about this planet. Planets form from broad disks of material orbiting the star when it’s young. Close in it’s hot (duh) so you don’t get much gas or ice. The material in the disk is mostly metal and rock. Farther out there’s still metal and rock, but water is in the form of ice (this distance is called the “snow line,” a term I like), and there’s lots of it. Giant planets that form at least that far out have a lot more ice than ones farther in, and we call them ice giants. To be clear, these aren’t giant ice balls they look a lot like gas giants but have more ice in them as opposed to rock and denser stuff.

In our solar system, Uranus and Neptune are ice giants. Given Kepler-421b’s location, it should be one as well. If we assume it’s about as dense as Uranus, it has 16 times the mass of the Earth. That will likely give it a thick atmosphere (and it’s very cold, remember) so it’s not Earth-like at all.

But it’s the first ice giant seen orbiting another star. We’ve seen other planets with similar masses and sizes, but they orbit closer in, and are likely gas giants. Ice giants may very well be pretty common among exoplanets, but they’re pretty hard to detect. For one, the long period means you have to wait a long time to confirm them. Also, the bigger the orbit is, the less likely it is we’ll get a transit — a planet close in to its star can be seen to transit from a wide range of viewing angles, but a more distant planet needs a more tightly constrained viewing geometry (the orbit has to be more precisely edge-on) for us to spot it.

Finding Kepler-421b means that astronomers may be able to start finding more. Seeing one planet might be an anomaly, but if you find 20 more like it you can start categorizing them. This means they can use physics and models to understand better how planets form, especially that far from their parent star. We’re still figuring that out for our own solar system, so having other examples with which to compare and contrast is very helpful.

And so that’s why I’m willing to write about a record-breaker, even if that record is soon broken. As usual in astronomy, I hope it is! That turns this planet from a weirdo into the first member of its class, and that means we get to learn stuff. And astronomers love learning stuff.

*Correction, July 23, 2014: This article originally stated that Kepler-421b has the longest year of any known exoplanet. It has the longest year of any exoplanet found by the transit method.

In looking for so-called “ Goldilocks'”exoplanets, here are a few of the desirable characteristics for one to have:

  • The planet needs to lie within a certain distance from its parent star, where the planet would hypothetically be able to retain liquid water on the surface without it evaporating into space or freezing. This region has no set distance, as it depends on the size, mass and temperature of the star.
  • The planet needs to remain in a stable orbit that wouldn’t take it too far beyond the habitable zone of its planetary system. Most of the planets we’ve found have highly eccentric orbits that regularly take the planet too close to its star and too far away. Any existing life on the planet would have difficulties adjusting to the harsh temperature jumps.

On that note, we shouldn’t rule any planet in one of these oblong orbits out, as we have discovered certain life-forms on Earth – like bacteri a, fungi and archaeas – that thrive in some very harsh, seemingly inhospitable environments. According to Stephen Kaine – an astronomer, who helped create the Habitable Zone gallery , which basically estimates the distance any specific planet would need to be from its parent star for any existing water on the exoplanet to remain in liquid form (no water = no carbon based life):

“Some organisms can basically drop their metabolism to zero to survive very long-lasting, cold conditions. We know that others can withstand very extreme heat conditions if they have a protective layer of rock or water. There have even been studies performed on Earth-based spores, bacteria and lichens, which show they can survive in both harsh environments on Earth and the extreme conditions of space.”

[Reference: “ Extreme Life Forms Might be Able to Survive on Eccentric Exoplanets “]

He is also quick to point out that we shouldn’t necessarily limit our search to ‘super-Earth’ exoplanets. As we’ve seen with our solar system, the most habitable celestial bodies aren’t necessarily other planets, but the moons in orbit around other large, gaseous bodies. Thus, we must conclude that with our limited knowledge of alien solar system, it might not be too far from the mark to assume that moon-baring planets are the rule, not the exception, which opens up a whole new layer to the habitable planet front. I’ll leave you with one more thing to contemplate: a paraphrased quote said by Stephen Hawking : “It is more likely for there to be an unfathomable amount of foreign, alien species instead of there being none at all.” I think that definitely applies here.

Just How "Earth-like" is the Newest Planet?

In the land rush known as extrasolar planet hunting, the most prized real estate is advertised as "Earth-like." On Monday, June 13, scientists raced to plant their flag on a burning hunk of rock orbiting a red star.

This newly discovered planet is about seven times the mass of Earth, and therefore the smallest extrasolar planet found to orbit a main sequence, or "dwarf" star (stars, like our sun, that burn hydrogen).

There are even smaller planets known to exist beyond our solar system, but they have the misfortune to encircle pulsars, those rapidly spinning husks of dying stars. Such planets aren’t thought to be remotely habitable, due to the intense radiation emitted by pulsars.

Planets that are ten Earth masses or less are thought to be rocky, while more massive planets are probably gaseous, since their stronger gravity means they collect and retain more gas during planetary formation. 155 extrasolar planets have been found so far, but most of them have masses that are more comparable to gaseous Jupiter than rocky Earth (Jupiter is 318 times the mass of Earth).

Although this new planet is advertised as Earth-like because of its relatively low mass, earthlings wouldn’t want to rent a house there any time soon. For one thing, the house would melt. The surface temperatures estimated for this planet – 200 to 400 degrees Celsius (400 to 750 degrees Fahrenheit) – are due to the planet’s kissing-close distance from its star.

The planet resides a mere 0.021 AU from the star Gliese 876 (1 AU is the distance between the Earth and the sun), and completes an orbit in less then two Earth days. The closest planet to the sun in our own solar system – blazing hot Mercury – is nearly 20 times further away, orbiting at about 0.4 AU.

"Because the planet is in a two-day orbit, it is heated to oven-like temperatures, so we do not expect life," says science team member Paul Butler of the Carnegie Institution of Washington.

In our solar system, the habitable zone – the temperate region where water could exist as a liquid on a planet’s surface – is roughly 0.95 to 1.37 AU, or between the orbits of Venus and Mars. The star Gliese 876 is about 600 times less luminous than our sun, so the proposed habitable zone is much closer in, roughly between 0.06 and 0.22 AU.

At 0.021 AU, the new planet is too close to the star to be in the habitable zone, and it also is subjected to greater amounts of high energy radiation like ultraviolet light and X-rays. While red dwarfs like Gliese 876 emit lower levels of UV than stars like our sun, they do emit violent X-ray flares.

Another complication from such a close orbit is that the planet may be tidally locked, with the same side of the planet always facing the star. Unless there is a substantial atmosphere to distribute heat, one side of the planet will be overcooked while the other will remain cold.

Gliese 876 is thought to be about 11 billion years old, making it more than twice as old as our sun. But in a way, Gliese is a teenager to our sun’s middle-aged adult. G-class stars like our sun live about 10 billion years, while M-class red dwarfs are thought to live for 100 billion years (older than the age of the universe!).

Science team member Geoff Marcy of the University of California, Berkeley, says that M stars take a long time to cool off and shrink down to their main sequence size and luminosity. He says that if the planet migrated inwards to its present day close orbit, it probably made this move during the first few million years, and then was subjected to much more radiation than at present for hundreds of millions of years.

By combining the high sensitivity of space telescopes with the sharply detailed pictures from an interferometer, TPF will be able to reduce the glare of parent stars to see planetary systems as far away as 50 light years.
Credit: NASA

Gliese 876 is thought to be metal-poor (to an astronomer, any element heavier than hydrogen and helium is classified as a "metal"). The formation of planets may be related to the metallicity of the star, since both the star and the planets form from the same original material. So a rocky planet like the Earth, made out of elements such as silicates and iron, is expected to orbit a star that is metal-rich.

Despite being metal-poor, Gliese 876 is a multiple planet system. Two gas giant planets are known to orbit Gliese 876: the outermost planet is nearly twice the mass of Jupiter, and orbits at 0.21 AU the middle planet is about half the mass of Jupiter, orbiting at 0.13 AU.

"The whole planetary system is sort of a miniature of our solar system," says Marcy. "The star is small, the orbits are small, and in closer is the smallest of them, just as the architecture is in our own solar system, with the smallest planets orbiting inward of the giants."

We have a lot more elbow room in our solar system. Mercury is further away from the sun than the distances of all these planets combined. The planets in the Gliese 876 system are so close together, they gravitationally interact with each other. This sort of gravitational tug of war was how the scientists were able to detect the planets in the first place.

Over the course of an orbit, planets will gravitationally pull on their star from different sides. Scientists measure the resulting shift in star light to determine the existence of orbiting planets.

The Real Earth-like Pale Blue Dot. View from Space.
Credit: NASA

To learn more about Gliese 876’s smallest planet, scientists would need to use another planet-hunting technique called transit photometry. This method looks at how a star’s light seems to dip when a planet passes in front of the star from our field of view. The eclipse of the orbiting planet allows astronomers to determine that planet’s mass and radius. Pinning down those numbers indicates the planet’s density, which then suggests what the planet is made of, and whether the planet is rocky or gaseous.

Transit photometry can’t be used to tell us anything about planets orbiting Gliese 876, however, because the system is inclined 40 degrees from our point of view. This angle means the planets won’t block any of the starlight that reaches Earth.

Red dwarfs are the most common type of star in our galaxy, comprising about 70 percent of all stars. Yet out of the 150 red dwarfs they have studied over the years, Marcy and Butler only have found planets orbiting two of them. Because most of the planets found so far are gas giants, this could mean that red dwarfs are less apt to harbor those kinds of worlds.

Marcy says they will continue to monitor Gliese 876 for any hints of a fourth or fifth planet. "This will definitely be one of our favorite stars from now on," he notes.

A Race to the Finish Line

The research paper describing this discovery has been submitted to the Astrophysical Journal. The scientists say they received a favorable preliminary referee’s report, and they expect their paper will be accepted and then published in a few months. During Monday’s press conference, the scientists were asked why they decided to publicize their finding now, before the paper had been accepted for publication. Was it to beat out other planet hunters who might be hot on their heels?

Marcy replied that they wanted to prevent news of their discovery from leaking out. "We knew about it three years ago, we’ve been following it quietly, carefully, guarding the secret while we double and triple checked. Then about a month ago I talked with Michael Turner here, people at NSF (National Science Foundation), and jointly we decided that this discovery was so extraordinary, maybe what you would call a milestone in planetary science, that it was difficult to imagine keeping the lid on this for very much longer. So we decided that rather than have it leak out to the news media, and be dribbled around, with one newspaper learning about it early and so on, that it would be better to quickly announce this."

Marcy then launched into a defense for why he believed their finding is correct, and he was quickly backed by his fellow team members. However, the accuracy of their finding had not been questioned. Perhaps their early announcement, combined with the need for secrecy beforehand, is evidence of the intense competition that has marked planet hunting since the beginning.

The first extrasolar planet discovery was announced October 5, 1995 by Michel Mayor and Didier Queloz of the Geneva Observatory, and Marcy and Butler confirmed the observations the following week. A recent example of the competition to grab other extrasolar planet "firsts" occurred last summer, when on August 25, 2004, Mayor, Nuno Santos, and colleagues announced the discovery of the first extrasolar Neptune-mass planet — at the time the smallest extrasolar planet known to orbit a sun-like star. This announcement came less than a week before two other Neptune-mass planet discoveries were announced by Marcy and Butler.

Mayor and his colleagues also have studied Gliese 876. At an astronomy conference in June 1998, Mayor and Marcy each independently announced the detection of the more massive gas giant orbiting this star. Marcy and Butler were first to follow up on this finding, announcing the discovery of the star’s second gas giant planet in 2001.

The Kepler mission, due to launch in June 2008, will search for terrestrial planets orbiting distant stars. The mission defines an Earth-size planet as being between 0.5 and 2.0 Earth masses, or between 0.8 and 1.3 Earth’s diameter. Planets between 2 and 10 Earth masses, such as the planet announced on Monday, are defined as Large Terrestrial planets.

Why do planets like Neptune and Uranus have rocky cores the size of Earth and yet insanely huge atmospheres, and yet the Earth has such a thin atmosphere?

Side question - Is the Earth the "rocky core" of our planet?

Fundamentally, this has to do with where in the Solar System the planet formed.

First, there's a concept in planetary science known as the "frost line. Currently this is located around 5 AU, where 1 AU = Earth-Sun distance, though 4.6 billion years ago when the planets were forming, we think it was closer to 3 AU.

Second, planets form by first slowly accreting solid clumps through mutual gravitational attraction. At some point the protoplanet's gravitational pull is strong enough that it can start holding onto gases. Heavy gases like carbon dioxide move almost 7x slower than light gases like hydrogen, so heavy gases have a much harder time reaching the planet's escape velocity. As a result, a forming protoplanet holds on to heavy gases first if it can get to

10 Earth-masses, its gravitational pull will be strong enough to hold on to light gases like hydrogen, too.

Now let's put those two together: inside the frost line, the only solid that protoplanets can use to start forming is rock. Outside the frost line, both rock and ice are solid, so forming planets can use both of those. and there's a lot of ice. If you're far enough out, that can also include carbon dioxide ice, ammonia ice, nitrogen ice, etc.

In the case of Earth, it formed from what rock was around - about 1 Earth-mass of it. That provided enough gravity to hold onto heavier gases like nitrogen and carbon dioxide, but not light gases like hydrogen or helium.

In the case of Neptune, it was far enough out to form from rock as well as several varieties of ice. and there's a lot of ice. By mass, Neptune formed from about 80% water + ammonia ice, about 5% rock, and about 15% hydrogen + helium gas. If you add together just the rock and ice, you get about 14 Earth-masses. That's just past the 10 Earth-mass threshold to hold onto hydrogen, but it probably only crossed that threshold late in the game, and so only managed to collect about 3 Earth-masses worth of hydrogen before the solar nebula dissipated. This is exactly why we prefer the term "ice giant" for Uranus and Neptune rather than gas giant.

Side question - Is the Earth the "rocky core" of our planet?

Sure, to a very reasonable first approximation, you could say Earth is a rocky core. The difference is that within giant planets, the rocky core is under incredible pressures, far greater than anything in the center of our own planet. Things get unusually heated and compressed own there (rock is about 4 times as dense in the core of Jupiter as it is on Earth, and very likely not solid), and exotic states of matter can arise in such high-pressure conditions.

There Are 6 'Strongest Materials' On Earth That Are Harder Than Diamonds

Atomic and molecular configurations come in a near-infinite number of possible combinations, but the . [+] specific combinations found in any material determine its properties. While diamonds are classically viewed as the hardest material found on Earth, they are neither the strongest material overall nor even the strongest naturally occurring material. There are, at present, six types of materials that are known to be stronger, although that number is expected to increase as time goes onwards.

Carbon is one of the most fascinating elements in all of nature, with chemical and physical properties unlike any other element. With just six protons in its nucleus, it's the lightest abundant element capable of forming a slew of complex bonds. All known forms of life are carbon-based, as its atomic properties enable it to link up with up to four other atoms at a time. The possible geometries of those bonds also enable carbon to self-assemble, particularly under high pressures, into a stable crystal lattice. If the conditions are just right, carbon atoms can form a solid, ultra-hard structure known as a diamond.

Although diamonds commonly known as the hardest material in the world, there are actually six materials that are harder. Diamonds are still one of the hardest naturally occurring and abundant materials on Earth, but these six materials all have it beat.

The web of the Darwin's bark spider is the largest orb-type web produced by any spider on Earth, and . [+] the silk of the Darwin's bark spider is the strongest of any type of spider silk. The longest single strand is measured at 82 feet a strand that circled the entire Earth would weigh a mere 1 pound.

Carles Lalueza-Fox, Ingi Agnarsson, Matjaž Kuntner, Todd A. Blackledge (2010)

Honorable mention: there are three terrestrial materials that aren't quite as hard as diamond is, but are still remarkably interesting for their strength in a variety of fashions. With the advent of nanotechnology — alongside the development of nanoscale understandings of modern materials — we now recognize that there are many different metrics to evaluate physically interesting and extreme materials.

On the biological side, spider silk is notorious as the toughest. With a higher strength-to-weight ratio than most conventional materials like aluminum or steel, it's also remarkable for how thin and sticky it is. Of all the spiders in the world, Darwin's bark spiders have the toughest: ten times stronger than kevlar. It's so thin and light that approximately a pound (454 grams) of Darwin's bark spider silk would compose a strand long enough to trace out the circumference of the entire planet.

Silicon carbide, shown here post-assembly, is normally found as small fragments of the naturally . [+] occurring mineral moissanite. The grains can be sintered together to form complex, beautiful structures such as the one shown here in this sample of material. It is nearly as hard as diamond, and has been synthesized synthetically and known naturally since the late 1800s.

For a naturally occurring mineral, silicon carbide — found naturally in the form of moissanite — is only slightly less in hardness than diamonds. (It's still harder than any spider silk.) A chemical mix of silicon and carbon, which occupy the same family in the periodic table as one another, silicon carbide grains have been mass produced since 1893. They can be bonded together through a high-pressure but low-temperature process known as sintering to create extremely hard ceramic materials.

These materials are not only useful in a wide variety of applications that take advantage of hardness, such as car brakes and clutches, plates in bulletproof vests, and even battle armor suitable for tanks, but also have incredibly useful semiconductor properties for use in electronics.

Ordered pillar arrays, shown here in green, have been used by scientists as advanced porous media to . [+] separate out various materials. By embedding silica nanospheres, here, scientists can increase the surface area used to separate and filter out mixed materials. The nanospheres shown here are just one particular example of nanospheres, and the self-assembling variety are almost on par with diamonds for material strength.

Oak Ridge National Laboratories / flickr

Tiny silica spheres, from 50 nanometers in diameter down to just 2 nanometers, were created for the first time some 20 years ago at the Department of Energy's Sandia National Laboratories. What's remarkable about these nanospheres is that they're hollow, they self-assemble into spheres, and they can even nest inside one another, all while remaining the stiffest material known to humankind, only slightly less hard than diamonds.

Self-assembly is an incredibly powerful tool in nature, but biological materials are weak compared to synthetic ones. These self-assembling nanoparticles could be used to create custom materials with applications from better water purifiers to more efficient solar cells, from faster catalysts to next-generation electronics. The dream technology of these self-assembling nanospheres, though, is printable body armor, custom to the user's specifications.

Diamonds may be marketed as forever, but they have temperature and pressure limits just like any . [+] other conventional material. While most terrestrial materials cannot scratch a diamond, there are six materials that, at least by many measures, are stronger and/or harder than these naturally occurring carbon lattices.

Diamonds, of course, are harder than all of these, and still clock in at #7 on the all-time list of hardest materials found or created on Earth. Despite the fact that they've been surpassed by both other natural (but rare) materials and synethetic, human-made ones, they do still hold one important record.

Diamonds remain the most scratch-resistant material known to humanity. Metals like titanium are far less scratch-resistant, and even extremely hard ceramics or tungsten carbide cannot compete with diamonds in terms of hardness or scratch-resistance. Other crystals that are known for their extreme hardness, such as rubies or sapphires, still fall short of diamonds.

But six materials have even the vaunted diamond beat in terms of hardness.

Much like carbon can be assembled into a variety of configurations, Boron Nitride can take on . [+] amorphous, hexagonal, cubic, or tetrahedral (wurtzite) configurations. The structure of boron nitride in its wurtzite configuration is stronger than diamonds. Boron nitride can also be used to construct nanotubes, aerogels, and a wide variety of other fascinating applications.

Benjah-bmm27 / public domain

6.) Wurtzite boron nitride. Instead of carbon, you can make a crystal out of a number of other atoms or compounds, and one of them is boron nitride (BN), where the 5th and 7th elements on the periodic table come together to form a variety of possibilities. It can be amorphous (non-crystalline), hexagonal (similar to graphite), cubic (similar to diamond, but slightly weaker), and the wurtzite form.

The last of these forms is both extremely rare, but also extremely hard. Formed during volcanic eruptions, it's only ever been discovered in minute quantities, which means that we've never tested its hardness properties experimentally. However, it forms a different kind of crystal lattice — a tetrahedral one instead of a face-centered cubic one — that is 18% harder than diamond, according to the most recent simulations.

Two diamonds from Popigai crater, a crater formed with the known cause of a meteor strike. The . [+] object at right (marked a) is composed purely of diamond, while the object at left (marked b) is a mixture of diamond and small amounts of lonsdaleite. If lonsdaleite could be constructed without impurities of any type, it would be superior in terms of strength and hardness to pure diamond.

Hiroaki Ohfuji et al., Nature (2015)

5.) Lonsdaleite. Imagine you have a meteor full of carbon, and therefore containing graphite, that hurtles through our atmosphere and collides with planet Earth. While you might envision a falling meteor as incredibly hot body, it's only the outer layers that become hot the insides remain cool for most (or even, potentially, all) of their journey towards Earth.

Upon impact with Earth's surface, however, the pressures inside become larger than any other natural process on our planet's surface, and cause the graphite to compress into a crystalline structure. It doesn't possess the cubic lattice of a diamond, however, but a hexagonal lattice, which can actually achieve hardnesses that are 58% greater than what diamonds achieve. While real examples of Lonsdaleite contain sufficient impurities to make them softer than diamonds, an impurity-free graphite meteorite striking the Earth would undoubtedly produce material harder than any terrestrial diamond.

This image shows a close-up of a rope made with LIROS Dyneema SK78 hollowbraid line. For certain . [+] classes of applications where one would use a fabric or steel rope, Dyneema is the strongest fiber-type material known to human civilization today.

Justsail / Wikimedia Commons

4.) Dyneema. From hereon out, we leave the realm of naturally occurring substances behind. Dyneema, a thermoplastic polyethylene polymer, is unusual for having an extraordinarily high molecular weight. Most molecules that we know of are chains of atoms with a few thousand atomic mass units (protons and/or neutrons) in total. But UHMWPE (for ultra-high-molecular-weight polyethylene) has extremely long chains, with a molecular mass in the millions of atomic mass units.

With very long chains for their polymers, the intermolecular interactions are substantially strengthened, creating a very tough material. It's so tough, in fact, that it has the highest impact strength of any known thermoplastic. It has been called the strongest fiber in the world, and outperforms all mooring and tow ropes. Despite being lighter than water, it can stop bullets and has 15 times the strength of a comparable amount of steel.

Micrograph of deformed notch in palladium-based metallic glass shows extensive plastic shielding of . [+] an initially sharp crack. Inset is a magnified view of a shear offset (arrow) developed during plastic sliding before the crack opened. Palladium microalloys have the highest combined strength and toughness of any known material.

Robert Ritchie and Marios Demetriou

3.) Palladium microalloy glass. It's important to recognize that there are two important properties that all physical materials have: strength, which is how much force it can withstand before it deforms, and toughness, which is how much energy it takes to break or fracture it. Most ceramics are strong but not tough, shattering with vice grips or even when dropped from only a modest height. Elastic materials, like rubber, can hold a lot of energy but are easily deformable, and not strong at all.

Most glassy materials are brittle: strong but not particularly tough. Even reinforced glass, like Pyrex or Gorilla Glass, isn't particularly tough on the scale of materials. But in 2011, researchers developed a new microalloy glass featuring five elements ( phosphorous, silicon, germanium, silver and palladium), where the palladium provides a pathway for forming shear bands, allowing the glass to plastically deform rather than crack. It defeats all types of steel, as well as anything lower on this list, for its combination of both strength and toughness. It is the hardest material to not include carbon.

Freestanding paper made of carbon nanotubes, a.k.a. buckypaper, will prevent the passage of . [+] particles 50 nanometers and larger. It has unique physical, chemical, electrical and mechanical properties. Although it can be folded or cut with scissors, it's incredibly strong. With perfect purity, it's estimated it could reach up to 500 times the strength of a comparable volume of steel. This image shows NanoLab's buckypaper under a scanning electron microscope.

2.) Buckypaper. It is well-known since the late 20th-century that there's a form of carbon that's even harder than diamonds: carbon nanotubes. By binding carbon together into a hexagonal shape, it can hold a rigid cylindrical-shaped structure more stably than any other structure known to humankind. If you take an aggregate of carbon nanotubes and create a macroscopic sheet of them, you can create a thin sheet of them: buckypaper.

Each individual nanotube is only between 2 and 4 nanometers across, but each one is incredibly strong and tough. It's only 10% the weight of steel but has has hundreds of times the strength. It's fireproof, extremely thermally conductive, possesses tremendous electromagnetic shielding properties, and could lead to materials science, electronics, military and even biological applications. But buckypaper cannot be made of 100% nanotubes, which is perhaps what keeps it out of the top spot on this list.

Graphene, in its ideal configuration, is a defect-free network of carbon atoms bound into a . [+] perfectly hexagonal arrangement. It can be viewed as an infinite array of aromatic molecules.

AlexanderAlUS/CORE-Materials of flickr

1.) Graphene. At last: a hexagonal carbon lattice that's only a single atom thick. That's what a sheet of graphene is, arguably the most revolutionary material to be developed and utilized in the 21st century. It is the basic structural element of carbon nanotubes themselves, and applications are growing continuously. Currently a multimillion dollar industry, graphene is expected to grow into a multibillion dollar industry in mere decades.

In proportion to its thickness, it is the strongest material known, is an extraordinary conductor of both heat and electricity, and is nearly 100% transparent to light. The 2010 Nobel Prize in Physics went to Andre Geim and Konstantin Novoselov for groundbreaking experiments involving graphene, and the commercial applications have only been growing. To date, graphene is the thinnest material known, and the mere six year gap between Geim and Novoselov's work and their Nobel award is one of the shortest in the history of physics.

The K-4 crystal consists exclusively of carbon atoms arranged in a lattice, but with an . [+] unconventional bond angle compared to either graphite, diamond, or graphene. These inter-atomic properties can lead to drastically different physical, chemical, and material properties even with identical chemical formulas for a variety of structures.

Workbit / Wikimedia Commons

The quest to make materials harder, stronger, more scratch-resistant, lighter, tougher, etc., is probably never going to end. If humanity can push the frontiers of the materials available to us farther than ever before, the applications for what becomes feasible can only expand. Generations ago, the idea of microelectronics, transistors, or the capacity to manipulate individual atoms was surely exclusive to the realm of science-fiction. Today, they're so common that we take all of them for granted.

As we hurtle full-force into the nanotech age, materials such as the ones described here become increasingly more important and ubiquitous to our quality of life. It's a wonderful thing to live in a civilization where diamonds are no longer the hardest known material the scientific advances we make benefit society as a whole. As the 21st century unfolds, we'll all get to see what suddenly becomes possible with these new materials.

Giant Rings of Saturn and a Moon Full of Space Lakes

The planet Saturn takes its name from a Roman god of agriculture. And of all the planets revolving around our sun, it’s “cultivated” — if you will — the greatest ring system by far.

Beautiful rings filled with ice, dust and rock orbit its equator. The widest one, called the Phoebe Ring, has an outer edge that’s 3.8 to 10.1 million miles (or 6 to 16.2 million kilometers) away from Saturn itself. For comparison, do you know what the average distance is between Earth and its moon? A paltry 238,855 miles, or 384,400 kilometers. Once again, astronomy puts the human ego in check.

Saturn’s rings get all the attention, but science buffs shouldn’t ignore its other attributes. The sixth planet in our solar system, it’s also the second biggest after Jupiter. Those two are in a league of their own. If you mushed every planet from Mercury to Neptune together, Saturn and Jupiter alone would account for over 90 percent of their cumulative mass.

Despite its immense size, Saturn is the least dense planet in the sun’s orbit — and the least spherical, too. We’ll need to look at its physical makeup to understand why.

The Oblong World of Saturn

Research published in 2019 showed that a day on Saturn lasts just 10 hours, 33 minutes and 38 seconds. Its spin rate helps explain one of the ringed world’s stranger qualities.

You see Saturn has a huge waistline. The planet’s equator is 74,898 miles (120,536 kilometers) in diameter. Yet Saturn’s pole-to-pole diameter is much smaller, equivalent to just 67,560 miles (108,728 kilometers). So in a manner of speaking, Saturn is 10 percent wider than it is tall.

Astronomers call that kind of disparity an equatorial bulge. Every planet in the solar system has one, but Saturn’s is the most extreme. Spin an object — any object — and its outside edge will move at a faster rate than its center does. That’s physics for you.

Saturn rotates around its axis at a very high speed hence, the brevity of its days. And here’s where density comes into play. Like Jupiter, Saturn is a gas giant. Such worlds predominantly consist of hydrogen and helium — and whereas Earth is solid on the outside, gas giants are not. (They may, however, have hard inner cores.)

Now Saturn is downright huge in terms of volume. Some 764 Earth-sized objects could fit inside it and the planet’s 95 times as massive as our home world. And yet relative to its size, Earth is eight times denser.

In fact, water — yes, plain water — is denser than Saturn. (Although that doesn’t mean the planet would float, contrary to popular belief.) Thanks to its low, low density and zippy rotation speed, Saturn’s been deformed into an oblong world that looks kind of squished in profile.

Spots, Loops and Hexagons

Jupiter’s southern hemisphere has an ongoing storm called the Great Red Spot. The Saturnian answer to this is the Great White Spots, periodic tempests that arise every 20 to 30 Earth years. First detected in 1876, the weather events are colossal in scale.

NASA’s Cassini spacecraft spent 13 productive years hovering around Saturn. On Dec. 5, 2010, it witnessed the most recent iteration of the Great White Spot phenomenon.

The storm was about 800 miles (1,300 kilometers) wide by 1,600 miles (2,500 kilometers) long when it first began.

But over the next six months, the “spot” expanded longitudinally until it had looped itself around the planet in a gigantic circle.

Some researchers think the Great White Spots might be part of a cycle that sees the outer layer of Saturn’s atmosphere slowly lose heat, allowing the warm air from lower levels to burst upward.

Up at the Saturnian north pole, there’s a cloud pattern shaped like a giant hexagon. This pleasantly symmetrical jet stream spins counterclockwise, measures about 20,000 miles (32,000 kilometers) across and includes a hurricane that’s been swirling right over the pole ever since it was discovered back in 1988.

Saturn’s the Ring Leader

Of course, it’s not the hexagon that earned Saturn a place on Chuckie Finster’s T-shirt. The gas giant owes its popularity to the ring system encircling it.

Planetary rings aren’t rare per se: Jupiter, Uranus and Neptune have them as well. Yet in terms of sheer scale, the network around Saturn is totally unrivaled.

Most of the primary rings come with letter names. The closest one to the home planet is called the “D” Ring, which has an inner radius of about 66,900 kilometers (41,569 miles). It’s surrounded by the C, B, A, F, G and E Rings — in that order. By the way, the rings aren’t arranged alphabetically because this naming system reflects the dates of their discovery. “A,” “B” and “C” were sighted before the rest.

When measured from its outside edge, the “E” ring showcases an impressive 480,000-kilometer (298,258-mile) radius. Or at least, that looks impressive until you get to know the big bad Phoebe Ring we mentioned earlier. First spotted in 2009, this one was named after a Saturnian moon.

Untold trillions of ice, rock and dust particles make up these rings. Some bits are the size of a sugar grain others could probably dwarf your house. In any case, the ring material is stretched remarkably thin. Saturnian rings range from 1.9 miles (3 kilometers) to just 32 feet (10 meters).

So proportionately, the gas giant’s iconic rings are thinner than a typical sheet of writing paper, noted astronomer Phil Plait.

Whereas Saturn itself is probably around 4.5 billion years old, the age of its rings isn’t as clear. Some scientists think they were formed 10 million to 100 million years ago, when an icy comet — or some ice-covered moons — came too close to the planet. The visitor(s) met a grisly end, getting ripped to pieces by Saturn’s gravity. As those fragments collided, they grew smaller and multiplied, giving rise to the skinny system we all know today.

On the other hand, a 2019 paper argued the rings might’ve originated at an early stage in the history of our solar system. We’ll have to see how the debate unfolds as new evidence arises.

There’s never been a better time to join Saturn’s fan club. On Oct. 7, 2019, the International Astronomical Union heralded the discovery of 20 newfound moons orbiting the gas giant. With these bodies added to the mix, there are now 82 verified Saturnian moons altogether. No other planet in the solar system has that many natural satellites — not even mighty Jupiter!

You can find Saturn’s moons in, around and beyond the ring system. Before Cassini was retired in 2017, it revealed that some of them gather clumps of dust and ice from the rings.

Arguably no Saturnian moon has attracted more interest than Titan. The solar system’s second-biggest moon overall, it’s dotted with seas, lakes and rivers of liquid methane and ethane. There’s only one other body within the sun’s orbit that has standing pools of liquid. Here’s a hint: You’re sitting on it right now.

Titan is also noteworthy for having an atmosphere. And it’s theorized there could be “ice volcanoes” that spew water instead of lava. Sounds like a paradise. Maybe that’s where “Frozen III” should take place.


The biggest tragedy in the history of the Universe

Not too long ago we used the tools from the Building the Ultimate Solar System series to build a Hulk of a planetary system. Our mega-system boasts 16 stars, spans 1000 Astronomical Units, and is host to more than 400 habitable worlds! It looks like this:

Our Ultimate Solar System, a planetary system built on the infrastructure of a gravitationally-bound system of 16 stars. This post explains how this system was built.

I have a story to tell you about this titanic system. But be warned: it is the most tragic story you have every heard. In fact, it is the most tragic story that anyone has ever heard, not only on Earth but in the history of the entire Universe! This may sound overly dramatic but I can prove it. I’ll explain at the end.

The story has a cheerful start. Within a giant swirling cloud of molecular gas, a marvelous planetary system was born. The system was more bountiful, more beautiful, more fertile than any other. It was perfect in every way.

This spectacular system was home to 480 worlds capable of hosting life (half of the stars hosted what we called Ultimate Solar System 1 and half hosted Ultimate Solar System 2 see here for details). They blossomed into a diversity of life-bearing planets and moons. Some were covered in oceans while others were mostly land. Some had thick atmospheres and some had thin atmospheres. Some had broad ice-covered plateaus and mountains, and others were hot with expansive deserts.

Life developed on some planets and moons and spread through the system. Every time a life-bearing planet was hit by a stray comet or asteroid, pieces of rock containing microbes were launched into orbit. These microbe-infested rocks landed on other planets and moons in the system and delivered the seeds of life.

Within just a few hundred million years all 480 worlds had life. Some only hosted single-celled creatures but others had complex life like plants and animals. A handful of planets and moons even developed intelligent life, advanced life that started to observed the heavens. Space travel and colonization of other planets were not far off.

But trouble was brewing. Big trouble.

The villain in this story is the Galaxy itself. But it is an unwitting villain. The Galaxy is not evil, it just can’t help itself. What does the Cookie Monster do if you put Cookie in front of it? He eats it. That’s just what he does, it is his nature. The same goes for the Galaxy.

What did the Galaxy do that was so terrible, that caused such tragedy? The same thing it always does and is doing right now. It torqued.

Let me explain. Our Milky Way Galaxy looks like a giant pancake with a golf ball in the middle. The Sun is located within the pancake, about two thirds of the way out from the center.

Most nearby stars live within the Galactic pancake. That’s why at night (in a dark place far from city lights) the Milky Way looks like a band stretching across the sky. That band is the combined light of countless millions of stars that are all in the same pancake as us.

The Galactic pancake is not perfectly smooth. It has the most stars in a very thin layer (the thin disk) and fewer stars above and below. It also has clumps and spirals. This matters because this non-smoothness equals differences in gravity.

Imagine a comet orbiting a star within the Galaxy. Because the Galaxy is not perfectly smooth, the star and planet feel slightly gravity from the surrounding stars and gas in the Galaxy. This difference in gravity kicks the comet’s orbit around the star. Sometimes a star whizzes kind of close by (maybe only half a light year away) and gives an extra kick.

Galactic kicks are pretty wimpy. The planets orbiting the Sun don’t even feel these kicks. Only comets on very wide orbits do. Why does the size of the orbit matter? Because to change an orbit requires torque, a measure of twisting force. To unscrew something you need torque. When you get stuck trying to unscrew a nut, what do you do? You get a longer wrench. The longer the wrench, the stronger the torque.

It’s the same for comets orbiting the Sun. The size of the orbit is like the size of the wrench. The Galaxy only kicks very weakly, so it only torques very wide orbits.

The orbits of Oort cloud comets around the Sun are shaped by kicks from the Galaxy. It is these kicks that transform their orbits into a cloud rather than a thick pancake. As you can see in this image, the division between pancake orbits (the Kuiper belt) and cloud orbits (the Oort cloud) happens at about 1000 Astronomical Units away from the Sun.

The Solar System’s populations of comets. The Kuiper belt is located just outside the planets’ orbits and is mainly pancake-shaped. The Oort cloud starts at about 1000 AU (Astronomical Units) and is spherical, like a cloud, because of Galactic torques. Credit:

When the Galaxy torques an orbit, the orbit’s shape changes. The average size of the orbit does not change, but the shape does. The inclination of the orbit can change — this is why the Oort cloud is a cloud and not a pancake. More importantly for us, the the eccentricity of the orbit changes. Eccentricity is a measure of how stretched-out an orbit is.

Orbits with the same average distance (also called semimajor axis) but different eccentricities e. The higher the eccentricity, the more stretched out the orbit. Credit: NASA Earth Observatory.

Galactic torques transform circular orbits into stretched-out orbits, and stretched-out orbits back to circular ones. When an orbit becomes stretched-out, its closest approach to the star shrinks. This is the dagger the Galaxy will use to slay our beautiful planetary system.

So let’s take another look at our 16-star system but to make things simpler let’s take the point of view of one 8-star clumps and put it in the center. Here is what that looks like.

There are a bunch of orbits in the system. 8 tiny orbits of just 1 Astronomical Unit in size, 4 orbits of 10 Astronomical Units, 2 of 100 Astronomical Units, and finally one huge orbit that is 1000 Astronomical Units in size.

Galactic torques only affect the biggest orbit. But the torques are so small that they act slowly. It takes about a billion years for the orbit to change shape, to be transformed from a pristine circle into a deranged ellipse.

From its birth, our beloved system was living on borrowed time. A Galactic time bomb was hanging above its head and a billion-year fuse was already lit.

Yet this left a full billion years for our beloved system to flourish. A billion years for life to take hold, to envelop first one world then many. For intelligence to emerge and spread. Animals and plants have only existed on Earth for the past 500 million years of our planet’s 4.5 billion year history. Life’s baby steps were a little bit quicker on some of the planets in our system so a billion years was plenty for intelligent life to emerge and thrive. Kingdoms rose and fell. The abundance of nearby planets and moons was a carrot dangling in the sky. Technological civilizations reached for the stars, so much closer in their sky than in ours. And they made it, they reached the other planets and discovered hundreds of hospitable oases in the sky. They colonized every last life-bearing nook among the 480 habitable worlds in the system. Empires rose, the largest claiming hundreds of planets under a single flag. And empires fell in devastating interplanetary wars.

While these civilizations grew extremely adept with physics (and astrophysics in particular), they could not compete with the Galaxy’s tiny persistent torques. And so, when a billion years were up, our system had shifted into this setup:

From the point of view of one clump of 8 stars, the other clump follows an elliptical path around it. As the orbit gets more and more stretched out, the closest approaches between the clumps get closer and closer.

This was really bad. Our little angel of a system was doomed. While the Galaxy’s dagger had yet to pierce our dear system’s heart, all hope was lost. I hope that you, dear reader, enjoy gruesome scenes because I will lay out the details of the dismemberment of our fair damsel of a planetary system.

As the widest orbit became more and more stretched out, the closest approaches between the two clumps of 8 stars (which only happened every twenty thousand years or so) got closer and closer. The clumps of stars starting giving each other stronger and stronger gravitational kicks every close passage. This started to affect the shapes of the next-largest orbit in the system, the 100 Astronomical Unit-sized orbits of the clumps of 4 stars. Those 100 Astronomical Unit orbits started to get stretched out as well.

This was a trickle-down process. New fashion trends are often started by the uppermost classes of society and then spread down to the upper, middle and finally lower classes. Likewise, the Galaxy only kicked the largest orbits in our beautiful system but its effects spread to smaller and smaller orbits.

Here is a snapshot of our marvelous system in the process of being stretched out:

As the Galactic torques trickled through the system, all of the orbits became more and more stretched out.

This was getting bad for the orbits of the planets around their stars. What would happen when the kicks could no longer trickle down to the orbits of clumps of stars?

Until that point the planets’ orbits had remained blissfully unaffected. Of course, the night sky had changed a little, and the local astronomers may very have been aware of the impending doom, but the planets trucked on along their orbits like soldiers following orders until the end.

As the smallest orbits in the system — the 1 Astronomical Unit orbits of each pair of stars around each other — began the stretch, the planets’ orbits finally started to feel the Galaxy breathing down their back.

Ultimate Solar Systems 1 and 2 have habitable zones that are tightly packed with planets. That is how we designed them. The bad thing is, you can’t kick those systems very hard without breaking them.

On our system’s last morning, she looked like this:

The beginning of the end for our beautiful system. As the orbits of close pairs of stars grew elliptical, the orbits of planets in each star’s habitable zone were perturbed.

Let’s focus for a moment on one star within our system, with a habitable zone full of planets on carefully chosen orbits. There are two ways this system can break: 1) the delicate balance of the planets’ orbits can be lost, but planets (or some remnants) remain in orbit, or 2) the planets can be completely lost from the star. The first is like someone spitting in your beer the second is like someone smashing your beer on the floor.

It started with a nudge. A close passage of the companion star shifted the position of the outermost planet just a off of its trajectory. This was just enough to destabilize the orbital layout of the whole system. The planets’ elegant orbital configuration will be thrown off if a single planet’s orbit gets stretched out, because that orbit crosses the orbits of other planets. The ever-approaching companion star set a chain reaction in motion by disturbing the orbits of the outermost planet. Then the entire system went boom.

The stable setup has planets orbiting the star in concentric circles. If just one of those orbits becomes stretched-out, that planet crosses the orbits of the other planets in the system. This quickly disrupts the entire system, generating close passages between planets and giant collisions. In this image it is one of the middle planets’ orbits that becomes stretched out, although in our system it is likely to have been the outermost orbit that was stretched-out first.

When the orbits of two planets cross, it means that the two planets can be in the same place at the same time. You are probably thinking of a giant collision between planets. Something like this:

Artist’s impression of a giant impact between two large rocky planets. This impact represents the last large impact on Earth, which formed the Moon. Credit: Hagai Perets

There were truckloads of mammoth collisions during the death of our beautiful system. Full-grown, life-bearing planets — Earths, Naboos, Dagobahs, and Pandoras — crashed into each other and were pulverized. The plants and animals and civilizations on those planets were entirely obliterated, smashed into smithereens. Remember in Star Wars when Obi-Wan sensed a disturbance in the Force because the planet Alderaan was blown up? Multiply that by a few hundred!

But collisions were not the only face of our system’s death. Half of our stars hosted Ultimate Solar System 2, where most of the habitable worlds were moons of gas giant planets. When a system with gas giants goes unstable the outcome is different than for rocky planets. Gas giants are so massive, and their gravity is so strong, that they scatter instead of colliding.

When giant planets scatter, one planet usually receives such a strong kick that it is launched out of the system. Surviving gas giants have stretched-out orbits. Here is a computer simulation of this process (by Eric Ford):

When giant planets scatter, smaller worlds are caught in the crossfire (see here for some animations on my research website).

Around the stars with unstable gas giants, small worlds were launched in every direction. Most small worlds were doomed. Some fell onto their stars and ended their lives in fiery blaze:

Artist’s image of a planet falling onto its star. As the planet spirals inward, a disk of evaporated material is kept in orbit. Credit: NASA/ESA/G. Bacon.

Other small worlds were thrown so high that they never came down. They were launched into interstellar space, destined to live out their days as Galactic nomads. These free-floating or rogue planets had to endure the near-absolute zero temperature of empty space, far away from the campfire provided by a star. Most rogue planets freeze over into iceballs. But those with thick-enough atmospheres to use for blankets might be able to tough it out and remain habitable on their frigid journey among the stars.

Whether frozen-over or blanketed, rogue planets are so faint that they emit no visible light (and barely any radiation at all):

What a “rogue” or “free-floating” rocky planet would look like. The planet is so cold that it emits no visible light. However, it is possible for rogue planets to host life (see here).

The end-result of scattering is a system with one or two surviving gas giants on stretched-out orbits. On occasion, a surviving giant planet can hold on to one of its moons (but not all five, and the survivor may well have undergone a giant collision).

As darkness fell on our beloved system, 3 of the 8 stars with gas giants retained habitable moons. Two moons had been crushed by giant impacts other large moons. But the third surviving moon was pristine. Its orbit around the giant planet was changed, as were the orbits of the giant planet around the star, and of the star within the 16-star system. Yet life, and hope, persisted on this one single moon.

Back to the big picture. As the Galaxy kept torquing, the orbits in our 16-star system grew more and more stretched-out. Eventually, stars came so close to each other that stars themselves dislodged some (but not all) of the remaining planets and launched them out into space.

Stars kicked each other hard enough to break the bonds that tied them. The first to break was the widest orbit, and our 16-star system was split in two. This turned off the Galactic torques and protected the 8-star systems. But too much damage was already done to one of the 8-star systems, and it broke into one 4-star system and two binaries (2-star systems). The four different systems went their separate ways in the Galaxy, never to meet again.

Our beautiful, precious system died. It was born with 16 stars and 480 life-bearing worlds. Each habitable zone was packed with habitable planets. It was as astrophysical paradise. Life flourished and spread over its all-too-short, billion year life.

But the Galaxy couldn’t help itself. It torqued the largest (1000 Astronomical Unit-wide) orbits and those kicks trickled down all the way to the planets’ orbits. Hundreds of rocky planets crashed into each other. Systems with gas giant planets were scattered, launching worlds in all directions, some into interstellar space and others crashing onto their stars. The system itself was torn apart and split into four systems with 8, 4, 2 and 2 stars each.

Some planets survived in orbit around the stars, but most were in bad shape. Almost all had been sterilized by giant impacts with other planets. Only two had avoided large collisions, and their new orbits were stretched-out and only crossed the habitable zone instead of residing there permanently. Still, planets on stretched-out orbits are good candidates for life, even if their orbits bounce around.

A single life-bearing moon remained in orbit around a gas giant. The moon’s orbit around the gas giant was stretched-out, but since the gas giant’s orbit around the star (which was also stretched-out) remained in the habitable zone, this world was another ray of hope.

A hundred worlds were launched into interstellar space. Most of these rogue planets froze over into permanent iceballs in the frigid emptiness between the stars. But a handful — the ones with thick atmospheres — held on to their heat and maintained livable conditions on their surfaces or in subsurface oceans. The daughters of our lost system spread throughout the Galaxy.

This marks the end of the most tragic story in the history of the Universe. Have you ever read a story in which more than 400 life-covered worlds were roasted, pulverized or completely frozen? Imagine the diversity of plants and animals that was lost, the sheer number and diversity of living organisms. I know stories where one or two planets are destroyed, but to be knowledge, there is more death and destruction in this story than any other in history, anywhere. (Let me know in the comments if you know of a more tragic tale).

It’s really sad when a good planetary system goes bad. Boom!

Final note. The Galactic torque idea in this story is due in large part to Nate Kaib, astrophysicist extraordinaire. (See here for a summary of our 2013 study).

A few footnotes:

  1. I’m aware that there is one small passage in Maria Valtorta’s writings that seem to speak of aliens. It’s not the only error in her writings. (I’m making no claims regarding Valtorta’s authenticity here even authentic mystics’ private revelations can, and often do, contain errors! I do not know much about Valtorta, so I cannot comment on her, but I do know that many people I love and trust regard her highly, so please don’t take my insistence that she is wrong on one small thing as an attack on her or her mystical writings. Even St. Catherine of Siena’s private revelations had at least one glaring error! [i.e. that Our Lady was not immaculately conceived])
  2. I’m also aware of the many claims of UFO/Alien phenomena. Although the vast majority of these can be explained by military testing/ atmospheric phenomena/ optical illusions/manipulated media/ weather balloons/ mentally unstable people “seeing” things/etc., it is also true that some testimonies are not so easily cast aside. I am not one to ignore what a person — who by all accounts appears trustworthy — insists that he himself directly observed. Indeed, we must take such testimonies seriously. However, when one reads these testimonies, they almost universally include elements of incredible darkness and evil. The people themselves who give the testimonies usually speak of some horrible, dark, evil feeling pervading them when they witnessed the “UFO” or the “alien.” Often heinous sexual things are described. All of this just confirms my thesis: yes, there may well be alleged “aliens,” but, again, they aren’t aliens at all rather, they are demonic manifestations. This just redoubles the importance of rejecting the possibility of actual aliens, so that we may remain firm in our insistence to have nothing to do with these “aliens” when they appear.
  3. Consider as well that any alien race would either be 1) Unfallen, or 2) Fallen, thus in need of Redemption. If they were 1) Unfallen, then they would each be Immaculate Conceptions, which would itself be contrary to Catholic Dogma on Our Lady being the only Immaculate Conception. If they were 2) In need of Redemption, then this would be abhorrent, since they could not receive it — it is Catholic Dogma that there is one and only one Incarnation (which itself is necessary for Redemption).
  4. The typical Catholic response to this question these days, i.e. “Well, there’s no Church teaching on this, so who knows,” may not, after all, be accurate. Pope Zachary may indeed have condemned this notion . Here is an excerpt from Ireland and the Antipodes: The Heterodoxy of Virgil of Salzburg, by John Carey.

Now, the cleric in question, “Virgil,” did later become a Bishop (and was canonized a saint!), so we can presume he recanted this view — plenty of saints have believed errors and then recanted. Nevertheless, Pope Zachary evidently regarded this error of positing the existence of “other men” in “another world” beneath the earth (or perhaps even on the sun and moon) as such an egregious opposition to God that it was “abominable,” a detriment to one’s very soul, and a just cause for expelling this priest from the Church and stripping him of his priesthood. Perhaps Pope Zachary was particularly condemning the ancient Irish pagan belief in elves who existed in “fairy mounds” underground in any event, this condemnation clearly covers aliens as well. So, dear Catholics, weigh what we have here: on the one hand, an extremely strong denunciation, in a Papal letter, of aliens as an “abominable teaching,” and, on the other hand, Pope Francis making a verbal remark that he’d “baptize Martians.” Discerning which is the weightier teaching is not difficult. Obviously I am not claiming we can have certainty in Pope Zachary’s condemnation merely from John Carey’s work here quoted, but we should presume its validity absent legitimate reasons to doubt it.

7 Answers 7

Okay, so what do you need to have interesting life?

It should be capable of movement. This is handy, because it makes it active. Not entirely necessary, depending on the kind of story you're making (an interstellar fungus that infects a space ship might be enough). There's a few options for that:

Solar sails - this would imply extremely light and sparse being, built around a wide area. By deforming the sail, it could control its movement. The cool thing about this is that it potentially allows the being to travel pretty much anywhere - in a nebula, a planetary ring system, whatever. It doesn't need a solid surface at all.

If there is some solid surface, for example with the planetary ring systems, there's a lot more options. It could simply jump between the rocks (probably with some kind of safety tether). In fact, jumping in free-fall environment with the help of a line would allow both speed and control.

And of course, there's the option of just living on one small body. However, that wouldn't really allow anything big, and it's easy to imagine a deadly catastrophe happening very often.

Source of energy is trickier than it might seem. Of course, there's solar power - a good bet, if you can make a collector of some sort. However, your beings will most likely have extremely low body temperatures (I'll discuss this further later), which limits the usefulness of traditional terrestrial fuels like sugars - the reaction rates might simply be too low to allow much to happen. This can be limited somewhat if it can collect enough solar thermal power to keep itself significantly warm, but that of course comes at a cost as well - more damage to be repaired. The huge problem with solar power is the square-cube law - it's hard to imagine how such an organism could evolve in outer space, if it has no way of regulating its own temperature. Perhaps the nebula it evolved in had enough rocky matter for it to find shelter from the deadly radiation (and heat)?

Now, in the nebula scenario, you probably need to traverse a lot of volume to get a meaningful amount of food, both for energy and as a construction material. This implies low metabolism (and low body temperature), because you need to be able to replace failing parts faster than they break. The ring scenario doesn't have as much problem with that, but there's another problem - it seems that the ring particles tend to be pretty homogenous, so there's little chance there would ever appear one that has enough material of all the different kinds necessary to build any autonomous working machine.

  • An animal-plant, built around a large solar sail, harvesting construction materials like a sperm whale, while getting energy from a sun.
  • A jumper, flying from rock to rock in search of food, with a long "tail" (or maybe multiple tentacles) used to tether itself to the passing rocks (and its prey).

The two could even co-exist, the jumper preying on the sail (or vice versa, if the jumpers are really small). Of course, the sail sounds somewhat more likely to evolve in such an evironment.

The cool thing about the sail is that it could mostly be two-dimensional, so it would have a lot of control over its heating etc. If it's a cold animal, it would be able to keep itself from overheating (the unlit part would serve as a radiator, while the lit part absorbs heat). In fact, it might be a rather good thermal balance mechanism, whether you're relatively cold or warm.

The cold one has another benefit - it could get away with being almost invisible, which would help against predators (if any), and it would allow your heroes to run into them without noticing (the big facepalm moment for the science crew) - the comparatively hot hull of the spaceship might destroy it quite easily.

Watch the video: Ο ΝΑΝΟΣ ΠΛΑΝΗΤΗΣ ΠΛΟΥΤΩΝ από το Ηλιακό Σύστ. στο Διάστημα 13. Κωννος Αθ. Οικονόμου (June 2022).