Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.
The list of confirmed exoplanets now exceeds six thousand. Considering the fact that the three main ways they're detected -- direct measure of stellar wobbles, transit photometry, and Doppler spectroscopy -- all require either that the host star be close, that the planets be massive, or that the planetary orbit be aligned just right from our perspective, or all three, it's almost certain that there are vast numbers of exoplanets going undetected.
All of which bodes well for those of us who would love for there to be extraterrestrial life out there somewhere.
On the other hand, of the exoplanets we've found, a great many of them are inhospitable to say the least, and some of them are downright bizarre. Here are a few of the weirder ones:
TrES-2b, which holds the record as the least-reflective planet yet discovered. It's darker than a charcoal briquet. This led some people to conclude that it's made of dark matter, something I dealt with here at Skeptophilia a while back. (tl:dr -- it's not.)
CoRoT-7b, one of the hottest exoplanets known. Its composition and size are thought to be fairly Earth-like, but it orbits its star so closely that it has a twenty-day orbital period and surface temperatures around 3000 C. This means that it is likely to be completely liquid, and experience rain made of molten iron and magnesium.
PSR J1719−1438, a planet orbiting a pulsar (the collapsed, rapidly rotating core of a giant star), and therefore somehow survived its host star going supernova. It has one of the fastest rates of revolution of any orbiting object known, circling in only 2.17 hours.
V1400 Centauri, a planet with rings that are two hundred times wider than the rings of Saturn. In fact, they dwarf the planet itself -- the whole thing looks a bit like a pea in the middle of a dinner plate.
BD+05 4868 Ab, in the constellation of Pegasus. Only 140 light years away, this exoplanet is orbiting so close to its parent star -- twenty times closer than Mercury is to the Sun -- that its year is only 30.5 hours long. This proximity roasts the surface, melting and then vaporizing the rock it's made of. That material is then blasted off the surface by the stellar wind, so the planet is literally evaporating, leaving a long, comet-like trail in its wake.
Today, though, we're going to look at some recent research about a planet that should be near the top of the "Weirdest Exoplanets Known" list. It's 55 Cancri Ae, the innermost of four (possibly six; two additional ones are suspected but unconfirmed) planets around the star 55 Cancri A, a K-type orange star a little over forty light years away. 55 Cancri Ae orbits its host star twice as close as Mercury does the Sun, making a complete ellipse around it in only a bit under three days. This means that like CoRoT-7b and BD+05 4868 Ab, it's crazy hot.
This is where some new research comes in. A presentation at an exoplanet conference in Groningen, Netherlands last week considered a puzzling feature of 55 Cancri Ae -- a measure of its heat output shows odd, non-cyclic fluctuations that don't seem to be in sync with its orbital period (or anything else). The fluctuations aren't small; some of them have approached a 1,000 C difference from peak to trough. They were first detected ten years ago, and physicists have been at a loss to account for the mechanism responsible.
But now, we might have an explanation -- and it's a doozy. Models developed by exoplanet astrophysicist Mohammed Farhat of the University of California - Berkeley found that the anomalous temperature surges could be explained as moving hotspots.
Which sounds pretty tame until you read Farhat's description of what this means. We're talking about a planet close in to a star not much smaller than the Sun, being whirled around at dizzying speeds. This means it's experiencing enormous tidal forces. The planet itself is so hot it's probably liquid down to its core. Result: tidal waves of lava several hundred meters high, moving at the speed of a human sprinter.
The presentation definitely got the attendees' attention. "This is right in the sweet spot of something that is interesting, novel, and potentially testable," said planetary astronomer Laura Kreidberg, of the Max Planck Institute for Astronomy. "I had this naïve idea that lava flows were too slow-moving to have an observable impact, but this new work is pointing otherwise."
The whole thing reminds me of the planet Excalbia from Star Trek, from the episode "The Savage Curtain," which was completely covered by churning seas of lava -- except for the spot made hospitable by some superpowerful aliens so Captain Kirk could have a battle involving Abraham Lincoln, Genghis Khan, and various other historical and not-so-historical figures to find out whether good was actually stronger than evil.
Put that way, I know the plot sounds pretty fucking ridiculous, but don't yell at me. I didn't write the script.
In any case, I doubt even the Excalbians would find 55 Cancri Ae hospitable. But it is fascinating. It pushes the definition of what we even consider a planet to be -- a sloshing blob of liquid rock with lava waves taller than a skyscraper. Makes me thankful for the calm, temperate climes of Earth.
I'll start today with a quote (often misquoted) from William Shakespeare -- more specifically, Hamlet, Act I, Scene 5:
Horatio:
O day and night, but this is wondrous strange!
Hamlet:
And therefore as a stranger give it welcome. There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy.
Horatio and Hamlet, of course, are talking about ghosts and the supernatural, but it could equally well be applied to science. It's tempting sometimes, when reading about new scientific discoveries, for the layperson to say, "This can't possibly be true, it's too weird." But there are far too many truly bizarre theories that have been rigorously verified over and over -- quantum mechanics and the General Theory of Relativity jump to mind immediately -- to rule anything out based upon our common-sense ideas about how the universe works.
That was my reaction while watching a YouTube video about an astronomical object I'd never heard of -- Przybylski's Star, named after its discoverer, Polish-born Australian astronomer Antoni Przybylski. The video comes from astronomer David Kipping's channel Cool Worlds Lab, which looks at cutting-edge science -- and tantalizing new data about the universe we live in. (You should subscribe to it -- you won't be sorry.) Przybylski's Star is 355 light years from Earth, in the constellation of Centaurus, and is weird in so many ways that it kind of boggles the mind.
It's classified as a Type Ap star. Type A stars are young, compact, luminous, and very hot; the brightest star in the night sky, Sirius, is in this class.
Przybylski's Star rotates slowly. I mean, really slowly. Compared to the Sun, which rotates about once every 27 days, Przybylski's Star rotates once every two hundred years. Most type A stars rotate even faster than the Sun; in fact, a lot of them rotate so quickly that the light from their receding hemisphere and that from their approaching hemisphere experience enough red-shift and blue-shift (respectively) to smear out their spectral lines, making it impossible for us to tell exactly what they're made of.
You probably know that most ordinary stars are primarily composed of hydrogen, and of the bit that's not hydrogen, most of it is helium. Hydrogen is the fuel for the fusion in the core of the star, and helium is the product formed by that fusion. Late in their life, many stars undergo core collapse, in which the temperatures heat up enough to fuse helium into heavier elements like carbon and oxygen. Most of the rest of the elements on the periodic table are generated in supernovas and in neutron stars, a topic I dealt with in detail in a post I did about six years ago.
My point here is that if you look at the emission spectra of your average star, the spectral lines you see should mostly be the familiar ones from hydrogen and helium, with minuscule traces of the spectra of other elements. The heaviest element that should be reasonably abundant, even in the burned-out cores of stars, is iron -- it represents the turnaround point on the curve of binding energy, the point where fusion into heavier elements starts consuming more energy than it releases.
So elements that are low in abundance pretty much everywhere, such as the aptly-named rare earth elements (known to chemists as the lanthanides), should be so uncommon as to be effectively undetectable. Short-lived radioactive elements like thorium and radium shouldn't be there at all, because they don't form in the core of your ordinary star, and therefore any traces present had to have formed prior to the star in question's formation -- almost always, enough time that they should have long since decayed away.
The composition of Przybylski's Star, on the other hand, is so skewed toward heavy elements that it elicits more in the way of frustrated shrugs than it does in viable models that could account for it. It's ridiculously high in lanthanides like cerium, dysprosium, europium, and gadolinium -- not elements you hear about on a daily basis. There's more praseodymium in the spectrum of its upper atmosphere than there is iron. Even stranger is the presence of very short-lived radioactive elements such as plutonium -- and actinium, americium, and neptunium, elements for which we don't even know a naturally-occuring nuclide synthesis pathway capable of creating them.
So where did they come from?
"What we’d like to know... is how the heavy elements observed here have come about," said astronomy blogger Paul Gilster. "A neutron star is one solution, a companion object whose outflow of particles could create heavy elements in Przybylski’s Star, and keep them replenished. The solution seems to work theoretically, but no neutron star is found anywhere near the star."
"[T]hat star doesn’t just have weird abundance patterns; it has apparently impossible abundance patterns," said Pennsylvania State University astrophysicist Jason Wright, in his wonderful blog AstroWright. "In 2008 Gopka et al. reported the identification of short-lived actinides in the spectrum. This means radioactive elements with half-lives on the order of thousands of years (or in the case of actinium, decades) are in the atmosphere... The only way that could be true is if these products of nuclear reactions are being replenished on that timescale, which means… what exactly? What sorts of nuclear reactions could be going on near the surface of this star?"
All the explanations I've seen require so many ad-hoc assumptions that they're complete non-starters. One possibility astrophysicists have floated is that the replenishment is because it was massively enriched by a nearby supernova, and not just with familiar heavy elements like gold and uranium, but with superheavy elements that thus far, we've only seen produced in high-energy particle accelerators -- elements like flerovium (atomic number 114) and oganesson (atomic number 118). These elements are so unstable that they have half-lives measured in fractions of a second, but it's theorized that certain isotopes might exist in an island of stability, where they have much longer lives, long enough to build up in a star's atmosphere and then decay into the lighter, but still rare, elements seen in Przybylski's Star.
There are several problems with this idea, the first being that every attempt to find where the island of stability lies hasn't succeeded. Physicists thought that flerovium might have the "magic number" of protons and neutrons to make it more stable, but a paper released not long ago seems to dash that hope.
The second, and worse, problem is that there's no supernova remnant anywhere near Przybylski's Star.
The third, and worst, problem is that it's hard to imagine any natural process, supernova-related or not, that could produce the enormous quantity of superheavy elements required to account for the amount of lanthanides and actinides found in this star's upper atmosphere.
Which brings me to the wildest speculation about the weird abundances of heavy elements. You'll never guess who's responsible.
Go ahead, guess.
There is a serious suggestion out there -- and David Kipping does take it seriously -- that an advanced technological civilization might have struck on the solution for nuclear waste of dumping it into the nearest star. This explanation (called "salting"), bizarre as it sounds, would explain not only why the elements are there, but why they're way more concentrated in the upper atmosphere of the star than in the core.
"Here on Earth... people sometimes propose to dispose of our nuclear waste by throwing it into the Sun,” Wright writes. “Seven years before Superman thought of the idea, Whitmire & Wright (not me, I was only 3 in 1980) proposed that alien civilizations might use their stars as depositories for their fissile waste. They even pointed out that the most likely stars we would find such pollution in would be… [type] A stars! (And not just any A stars, late A stars, which is what Przybylski’s Star is). In fact, back in 1966, Sagan and Shklovskii in their book Intelligent Life in the Universe proposed aliens might 'salt' their stars with obviously artificial elements to attract attention."
A curious side note is that I've met (Daniel) Whitmire, of Whitmire & Wright -- he was a professor in the physics department of the University of Louisiana when I was an undergraduate, and I took a couple of classes with him (including Astronomy). He was known for his outside-of-the-box ideas, including that a Jupiter-sized planet beyond the orbit of Pluto was responsible for disturbing the Oort Cloud as it passed through every hundred million years or so (being so far out, it would have a super-long rate of revolution). This would cause comets, asteroids, and other debris to rain in on the inner Solar System, resulting in a higher rate of impacts with the Earth -- and explaining the odd cyclic nature of mass extinctions.
So I'm not all that surprised about Whitmire's suggestion, although it bears mention that he was talking about the concept in the purely theoretical sense; the weird spectrum of Przybylski's Star was discovered after Whitmire & Wright's paper on the topic.
Curiouser and curiouser.
So we're left with a mystery. The "it's aliens" explanation is hardly going to be accepted by the scientific establishment without a hell of a lot more evidence, and thus far, there is none. The problem is, the peculiar abundance of heavy elements in this very odd star remains unaccounted for by any science we currently understand. The fact that Kipping (and others) are saying "we can't rule out the alien salting hypothesis" is very, very significant.
I'll end with another quote, this one from eminent biologist J. B. S. Haldane: "The universe is not only queerer than we imagine, it is queerer than we can imagine."
One of the most curious unsolved problems in physics is the three-body problem, which despite its name is not about a ménage-à-trois. It has to do with calculating the trajectory of orbits of three (or more) objects around a common center of mass, and despite many years of study, the equations it generates seem to have no general solution.
There are specific solutions for objects of a particular mass starting out with a particular set of coordinates and velocities, and lots of them result in highly unstable orbits. But despite the fact that there are computer models that can predict the movements of three objects in a gravitational dance -- such as the members of a triple-star system -- the overarching mathematical framework has proven intractable.
How, then, can we predict the orbits of the eight planets (and countless dwarf planets, asteroids, and comets) around the Sun to such high precision? Some of the great names of physics and astronomy in the sixteenth and seventeenth centuries -- Galileo Galilei, Tycho Brahe, Johannes Kepler, and Isaac Newton, especially -- used highly accurate data on planetary positions to conclude that the planets in the Solar System go around the Sun in elliptical orbits, all powered by the Universal Law of Gravitation. The mathematical model they came up with worked to a high degree of accuracy, allowing earthbound astronomers to predict where the planets were in the sky, and also such phenomena as eclipses.
The reason it works, and doesn't fall prey to the three-body problem chaos, is that the Sun is so massive in comparison to the objects orbiting it. Because the Sun is huge -- it has a thousand times more mass than the largest planet, Jupiter -- its gravitational pull is big enough that it swamps the pull the planets exert on each other. For most purposes, you can treat each orbit as independent two-body problems; you can (for example) look at the masses, velocities, and distances between the Sun and Saturn and ignore everything else for the time being. (Interestingly, it's the slight deviation of the orbit of Uranus from the predictions of its position using the two-body solution that led astronomers to deduce that there must be another massive planet out there pulling on it -- and in 1846 Neptune was observed for the first time, right where the deviations suggested it would be.)
I said it was "lucky" that the mass imbalance is so large, but I haven't told you how lucky. It turns out that all you have to do is add one more object of close to the same size, and you now have the three-body problem, and the resulting orbit becomes unpredictable, chaotic, and -- very likely -- unstable.
It's what I always think about when I hear woo-woos burbling on about Nibiru, a huge extrasolar planet that has been (repeatedly) predicted to come zooming through the Solar System. We better hope like hell this doesn't happen, and not because there could be collisions. A huge additional mass coming near the Earth would destabilize the Earth's orbit, and could cause it to change -- very likely making it more elliptical (meaning we'd get fried at perigee and frozen at apogee). Interestingly, this is one thing that even the writers of Lost in Space got right, at least temporarily. The planet John Robinson et al. were on had a highly elliptical orbit, leading to wild climatic fluctuations. The "temporarily" part, though, came about because apparently the writers found it inconvenient to have the Robinson Family deal with the alternating icebox/oven climate, and after a short but dramatic story arc where they were contending with it, it never happened again.
Or maybe the planet just decided to settle down and behave. I dunno.
An unstable orbit can also have one other, even more dire outcome; it can cause a planet to get ejected from its star system entirely. This would be seriously bad news if it happened here, because very quickly we'd exit the habitable zone and be frozen solid. This is likely the origin of rogue planets -- planets that started out orbiting a star, but somehow have lost their gravitational lock, and end up floating in the vast dark of interstellar space.
This does bring up an interesting question, though; if they're out in outer space, but emit no light, how do we know they're there? Well, they were conjectured for decades, based on the argument above, about orbital instability; but as far as detection goes, that's proven harder. But now, we have actually detected one, and how we did it is absolutely staggering.
One of the outcomes of Einstein's General Theory of Relativity is that the presence of matter warps space. A common two-dimensional analogy is a bowling ball sitting on a trampoline, deflecting the membrane downward. If you roll a marble on the trampoline, it'll curve around the bowling ball, not because the bowling ball is magically attracting the marble, but because its presence has changed the shape of the space the marble is moving through. Scale that up by one dimension, and you've got the idea.
What's cool about this is that because it's the shape of spacetime that has warped, everything passing through that region is affected -- including light. This is called gravitational lensing, and has been used to infer the positions and masses of black holes, which (duh) are black and therefore hard to see. But by detecting the distortion of light emitted by objects behind the black hole, we can see its effects.
And now, that's been done with a rogue exoplanet. Judging by the lensing effect it created, it's about the mass of Saturn, and the conclusion based on its mass and velocity was that it was indeed once part of a planetary system -- and then got ejected, probably because of a close encounter with another massive object, or perhaps because it was part of a multiple star system and was in an unstable orbit from the get-go.
Now, though, it's lost -- a lonely wanderer tracking its way through the vastness of interstellar space. How many of these rogue planets there are is unknown; as you probably concluded, detection isn't easy, relying on having a powerful telescope aimed in the right direction at the moment the planet passes in front of a distant star. But given how easy it is to destabilize an orbit, there are likely to be millions.
Which, we have to hope, will all stay the hell away from us. Nibiru notwithstanding, having a rogue planet pass through the Solar System would make even Donald Trump drop to number two on the List Of The Biggest Current Threats To Humanity. Fortunately, it's unlikely; space is big. We'd also likely have a decent amount of warning, because as soon as it got near enough (right around the orbit of Pluto), it'd reflect enough of the Sun's light that it'd become visible to astronomers.
Unfortunately, though, there's probably nothing much we could do about it. We've just begun to experiment with the possibility of deflecting small asteroids; deflecting an entire planet, especially one the size of Saturn, would be a case where the best strategy would be to stick your head between your legs and kiss your ass goodbye.
I mean, not to end on a pessimistic note. Let's all focus on the "unlikely" part. And continue working on the next biggest threat, which frankly is occupying more of my anxiety at the moment.
If you own anything made of gold, take a look at it now.
I'm looking at my wedding ring, made of three narrow interlocked gold bands. It's a little scratched up after twenty-three years, but still shines.
Have you ever wondered where gold comes from? Not just "a gold mine," but before that. If you know a little bit of physics, it's kind of weird that the periodic table doesn't end at 26. The reason is a subtle but fascinating one, and has to do with the binding energy curve.
The vertical axis is a measure of how tightly the atom's nucleus is held together. More specifically, it's the amount of energy (in millions of electron-volts) that it would take to completely disassemble the nucleus into its component protons and neutrons. From hydrogen (atomic number = 1) up to iron (atomic number = 26), there is a relatively steady increase in binding energy. So in that part of the graph, fusion is an energy-releasing process (moves upward on the graph) and fission is an energy-consuming process (moves downward on the graph). This, in fact, is what powers the Sun; going from hydrogen to helium is a jump of seven million electron-volts per proton or neutron, and that energy release is what produces the light and heat that keeps us all alive.
After iron, though -- specifically after an isotope of iron, Fe-56, with 26 protons and 30 neutrons -- there's a slow downward slope in the graph. So after iron, the situation is reversed; fusion would consume energy, and fission would release it. This is why the fission of uranium-235 generates energy, which is how a nuclear power plant works.
It does generate a question, though. If fusion in stars is energetically favorable, increasing stability and releasing energy, up to but not past iron -- how do the heavier elements form in the first place? Going from iron to anywhere would require a consumption of energy, meaning those will not be spontaneous reactions. They need a (powerful) energy driver. And yet, some higher-atomic-number elements are quite common -- zinc, iodine, and lead come to mind.
Well, it turns out that there are two ways this can happen, and they both require a humongous energy source. Like, one that makes the core of the Sun look like a wet firecracker. Those are supernova explosions, and neutron star collisions. And two astrophysicists -- Szabolcs Marka of Columbia University and Imre Bartos of the University of Florida -- have found evidence that the heavy elements on the Earth were produced in a collision between two neutron stars, on the order of a hundred million years before the Solar System formed.
This is an event of staggering magnitude. "If you look up at the sky and you see a neutron-star merger a thousand light-years away," Marka said, "it would outshine the entire night sky."
What apparently happens is when two neutron stars -- the ridiculously dense remnants of massive stellar cores -- run into each other, it is such a high-energy event that even thermodynamically unfavorable (energy-consuming) reactions can pick up enough energy from the surroundings to occur. Then some of the debris blasted away from the collision gets incorporated into forming stars and planets -- and here we are, with tons of lightweight elements, but a surprisingly high amount of heavier ones, too.
But how do they know it wasn't a nearby supernova? Those are far more common in the universe than neutron star collisions. Well, the theoretical yield of heavy elements is known for each, and the composition of the Solar System is far more consistent with a neutron star collision than with a supernova. And as for the timing, a chunk of the heavy isotopes produced are naturally unstable, so decaying into lighter nuclei is favored (which is why heavy elements are often radioactive; the products of decay are higher on the binding energy curve than the original element was). Since this happens at a set rate -- most often calculated as a half-life -- radioactive isotopes act like a nuclear stopwatch, analogous to the way radioisotope decay is used to calculate the ages of artifacts, fossils, and rocks. Backtracking that stopwatch to t = 0 gives an origin of about 4.7 billion years ago, or a hundred million years before the Solar System coalesced.
So next time you look at anything made of heavier elements -- gold or silver or platinum, or (more prosaically) the zinc plating on a galvanized steel pipe -- ponder for a moment that it was formed in a catastrophically huge collision between two neutron stars, an event that released more energy in a few seconds than the Sun will produce over its entire lifetime. Sometimes the most ordinary things have a truly extraordinary origin -- something that never fails to fascinate me.
Today I'm going to focus on outer space, because if I don't I'll be forced to deal with events down here on Earth, and it's a little early to start drinking.
The James Webb Space Telescope just posted information on a structure called the Saraswati Supercluster, which at a diameter of 650 million light years and a mass of twenty quadrillion times the mass of the Sun, is one of the largest gravitationally-bound structures known. If you look toward the constellation Pisces, visible in the Northern Hemisphere from August to early January, you're staring right at the Saraswati Supercluster.
Not that you can see it with the naked eye. Its center is about four billion light years away, meaning not only that it's extremely faint, the light from it has taken about a third of the age of the universe to get here, so it's really red-shifted. Here's the rather mind-blowing image the JWST team just posted on their site:
On this diagram, the Sun and Solar System are at the center, and as you move outward the scale increases exponentially, allowing us to visualize -- or at least imagine -- the astonishing vastness of the universe. (Saraswati is just slightly to the left of top center on the diagram.)
The name of the supercluster is from a Sanskrit word meaning "ever-flowing stream with many pools," which is appropriate. It's made of forty-three galaxy clusters -- not galaxies, mind you, but galaxy clusters -- of which the largest, Abell 2631, is thought to be made up of over a thousand galaxies (and something on the order of a hundred trillion stars).
If your mind is not boggling yet, you're made of sterner stuff than I am.
Because of its distance and faintness, we haven't known about Saraswati for all that long. It was discovered in 2017 by a team of Indian astronomers led by Joydeep Bagchi from the Inter-University Centre for Astronomy and Astrophysics (IUCAA) in Pune, India, and since has been the object of intense study by astrophysicists for two main reasons. First -- although it's phenomenally massive, its vast diameter makes it remarkable that it hangs together gravitationally. (Remember that gravitational attraction falls off as the square of the distance; it never goes to zero, but it does get really weak.) The fact that it does seem to be acting as a single structure could give us valuable information about the role of the elusive dark matter in making large objects stick together over time.
Second, it might provide some insight into solving another mystery, the question of how (or if) dark energy, the strange force that seems to be making the expansion of the universe speed up, is changing over time. You may recall that just this past August, a pair of papers came out suggesting that the strength of this peculiar phenomenon might be decreasing; that instead of heading toward the rather ghastly prospect of a "Big Rip," where dark energy overpowers every other known force and tears matter apart into a soup of subatomic particles, the expansion might eventually stop or even reverse. The old "oscillating universe" idea, that the universe goes through an endless series of expansions and collapses -- popularized by such brilliant luminaries of physics as Paul Steinhardt and Roger Penrose -- might have legs after all. Studying Saraswati might give us more information about how the strength of dark energy has changed in the four-billion-odd years it's taken the light from the supercluster to arrive here.
So next time you look up into a clear night sky, think of what lies beyond the bit you can actually see. Every individual star visible to the naked eye lives in a (relatively) tiny sphere in the Orion Arm of the Milky Way. The few bits that visible but are farther away -- the smear of light that is all we can discern of the rest of our own galaxy, as well as the few other galaxies we can see without a telescope (like Andromeda and the two Magellanic Clouds) are so distant that individual stars can't be resolved without magnification. What we think of as the impressive grandeur of the night sky is, basically, like thinking you're a world traveler because you drove around your own neighborhood once or twice.
But I guess I need to come back down to Earth. Unfortunately. On the whole, I'm much happier looking up. It makes the current horror show we're living through at least seem a little less overwhelming, and puts our own place in the universe into perspective.
Maybe if our so-called leaders spent more time stargazing, it might provide them with some much-needed humility.
The whole thing depends on the the concept of "the fabric of space-time," something that got ripped so often on Star Trek that you'd swear the universe was made of cheap pantyhose. To be fair, the idea isn't easy to wrap your brain around, something that becomes obvious when you hear some laypeople talking about the Big Bang.
I mean, I try to be tolerant, but if I hear one more person say, "It's a stupid idea -- that nothing exploded and became everything," I swear, I'm going to hurl a heavy object at 'em.
The problem hinges on trying to draw an analogy between the Big Bang (or in general, the expansion of the Universe) with a conventional explosion, where something blows up and spreads out into space that was already there. With the Big Bang, it was space itself that was stretching -- if the idea of cosmic inflation turns out to be correct, at first it was at a rate that I can't even begin to comprehend -- so the matter in the Universe moved, and is still moving, not because something was physically pushing on it (as in the explosion of a stick of dynamite), but because the space it was embedded in was expanding.
(For what it's worth -- no, at this point we don't understand why this happened, what initiated it, or why the rate changed so suddenly after the "inflationary era" was over. There is a lot still to figure out about this. But one thing that's nearly certain is that it did happen, and the evidence still left behind of the Big Bang is incontrovertible.)
In any case, it's useful to change the comparison. The Big Bang, and the expansion that followed, is much less like a conventional explosion than it is like blowing up a balloon. Astronomer Edwin Hubble realized this when he first observed red shift, and found that everywhere he looked in the universe, objects seemed to be flying away from us -- the farther away, the faster they were moving. It looked very much like we were the center of the Universe, the middle of the explosion, as if you were at the very point where a bomb exploded and were watching the bits and pieces rush away from you.
The truth, Hubble realized, was more subtle, but also way more interesting. The fabric of space itself was stretching. Picture a deflated balloon covered with dots. You're a tiny person standing on one of the dots. The balloon inflates -- and all the other dots appear to be rushing away from you. But the weird thing is that it doesn't matter which dot you're standing on. You could be on any dot, and still all the others would appear to be moving away, because the surface itself is expanding. So an alien in a distant galaxy would also think everything was moving away from him, and he and Hubble would both be right.
There is no center of the Universe. Or everywhere is the center.
Which amounts to the same thing.
So it's much more accurate, if you're trying to picture the whole thing, to think of space as being some kind of "stuff" capable of being deformed or stretched.
Which leads us to this week's mind-blowing discovery in astronomy.
One of the stranger predictions of the General Theory of Relativity -- and there's a lot of competition in that regard -- is that a massive spinning object would drag space-time along with it, twisting it out of shape in a phenomenon called Lense-Thirring frame dragging after the Austrian physicists who predicted it based on Einstein's theories, Josef Lense and Hans Thirring. The problem is, like most of the phenomena associated with Relativity, the Lense-Thirring effect would only be observed in extreme conditions -- in this case a very high-mass object spinning really fast.
Now some scientists led by Cosimo Inserra of Cardiff University have found a remarkable pair of stellar remnants that provide the perfect laboratory for observing frame-dragging -- a star undergoing a "tidal disruption event" from a supermassive black hole (i.e. it's being messily devoured). This is an ideal pairing to study because the star is orbiting the black hole once every twenty days, and the lighthouse-like beam of x-rays and radio waves produced as the material gets swallowed appears from our perspective to flicker on and off. Conservation of Angular Momentum makes the flicker rate extremely constant.
But because of the Lense-Thirring effect, both the jets and the accretion disk of material swirling around the black hole have developed a wobble, which makes the entire system precess like a spinning top. And the rate of precession...
... is exactly what is predicted from the General Theory of Relativity.
"Our study shows the most compelling evidence yet of Lense-Thirring precession -- a black hole dragging space time along with it in much the same way that a spinning top might drag the water around it in a whirlpool," Inserra said. "This is a real gift for physicists as we confirm predictions made more than a century ago. Not only that, but these observations also tell us more about the nature of TDEs -- when a star is shredded by the immense gravitational forces exerted by a black hole. Unlike previous TDEs studied, which have steady radio signals, the signal for AT2020afhd showed short-term changes, which we were unable to attribute to the energy release from the black hole and its surrounding components. This is further confirmed the dragging effect in our minds and offers scientists a new method for probing black holes."
The whole thing is staggering when you think about it. Even the fact that we can detect such a small effect from this distance is a testimony to how far science has come.
"By showing that a black hole can drag space time and create this frame-dragging effect, we are also beginning to understand the mechanics of the process," Inserra said. "It's a reminder to us, especially during the festive season as we gaze up at the night sky in wonder, that we have within our grasp the opportunity to identify ever more extraordinary objects in all the variations and flavors that nature has produced."
So Einstein wins again. Pretty impressive for a guy who once said to a friend struggling in a math class, "Do not worry too much about your difficulties in mathematics. I can assure you that mine are still greater."
So that's our mindblowing science of the day. Spinning stars, twisting space-time, and tilted black holes. I don't know how anyone can read about this stuff and not be both fascinated at how weird our universe is, and astonished that we've progressed to the point where we can understand at least a bit of it. Here, several hundred quadrillion kilometers away, we've detected minuscule tilts in a whirling stellar remnant, and used it to support a theory that describes how matter and energy work throughout the Universe.
If that's not an impressive accomplishment, I don't know what is.
I've shown a bunch of people, and I've gotten answers from an electron micrograph of a sponge to a close-up of a block of ramen to the electric circuit diagram of the Borg Cube. But the truth is almost as astonishing:
Most everyone knows that the stars are clustered into galaxies, and that there are huge spaces in between one star and the next, but far bigger ones between one galaxy and the next. Even the original Star Trek got that right, despite their playing fast and loose with physics every episode. (Notwithstanding Scotty's continual insistence that you canna change the laws thereof.) There was an episode called "By Any Other Name" in which some evil aliens hijack the Enterprise so it will bring them back to their home in the Andromeda Galaxy, a trip that will take three hundred years at Warp Factor Ten. (And it's mentioned that even that is way faster than a Federation starship could ordinarily go.)
So the intergalactic spaces are so huge that they're a bit beyond our imagining. But if you really want to have your mind blown, consider that the filaments of the above diagram are not streamers of stars but streamers of galaxies. Billions of them. On the scale shown above, the Milky Way and the Andromeda Galaxy are so close as to be right on top of each other.
What is kind of fascinating about this diagram -- which, by the way, is courtesy of NASA/JPL -- is not only the filaments, but the spaces in between them. These "voids" are ridiculously huge. The best-studied is the Boötes Void, which is centered seven hundred million light years away from us. It is so big that if the Earth were at the center of it, we wouldn't have had telescopes powerful enough to see the nearest stars until the 1960s, and the skies every night would be a uniform pitch black.
That, my friends, is a whole lot of nothing.
The reason all this comes up is a paper that appeared last week in Monthly Notices of the Royal Astronomical Society about some research out of Cambridge and Oxford Universities into the structure of one of those cosmic filaments, which found that it shows some pretty peculiar properties. The particular filament studied is "only" about 450 million light years away -- for reference, that's about two hundred times farther than the Andromeda Galaxy -- and contains just shy of three hundred galaxies.
Astronomers can now make amazingly accurate determinations of the rotational speed and direction of galaxies, despite the distances involved and the fact that galaxies are enormous enough that on a human timescale, you can't see the individual stars moving. They use the Doppler effect -- the fact that if you're looking at a rotating galaxy (especially one that's edge-on), half the stars are moving away from us and half are moving towards us. This means that the first bunch have their light stretched out (red-shifted) and the others have their light compressed (blue-shifted). From the light coming from the center, you can tell what the galaxy's overall motion is with respect to us, so voilà -- you have the rotational speed and overall linear velocity.
I mean, it's not as simple as I'm making it sound in practice, but the principle is actually relatively straightforward.
And what they found is that within this filament, the individual galaxies are all rotating in approximately the same plane, and the filament as a whole is rotating -- in the same direction.
"What makes this structure exceptional is not just its size, but the combination of spin alignment and rotational motion," said co-lead author Dr. Lyla Jung, of the University of Oxford, in a press release. "It’s like the teacups ride at a theme park. Each galaxy is like a spinning teacup, but the whole platform -- the cosmic filament -- is rotating too. This dual motion gives us rare insight into how galaxies gain their spin from the larger structures they live in."
It's kind of dizzying to think about, isn't it? We're on a spinning globe, whirling in orbit around a star; the star, and its attendant planets and other oddments, are sitting in the spiral arm of a galaxy that is itself rotating at a breakneck speed; the entire "Local Group" of galaxies is spinning, too; and the Laniakea Supercluster, to which the Local Group and about a hundred thousand galaxies belongs, is zooming toward an unseen point called the "Great Attractor" about whose nature we haven't the first clue. Now, we find that in addition to all this, each strand in the spiderweb of galaxy clusters that spans the entire cosmos is itself rotating, and has imparted that rotational direction to the galaxies within it.
I'm getting vertigo just thinking about it.
So think about this the next time you're tempted to say you're "going nowhere fast." You're definitely going somewhere. Really quickly. In fact, the entire universe is kind of like a giant Tilt-O-Whirl.
One thing that never fails to leave me feeling awestruck is when I consider that astronomers figured out the shape and size of the Milky Way Galaxy while residing inside it.
I mean, think about it. Imagine you're a tiny being (with a telescope) sitting on a raindrop near one edge of a huge cloud, and your task is to try to measure the distances and positions of enough other raindrops to make a good guess about the size and shape of the entire cloud. That's what the astronomers have accomplished -- enough to state with reasonable confidence that we're in one of the arms of a barred spiral galaxy.
If ever there was an image you need to study in detail, this is it. Take a look at the original, close up. The Solar System is in the Orion Arm, directly down from the center of the galaxy. The thing that blew me away is the circle marked "Naked Eye Limit" -- literally every star you have ever seen without the use of a telescope is in that little circle. [Image licensed under the Creative Commons Pablo Carlos Budassi, Milky Way map, CC BY-SA 4.0]
What's even more astonishing is that the stars making up the Milky Way (and every other galaxy) are moving. Not fast enough, on that kind of a size scale, that the map will be inaccurate any time soon; but fast enough to be measurable from here on Earth. In fact, it was anomalies in galactic rotation curves -- the plot of the orbital speed of stars around the center of the galaxy, as a function of their distance from the center -- that clued in the brilliant astrophysicist Vera Rubin that there was (far) more matter in galaxies than could be seen, leading to the bizarre discovery that there is five times more dark matter (matter that only interacts via gravity) than there is the ordinary matter that makes up you, me, the Earth, the Sun, and the stars.
All of this makes the new study out of the European Space Agency even more incredible. New data from the Gaia Telescope has found that the entire Milky Way is rippling as it rotates, a little like the fluttering of a Spanish dancer's frilly skirt. The period of this wave-like motion is on the order of ten thousand light years, and it appears to affect the entire galaxy.
The astrophysicists are still trying to figure out what's causing it.
"What makes this even more compelling is our ability, thanks to Gaia, to also measure the motions of stars within the galactic disc," said lead author Eloisa Poggio, an astronomer at the Istituto Nazionale di Astrofisica (INAF) in Italy. "The intriguing part is not only the visual appearance of the wave structure in 3D space, but also its wave-like behavior when we analyze the motions of the stars within it."
The discovery hinged on the use of standard candles, something you may be familiar with if you've read any cosmology. Calculating distances of astronomical objects is tricky, for the same reason that it's difficult to tell how far away a single light is at night. If the light seems bright, is it intrinsically bright (and perhaps quite distant), or are you looking at something that is dimmer, but close to you? The only way to calculate astronomical distances is to use the small number of objects for which we know the intrinsic brightness. The two most common are Cepheid variables, stars for which the oscillation period of luminosity is directly related to their brightness, and type 1a supernovas, which always have about the same peak luminosity. Between these two, astrophysicists have been able to measure the changing positions of stars as the ripple of the wave passes them.
So the stars in our galaxy are riding the cosmic surf, and at the moment no one knows why. One possibility is that this is a leftover gravitational effect from a collision with a dwarf galaxy some time in the distant past -- a little like the ripples from dropping a pebble into a pond lasting long after the pebble has come to rest on the bottom. But the truth is, it will take further study to figure out for sure what's causing the wave.
Me, I find the whole thing staggering. To think that only a little over a hundred years ago, there were still astronomers arguing (vehemently) that the only galaxy in the universe was the Milky Way, and all of the other galaxies were merely small local nebulae. The last century has placed us into a universe vaster than the ancients could ever have conceived -- and I have no doubt that the next century will astonish us further, and in ways we never could have imagined.
I was an undergraduate when the original Cosmos first aired.
It was back in 1980, and I still remember being blown away by it all -- the melding of science with animation and gorgeous music, and Carl Sagan's lyrical, almost poetic way of expressing his enduring love for astronomy. My friends and I always waited excitedly for the next episode to air, and the day afterward spent an inordinate amount of time chatting about what we'd learned.
One of the episodes that resonated the most strongly with me was entitled "Encyclopedia Galactica." Sagan predicted a day when we'd know so much about the universe that we'd have an encyclopedia of alien planets, each page of which would be accompanied by a list of their physical characteristics -- and types of life forms. He was unequivocal in his belief that we were not alone in the universe, and that in fact life would turn out to be common. Not, perhaps, "life as we know it, Jim" -- and much of it almost certainly pre-technological -- but life, he thought, would turn out to be pretty much everywhere we looked.
In the forty-five years since it aired, our detecting equipment has gotten better and better, but we're still up against the Fermi Paradox -- that famous quip from physicist Enrico Fermi who, when told that life was likely to be common in the universe, said, "Then where is everybody?" Long-time readers of Skeptophilia may recall that a few years ago I did a deeper dive into the Fermi Paradox and the infamous "three f's," but the fact remains that despite getting better and better at astronomy and astrophysics, we still have no incontrovertible evidence of extraterrestrial life (intelligent or otherwise).
But extrasolar planets? Those are kind of a dime a dozen. As of this month, there have been a bit over six thousand exoplanets conclusively identified, and some of them have challenged our models of what planets can be. (I took a look at a few of the weirder ones in a post earlier this year.) So even if we don't yet have aliens in our back yard, there's been a lot of really cool information discovered -- three examples of which have just come out in the past couple of weeks.
No Andorians yet, more's the pity.
The first is about the TRAPPIST-1 system, which was one of the first multi-planet systems discovered. Not only that, it has four planets in the "Goldilocks zone" -- the region around the host star that is "just right" for having temperatures where water could be in its liquid state. (This doesn't mean there is water; just that if other factors were favorable, there could be liquid water.) Not only that, but we lucked out that TRAPPIST-1 is fairly close (a little over forty light years away, in the constellation of Aquarius), and that its planets' orbits are aligned so that from our perspective, they cross in front of their host star, allowing astrophysicists to use the transits to take a stab at the composition of their atmospheres.
The outstanding YouTuber Dr. Becky Smethurst did a wonderful video explaining how this all works (and why the planet TRAPPIST-1d probably doesn't have an atmosphere), but a capsule summary is that when the planet passes in front of the star, its light passes through the planet's atmosphere (if it has one), and any gases present absorb and scatter characteristic frequencies of light. Compared to the unobstructed spectrum of the star, those frequencies are then missing (or at least diminished in intensity), and from that information astrophysicists can deduce what might be present in the atmosphere.
Well, the other three planets in the habitable zone -- TRAPPIST-1b, c, and d -- have pretty conclusively been shown to lack an atmosphere. So it all hinges on 1e, the farthest one out, and a study at the University of Bristol, using data from the James Webb Space Telescope, has said that it cannot rule out the presence of an atmosphere on that one. Not a ringing endorsement, that, but at least not a categorical no -- so we'll keep our eyes on TRAPPIST-1e and hope future studies will give us good news.
The other two stories are about "rogue exoplanets" -- planets out there floating in space that don't (or at least, don't now) orbit a star. Whether they formed that way, or started out in a stellar system and then were ejected gravitationally, is unknown (and may well be different in different cases). These, for obvious reasons, are considered poor candidates for life, but they still are pretty amazing -- and the fact that we know about them at all is a tribute to our vastly improved ability to detect objects out there in interstellar space.
The first one, CHA-1107-7626, is currently accreting material like mad -- something not seen before in an exoplanet, rogue or otherwise. It is estimated to be between five and ten times the mass of Jupiter, so on the verge of being a "brown dwarf" -- a superplanet that has sufficient mass and pressure to fuse deuterium but not hydrogen. They emit more energy than they absorb, but don't quite have enough for the nuclear furnace to turn on in a big way.
But if CHA-1107-7626 keeps going the way its going, it may get there. It's hoovering up an estimated Jupiter's worth of material every ten million years or so, which is the largest accretion rate of any planet-sized object ever observed. So what we might be witnessing is the very earliest stages of the formation of a new star.
The final study is about the rogue exoplanet SIMP-0136, which came out of Trinity College Dublin and again uses data from JWST. But this exoplanet is bizarre for two different reasons -- it has vast storms of what amounts to liquid droplets of sand... and it has auroras.
Once again, I'm staggered by the fact that we could detect this from so far away. The temperature of the surface of the planet is around 1,500 C -- hotter than my kiln at full throttle -- and it has three hundred kilometer per hour winds that blow around bits of molten silica. But most peculiar of all, the planet's atmosphere shows the characteristic polar light flashes we see down here as auroras.
What's weirdest about that is that -- at least on Earth -- auroras are caused by solar activity, and this planet isn't orbiting a star. The way they form down here is that the solar wind ionizes gases in the upper atmosphere, and when those ions grab electrons, and the electrons descend back to the ground level, they emit characteristic frequencies of light (the same ones, not coincidentally, that are swiped by gases in the atmospheres of planets during transits). Red for monoatomic oxygen, green for diatomic oxygen, blue for molecular nitrogen, and so on.
What is ionizing the gases on SIMP-0136? Astrophysicists aren't sure. Sandstorms here on Earth can certainly cause static electrical discharges (what we laypeople refer to as "bigass lightning bolts"), so it's possible we're seeing the light emitted from interactions between the molten silica and whatever gases make up the planet's atmosphere. But it's too soon to be sure.
So even if we haven't yet discovered Skithra or Slitheen or Sontarans or whatnot, we're still adding some pretty amazing things to our Encyclopedia Galactica. Carl Sagan, as usual, was prescient. As he put it, "Somewhere, something incredible is waiting to be known."
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