Gravitational blink

To end the week on an appropriately surreal note: no, the Earth will not "lose its gravity" for seven seconds on August 12.

I found out about this rumor, currently making the rounds on social media, from a friend and loyal reader of Skeptophilia.  The whole thing apparently started with a video posted on Instagram by user @mr_danya_of; the video was subsequently removed, but not before it was reshared thousands of times, downloaded, and posted all over the place.  The claim is that there were gravitational waves emitted from two different black holes equidistant from the Earth, and that they are 180 degrees out of phase with each other, so where they intersect -- here, evidently -- they'll undergo destructive interference.  The result is that it will "cancel Earth's gravity" for the seven seconds it takes them to pass by us, and we all need to, I dunno, make sure everything is tied down securely or something, because otherwise it's going to cause huge amounts of death and destruction.

Whoo.  Okay.  Where do I start?

First of all, the information was alleged to come from NASA (of course), from something called "Project Anchor."  Which doesn't exist.  Of course, over at NASA they would say that, wouldn't they?  So let's move on to a few other, harder-to-argue-with objections.

Second, according to the General Theory of Relativity, gravitational waves travel at the speed of light, whereof nothing travels faster, remember?  So if there were gravitational waves headed toward us from a black hole (let alone two of them), we wouldn't have any way of knowing about it ahead of time.  Now, you might be thinking, what about the gravitational waves that have been detected by the interferometer array LIGO?  Well, there, we knew there were two neutron stars that had been orbiting each other and were about to merge, so all we had to do was watch until it happened.  (Okay, I'm making it sound simple; in practice it was a lot more complicated than this, but the point is we did have some advance warning in that case.)  Here, we just supposedly have black holes out there emitting gravitational waves for some undisclosed reason, and we've somehow found out about this eight months ahead of their arrival, which Einstein says is impossible, and on the whole I'm inclined to side with Einstein over "mr_danya_of."

Third, what was immediately obvious is that whoever is taking this seriously has no idea how destructive interference actually works.  Simply put, destructive interference occurs where two waves in the same medium intersect in such a way that the crest of one wave overlaps the trough of the other.  At that point, their amplitudes will cancel.  Here, supposedly these two gravitational waves are exactly 180 degrees out of phase, so they'd cancel completely wherever they intersect.

But if that happened, what we'd see is... nothing.  If the two waves did completely cancel, the result at that point would be an amplitude of zero.  In other words, they'd be undetectable.  This would not somehow "erase Earth's gravity."

Fourth, the Earth's diameter is about 0.04 light seconds, so if a gravitational wave or two passed across us, that's how long the effect would last.  How this person came up with seven seconds as a plausible time duration for something traveling at the speed of light, I have no idea.

Fifth, the gravitational field of the Earth at a given distance is dependent on only one thing: its mass.  As long as the Earth's mass doesn't change, the strength of the field won't, either, regardless how it's jostled by gravitational waves (or anything else).

Sixth, what the actual fuck?

[Image licensed under the Creative Commons AllenMcC., GravityPotential, CC BY-SA 3.0]

I mean, it's a good thing the Earth's gravity isn't going to disappear, even for seven seconds.  If you, unlike the people posting this story, passed high school physics, you may recall that the reason we're all happily glued to the Earth's surface is the pull of gravity -- and without it, Newton's First Law (an object experiencing no unbalanced forces continues at rest or moving in a straight line at a constant velocity) takes over.  We're all right now moving at a good clip -- at the Equator, about 1,670 kilometers an hour -- but our tendency to fly off is counterbalanced by the centripetal (center-pointing) pull of gravity.  If gravity suddenly disappeared, we'd continue moving at our original speed, but tangent to the circle we're currently traveling in.  The Earth, presumably unperturbed, would continue to rotate out from underneath us, and when the gravity switched back on seven seconds later, we (and everything else not moored) would come crashing back down.

I did a quick back-of-the-envelope calculation for my own latitude, just shy of halfway between the Equator and the North Pole, and found that in seven seconds unsecured objects traveling tangent to the Earth's surface would end up about twenty centimeters up in the air.  Falling back to Earth from that height would be a bit of a jolt, and no doubt the sudden change in stress would damage some buildings, but it's far from the carnage mr_danya_of and others are claiming.

But to reassure you that you have no cause for concern, even in that regard... no, NASA isn't "94.7% certain" that the Earth's gravity is going to blink for seven seconds on August 12.  There is no such thing as Project Anchor.  Gravitational waves, and in fact waves in general, do not work this way.  We have far more important things to worry about right now, such as trying to figure out what country FIFA Peace Prize Winner Donald Trump is going to declare war on next.

If you see anyone posting hysterical nonsense about how NASA Admits We're All Gonna Die In August, you should definitely inform them that this is complete horseshit, and suggest that maybe at least reading the Wikipedia pages about the relevant physics concepts might be a good idea before publicly humiliating themselves by pretending they understand science.

So anyway, there you have it.  To the friend who sent me the link, thanks just bunches for further reducing my already-abysmal assessment of humanity's overall intelligence.  Me, I'm going to go back to fretting about real stuff.  Not that this is productive either, mind you.  But at least it's better than making shit up so you have additional imaginary stuff to fret about.

Even I am not that neurotic.

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A twist in the fabric

I hope y'all will indulge me one more astronomical post, because just this week in the journal Science Advances there was a very cool paper about an observational verification of the phenomenon of frame-dragging.

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.

To give you an idea of what kind of extremes I'm talking about, here: with the Earth's mass and spin, the Lense-Thirring effect would cause an angular shift of about one degree every 100,000 years.

Not exactly something that jumps out at you.

[Image licensed under the Creative Commons ALMA (ESO/NAOJ/NRAO)/H. Kim et al., Celestial spiral with a twist, CC BY 4.0]

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.

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Rough neighborhood

Most likely all of you know about Sagittarius A*, the supermassive black hole that sits at the center of the Milky Way Galaxy.

It's hard to talk about it without lapsing into superlatives.  It has a mass about 4.3 million times that of the Sun.  It's event horizon -- the "point of no return," the closest you can get to a black hole without being trapped by its gravitational pull -- has a radius of 11.3 million kilometers.  It sits at the center of a fifteen-light-year-wide whirlpool of gas and dust called the accretion disk, which we know about because the material in it is moving so fast it has heated up to as high as ten million degrees Celsius, resulting in a steady emission of high-frequency x-rays.

[Image licensed under the Creative Commons EHT Collaboration, EHT Sagittarius A black hole, CC BY 4.0]

It's curious that something this luminous wasn't immediately obvious to astronomers.  First, it doesn't emit a lot of visible light; we didn't have telescopes capable of detecting the x-rays that are its fingerprint until 1933.  By the 1970s, more precise observations showed that whatever the x-ray source was, it was extremely compact.  It wasn't until 1994 that Charles H. Townes and Reinhard Genzel showed that its mass and diameter were consistent with its being a black hole.  Another reason it took that long is that between us and the center of the galaxy there are massive dust clouds, so any visible light it does emit (or which is emitted by the dense clouds of glowing gas near it) mostly gets blocked.  (Even so, looking toward the center of the Milky Way in the constellation Sagittarius, visible where I am in late summer, is pretty damn spectacular.)

The third reason that we don't get the full luminosity of whatever electromagnetic radiation is emitted from Sagittarius A* is a fortunate one for us; because of the black hole's immense magnetic field, any bursts of light tend to get funneled away along the axis of its spin, creating jets moving perpendicularly to the galactic plane.  We, luckily, are comfortably out in the stellar suburbs, in one of the Milky Way's spiral arms.  Our central black hole is fairly quiet, for the most part, but even so, looking down the gun barrel of its magnetic field axis would not be a comfortable position to reside.

The reason this comes up is some new research out of the University of Colorado - Boulder, which used data from the James Webb Space Telescope to solve a long-standing question about why, given the high density of hydrogen and helium gas near the galactic center, the rate of star formation there is anomalously low.  This region, called Sagittarius C, extends about two hundred light years from the central black hole (by comparison, the Solar System is twenty-six thousand light years away).  And what the team of researchers found is that threading the entire region are filaments of hot, bright plasma, some of them up to several light years in length.

The reason for both the filaments and the low star formation rate is almost certainly the black hole's magnetic field, which acts to compress any gas that's present along the field lines, heating it up dramatically.  This, in turn, creates an outward pressure that makes the gas resist collapsing and forming stars.

"It's in a part of the galaxy with the highest density of stars and massive, dense clouds of hydrogen, helium and organic molecules," said Samuel Crowe, who co-authored the paper, which appeared this week in The Astrophysical Journal.  "It's one of the closest regions we know of that has extreme conditions similar to those in the young universe...  Because of these magnetic fields, Sagittarius C has a fundamentally different shape, a different look than any other star forming region in the galaxy away from the galactic center."

It is, to put it mildly, a rough neighborhood.

It's staggering how far we've come in our understanding of what our ancestors called the "fixed stars" -- far from being eternal and unchanging, the night sky is a dynamic and ever-evolving place, and with new tools like the JWST we're finding out how much more we still have to learn.  Something to think about the next time you look up on a clear, starry night.  The peaceful, silent flickering, set against the velvet black background, is an illusion; the reality is far wilder -- and far more interesting.

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Up, down, round and round

I recall seeing a comic strip a while back making fun of one of the features of Star Trek that doesn't seem ridiculous until you think about it a little.  Have you noticed that whenever two starships are near each other -- whether it's the Enterprise and other Federation ships, or they're being threatened by the Romulans or Klingons or whatnot -- the ships are almost always oriented the same way?  The only time this is not the case is when the showrunner wanted to make it clear that the other ship was disabled and drifting.  Then it was shown at some odd angle relative to the Enterprise.  In the comic strip, it showed what it would look like if all the ships were at random orientations -- how ridiculous it appeared -- but really, isn't that what you'd expect?  In the Star Trek universe, each ship is supposed to come with its own artificial gravity, so within any ship, up is "toward the ceiling" and down is "toward the floor."  It wouldn't need to line up with any other ship's artificial gravity, so except for an occasional coincidence, they should all be at various angles.

In space, there's no preferred direction, no "up" or "down."  You always have to describe position relative to something else -- to the axis of the Earth's rotation, or the plane of the Solar System, or the plane of revolution of the Milky Way.  But even those aren't some kind of universal orientation; as I described in a recent post, the universe is largely isotropic (the same in every direction).  Just like the starships in Star Trek, there shouldn't be any preferred directionality.

Well, that's what we thought.

A new paper this week in the journal Monthly Notices of the Royal Astronomical Society describes a set of data from the James Webb Space Telescope that is absolutely astonishing.  Here's how the authors describe it:

JWST provides a view of the Universe never seen before, and specifically fine details of galaxies in deep space.  JWST Advanced Deep Extragalactic Survey (JADES) is a deep field survey, providing unprecedentedly detailed view of galaxies in the early Universe.  The field is also in relatively close proximity to the Galactic pole.  Analysis of spiral galaxies by their direction of rotation in JADES shows that the number of galaxies in that field that rotate in the opposite direction relative to the Milky Way galaxy is ∼50 per cent higher than the number of galaxies that rotate in the same direction relative to the Milky Way.  The analysis is done using a computer-aided quantitative method, but the difference is so extreme that it can be noticed and inspected even by the unaided human eye.  These observations are in excellent agreement with deep fields taken at around the same footprint by Hubble Space Telescope and JWST.

This adds a whole new twist (*rimshot*) to the horizon problem and the isotropy of the universe as a whole.  Not only do we have the issue that causally-disconnected regions of the cosmic microwave background radiation, that are too far apart to have ever influenced each other (something I describe more fully in the above-linked post), are way more similar in temperature than you'd expect -- now we have to figure out how causally-disconnected galaxies on opposite sides of the universe could possibly have ended up with correlated rotational axes.

The authors admit it's possible that this measurement is due to something about the Milky Way's own rotation that we're not compensating for in the data, but there's a more out-there explanation that the paper's authors are seriously considering.

"It is not clear what causes this to happen," said study co-author Lior Shamir, of Kansas State University, in an interview with Independent.  "[But] one explanation is that the universe was born rotating.  That explanation agrees with theories such as black hole cosmology, which postulates that the entire universe is the interior of a black hole."

Black holes are defined by three properties -- mass, electric charge, and... angular momentum.  That we're inside a rotating black hole would explain the anomaly JWST just observed.  Since -- at least as far as our current understanding goes -- anything inside a black hole's event horizon is forever inaccessible, perhaps this means that event horizons are boundaries between universes.  As bizarre as that sounds, there is nothing about what we know of the laws of physics and cosmology that rules that out.  Which would mean that...

... black holes are bigger on the inside.

The Doctor tried to tell us.

Of course, the more prosaic explanation -- that the data were somehow influenced by our own motion through space -- has yet to be decisively ruled out.  I can't help but feel, though, that if the authors thought that was likely, they (or their reviewers) would have suggested waiting and re-analyzing before publishing in a prestigious journal like MNRAS.  The greater likelihood is that this is a real signal, and if so, it's mighty odd.

As far as what it would mean if we found out we are inside a black hole, well -- I'm hardly qualified to weigh in.  It probably wouldn't affect our day-to-day life any.  After all, it's not like we were going to find a way out of the universe anyhow, much as recent events here on Earth have made many of us wish we could.  All I can say is stay alert for further developments, and keep looking up.

Whatever direction that actually is.

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Stellar slingshot

Sometimes there's a scientific discovery that's just such an "oh, wow!" that I have to tell you about it.

Like the research that I ran into in the Astrophysical Journal recently.  "Origin of a Massive Hyper-runaway Subgiant Star LAMOST-HVS1: Implication from Gaia and Follow-up Spectroscopy," by Kohei Hattori, Monica Valluri, Norberto Castro, Ian U. Roederer, Guillaume Mahler, and Gourav Khullar, of the University of Michigan - Ann Arbor, describes a star that was ejected from our galaxy at a speed that boggles the imagination.

This star -- the euphoniously-named LAMOST-HVS1 -- is traveling at about 570 kilometers per second, on a trajectory almost perpendicular to the plane of the Milky Way Galaxy.  (If it helps, that's over a million miles an hour.)  It was initially thought that the star might have been evicted from the center of the galaxy, where there is an enormous black hole -- only something that massive, scientists thought, could impart enough energy to a star to get it traveling that fast. But tracking its path backward showed that it didn't come from the center, but from a region called the Norma Spiral Arm.

[Image is in the Public Domain, courtesy of NASA/JPL]

What this seems to indicate is that there are massive black holes scattered throughout the galaxy, not concentrated at the center.  Which is vaguely terrifying.  The scenario is apparently that a binary star was drawn in toward the black hole, and as it fell toward the event horizon, one of the two gained enough energy to be flung free -- what's called the "gravitational slingshot effect."  This phenomenon has been used to get countless television and movie spacefarers out of sticky situations, most notably in the 1998 film Lost in Space, wherein we learn that something being a truly awful television show is not sufficient to stop producers from turning it into an even worse movie.  I say "worse," even though the 1960s Lost in Space television show was uncategorically abysmal, because the movie took itself so damn seriously.  When the television show brought out space vikings or space cowboys or space hippies or a space motorcycle gang -- none of which, by the way, I'm making up -- at least they knew they were being campy.

But here, we're actually supposed to believe the intrepid crew of the Jupiter 2, having just escaped from Gary Oldman as a Dr. Smith who has turned into a giant humanoid spider (for the record, I'm not making that up, either), realizes that they don't have enough oomph to escape from the planet that's disintegrating around them, so Matt LeBlanc as Major Don West decides to use the "gravity well" of the planet to fling them free.  So he puts the Jupiter 2 into a power dive, and somehow they go all they way through the planet, miraculously dodging all of the rocks and debris, not to mention an entire mantle and core's worth of molten lava, and get squirted out of the other side like someone spitting out a grapefruit pit.

But I digress.

In any case, the writers of the script actually were referencing a real phenomenon, but one which would be unlikely to save you if you are ever in the situation of having your spaceship run out of gas while trying to escape from an exploding planet.  "This discovery dramatically changes our view on the origin of fast-moving stars," said study co-author Monica Valluri, in a press release.  "The fact that the trajectory of this massive fast-moving star originates in the disk rather that at the Galactic center indicates that the very extreme environments needed to eject fast-moving stars can arise in places other than around supermassive black holes."  (The press release also has a nice gif showing the star's path, which you should all check out.)

All of which is pretty cool, especially since there have only been around thirty of these "hyper-runaway" stars ever observed.  Given its current position, it's interesting to think about what the sky would look like to a denizen of one of its planets (yes, I know, any denizens it may have had surely wouldn't have survived a close encounter with a black hole, but just bear with me here).  I'm reminded of Carl Sagan's comment about a star in that position experiencing not a sunrise but a galaxy-rise -- from where it is, the disc and arms of the Milky Way would fill the entire night sky.

So there's some awe-inspiring research from the astronomers.  I don't see how anyone would not find this astonishing.  Maybe if you were like the Robinson family, meeting hordes of aliens every week, you'd get inured, but I can't help but think I'd still be pretty blown away even so.

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Bubbles, dimensions, and black holes

One of the weirder claims of modern physics, which I first ran into when I was reading about string theory a few years ago, is that the universe could have more than three spatial dimensions -- but the extra ones are "curled up" and are (extremely) sub-microscopic.

I've heard it explained by an analogy of an ant walking on a string.  There are two ways the ant can go -- back and forth on the string, or around the string.  The "around the string" dimension is curled into a loop, whereas the back-and-forth one has a much greater spatial extent.

Scale that up, if your brain can handle it, to three dimensions of the back-and-forth variety, and as many as nine or ten of the around-the-string variety, and you've got an idea of what the claim is.

The problem is, those extra dimensions have proven to be pretty thoroughly undetectable, which has led critics to quote Wolfgang Pauli's quip, that it's a theory that "is not even wrong," it's unverifiable -- which is synonymous to saying "it isn't science."  But the theorists are still trying like mad to find an indirect method to show the existence of these extra dimensions.

To no avail at the present, although we did have an interesting piece added to the puzzle a while back that I somehow missed the first time 'round.  Astronomers Katie Mack of North Carolina State University and Robert McNees of Loyola University published a paper in arXiv that puts a strict limit on the number of macroscopic dimensions -- and that limit is three.

So sorry, fans of A Wrinkle in Time, there's no such thing as the tesseract.  The number of dimensions is three, and three is the number of dimensions.  Not four.  Nor two, unless thou proceedest on to three. 

Five is right out.

The argument by Mack and McNees -- which, although I have a B.S. in physics, I can't begin to comprehend fully -- boils down to the fact that the universe is still here.  If there were extra macroscopic spatial dimensions (whether or not we were aware of them) it would be possible that two cosmic particles of sufficient energy could collide and generate a miniature black hole, which would then give rise to a universe with different physical laws.  This new universe would expand like a bubble rising in a lake, its boundaries moving at the speed of light, ripping apart everything down to and including atoms as it went.

"If you’re standing nearby when the bubble starts to expand, you don’t see it coming," Mack said.  "If it’s coming at you from below, your feet stop existing before your mind realizes that."

This has been one of the concerns about the Large Hadron Collider, since the LHC's entire purpose is to slam together particles at enormous velocities.  Ruth Gregory of Durham University showed eight years ago that there was a non-zero possibility of generating a black hole that way, which triggered the usual suspects to conjecture that the scientists were trying to destroy the universe.  Why they would do that, when they inhabit said universe, is beyond me.  In fact, since they'd be standing right next to the Collider when it happened, they'd go first, before they even had a chance to cackle maniacally and rub their hands together about the fate of the rest of us.

"The black holes are quite naughty," Gregory said, which is a sentence that is impossible to hear in anything but a British accent.  "They really want to seed vacuum decay.  It’s a very strong process, if it can proceed."

"No structures can exist," Mack added.  "We’d just blink out of existence."

Of course, it hasn't happened, so that's good news.  Although I suppose this wouldn't be a bad way to go, all things considered.  At least it would be over quickly, not to mention being spectacular.  "Here lies Gordon, killed during the formation of a new universe," my epitaph could read, although there wouldn't be anyone around to write it, nor anything to write it on.

Which is kind of disappointing.

Anyhow, what Mack and McNees have shown is that this scenario could only happen if there was a fourth macroscopic dimension, and since it hasn't happened in the universe's 13.8 billion year history, it probably isn't going to.

So don't cancel your meetings this week.  Mack and McNees have shown that any additional spatial dimensions over the usual three must be smaller than 1.6 nanometers, which is about three times the diameter of your average atom; bigger than that, and we would already have become victims of "vacuum decay," as the expanding-bubble idea is called.

A cheering notion, that.  Although I have to say, it's an indication of how bad everything else has gotten that "We're not dead yet" is the best I can do for good news.

That's our news from the world of scientific research -- particle collisions, expanding black holes, and vacuum decay.  Myself, I'm not going to worry about it.  I figure if it happens, I'll be gone so fast I won't have time to be upset at my imminent demise, and afterwards none of my loved ones will be around to care.  Another happy thought is that I'll take Nick Fuentes, Tucker Carlson, Elon Musk, Stephen Miller, and Andrew Tate along with me, which might almost make destroying the entire universe worth it.

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Hit by the firehose

An impending astronomical event has brought to the general attention a phenomenon called a nova.  Misleadingly named after the Latin word for "new," a nova isn't a new star at all -- it's an old star (some of them very old) that suddenly flares up and becomes visible to the naked eye.  The nova in question is T Coronae Borealis, a star that is ordinarily around an apparent magnitude of +10 (making it far too faint to see without a telescope), but every eighty or so years flares up to a magnitude of around +2, becoming easily visible for a short time before fading to its original unimpressive luminosity.

Novas of this type are double star systems.  One member of the pair is a white dwarf -- the white-hot core of a Sun-like star at the end of its life -- and the other one is usually a giant.  What happens is that the super-dense white dwarf gradually siphons off gas from its larger but less dense partner, and as the gas falls onto the white dwarf's surface it heats and compresses, finally becoming hot enough to fuse into helium.  This releases more heat energy still, and causes a runaway chain reaction, resulting in the flare-up.  But the total amount of hydrogen available isn't really that great -- it's only a shell of material on the surface -- so the reaction runs out of steam, and the pair settles down again until enough more gas is siphoned off to trigger another flash.

T Coronae Borealis is due -- overdue, according to some astrophysicists -- for a blaze-up.  So those of you in the Northern Hemisphere, watch for this "new star" -- it's something you'll likely never get another chance to see.

The reason the topic comes up is some new data from the Hubble Space Telescope about novas in another galaxy -- M87, a supergiant elliptical galaxy in the constellation Virgo.  

[Image licensed under the Creative Commons Ngc1535, M87 Galaxy from the Mount Lemmon SkyCenter Schulman Telescope courtesy Adam Block, CC BY-SA 4.0]

M87 became famous because it was the galaxy whose massive central black hole became the first ever to be photographed.  Since then, it's been studied extensively, and the most recent information we've learned about it is downright puzzling.

Most black holes are surrounded by an accretion disk -- a violent whirlpool of gas spiraling down toward the event horizon.  As it spins, the ionized atoms release energy in the form of x-rays; some of them are accelerated enough to escape completely.  The result is a narrow jet of plasma and electromagnetic radiation, aligned with the poles of the black hole's magnetic field.

Especially with a supermassive black hole like the ones at the center of galaxies, having the jet aimed at you personally would be a very bad thing.  Anything less than a thousand light years away would be deep fried.  Even farther away, the effects of the plasma stream would be devastating.

And what the recent study found is that stars that are hit by this blast of radiation are much more likely to go nova -- and no one is really sure why.

"There's something that the jet is doing to the star systems that wander into the surrounding neighborhood. Maybe the jet somehow snowplows hydrogen fuel onto the white dwarfs, causing them to erupt more frequently," said astrophysicist Alec Lessing of Stanford University, who co-authored the study, in an interview with Science Daily.  "But it's not clear that it's a physical pushing.  It could be the effect of the pressure of the light emanating from the jet.  When you deliver hydrogen faster, you get eruptions faster.  Something might be doubling the mass transfer rate onto the white dwarfs near the jet."

The bottom line is, the astrophysicists are not sure why it's happening, but some interaction between the jet and the stars caught in it is making candidate stars "pop off like camera flashes."

I guess it's not surprising that when you put two of the most violent astronomical phenomena together -- the massive hydrogen bomb of novas, and the giant firehose of plasma from a supermassive black hole -- they behave in surprising ways.  The astrophysicists will be working their models trying to figure out just what exactly is going on here.

And for those of you who are worriers, M87 and its accompanying jets of radiation are a comfortable 53 million light years away.  Even our own galactic core is 26,000 light years away, and its radiation jets are aimed in a direction almost exactly ninety degrees away from us; the Solar System lies in one of the outer spiral arms, which are arrayed pretty much in a flat plane perpendicular to the rotational and magnetic axis of the galaxy.

So this phenomenon is certainly awe-inspiring, but it's not dangerous.  At least not to us.  As far as any inhabited planets caught in the outflow, well... good luck to them.

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Vanishing act

In Madeleine L'Engle's seminal young-adult fantasy novel The Wind in the Door, there's something that is making the stars go out.

Not just stop shining, but disappear entirely.  Here's the scene where the protagonist, Meg Murry, first witnesses it happening:

The warm rose and lavender of sunset faded, dimmed, was extinguished.  The sky was drenched with green at the horizon, muting upwards into a deep, purply blue through which stars began to appear in totally unfamiliar constellations.

Meg asked, "Where are we?"

"Never mind where.  Watch."

She stood beside him, looking at the brilliance of the stars.  Then came a sound, a violent, silent, electrical report, which made her press her hands in pain against her ears.  Across the sky, where the stars were clustered as thickly as in the Milky Way, a crack shivered, slivered, became a line of nothingness.

Within that crack, every star that had been there only a moment ago winked out of existence.

A central point in the story is that according to the laws of physics, this isn't supposed to happen.  Stars don't just vanish.  When they end their lives, they do so in an obvious and violent fashion -- even small-mass stars like the Sun swell into a red giant, and eventually undergo core collapse and blow off their outer atmospheres, creating a planetary nebula.  

The Cat's Eye Nebula [Image is in the Public Domain courtesy of NASA/JPL and the ESO]

Larger stars end their lives even more dramatically, as supernovas which lead to the formation of a neutron star or a black hole depending on how much matter is left over once the star blows up.

Well, that's what we thought always happened.

A study out of the University of Copenhagen has found that like in A Wind in the Door, sometimes stars simply... vanish.  A team of astrophysicists has found that instead of the usual progression of Main Sequence > Giant or Supergiant > BOOM! > White Dwarf, Neutron Star, or Black Hole, there are stars that undergo what the astrophysicists are (accurately if uncreatively) calling "complete collapse."  In a complete collapse, the gravitational pull is so high that even considering the power of a supernova, there's just not enough energy available for the outer atmosphere to achieve escape velocity.  So instead of exploding, it just kind of goes...

... pfft.

Unlike what Meg Murry witnessed, though, the matter that formed those stars is still there somewhere; the Law of Conservation of Matter and Energy is strictly enforced in all jurisdictions.  The star that was the focus of the study, VFTS 243, is part of a binary system -- and its companion star continued in its original orbit around their mutual center of mass without so much as a flutter, so the mass of its now-invisible partner is still there.  But the expected cataclysmic blast that usually precedes black hole formation never happened.

"We believe that the core of a star can collapse under its own weight, as happens to massive stars in the final phase of their lives," said Alejandro Vigna-Gómez, who co-authored the study.  "But instead of the contraction culminating into a bright supernova explosion that would outshine its own galaxy, expected for stars more than eight times as massive as the Sun, the collapse continues until the star becomes a black hole.  Were one to stand gazing up at a visible star going through a total collapse, it might, just at the right time, be like watching a star suddenly extinguish and disappear from the heavens.  The collapse is so complete that no explosion occurs, nothing escapes and one wouldn't see any bright supernova in the night sky.  Astronomers have actually observed the sudden disappearance of brightly shining stars in recent times.  We cannot be sure of a connection, but the results we have obtained from analyzing VFTS 243 has brought us much closer to a credible explanation."

You can see why I was immediately reminded of the scene in L'Engle's book.  And while I'm sure the answer isn't evil beings called Echthroi who are trying to extinguish all the light in the universe, the actual phenomenon is still a little on the unsettling side.

Once again showing that we are very far from understanding everything there is out there.  This sort of vanishing act has been high on the list of Things That Aren't Supposed To Happen.  It'll be interesting to see what the theorists propose with when they've had a shot at analyzing the situation, and if they can come up with some sort of factor that determines whether a massive star detonates -- or simply disappears.

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Biggest and brightest

If you're the kind of person who likes having your mind blown by superlatives, astrophysics is the science for you.

I ran into two really good examples of that last week.  In the first, a paper in the journal Monthly Notices of the Royal Astronomical Society, from research led by astrophysicist Ruth Daly of Pennsylvania State University, found that the massive black hole at the center of the Milky Way -- Sagittarius A* -- is spinning so fast it's actually warping the fabric of space time around it, flattening it into the shape of a football.

The "no-hair theorem" of the physics of black holes states that they are rather simple beasts.  They can be completely characterized using only three parameters: their mass, charge, and angular momentum.  The name comes from the quip by physicist John Archibald Wheeler that "black holes have no hair," by which he meant that there are no other adornments you need to describe to get a full picture of what they're doing.  However, I've always been puzzled by what exactly it means to say that a black hole has angular momentum; objects with mass and spin, such as a twirling top or the rotating Earth, have angular momentum, but since the mass in a black hole has (at least as far as we understand them) collapsed into a singularity, what exactly is spinning, and how could you tell?

Last week's paper at least answers the second half of the question.  Using data from x-ray and radio wave collimation and material outflow from Sagittarius A*, astrophysicists can determine how much spacetime is being deformed by the angular momentum of the black hole, and from that determine its rate of spin.

And it's spinning fast -- an estimated sixty percent of the maximum possible rate, which is set by the universal speed limit that matter can't travel at or faster than the speed of light.  The deformation is so great that the fabric of spacetime is compressed along the spin axis, so it appears spherical from above but flattened from the side.

[Image is in the Public Domain courtesy of NASA/JPL]

The second piece of research comes from a study at the European Southern Observatory, and was published in Nature Astronomy.  It looks at the recent discovery of the brightest object known, a quasar (an active galactic nucleus containing a supermassive black hole) that -- get ready for the superlatives -- is five hundred trillion times more luminous than the Sun, contains a black hole that has seventeen billion times the mass of the Sun, and is consuming one Sun's worth of mass a day.  This object, given the unassuming name of J0529-4351, is twelve billion light years away, making it also one of the most distant objects ever studied.

"All this light comes from a hot accretion disk that measures seven light-years in diameter -- this must be the largest accretion disk in the Universe," said study co-author Samuel Lai, of Australian National University.  If he sounds a little blown away by this -- well, so are we all.  A seven-light-year accretion disk means that if it were placed where the Sun is, not only would its accretion disk engulf the entire Solar System, it would extend outward past the five nearest stars -- the triple-star system of Alpha/Proxima Centauri, Barnard's Star, and Luhman 16.

I don't know about you, but something on that scale boggles my mind.

And that's not a bad thing, really.  I think we need to be reminded periodically that in the grand scheme of things, the problems we lose so much sleep over down here are pretty minuscule.  Also, it's good to have our brains overwhelmed by the grandeur of the universe we live in, to be able to look up into the night sky and think, "Wow.  How fortunate I am to be able to witness -- and in some small way, understand -- such wonders."

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The fingerprints of the Manatee

Cosmic ray is a catch-all term for the high-energy particles that constantly bombard the Earth's upper atmosphere.  The majority of them are deflected by the Earth's magnetic field or absorbed by the atmosphere, but a very few are energetic enough to reach the surface of the planet.  About 90% of cosmic rays are protons; a good chunk of the remaining ten percent are alpha particles (helium nuclei, consisting of two protons and two neutrons bound together).  The rest are varying mixes of particles from the subatomic zoo, sometimes even including positrons and antiprotons -- particles of antimatter.  They were discovered in 1912 by Austrian-American physicist Victor Hess in 1912, for which he won the 1936 Nobel Prize in Physics.

The lion's share of cosmic rays that strike the Earth originate from the Sun, but some come from much farther away.  As we've seen here several times at Skeptophilia, the universe is an energetic and often violent place, not lacking in mechanisms for sending bits of matter careening across the universe at a significant fraction of the speed of light.  As you might expect, supernovae produce cosmic rays; so do gamma ray bursters, Wolf-Rayet stars, and quasars.  The last-mentioned are thought to be supermassive black holes surrounded by an inward-spiraling accretion disk of gas and dust, which accelerates as it tumbles toward the event horizon and gives of one final death scream of radiation.  This makes quasars one of the brightest objects in the known universe, with luminosities tens of thousands of times that of the Milky Way.

Trying to pinpoint the origin of particular cosmic rays is tricky.  Being mostly made of charged particles, they're deflected by magnetic fields; so even if you find one and know the direction it was traveling when it hit your detector, you can't just trace the line backwards and assume that's the point in the sky where it originated.  So scientists who are interested in figuring out where the highest-energy cosmic rays come from -- ones that almost certainly weren't created by our placid, stable home star -- have a difficult task.

A team led by Laura Olivera-Nieto of the Max Planck Institute for Nuclear Physics has tackled this problem, and in a paper published last week in Science, came up with an answer for at least some of these mysterious particles.  Working at the High-Energy Stereoscopic System (HESS -- a nice nod to the discoverer of cosmic rays) in Namibia, Olivera-Nieto and her team are studying a curious source of cosmic rays -- black holes that are in a binary system with another star.

The current study is of an object called SS 433, a source of x-rays so powerful it's been nicknamed a "microquasar."  It lies in the middle of the Manatee Nebula in the constellation Aquila, a shell of gas and dust blown outward when a star went supernova between ten and a hundred thousand years ago.  The supernova resulted in a black hole as the doomed star's core collapsed, but its companion star lived on.

The Manatee Nebula [Image credit: B. Saxton, (NRAO/AUI/NSF) from data provided by M. Goss, et al.]

Well, after a fashion.  The enormous gravitational pull of the black hole is siphoning off matter from the companion star, and as that plume of gas spirals inward, it accelerates and gives off radiation -- just as the accretion disk of a quasar does.  The result is a jet of cosmic rays, including not only the typical charged particles but x-rays and gamma rays, which (unlike charged particles) are unaffected by magnetic fields.  This allows astronomers to pinpoint their sources.

So in the midst of this seemingly placid bit of space is a whirling hurricane of gas and dust that is accelerated so strongly it creates jets of particles moving at nearly the speed of light.  (Exactly the speed of light, in the case of the x-rays and gamma rays.)  Some of those particles eventually reach the Earth -- a few of which are picked up by Olivera-Nieto's team at HESS.

And those cosmic rays allows us to discern the fingerprints of an incredibly violent process taking place eighteen thousand light years away.

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