Flash in the pan

"There are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy."

So wrote William Shakespeare in Hamlet, and if anything, it's a significant understatement.  If Shakespeare were writing today, considering recent discoveries in science, he might phrase it as, "Horatio, you seriously have no idea how weird it is out there.  I mean, literally," which gains in accuracy but does lose something in poetic diction.

To take just one example, consider the paper that appeared in Astrophysical Journal Letters this week, about a gamma ray burst that was discovered by the amusingly-named Very Large Telescope (they're currently building a bigger one down in Chile which will be called, I shit you not, the Extremely Large Telescope).  Gamma ray bursts are already pretty astonishing; NASA describes them as "second only to the Big Bang as the most energetic and luminous phenomena known."  There are several possible causes of these enormous releases of high-frequency electromagnetic radiation -- supernovae, the catastrophic merger of neutron stars, and flares from magnetars amongst them.  (You would not want to be looking down the gun barrel of one of these when it went off.  There is some suspicion that the Late Ordovician Mass Extinction -- one of the "Big Five" mass extinctions, and second only to the Permian-Triassic "Great Dying" event in terms of magnitude -- was caused by a nearby gamma ray burst.)

Most of these events are one-offs, and considering the energy they involve (most of them release more energy in a few seconds than the Sun will in its entire lifetime) you can understand why.  After one flare-up of that size, it's unsurprising that it wouldn't do it again any time soon.  So the astrophysicists were puzzled when they found a gamma-ray burster (GRB 250702B) that seems to recur -- it produced a sequence of five flares, and did that entire sequence three times.  Weirdest still, each time, the interval between the second and third flare in the sequence was an integer multiple of the interval between the first two!

What in the hell could cause that?

The gamma-ray burst seems to be extragalactic -- to be coming from a source outside the Milky Way.  The source is near a known galaxy, but whether the burst is coming from within the galaxy, or simply from a source that happens to be lined up with it, hasn't been determined yet.  The galaxy is one of the thousands that have been located by the Hubble and James Webb Space Telescopes but have yet to be studied; they don't even know what its red shift is (which would tell you how far away it is).  But because the red shift of gamma ray bursts is impossible to determine -- to calculate red shift, you need identifiable spectral lines, and those don't occur in something as massive and chaotic as a burst -- this still wouldn't tell you whether the source was actually inside the galaxy or not.

In fact, there's more that's unknown than known about this phenomena.  The periodicity led the researchers to suggest one possibility, that it was some unfortunate massive star in an elliptical orbit around a massive black hole, and having pieces torn off it every time it gets to perihelion.  Another possibility is an "atypical stellar core collapse," which is astrophysics-speak for "a collapsing star where we really have no idea why it's acting like it does."  A third is that the detected periodicity is an artifact caused by "dust echoes" -- reflection of the original gamma-ray burst from concentric shells of dust surrounding the remains of an exploded star.  The final possibility -- at least of the ones the authors came up with -- is that it's an example of gravitational lensing, where light emitted by a star (or other astronomical object) travels close to a black hole, the curved space around the black hole causes the light beam to split along more than one path, and different parts of it arrive at different times.

The paths of light traveling through a gravitational lens [Image is in the Public Domain courtesy of NASA/JPL]

The upshot is that we simply don't know what's going on here.  The authors write:

We have... new, multiwavelength observations of a superlative series of associated GRB triggers, GRB 250702B.  Our observations reveal a rapidly fading, multiwavelength counterpart likely to be embedded in a galaxy with a complex and asymmetric morphology.  We... conclude that GRB 250702B is an extragalactic event.  The relatively bright and extended host suggest the redshift is moderate (z < 1).

GRB 250702B is observationally unprecedented in its timescale, morphology, and the onset of X-ray photons prior to the initial GRB trigger.  In addition, we find a striking, near-integer time step between the GRB outbursts, suggesting (although not proving) possible periodicity in the events.

All of this is absolutely fascinating to the astronomers, because it opens up the perennial question of "Is this a phenomenon we've already seen and know how to explain, or is it actually new physics?"  At present, there's no way to answer this with any certainty.  All that's known is something really weird is going on out there, and we're going to have to do a lot more observation before we'll be able to figure out what the explanation is.

So like I said, Shakespeare was spot-on.  And the more we look out into the skies, the more we find that is Not Dreamt Of In Our Philosophy.  Only now we have astrophysicists working on actually explaining these phenomena -- so perhaps this very peculiar flash-in-the-pan won't remain a mystery forever.

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The lure of the unknown

Carl Sagan once said, "Somewhere, something incredible is waiting to be known."

I think that's one of the main things that attracted me to science as a child; its capacity to astonish.  I still remember reading the kids' books on various scientific stuff and being astounded to find out things like:

• dinosaurs, far from being the "failed experiment" they're often characterized as, "ruled the Earth" (as it were) for about five hundred times longer than humans have even existed.  (I only much later found out that dinosaurs still exist; we call 'em birds.)
• when supergiant stars end their lives, they detonate in a colossal explosion called a supernova that gives off in a few seconds as much energy as the Sun will emit in its entire lifetime.  What's left is called a black hole, where the gravitational pull is so powerful even light can't escape.
• bats can hear in a frequency range far above humans, and are so sensitive to their own vocalizations that they can hear the echoes of their own voices and distinguish them from the cacophony their friends and relatives are making.
• when an object moves, its vertical and horizontal velocities are completely independent of each other.  If you shoot a gun horizontally on a level surface, and simultaneously drop a bullet from the gun's muzzle height, the shot bullet and the dropped bullet will hit the ground at the same time.

And that's all stuff we've known for years, because (not to put too fine a point on it) I'm so old that when I was a kid, the Dead Sea was just sick.  In the intervening fifty years since I found out all of the above (and lots of other similar tidbits) the scientists have discovered tons of new, and equally amazing, information about our universe and how it works.  We've even found out that some of what we thought we understood was wrong, or at least incomplete; a good example is photoperiodism, the ability of flowering plants to keep track of day length and thus flower at the right time of year.  It was initially thought that they had a system that worked a bit like a chemical teeter-totter.  A protein called phytochrome has a "dark form" and a "light form" -- the dark form changes to the light form during the day, and the reverse happens at night, so the relative amounts of the two might allow plants to keep track of day length.  But it turns out that all it takes is a flash of red light in the middle of the night to completely upend the plant's biological clock -- so whatever is going on is more complex that we'd understood.

This sudden sense of "wow, we don't know as much as we thought!", far from being upsetting, is positively thrilling to scientists.  Scientists are some of the only people in the world who love saying, "I don't understand."  Mostly because they always follow it up with "... yet."  Take, for example, the discovery announced this week by the National Radio Astronomy Observatory of a huge cloud of gas and dust in our own Milky Way Galaxy that prior to this we hadn't even known was there.

It's been named the Midpoint Cloud, and it's about two hundred light years across.  It's an enormous whirlpool centered on Sagittarius A*, the supermassive black hole at the galaxy's center, and seems to act like a giant funnel drawing material inward toward the accretion disk.

"One of the big discoveries of the paper was the giant molecular cloud," said Natalie Butterfield, lead author of the paper on the phenomenon, which appeared this week in The Astrophysical Journal.  "No one had any idea this cloud existed until we looked at this location in the sky and found the dense gas.  Through measurements of the size, mass, and density, we confirmed this was a giant molecular cloud.  These dust lanes are like hidden rivers of gas and dust that are carrying material into the center of our galaxy.  The Midpoint Cloud is a place where material from the galaxy's disk is transitioning into the more extreme environment of the galactic center and provides a unique opportunity to study the initial gas conditions before accumulating in the center of our galaxy."

[Image credit: NSF/AUI/NSF NRAO/P.Vosteen]

Among the amazing features of this discovery is that it contains a maser -- an intense, focused microwave source, in this case thought to be caused by compression and turbulence in the ammonia-rich gas of the cloud.  Additionally, there are several sites that seem to be undergoing collapse; we might be witnessing the birth of new stars.

What's astonishing to me is that this cloud is (1) humongous, (2) in our own galaxy, and (3) glowing like crazy in the microwave region of the spectrum, yet no one had any idea it was there until now.  How much more are we overlooking because we haven't tuned into the right frequency or turned our telescopes to the right coordinates?

The universe is a big place.  And, I suspect, it's absolutely full of surprises.  Hell, there are enough surprises lying in wait right here on the Earth; to give just one example, I've heard it said that we know more about the near side of the Moon than we do about the deep oceans.

How could anyone not find science fascinating?

This is also why I've never understood how people think that science's progress could be turned into a criticism -- I used to hear it from students phrased as, "why do we have to learn all this stuff when it could all be proven wrong tomorrow?"  Far from being a downside, science's capacity to update and self-correct is its most powerful strength.  How is it somehow better to cling to your previous understanding in the face of evidence to the contrary?

That, I don't think I'll ever come close to comprehending.

I'll end with another quote from a scientific luminary -- the brilliant physicist Richard Feynman -- that I think sums it all up succinctly: "I'd much rather questions that cannot be answered than answers that cannot be questioned."

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Requiem for a dead planet

If I had to pick my favorite episode of Star Trek: The Next Generation, the clear winner would be "The Inner Light."  Some classic episodes like "Darmok," "Frames of Mind," "Yesterday's Enterprise," "The Offspring," "Cause and Effect," "Remember Me," "Time's Arrow," "The Chase," and "Best of Both Worlds" would be some stiff competition, but "The Inner Light" not only has a beautiful story, but a deep, heartwrenching bittersweetness, made even more poignant by a tour-de-force performance by Patrick Stewart as Captain Jean-Luc Picard.

If you've not seen it, the plot revolves around the Enterprise encountering a huge space station of some kind, of apparent antiquity, and in the course of examining it, it zaps Captain Picard and renders him unconscious.  What his crew doesn't know is that it's dropped him into a dream where he's not a spaceship captain but an ordinary guy named Kamin, who has a wife and children and a job as a scientist trying to figure out what to do about the effect of his planet's sun, which has increased in intensity and is threatening devastating drought and famine.

As Kamin, he lives for forty years, watching his children grow up, living through the grief of his wife's death and the death of a dear friend, and ultimately grows old without ever finding a solution to his planet's dire circumstances.  All the while, the real Captain Picard is being subjected to ongoing interventions by Dr. Crusher to determine what's keeping him unconscious, and ultimately unsuccessful attempts to bring him out of it.  In the end, which makes me ugly cry every damn time I watch it, Kamin lives to watch the launch of an archive of his race's combined knowledge, realizing that the sun's increase in intensity is leading up to a nova that will destroy the planet, and that their civilization is doomed.  It is, in fact, the same archive that the Enterprise happened upon, and which captured Picard's consciousness, so that someone at least would understand what the civilization was like before it was wiped out tens of thousands of years earlier.

"Live now," Kamin says to his daughter, Maribol.  "Make now always the most precious time.  Now will never come again."

And with that, Picard awakens, to find he has accumulated four decades of memories in the space of about a half-hour, an experience that leaves a permanent mark not only on his mind, but his heart.

*brief pause to stop bawling into my handkerchief*

I was immediately reminded of "The Inner Light" by a paper I stumbled across in Nature Astronomy, called, "Alkali Metals in White Dwarf Atmospheres as Tracers of Ancient Planetary Crusts."  This study, led by astrophysicist Mark Hollands of the University of Warwick, did spectroscopic analysis of the light from four white dwarf stars, which are the remnants of stellar cores left behind when Sun-like stars go nova as their hydrogen fuel runs out at the end of their lives.  In the process, they vaporize any planets that were in orbit around them, and the dust and debris from those planets accretes into the white dwarf's atmosphere, where it's detectable by its specific spectral lines.

In other words: the four white dwarfs in the study had rocky, Earth-like planets at some point in their past.

"In one case, we are looking at planet formation around a star that was formed in the Galactic halo, 11-12.5 billion years ago, hence it must be one of the oldest planetary systems known so far," said study co-author Pier-Emmanuel Tremblay, in an interview in Science Daily.  "Another of these systems formed around a short-lived star that was initially more than four times the mass of the Sun, a record-breaking discovery delivering important constraints on how fast planets can form around their host stars."

This brings up a few considerations, one of which has to do with the number of Earth-like planets out there.  (Nota bene: by "Earth-like" I'm not referring to temperature and surface conditions, but simply that they're relatively small, with a rocky crust and a metallic core.  Whether they have Earth-like conditions is another consideration entirely, which has to do with the host star's intrinsic luminosity and the distance at which the planet revolves around it.)  In the famous Drake equation, which is a way to come up with an estimate of the number of intelligent civilizations in the universe, one of the big unknowns until recently was how many stars hosted Earth-like planets; in the last fifteen years, we've come to understand that the answer seems to be "most of them."  Planets are the rule, not the exception, and as we've become better and better at detecting exoplanets, we find them pretty much everywhere we look.

When I read the Hollands et al. paper, I immediately began wondering what the planets around the white dwarfs had been like before they got flash-fried as their suns went nova.  Did they harbor life?  It's possible, although considering that these started out as larger stars than our Sun, they had shorter lives and therefore less time for life to form, much less to develop into a complex and intelligent civilization.  And, of course, at this point there's no way to tell.  Any living thing on one of those planets is long since vaporized along with most of the planet it resided on, lost forever to the ongoing evolution of the cosmos.

If that's not gloomy enough, it bears mention that this is the Earth's ultimate fate, as well.  It's not anything to worry about (not that worry would help in any case) -- this eventuality is billions of years in the future.  But once the Sun exhausts its supply of hydrogen, it will balloon out into a red giant, engulfing the inner three planets and possibly Mars as well, then blow off its outer atmosphere (that explosion is the "nova" part), leaving its exposed core as a white dwarf, slowly cooling as it radiates its heat out into space.

Whether by that time we'll have decided to send our collective knowledge out into space as an interstellar archive, I don't know.  In a way, we already have, albeit on a smaller scale than Kamin's people did; Voyager 2 carries the famous "golden record" that contains information about humanity, our scientific knowledge, and recordings of human voices, languages, and music, there to be decoded by any technological civilization that stumbles upon it.  (It's a little mind-boggling to realize that in the 48 years since Voyager 2 was launched, it has traveled about 20,000,000,000 kilometers, so is well outside the perimeter of the Solar System; and that sounds impressive until you realize that's only 16.6 light hours away, and the nearest star is 4.3 light years from us.)

So anyhow, those are my elegiac thoughts on this August morning.  Dead planets, dying stars, and the remnants of lost civilizations.  Sorry to be a downer. If all this makes you feel low, watch "The Inner Light" and have yourself a good cry.  It'll make you feel better.

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The phantom whirlpool

The universe is a dangerous place.

I'm not talking about crazy stuff happening down here on Earth, although a lot of that certainly qualifies.  The violence we wreak upon each other (and by our careless actions, often upon ourselves) fades into insignificance by comparison to the purely natural violence out there in the cosmos.  Familiar phenomena like black holes and supernovas come near the top of the list, but there are others equally scary whose names are hardly common topics of conversation -- Wolf-Rayet stars, gamma-ray bursters, quasars, and Thorne-Zytkow objects come to mind, not to mention the truly terrifying possibility of a "false vacuum collapse" that I wrote about here at Skeptophilia a while back.

It's why I always find it odd when people talk about the how peaceful the night sky is, or that the glory of the cosmos supports the existence of a benevolent deity.  Impressive?  Sure.  Awe-inspiring?  Definitely.

Benevolent?  Hardly.  The suggestion that the universe was created to be the perfectly hospitable home to humanity -- the "fine-tuning" argument, or "strong anthropic principle" -- conveniently ignores the fact that the vast majority of the universe is intrinsically deadly to terrestrial life forms, and even here on Earth, we're able to survive the conditions of less than a quarter of its surface area.

I'm not trying to scare anyone, here.  But I do think it's a good idea to keep in mind how small and fragile we are.  Especially if it makes us more cognizant of taking care of the congenial planet we're on.

In any case, back to astronomical phenomena that are big and scary and can kill you.  Even the ones we know about don't exhaust the catalog of violent space stuff.  Take, for example, the (thus far) unexplained invisible vortex that is tearing apart the Hyades.

The Hyades is a star cluster in the constellation Taurus, which gets its name from the five sisters of Hyas, a beautiful Greek youth who died tragically.  Which brings up the question of whether any beautiful Greek youths actually survived to adulthood.  When ancient Greeks had kids, if they had a really handsome son, did they look at him and shake their heads sadly, and say, "Well, I guess he's fucked"?

To read Greek mythology, you get the impression that the major cause of death in ancient Greek was being so beautiful it pissed the gods off.

Anyhow, Hyas's five sisters were so devastated by the loss of their beloved brother that they couldn't stop crying, so the gods took pity on them even though Zeus et al. were the ones who caused the whole problem in the first place, and turned them into stars.  Which I suppose is better than nothing.  But even so, the sisters' weeping wouldn't stop -- which is why the appearance of the Hyades in the sky in the spring is associated with the rainy season. (In fact, in England the cluster is called "the April rainers.")

The Hyades [Image licensed under the Creative Commons NASA, ESA, and STScI, Hyades cluster, CC BY-SA 4.0]

In reality, the Hyades have nothing to do with rain or tragically beautiful Greek youths.  They are a group of fairly young stars, on the order of 625 million years old (the Sun is about ten times older), and like most clusters was created from a collapsing clump of gas.  The Hyades are quite close to us -- 153 light years away -- and because of that have been intensively studied.  Like many clusters, the tidal forces generated by the relative motion of the stars is gradually pulling them away from each other, but here there seems to be something else, something far more violent, going on.

A press release from the European Space Agency describes a study of the motion of the stars in the Hyades indicating that their movements aren't the ordinary gentle dissipation most clusters undergo.  A team led by astrophysicist Tereza Jerabkova used data from the European Southern Observatory to map members of the cluster, and to identify other stars that once were part of the Hyades but since have been pulled away, and they found that the leading "tidal tail" -- the streamer of stars out ahead of the motion of the cluster as a whole -- has been ripped to shreds.

The only solution Jerabkova and her team found that made sense of the data is that the leading tail of the Hyades collided -- or is in the process of colliding -- with a huge blob of some sort, containing a mass ten million times that of the Sun.  The problem is, an object that big, only 153 light years away, should be visible, or at least detectable, and there seems to be nothing there.

"There must have been a close interaction with this really massive clump, and the Hyades just got smashed," Jerabkova said.

So what is this "really massive clump" made of?  Given the absence of anything made of ordinary matter that is anywhere nearby, the team suggests that it might be something more exotic -- a "dark matter sub-halo."  These hypothesized objects could be scattered across the universe, and might provide the energetic kick to objects whose trajectories can't be explained any other way. But what exactly they are other than a bizarre phantom gravitational whirlpool, no one knows.

Nor what the risk is if we're close to one.

So add "dark matter sub-halos" to our list of scary astronomical phenomena.  I find the whole thing fascinating, and a little humbling.  I'll still find the beauty of a clear night sky soothing, but that's only if I can get my scientific mind to shut the hell up long enough to enjoy it.  Because the truth is, a lot of those twinkling lights are anything but peaceful.

But I suppose it's still better than the gods killing you if you're too handsome.  That would just suck, not that I personally am in any danger.

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Tense situation

In my Critical Thinking classes, I did a unit on statistics and data, and how you tell if a measurement is worth paying attention to.  One of the first things to consider, I told them, is whether a particular piece of data is accurate or merely precise -- two words that in common parlance are used interchangeably.

In science, they don't mean the same thing.  A piece of equipment is said to be precise if it gives you close to the same value every time.  Accuracy, though, is a higher standard; data are accurate if the values are not only close to each other when measured with the same equipment, but agree with data taken independently, using a different device or a different method.

A simple example is that if my bathroom scale tells me every day for a month that my mass is (to within one kilogram either way) 239 kilograms, it's highly precise, but very inaccurate.

This is why scientists always look for independent corroboration of their data.  It's not enough to keep getting the same numbers over and over; you've got to be certain those numbers actually reflect reality.

This all comes up because of a new look at one of the biggest scientific questions known -- the rate of expansion of the entire universe.

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

A while back, I wrote about some experiments that were allowing physicists to home in on the Hubble constant, a quantity that is a measure of how fast everything in the universe is flying apart.  And the news appeared to be good; from a range of between 50 and 500 kilometers per second per megaparsec, physicists had been able to narrow down the value of the Hubble constant to between 65.3 and 75.6.

The problem is, nobody's been able to get closer than that -- and in fact, recent measurements have widened, not narrowed, the gap.

There are two main ways to measure the Hubble constant.  The first is to use information like red shift, Cepheid variables (stars whose period of brightness oscillation varies predictably with their intrinsic brightness, making them a good "standard candle" to determine the distance to other galaxies), and type 1a supernovae to figure out how fast the galaxies we see are receding from each other.  The other is to use the cosmic microwave background radiation -- the leftovers from the radiation produced by the Big Bang -- to determine the age of the universe, and therefore, how fast it's expanding.

So this is a little like checking my bathroom scale by weighing myself on it, then comparing my weight as measured by the scale at the gym and seeing if I get the same answer.

And the problem is, the measurement of the Hubble constant by these two methods is increasingly looking like it's resulting in two irreconcilably different values.  

The genesis of the problem is that as our measurement ability has become more and more precise, the error bars associated with data collection have shrunk considerably.  And if the two measurements were not only precise, but also accurate, you would expect that our increasing precision would result in the two values getting closer and closer together.

Exactly the opposite has happened.

"Five years ago, no one in cosmology was really worried about the question of how fast the universe was expanding," said astrophysicist Daniel Mortlock of Imperial College London.  "We took it for granted.  Now we are having to do a great deal of head scratching – and a lot of research...  Everyone’s best bet was that the difference between the two estimates was just down to chance, and that the two values would converge as more and more measurements were taken. In fact, the opposite has occurred.  The discrepancy has become stronger.  The estimate of the Hubble constant that had the lower value has got a bit lower over the years and the one that was a bit higher has got even greater."

This discrepancy -- called the Hubble tension -- is one of the most vexing problems in astrophysics today.  Especially given that repeated analysis of both the methods used to determine the expansion rate have resulted in no apparent problem with either one.

The two possible solutions to this boil down to (1) our data are off, or (2) there's new physics we don't know about.  A new solution that falls into the first category was proposed last week at the annual meeting of the Royal Astronomical Society by Indranil Banik of the University of Portsmouth, who has been deeply involved in researching this puzzle.  It's possible, he said, that the problem is with one of our fundamental assumptions -- that the universe is both homogeneous and isotropic.

These two are like the ultimate extension of the Copernican principle, that the Earth (and the Solar System and the Milky Way) do not occupy a privileged position in space.  Homogeneity means that any randomly-chosen blob of space is equally likely to have stuff in it as any other; in other words, matter and energy are locally clumpy but universally spread out.  Isotropy means there's no difference dependent on direction; the universe looks pretty much the same no matter which direction you look.

What, Banik asks, if our mistake is in putting together the homogeneity principle with measurements of what the best-studied region of space is like -- the parts near us?

What if we live in a cosmic void -- a region of space with far less matter and energy than average?

We've known those regions exist for a while; in fact, regular readers might recall that a couple of years ago, I wrote a post about one of the biggest, the Boötes Void, which is so large and empty that if we lived right at the center of it, we wouldn't even have been able to see the nearest stars to us until the development of powerful telescopes in the 1960s.  Banik suggests that the void we're in isn't as dramatic as that, but that a twenty percent lower-than-average mass density in our vicinity could account for the discrepancy in the Hubble constant.

"A potential solution to [the Hubble tension] is that our galaxy is close to the center of a large, local void," Banik said.  "It would cause matter to be pulled by gravity towards the higher density exterior of the void, leading to the void becoming emptier with time.  As the void is emptying out, the velocity of objects away from us would be larger than if the void were not there.  This therefore gives the appearance of a faster local expansion rate...  The Hubble tension is largely a local phenomenon, with little evidence that the expansion rate disagrees with expectations in the standard cosmology further back in time.  So a local solution like a local void is a promising way to go about solving the problem."

It would also, he said, line up with data on baryon acoustic oscillations, the fossilized remnants of shock waves from the Big Bang, which account for some of the fine structure of the universe.

"These sound waves travelled for only a short while before becoming frozen in place once the universe cooled enough for neutral atoms to form," Banik said.  "They act as a standard ruler, whose angular size we can use to chart the cosmic expansion history.  A local void slightly distorts the relation between the BAO angular scale and the redshift, because the velocities induced by a local void and its gravitational effect slightly increase the redshift on top of that due to cosmic expansion.  By considering all available BAO measurements over the last twenty years, we showed that a void model is about one hundred million times more likely than a void-free model with parameters designed to fit the CMB observations taken by the Planck satellite, the so-called homogeneous Planck cosmology."

Which sounds pretty good.  I'm only a layperson, but this is the most optimistic I've heard an astrophysicist get on the topic.  Now, it falls back on the data -- showing that the mass/energy density in our local region of space really is significantly lower than average.  In other words, that the universe isn't homogeneous, at least not on those scales.

I'm sure the astrophysics world will be abuzz with this new proposal, so keep your eyes open for developments.  Me, I think it sounds reasonable.  Given recent events here on Earth, it's unsurprising the rest of the universe is rushing away from us.  I bet the aliens lock the doors on their spaceships as they fly by.

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The edges of knowledge

The brilliant British astrophysicist Becky Smethurst said, "The cutting edge of science is where all the unknowns are."  And far from being a bad thing, this is exciting.  When a scientist lands on something truly perplexing, that opens up fresh avenues for inquiry -- and, potentially, the discovery of something entirely new.

That's the situation we're in with our understanding of the evolution of the early universe.

You probably know that when you look out into space, you're looking back into time.  Light is the fastest information carrier we know of, and it travels at... well, the speed of light, just shy of three hundred thousand kilometers per second.  The farther away something is, the greater the distance the light had to cross to get to your eyes, so what you're seeing is an image of it when the light left its surface.  The Sun is a little over eight light minutes away; so if the Sun were to vanish -- not a likely eventuality, fortunately -- we would have no way to know it for eight minutes.  The nearest star other than the Sun, Proxima Centauri, is 4.2 light years away; the ever-intriguing star Betelgeuse, which I am so hoping goes supernova in my lifetime, is 642 light years away, so it might have blown up five hundred years ago and we'd still have another 142 years to wait for the information to get here.

This is true even of close objects, of course.  You never see anything as it is; you always see it as it was.  Because right now my sleeping puppy is a little closer to me than the rocking chair, I'm seeing the chair a little further in the past than I'm seeing him.  But the fact remains, neither of those images are of the instantaneous present; they're ghostly traces, launched at me by light reflecting off their surfaces a minuscule fraction of a second ago.

Now that we have a new and extremely powerful tool for collecting light -- the James Webb Space Telescope -- we have a way of looking at even fainter, more distant stars and galaxies.  And as Becky Smethurst put it, "In the past four years, JWST has been taking everything that we thought we knew about the early universe, and how galaxies evolve, and chucking it straight out of the window."

In a wonderful video that you all should watch, she identifies three discoveries JWST has made about the most distant reaches of the universe that still have yet to be explained: the fact that there are many more large, bright galaxies than our current model would predict are possible; that there is a much larger amount of heavy elements than expected; and the weird features called "little red dots" -- compact assemblages of cooler red stars that exhibit a strange spectrum of light and evidence of ionized hydrogen, something you generally only see in the vicinity hot, massive stars.

Well, she might have to add another one to the list.  Using data from LOFAR (the Low Frequency Array), a radio telescope array in Europe, astrophysicists have found bubbles of electromagnetic radiation surrounding some of the most distant galaxies, on the order of ten billion light years away.  This means we're seeing these galaxies (and their bubbles) when the universe was only one-quarter of its current age.  These radio emissions seem to be coming from a halo of highly-charged particles between, and surrounding, galaxy clusters, some of the largest structures ever studied.

[Image credit: Chandra X-ray Center (X-ray: NASA/CXC/SAO; Optical: NASA/ESA/STScI; Radio: ASTRON/LOFAR; Image Processing: NASA/CXC/SAO/N. Wolk)

"It's as if we've discovered a vast cosmic ocean, where entire galaxy clusters are constantly immersed in high-energy particles," said astrophysicist Julie Hlavacek-Larrondo of the Université de Montréal, who led the study.  "Galaxies appear to have been infused with these particles, and the electromagnetic radiation they emit, for billions of years longer than we realized...  We are just scratching the surface of how energetic the early Universe really was.  This discovery gives us a new window into how galaxy clusters grow and evolve, driven by both black holes and high-energy particle physics."

Every once in a while I'd have a student tell me, in some disdain, "I don't know why we have to learn science when it could all be proven wrong tomorrow."  My response to that is that science's ability to self-correct is a strength, not a weakness.  How is desperately hanging on to your prior understanding when you're presented with new evidence a good thing?   People like to be sure of everything, but really, are we ever?  Nothing is ever absolutely settled; we sometimes kid ourselves that we've found The Answer, but that's honestly a response born of a combination of insecurity and the desire not to think about the matter any more.

Richard Feynman, in his wonderful book The Pleasure of Finding Things Out, summarized this brilliantly:

There is no learning without having to pose a question.  And a question requires doubt.  People search for certainty.  But there is no certainty.  People are terrified — how can you live and not know?  It is not odd at all.  You only think you know, as a matter of fact.  And most of your actions are based on incomplete knowledge and you really don't know what it is all about, or what the purpose of the world is, or know a great deal of other things.  It is possible to live and not know.

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Signals from the ice

I was maybe sixteen years old when I first read H. P. Lovecraft's atmospheric and terrifying short story "At the Mountains of Madness."  Unique amongst his fiction, it's set in Antarctica, which I thought was an odd choice; just about everything else I'd read by him was set somewhere in his home territory of New England.  But as I read, I realized what a good decision that was.  There's something inherently alien about the southernmost continent that makes it the perfect place for a spooky story.  Lovecraft writes:

The last lap of the voyage was vivid and fancy-stirring, great barren peaks of mystery looming up constantly against the west as the low northern sun of noon or the still lower horizon-grazing southern sun of midnight poured its hazy reddish rays over the white snow, bluish ice and water lanes, and black bits of exposed granite slope.  Through the desolate summits swept raging intermittent gusts of the terrible antarctic wind, whose cadences sometimes held vague suggestions of a wild and half-sentient musical piping, with notes extending over a wide range, and which for some subconscious mnemonic reason seemed to me disquieting and even dimly terrible.

Of course, being a Lovecraft story, the intrepid band of geologists and paleontologists who are the main characters make discoveries in Antarctica that very quickly lead them to regret ever going there.  Of the two who survive to the very end, one is clearly headed for a padded cell and a jacket with extra-long sleeves, and the other only marginally better-off.

Happy endings were never Lovecraft's forte.

[Image licensed under the Creative Commons Jerzy Strzelecki, Antarctica(js) 32, CC BY-SA 3.0]

The topic comes up because of a link sent to me by a dear friend and loyal reader of Skeptophilia about a peculiar discovery by some scientists working on a different kind of antarctic research -- astrophysics.  The project is called ANITA -- the Antarctic Impulsive Transient Antenna -- and is designed to detect neutrinos, those ghostly, fast-moving particles that were predicted by Wolfgang Pauli in 1930 based on the fact that momentum and spin seemed not to be conserved in beta decay, so there must be an additional undetected particle to (so to speak) make the equation balance.  Even knowing that it must be there, it still took twelve more years to detect it directly, because it almost never interacts with matter; neutrinos can (and do) pass all the way through the Earth unimpeded.

This is why the experiment is sited in such a remote place.  Signals from actual neutrino capture are so rare that if you put your detection apparatus in an area with lots of human-created electromagnetic noise, you'd never see them.

"You have a billion neutrinos passing through your thumbnail at any moment, but neutrinos don’t really interact," said Stephanie Wissel, of Pennsylvania State University, who leads the ANITA project.  "So, this is the double-edged sword problem.  If we detect them, it means they have traveled all this way without interacting with anything else."

Like Lovecraft's researchers, though, the ANITA team found something they weren't looking for -- and something they have yet to explain.

Fortunately for Wissel and her colleagues, it wasn't a bunch of Shoggoths waiting to tear them limb from limb.

It was radio signals that seemed to be coming from beneath the ice sheet.

"We have these radio antennas on a balloon that flies forty kilometers above the ice in Antarctica," Wissel said.  "We point our antennas down at the ice and look for neutrinos that interact in the ice, producing radio emissions that we can then sense on our detectors.  During those sweeps, we recorded a series of radio pulses.  However, unlike the expected detection of neutrino interactions caused by cosmic neutrinos, we saw bizarre radio pulses originating from the other direction...  The radio waves that we detected were at really steep angles, like thirty degrees below the surface of the ice."

What's weird is that although the neutrinos themselves can pass through huge, massive objects without being bothered, radio waves can't.  So whatever is causing the radio waves really does seem to be under the ice sheet -- but not very far under the ice sheet.

At the moment, the researchers have no good explanation for the detection, which they are calling "anomalous."

"My guess is that some interesting radio propagation effect occurs near ice and also near the horizon that I don’t fully understand, but we certainly explored several of those, and we haven’t been able to find any of those yet either," Wissel said.  "So, right now, it’s one of these long-standing mysteries."

Well, "the scientists can't explain it" opens the doors for the wackos to say "... but we can!"  I snooped a little around some of the sketchier subreddits and YouTube channels -- not a task recommended for the faint of heart -- and I'm already seeing the following:

• It's an auto-transmitter left over from an abandoned Nazi base.  Or... maybe... one that isn't abandoned.  *meaningful eyebrow raise*
• It's a relay station operated by the Illuminati.  One person recommended that the ANITA team get the hell out for their safety's sake, because "these people don't like anyone knowing of their existence."
• It's a leaking signal from inside the "hollow Earth."  So there must be an opening into the interior nearby, which the ANITA team should focus on finding.
• Something about the Schumann Resonance that was about ten paragraphs long, and which I tried unsuccessfully to paraphrase.  The best I can come up with is "weird cosmic shit is happening and the Earth is responding."
• Aliens.  (You knew they'd come up.)

Okay, folks, can we just hang on a moment?

"We don't know" means... "we don't know."  As astrophysicist Neil deGrasse Tyson put it, "If it's unidentified, then that's where the conversation should stop.  You don't go on and say 'so it must be' anything."  And call me narrow-minded, but I'm content to wait for the actual scientists to figure out what's going on here rather than listening to a bunch of wackos who are using an anomalous radio signal to support whatever particular brand of lunacy they happen to favor.

And I can guarantee that whatever it turns out to be, it won't be a Nazi Illuminati radio transmitter tuned by aliens to the Schumann Resonance sending signals from inside the hollow Earth.

So what we have here is a curious and unexpected detection of a radio signal that is currently unexplained, but probably will be at some point.  This is one of the exciting things about science, isn't it?  Stumbling upon something you didn't even know was there.  These sorts of discoveries often open up new avenues of research, and sometimes (albeit rarely) can completely turn our models on their heads.

Wissel and her team have some exciting times ahead.

Me, I'd just as soon watch their progress from a distance, however.  I do not like being cold.  I've found Antarctica fascinating for a very long time, but I don't know if I'd ever be brave enough to go there.

And that's not even counting the danger of being mauled by Shoggoths, which I'm sure would ruin your day.

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The signature

As much as I love the movie Contact, trying to find extraterrestrial life isn't just a matter of tuning in to the right radio frequency.

There's no guarantee that even intelligent life would use radio waves to communicate, and if they did, that they'd do it in such a way that we could decipher the message.  I must admit, though, that the whole "sequence of prime numbers" thing as a beacon was a pretty cool idea; it's hard to imagine a natural phenomenon that would result in blips in a pattern of prime numbers.

Even besides the issue with how exactly a technological species would choose to communicate, there's the problem that this method would miss the vast majority of life that's potentially out there.  Consider the fact that there's been life on Earth for 3.8 billion years, give or take a day or two, and until about a hundred years ago, we weren't producing any radio waves ourselves.  To a civilization two hundred light years away -- so, seeing us as we were two hundred years ago -- Earth would be, to borrow C. S. Lewis's pithy phrase, a completely silent planet, even though there was a thriving biosphere that included at least one intelligent, soon-to-be-technological species.

So except for those presumably few planets that host intelligent beings who communicate kind of like we do, detecting extraterrestrial life is a tricky question.  The most promising approach has been to look for biosignatures -- chemical traces that (as far as we know) can only be produced by living things.  One example on Earth is the fact that our atmosphere contains both oxygen and methane.  Both are highly reactive (especially with each other); to keep stable levels of these gases in the atmosphere requires that something is continuously producing them, because they're constantly being removed by oxidation/reduction reactions.  In this case, photosynthesis and bacterial methanogenesis, respectively, pump them into the atmosphere as fast as they're being destroyed, so the levels remain relatively stable over time.

Two other chemicals that, on the Earth at least, are entirely biological in origin are dimethyl sulfide and dimethyl disulfide.  You've undoubtedly encountered these before; they're partly responsible for the unpleasant smell when you cook cabbage.  They're produced by a variety of living things, including bacteria, plants, and fungi -- dimethyl sulfide is what truffle-hunting pigs are homing in on when they're after truffles. 

Well, data from the James Webb Space Telescope showed that an exoplanet called K2-18b has measurable quantities of both dimethyl sulfide and dimethyl disulfide -- to the point that even the astronomers, who ordinarily have zero patience with the "It's aliens!" crowd, are saying "this is the strongest hint yet of biological life on another planet."

So far, the spectroscopic data that found the chemicals is at a significance level of "3-sigma" -- meaning there's a 0.3% chance that the signal was a statistical fluke (or, put another way, a 99.7% chance that it's the real deal).  It's exciting, but we've seen 3-sigma data do a faceplant before, so I'm trying to restrain myself.  Generally 5-sigma -- a 0.00006% chance of it being a fluke -- is the standard for busting out the champagne.  But even so, this is pretty amazing.

K2-18b is 124 light years away, and is thought to be a "Hycean world" -- an ocean-covered world with a thick, hydrogen-rich atmosphere.  So whatever life is there is very likely to be marine.  But even if we're not talking about your typical Star Trek-style planet with lots of rocks and an orange sky and aliens that look like humans but with rubber facial appendages, the levels of DMS and DMDS suggest a thriving biosphere.

"Earlier theoretical work had predicted that high levels of sulfur-based gases like DMS and DMDS are possible on Hycean worlds," said Nikku Madhusudhan of Cambridge University, who co-authored the study, which appeared this week in Astrophysical Journal Letters.  "And now we've observed it, in line with what was predicted. Given everything we know about this planet, a Hycean world with an ocean that is teeming with life is the scenario that best fits the data we have."

The issue, of course, is not just the statistical significance; 99.7% seems pretty good to me, even if it doesn't satisfy the scientists.  The problem is that sneaky little phrase that was in my description of biosignatures earlier; "as far as we know."  We don't know of a way to produce DMS and DMDS in significant quantities except by biological processes, but that doesn't mean one doesn't exist.  It could be that in the weird chemical soup on an planet in another star system, there's an abiotic way to produce a stable amount of these two compounds, and we just haven't figured it out yet.

Be that as it may, it's still pretty damn exciting.  It's certainly the closest we've gotten to "there's life out there."  And being only 124 light years away -- in our stellar neighborhood, really -- it's right there for us to study more intensively.  Which the astronomers will definitely be doing.

So that's our cool news for today.  I don't know about you, but now I'm daydreaming about what kind of life there might be on a world entirely covered by water.  I'm sure that whatever they are, they'll be "forms most beautiful and most wonderful" beyond Charles Darwin's wildest dreams.

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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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