Worlds in collision

In 2021, University of Washington astronomer Anastasios (Andy) Tsanidakis was reviewing data collected by the European Space Agency's Gaia Mission, and discovered something really strange.

An ordinary, Sun-like star called Gaia20ehk -- eleven thousand light years away in the constellation Puppis -- had, up until 2016, a nearly flat energy output.  This is more or less what our Sun would look like from that distance; yes, there are minor fluctuations, but (fortunately for us) it's pretty stable over short time intervals.

Then... well, here it is in Tsanidakis's words: "The star's light output was nice and flat, but starting in 2016 it had these three dips in brightness," he said.  "And then, right around 2021, it went completely bonkers.  I can't emphasize enough that stars like our Sun don't do that.  So when we saw this one, we were like 'Hello, what's going on here?'"

The chaotic fluctuations in energy output were across the electromagnetic spectrum, but strongest in the infrared region.  And stranger still, a more detailed analysis showed that the peculiar behavior was not from the star itself, but because there was -- suddenly -- a huge, irregular debris cloud surrounding it.  This rock and dust eclipsed the star's light, but some of it was apparently radiating itself, accounting for the wild yo-yoing in the infrared.  "The infrared light curve was the complete opposite of the visible light," Tzanidakis said.  "As the visible light began to flicker and dim, the infrared light spiked.  Which could mean that the material blocking the star is hot -- so hot that it's glowing in the infrared."

Tsanidakis and his team figured out that there was only one phenomenon that fit all the observations; two of Gaia20ehk's planets had collided with each other.

"It's incredible that various telescopes caught this impact in real time," Tzanidakis said.  "There are only a few other planetary collisions of any kind on record, and none that bear so many similarities to the impact that created the Earth and Moon.  If we can observe more moments like this elsewhere in the galaxy, it will teach us lots about the formation of our world."

Artist's rendition of the collision of the two planets in the Gaia20ehk system [Image credit: A. Tsanidakis et al.]

Tsandiakis and his colleagues are particularly interested in watching how this all plays out, because -- as he mentioned -- it is very similar to the process that is thought to have formed the Moon.  The collision between the proto-Earth and a Mars-sized planet astronomers call Theia, something like 4.5 billion years ago, triggered the remelting of the entire combined mass; the energy of the collision sheared off a chunk of Theia, which collapsed into what would eventually become the Moon.  Now that we've actually seen something similar happening in another star system, astronomers will be on the lookout for more events like this.

"How rare is the event that created the Earth and Moon?  That question is fundamental to astrobiology," said James Davenport, senior author of the paper, which was published three days ago in Astrophysical Journal Letters.  "It seems like the Moon is one of the magical ingredients that makes the Earth a good place for life.  It can help shield Earth from some asteroids, it produces ocean tides and weather that allow chemistry and biology to mix globally, and it may even play a role in driving tectonic plate activity.  Right now, we don't know how common these dynamics are.  But if we catch more of these collisions, we'll start to figure it out."

Tsanidakis explains that while collisions are probably common in the early history of a stellar system, they can still occur in systems with stable, middle-aged stars like Gaia20ehk.  Near passes by other stars, or by rogue exoplanets, could destabilize planetary orbits, causing one of the system's planets either to be ejected, or (in this case) gradually to spiral inward.  This could explain the three dips in brightness that was his first clue something odd was happening -- they represent grazing passes as the two planets' orbits overlapped more and more.  But eventually, they got close enough that there was a head-on impact, and all hell broke loose.

Considering the quantity of data that missions like Gaia produce, I find it astonishing that Tsanidakis and his colleagues even picked up on it.  You have to wonder what other wonders might be hidden in the enormous hauls from JWST, Hubble, and (soon) the Vera Rubin Telescope.  Fortunately, a sharp-eyed astronomer caught this one, and as a result we've learned a huge amount about exoplanetary collisions.

It's staggering to think about.  The awe-inspiring vistas we're seeing through our best telescopes are only now being studied and analyzed, and who knows what else the astronomers will find?

All from following astrophysicist Neil deGrasse Tyson's adjuration -- "Keep looking up."

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Relics of a lost planet

It took astronomers a good long while to figure out how the Moon formed.

Some initial working models were found, upon analysis to... well, not work.  One early idea was that what is now the Moon sheared away from the Earth while it was molten because of centrifugal force, but the viscosity of molten rock is too high (or the rotational speed of the Earth is way too low) for that to be feasible.  Another possibility was the gravitational capture of a pre-formed body, but that makes it hard to explain the Moon's nearly perfect circular orbit.  (Captured objects -- a likely candidate is Neptune's moon Nereid -- tend to have highly elliptical orbits and/or orbits not parallel to their host planet's rotation, because there's no reason to suppose that their capture occurred at any particular angle.)

A big clue came from isotopic analysis of lunar rocks, which found that the ratios of isotopes for several different elements were nearly identical to terrestrial rocks, arguing for a common source.  The prevailing theory is that the Moon formed when, about 4.5 billion years ago, the proto-Earth was struck by a Mars-sized planet -- named Theia, after the Greek Titan who was the mother of Selene, the goddess of the Moon -- which caused a blob of material to shear away, propelling it into orbit where it coalesced into what we see today on a clear night.

Artist's depiction of the collision between Theia and the proto-Earth [Image is in the Public Domain courtesy of NASA/JPL]

The reason the topic comes up is because of a paper that appeared this week in Nature that I found out about from a friend and loyal reader of Skeptophilia.  A team led by geophysicist Qian Yuan of Arizona State University took a look at two large low-velocity provinces (LLVPs) in the Earth's lower mantle -- dense regions where seismic waves slow down, and which are hypothesized to have a significantly higher iron oxide content than the rest of the mantle -- and their models support the astonishing idea that these are the remnants of Theia.

It's wild that there are still relics discernible, between the violence of the collision and the fact that 4.5 billion years have passed since it happened.  You'd think this would be plenty enough time to stir the mantle and homogenize the material Theia brought in with whatever was present in the proto-Earth.  But Yuan et al. think that the collision's energy was mostly dissipated into the upper mantle, allowing the remnants of Theia's core to sink into the lower mantle without mixing completely -- where the pieces are still detectable today.

Like all good science, the Yuan et al. paper raises some interesting questions, such as what effect the collision had on the rest of Earth's evolution.  "A logical consequence of the idea that the LLVPs are remnants of Theia is that they are very ancient," said Paul Asimow, of the California Institute of Technology and senior author of the paper, in an interview with Science Daily.  "It makes sense, therefore, to investigate next what consequences they had for Earth's earliest evolution, such as the onset of subduction before conditions were suitable for modern-style plate tectonics, the formation of the first continents, and the origin of the very oldest surviving terrestrial minerals."

So that's today's cool scientific research, which I can say without fear of contradiction is pretty close to earthshattering.  Think about that next time you see our companion's ghostly white light in the night sky -- that despite its tranquil appearance, it may well have been born from a collision of almost unimaginable violence, billions of years ago.

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Collision of worlds

Recently I've done posts about exploding lakes and colossal solar storms and places where continents are being torn in two, so it seems fitting to end the week on an appropriately cataclysmic note with the discovery of the remnants of a collision between two giant ice planets.

The coolest part of all of this is that one of the people who first realized something weird was going on was an amateur astronomer named Arttu Sainio, of Järvenpää, Finland (who is listed as an author and credited as "Independent Researcher" in the paper that appeared in Nature this week -- how awesome is that?).  Matthew Kenworthy, of Leiden Observatory, was scouring the data looking for evidence of rings around stars that might be involved in planet formation, which would be indicated by a periodic dimming and brightening of the light from the parent star.  Kenworthy found a candidate -- a sunlike star called ASASSN-21qj, 1,800 light years from Earth -- and posted his find on Twitter, saying, "It's amazing, this star is fading!"  Sainio saw his tweet and responded, "But did you know that it is brightening in the infrared?"

Sainio had been looking at data from NASA's NEOWISE orbiting telescope, and found that nine hundred days before the star had begun dimming, it had shown a strong uptick in the infrared region of the spectrum.  This clued in Kenworthy that his hopes of finding a ring were dashed -- but that maybe there was something even cooler going on here.

He assembled a team of astronomers to analyze the data, including Sainio's peculiar discovery, and they came to the conclusion that the best explanation for the anomalous brightening in the infrared and dimming in the visible light region was the collision of two Neptune-sized planets -- leaving an incandescent cloud of debris orbiting the star which radiated in the infrared as the heat from the collision dissipated, but partially blocked the star's visible light at the same time.

Artist's conception of the planetary collision around ASASSN-21qj [Image courtesy of artist Mark Garlick]

What will happen to the debris cloud next is a matter of speculation, because this is the first time anyone's seen an event like this occur.  While planetary collisions aren't uncommon -- our own Moon, for example, is thought to have formed when a huge protoplanet slammed into the Earth, blowing a blob of molten rock into space that eventually coalesced as the Moon -- no one's ever watched it happen more-or-less in real time.  It's probable that the debris will pull together gravitationally and eventually form one or more planets, but there's no certainty about how long that'll take.

"It will be fascinating to observe further developments," said Zoe Leinhardt, of the University of Bristol, who co-authored the paper.  "Ultimately, the mass of material around the remnant may condense to form a retinue of moons that will orbit around this new planet, but whether that will take ten years or a thousand, we don't yet know."

So a sharp-eyed amateur astronomer tipped off a whole bunch of professional astronomers and astrophysicists to take a closer look at a star that was behaving oddly, and ended up discovering something no one had ever seen happening before.  Just goes to show what a dedicated enthusiast can accomplish.  I've often felt awkward about my lack of credentials in the field I worked in -- I taught biology for over three decades with a bachelor's degree in physics and a master's in historical linguistics -- but I suppose there's nothing wrong with being a deeply curious, passionate-if-uncredentialed amateur.

Dilettantes FTW!

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Life out of catastrophe

After yesterday's post about mysterious explosions in distant galaxies, today I want to look at a colossal explosion that happened much, much closer to home -- and may have jump-started life on Earth.

In a paper by Steven Benner of the Foundation for Applied Molecular Evolution in Alachua, Florida, presented at a conference last fall in Atlanta, we find out that there's geological evidence that early in Earth's history, there may have been a collision with an enormous object -- by some estimates, the size of the Moon -- that drastically altered the atmosphere.  4.47 billion years ago, only sixty million years after the Earth coalesced from the ring of planetary debris where it originated, it was struck so hard by planetoid that water molecules were ripped apart into oxygen and hydrogen, and superheated metallic debris was flung into the air and generated a torrential rain of molten iron.

Artist's conception of what the collision might have looked like from space

As the atmosphere (and everything else) cooled, the highly reactive oxygen bound to the iron, forming a thick layer of iron (and other metal) oxides that explains their prevalence in the Earth's crust today.  More interesting still is that the collision left behind the hydrogen in the atmosphere.  This created what is called a reducing atmosphere -- a collection of gases with an abundance of free electrons, essentially the opposite of what we have today (an oxidizing atmosphere, where oxygen and other electronegative elements mop up any available electrons, making organic matter and other reduced compounds fall apart).

The reducing atmosphere, Benner says, stuck around for two hundred million years, and it was during this time that the first organic compounds were formed.  This lines up neatly with the famous Miller-Urey experiment, where biochemists Stanley Miller and Harold Urey of the University of Chicago showed back in 1952 that in the presence of reducing gases and a source of energy, organic compounds formed readily, including DNA and RNA nitrogenous bases, amino acids, and simple sugars.

Benner believes that the critical one was RNA.  RNA is (as far as we know) unique in that it can not only replicate itself, it's autocatalytic -- it can catalyze its own reactions.  This pull-yourself-up-by-your-shoelaces ability is why a lot of scientists believe that the first genetic material was RNA, not the (currently) more ubiquitous DNA.  And Benner's theory about how the reducing atmosphere was generated explains not only how the building blocks of RNA could have formed, but why the Earth's atmosphere was reducing in the first place.

Benner believes the key is a set of biochemical reactions that involves repeated wetting and drying, along with interaction of the oxygen-free atmosphere with sulfur-containing gases released from volcanic eruptions.  He has demonstrated that in these conditions, formaldehyde -- CH₂O, one of the simplest organic compounds, would form "by the metric ton."  From there, reactions with the sulfur-bearing gases produced hydroxymethanesulfonate, which reacts readily to form glyceraldehyde (a simple sugar) and the four bases of RNA, adenine, cytosine, guanine, and uracil.

Once that happens, the autocatalytic ability of RNA means you're off to the races.  As Richard Dawkins pointed out in his tour-de-force The Blind Watchmaker, if you have two things -- an imperfect replicator, and a selecting mechanism -- you can generate order from disorder in the blink of an eye.  "[M]any experiments have confirmed that once RNA chains begin to grow, they can swap RNA letters and even whole sections with other strands, building complexity, variation, and new chemical functions," said science journalist Robert F. Service, writing for Science magazine.  "[T]he impact scenario implies organic molecules, and possibly RNA and life, could have originated several hundred million years earlier than thought.  That would allow plenty of time for complex cellular life to evolve by the time it shows up in the fossil record at 3.43 billion years ago."

This research not only confirms what Miller and Urey showed in their landmark experiment 67 years ago, but lines up beautifully with what is known from studies by geologists of the earliest rocks.  As for Benner, he's ready to put aside any doubt.  When Ramon Brasser, paleogeologist at the Tokyo Institute of Technology, laid out a timeline of the early Earth in his talk at the Atlanta conference, Benner asked him when the atmosphere would have likely dropped below a temperature of 100 C, the boiling point of water.  Brasser indicated a point about fifty million years after the impact with the planetoid.

"That's it, then!" Benner said excitedly, pointing to a spot at about 4.35 billion years ago on the timeline.  "Now we know exactly when RNA emerged. It's there—give or take a few million years."

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This week's Skeptophilia book recommendation is a little on the dark side.

The Radium Girls, by Kate Moore, tells the story of how the element radium -- discovered in 1898 by Pierre and Marie Curie -- went from being the early 20th century's miracle cure, put in everything from jockstraps to toothpaste, to being recognized as a deadly poison and carcinogen.  At first, it was innocent enough, if scarily unscientific.  The stuff gives off a beautiful greenish glow in the dark; how could that be dangerous?  But then the girls who worked in the factories of Radium Luminous Materials Corporation, which processed most of the radium-laced paints and dyes that were used not only in the crazy commodities I mentioned but in glow-in-the-dark clock and watch dials, started falling ill.  Their hair fell out, their bones ached... and they died.

But capitalism being what it is, the owners of the company couldn't, or wouldn't, consider the possibility that their precious element was what was causing the problem.  It didn't help that the girls themselves were mostly poor, not to mention the fact that back then, women's voices were routinely ignored in just about every realm.  Eventually it was stopped, and radium only processed by people using significant protective equipment,  but only after the deaths of hundreds of young women.

The story is fascinating and horrifying.  Moore's prose is captivating -- and if you don't feel enraged while you're reading it, you have a heart of stone.

[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]

End of the world, episode #452

I hate to be the bearer of bad tidings, but we're all gonna die.

Again.

I mean, what is this?  This 452nd time this has happened, or something?  Between Mayan apocalypses and Christian End Times predictions and the planet Nibiru and plagues and pandemics and the Harmonic Convergence and the Yellowstone Supervolcano (which is still overdue for an eruption!), it's kind of surprise we're all still here.

This time, the world is going to end because we're going to be destroyed by a rogue planet that is hurtling in toward the inner Solar System at a speed of 200 kilometers per second.  So says a report on Turner Radio Network, which claims that "Dr. Kaplan, a Professor in the Astronomy Department at the University of Texas at Austin" has discovered a large object that is heading toward us -- and that even if it doesn't hit us directly, "the gravity will affect the Earth in terrible ways long before it gets here."

[image courtesy of NASA and the Wikimedia Commons]

Dr. Kaplan made a video (linked on the website) wherein he projected the planet's arrival time as August 2014, which is the only thing I find that is cheerful about this prediction.  It gives me the summer to recover from the progressive hypothermia I've experienced this winter, so at least I'll finally be comfortably warm by the time I get vaporized.  And it also means that whatever else happens, I won't have to endure another upstate New York winter, because interaction with the planet will cause "shifting of the tectonic plates on a massive scale."  I can only hope that our tectonic plate will shift toward the equator.  If that's an outcome of a planetary collision, then all I can say is, bring it on, because I have had it with the snow.

Of course, the other predictions are more dire.  "(I)f Kaplan's scenario is true, the problems Earth will experience would begin with weather anomalies and tidal anomalies, will increase to earthquakes then volcanic eruptions as Earth's magma is pulled by the gravity of the approaching planet," the Turner Radio Broadcast report said.  "The experts went on to tell us the troubles would increase further to horrific tsunamis 1000 meters high, moving at 1200 kilometers per hour striking coastal regions around the Earth...  One expert even claimed that depending upon the size and gravity of the planet, and its angle of approach, the gravity of this other planet could actually STOP the Earth from rotating on its axis.  He likened it to a vehicle traveling at 1,000 miles per hour, and having the brakes slammed on; the resulting inertia of all objects on earth would cause them to continue moving while the earth was stopping; sort of like what happens in a car wreck when the car suddenly stops, but the passengers fly forward from their own inertia."

So that kind of sucks.  And after the article goes into all of that, they ask a few pertinent questions, such as "Could a planet be moving this fast?" (Yes), "Can gravity affect things at large distances?" (Yes), and "Isn't all of this pretty damn scary?" (Yes).

But then, after all of this terrifying talk, Turner Radio Network posted an update that suggested that a few teensy details about the foregoing story might be factually inaccurate.  First, (Kyle) Kaplan is a graduate student, not a professor of astronomy.  Second, he posted a second video in which he retracted what he'd said in the first, saying it was "a joke."

The most amazing part of all of this is that Turner Radio Network printed Kaplan's retraction, and posted a link to the video, and then said that they didn't believe his retraction.  Yes, you read that right; given the choice between (1) there being a huge rogue planet heading toward Earth, which was only observed by one graduate student amongst all of the astronomers in the world, and (2) some dumb college guy decided to play a prank and it got out of hand, they decided that scenario #1 was more likely.  "Who would want it retracted and why?" the TRN writer said, his eyebrows wiggling in a significant fashion.  "Well, if people think they're doomed, they may stop paying their taxes and their bills; there may be widespread panic and a breakdown of social order to the point of chaos.  The powers that be can't have any of THAT, can they?"

No.  They can't.  So our only other option is that a giant planet is going to hit the Earth this August.  q.e.d.

They end, though, with asking the right question: "Is this a HOAX?????? That's easy for all of you to verify: Grab a telescope and look at the coordinates yourself.  If there's a planet there, and you see it getting larger (i.e. closer) over a few nights, then this is real and we've got potential problems."  They give the planet's position -- at least as of a couple of days ago -- as Right Ascension: 04 hrs. 08 Min. 08 Sec.; Declination: 60 degrees 56 arc min. 43 arc sec.  So it should be easy enough to check.  It's sort of like the joke:  "I asked myself, 'Why is the baseball getting bigger?'  Then it hit me."

Me, I'm not losing sleep over it.  If there really were a planet heading our way, one or two other astronomers would have had a thing or two to say about it by now.  I'm just adding this as line #452 on the list of End of the World Predictions Wherein the World Did Not End, and sitting back and having a beer and waiting for #453.  I think the next one is gonna be zombies.  We haven't had a good zombie apocalypse lately.