Anyway, I seriously lucked out on my gifts this year, so I need to flail about them a little. I know that I have some Mass Effect fans over here on DW, so maybe some of you will of interest.
First, for a treat, I received a lovely piece of artwork. ♥ I absolutely adore F!Shepard/Garrus/Tali (to the point that 15% of the works on the AO3 about that relationship are fics by me), so I was absolutely thrilled to get the notification for that.
But my actual gift really wins everything. Because someone wrote me 22k words of Ashley/F!Shepard/Kaidan, based on a prompt that I've included in various exchanges for something like three or four years now. It's amazing, and you should totally go read it if you're even remotely intrigued by the idea of that relationship.
Oh my, this has been quite a week. A lot of poisonous things are happening politically in my beloved country. I am quite politically active — if you follow me on Twitter, Facebook, or read any of my political posts, you know this — and the past few days have been no exception.
And while I will not stop nor even rest for long, there are times when a short break is needed to detox the brain, what has become popularly known as “self-care.” So, as I sat in front of my computer, I thought to myself: “How about a beautiful time-lapse video, something with gorgeous imagery, uplifting music, interesting science, and a message that can be used to make the world better?”
So I searched my emails to see if anyone had sent me a note about such a video, and lo, I found just such a message. It was from photographer Sriram Murali, who, like me, is concerned that we’re losing the night sky. Light pollution — light from buildings, fixtures, and so on sent needlessly up instead of down, where we need it — is stealing the stars from us. To document this, he went to various locations with different levels of dark skies, and shot the same part of the sky from each to compare the view.
And to do so, he chose a celestial icon, something that almost anyone will recognize: Orion. The result is not only lovely, but (if you pardon the pun) eye-opening. So watch “Lost in Light II,” and you know the drill: Make it full screen, high-res, and enjoy the music, too:
Ooph. As the video progresses, and the sky gets darker, so many treasures become visible. Now, of course the camera captures more than the eye does; digital detectors are more sensitive, and time exposures get deeper and show fainter objects. Still, the lesson is told. Orion has bright enough stars to see even in pretty light-polluted skies, but the real power of it ramps up as the sky background light ramps down (incidentally, Murali made a video he called "Lost in Light," the precursor to this one, which showed the Milky Way in various conditions, but found it wasn't resonating since it's not as familiar a sight, so he redid it with Orion).
There’s a lot to look at in the video. Did you see Barnard’s Loop, a sweeping reddish glowing arc of hydrogen gas curling around the lower left of Orion? Not before the sky got to level 4 at worst. How about the Orion Nebula, the middle “star” in Orion’s dagger? In the first parts of the video it does look like a star, but as the sky grows darker, its true nature as a premier star-forming gas cloud becomes more obvious.
I enjoyed seeing geosynchronous satellites, too: satellites orbiting so high off the equator that they orbit in the same period it takes the Earth to spin. As the stars move, the satellites appear to remain stationary, and they’re obvious if you let the stars flow past your eye in the latter parts of the video. Orion’s belt is on the celestial equator, so the satellites are easiest to see there.
And while some people are familiar with the bulge of the central part of the Milky Way in videos like this, it’s easy to forget that the galaxy stretches all the way around the sky, and the bright stars of Orion punctuate it off to the side. That is apparent again only in the latter parts of the video, when light pollution drops.
And those red waves that look like clouds you can see sweeping across the sky? That’s airglow, gas molecules high in the atmosphere gently releasing the energy from sunlight they accumulated all day. That takes fairly dark skies to see at all, and is something you’ll never see at all from even a moderately light-polluted location.
Now, remember: All of these beauties are there in the sky all the time. You just can’t see them due to wasted light.
So, what can you do to make sure your skies are pristine? It’s not easy, but it’s not all that hard either. The International Dark Sky Association has a list of resources that can help. It mostly boils down to using light fixtures that don’t point up. Seems simple, right? The hard part is getting governments to invest in them. These features tend to save money in the long run, but do cost money initially. Still, a lot of towns and cities are moving in this direction, and there are even dark sky sanctuaries being established.
I find that hopeful. There are lots of practical reasons to do this, but in the end, what motivates me to talk about it is the beauty. The art. The way the stars touch us, move us, inspire us. They show us that there are concerns outside of our petty lives, there are vast things, ancient things, things that dwarf our human existence and yet remind us that we are a part of them and owe our existence to them.
Certainly, we need to remember that this past week. But there is never a time, never a moment, in my life where that much larger reality isn’t affecting my own much smaller one. I think it makes my life better. I hope it does yours, too.0
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The Sun is the closest star to us in the entire Universe, so you’d think we’d know the most about it. And in many senses we do; we can view the surface in high resolution and see details there we cannot in other stars.
But there’s still a lot about it we don’t know, and lots of questions remain unanswered. Some seem simple enough. For example: How fast does the Sun’s core rotate?
Now we know: It spins around almost exactly once a week. The weird thing is, that’s four times faster than the Sun’s surface rotation! The Sun’s insides spin faster than its outsides.
So there’s a bit to break down here, but it’s pretty cool. OK, fine: It’s hot. But the news is cool.
The Sun is not a solid ball, but is instead a gigantic sphere of gas (technically, it’s a plasma, a gas in which the atoms have lost one or more electrons; that’s actually important, as we’ll see in a sec). Overall, the Sun is about 1.4 million kilometers wide. At the center, the temperature and pressure are so high (15 million degrees C and hundreds of billion times Earth’s atmospheric pressure at sea level!) that hydrogen atoms slam into each other and through a complicated process fuse into helium. This releases a lot of energy — a lot — and that’s why the Sun shines. This energy works its way out of the solar interior and radiates away from the surface as light.
The region where hydrogen is transmogrified into helium is called the core, and it’s about 1/5th of the Sun’s diameter: roughly 280,000 km wide (somewhat less than the distance from the Earth to the Moon, for comparison). We know it’s there, despite being buried under a half million kilometers of raging plasma, due to the physics of how the Sun works — the discovery of nuclear fusion was a huge breakthrough in understanding solar dynamics.
When we look at the Sun from the outside, we see it spinning. Even though the surface isn’t solid and is always changing, there are a few ways to measure the rotation rate: For example, you can watch sunspots and use them as landmarks (well, plasmamarks, I guess). When you do, you find that the Sun rotates once every few weeks or so. Moreover, it rotates at a higher rate at the equator versus the poles; 25 versus 35 days. That “differential rotation” is again because the Sun isn’t a solid body, and sloshes around a bit.
But how fast does the core rotate? That number has been long sought, and has been maddeningly elusive. However, a new method has finally revealed the answer ... and it’s because the Sun is vibrating.
Between the core and the surface is a region of the Sun called the convective zone, where hot plasma rises and cool plasma sinks, similar to water boiling in a pan. There are thousands of these cells of plasma moving up and down inside the Sun, and they agitate the material around them. This creates a pressure wave, similar to a sound wave. When these reach the Sun’s surface they cause it to vibrate, and these vibrations can be measured. The physics of waves is well enough understood that the properties of these waves can be used to measure conditions inside the Sun, so we can figure out what’s going deep beneath the surface without ever seeing it directly. The science of this is called helioseismology.
The problem here is that these pressure waves (also called p-waves) travel pretty rapidly through the dense regions deep inside the Sun, so they’re not sensitive to the core’s relatively slow rotation. They can’t be used directly to measure how quickly the core rotates.
Ah, but there’s another type of wave, called a gravity wave (or g-wave, not to be confused with gravitational waves, which are very different). This is the same kind of wave you get when you move around in your bathtub: Water gets pushed up, and gravity pulls it back down. The water picks up speed as it falls and overshoots a little, dipping down and creating a trough between crests. Those crests get pulled down, and so on, creating the g-wave.
With the Sun, these waves are generated at the core, but they don’t make it out to the surface, so they can’t be measured directly. Arg!
But wait! There’s a solution here. It turns out that when p-waves pass through the core, the material moving under the influence of g-waves interacts with them, changing the way p-waves move through it. The effect is incredibly subtle, but with careful measurement it can be seen.
And it finally has been, using the venerable Solar and Heliospheric Observatory (SOHO), a space-based observatory dedicated to observing the Sun. An instrument on board SOHO, called Global Oscillations at Low Frequencies (or GOLF), was designed to look at solar p-waves. By taking measurements over a staggering 16.5 years (SOHO launched in 1995), astronomers were able to see the subtle effect of g-waves on them. It’s these measurements that indicate the solar core rotates much faster than the surface.
This has been suspected for years, and it’s nice to see it confirmed. And I have to admit, as soon as I heard this I did a mental forehead slap. I should’ve known the core would spin faster!
Why? From physical theories, we think stars spin rapidly when they’re born. We see lots of confirmation of this by observing young stars, too. But the Sun’s surface spins only once a month or so. This is most likely due to its magnetic field: the powerful magnetism generated inside the Sun. It’s not well understood exactly where the magnetism is created, but it’s certainly above the core, in or just above the convection zone. A very well-known property of physics is that moving charged particles create a magnetic field, and the plasma moving up and down in the Sun’s convective region therefore does just that.
Above the Sun’s surface, the magnetic field acts like a gigantic net, sweeping up subatomic particles emitted from the Sun and speeding them up, like a fishing net picking up fish. As it does, the particles push back a little bit on the magnetic field. Since the magnetism is anchored in the Sun’s material, this acts, over billions of years, to slow the Sun’s rotation down.
But the magnetic field isn’t anchored in the core. The outer layers slow down, but the core is still free to spin faster. Sure, friction will slow it down, but even after 4.5 billion years it will still be rotating faster than the Sun’s surface — a ball of plasma nearly 300,000 km across has a substantial amount of momentum. I don’t study the Sun specifically, but I knew all this, and I should’ve been able to piece it together myself. It never occurred to me, but it seems obvious now. Ah, well.
So, anyway, this is pretty nifty. We don’t have a lot of ways to study the Sun’s core, and now we have a new one that looks very promising. Rotation is just one of many properties of the core we can learn about using this method. It’s like a window that allows us to see past the septillions of tons of plasma in the Sun and get information on the depths below.
We’ve been studying the Sun for centuries, but there’s still so much to learn about it! It’s very welcome to have a new tool to use to study it.1
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First of all, relax! I'm far from being picky, and I can pretty much guarantee that I'll love whatever you decide to draw or write for me. These are nothing but guidelines, for you to take to heart or ignore to your heart's content. Also, hey! You're drawing and/or writing me femslash! What's not to love? ♥
That said, I thought that I'd elaborate a bit on my requests in case, like me, you're the type of person who likes to have something to work with. Feel free to use and/or ignore as much of this as you want. I've tried to include a mix of vague prompts as well as more detailed ones, to hopefully make things as helpful as possible whether you're drawing art or writing fic.
( More details under the cut. )
( Requests under the cut. )
Well, I now have even more books out of the library AND more new books on my kindle (In Other Lands by Sarah Rees Brennan!), but in fact, I haven't read any original fiction this week, just Les Mis contemporary AUs of the Combeferre/Enjolras/Grantaire variety, including a very good White Collar AU: Still the Same by tears_of_nienna.
Next up, probably Kept by Y. Euny Hong, since it's the library book that's due back soonest.
Finished Strong Woman Do Bong Soon, about a small young woman with super-strength, who's hired as a bodyguard for the CEO of a video games company. It started out intriguingly wacky and cartoony but turned into a giant mess: endless pointless subplots and a tonally whiplashy crime plot about a serial kidnapper. Similarly, the romance began promisingly but became obnoxiously cutesy by the end. Like, to the point where the leading man's secretary, Mr. Gong, on several occasions, had to politely interrupt their cooing at each other because it was making him super-uncomfortable. At which point, the couple would go, "Oh, are you still here?" and immediately resume giggling and fawning over each other, the moral apparently being that love makes you an asshole.
Also finished Capital Scandal, which was excellent. I chased it down solely for the time period (1930s, during the Japanese occupation), since I hadn't seen anything else set then, and I wasn't at all sure what to expect, but it was adorable and fun (and appropriately distressing in places), and did a great job of balancing romance and revolution. The female leads were outstanding, and the guys eventually caught up, more or less. :-)
Started Suspicious Partner on Sunday and am now nearly halfway through. Ahem. It's about ( spoilers for the first few episodes. )
Next week: starting a re-watch of Goblin with J.
Last Week Tonight. That's about it.
The Midwife (French): The last of our film festival films. It was good, and I liked the no-nonsense main character, but I wasn't quite in the mood to appreciate it, due to Life Things, and it didn't make much of an impression on me.
I had a plan to write pining fic for the Disguise challenge on fan_flashworks, but let's just say it hasn't been a fruitful week.
Sitting in the middle of our Milky Way galaxy is a monster black hole. And by “middle,” I mean the exact center of the galaxy; it probably formed at the same time as the galaxy, itself, billions of years ago, and grew large as the galaxy did, too. It sits right there at the core, like a drain in the middle of a vast bathtub, mostly minding its own business but occasionally eating the odd star or gas cloud.
We think every big galaxy has one of these supermassive black holes in their hearts. Mostly, those are detected because they have disks of gas swirling madly around them, and observations can detect the motion of the gas via the Doppler shift as it orbits (we don’t usually see the disks themselves, which are too small).
But our galaxy is different. We’re in it, so we’re close to the black hole, and we have a better view. Not too close; we’re still halfway out to the edge of the galaxy, so we’re safe! But there are a few dozen stars that orbit the black hole far more closely, and because of our closer seat we can actually see them move as they do!
As an aside, this is one of the all-time coolest things I know about astronomy. It takes the Sun over two hundred million years to circle the galaxy once, but these stars are so close to the center, so close to the black hole, that they only take decades. That means that we can literally see them move year after year:
Scientifically, this is a very big deal. We’ve known for centuries that if you can observe an object orbiting a more massive object, you can calculate the mass of that second object. If you know the first object’s orbital velocity (how fast it’s moving as it goes around) you can also calculate the distance to them.
So, if we observe the stars orbiting that black hole in the center of the Milky Way (astronomers call it Sgr A*, literally pronounced “Sagittarius A star” or “Saj A star” if you feel more informal about it), we can, in principle, figure out the mass of the black hole and our distance from it.
Not that that’s easy...but it’s been done. Powerful telescopes observing in the infrared (to make it easier to see the stars through all the dust and muck toward the center of the galaxy) have been able to watch these stars in their orbits, and also measure their Doppler shifts. That gives their velocities, too.
Using this method, we’ve been able to measure the mass of the black hole as being around 4 million times that of the Sun, and its distance as about 26,000 light years.
As amazing as that is, a team of astronomers decided they might be able to do more.
One of the stars orbiting the black hole is called S2. Its orbit brings it pretty close to Sgr A*, a hair-raising 18 billion kilometers, the equivalent of four times the distance from the Sun to Neptune. When it’s at that point in its orbit it’s screaming through space at the colossal speed of 6000 kilometers per second, 0.02 times the speed of light.
This is so close to the black hole that Einsteinian relativistic effects can kick in. There are quite a few, but one, in particular, is very interesting. If an object is in an elliptical orbit around something massive, the orientation of that ellipse will rotate over time. In other words, if you draw a line through the long axis of the ellipse, that line will rotate a little bit every time the object orbits. The effect is strongest at periapsis, the point when the orbiting object is closest to the object it orbits.
We actually have measured this effect; Mercury’s orbit does this. The effect is tiny, and difficult to measure, because the Sun isn’t very massive (in the relativistic sense) and mercury doesn’t get that close. But we do see it, and it’s exactly as Einstein’s equations of General Relativity predict.
This new team of astronomers thought that perhaps they could see this effect as the star S2 orbits Sgr A*. They looked at the observational data from 2002 (when S2 was last at periapsis) to 2015 and found that S2 maybe, barely, shows this effect. Their results certainly are at least consistent with what Einstein predicted.
That’s amazing. This has never been seen on this scale, before. And while their results are a touch iffy, we’ll know better soon enough: S2 reaches periapsis once again sometime between April and July 2018 (the orbital characteristics aren’t perfectly known, so there’s a bit of uncertainty there). During that time, telescopes will be peering intently at the center of our galaxy, very carefully measuring the position of the star.
...and a few others. S2 is just the nearest bright star to Sgr A*. There’s another that’s closer but fainter, and harder to get accurate positions for it, but quite a few other stars have been seen orbiting the black hole as well. The team looked at them too, and by calculating their orbits were able to narrow down the mass and distance to the black hole: 4.15 million times the mass of the Sun, and at a distance from us of 26,700 light years (with some small uncertainties).
Again being able to do this is, quite simply, incredible, in the awe-inspiring sense of the word. Scientifically, it’s amazing enough; we know that there are characteristics of these supermassive black holes that seem to correlate with the galaxy around them (the way stars orbit the center, for example, seems to scale with the mass of the black hole), so being able to nail down the mass and distance our own local supermassive beastie is stunning.
But the fact of the matter is that it’s astonishing that we can do this at all. This is a ridiculously finicky set of observations coupled with ridiculously complicated mathematics describing the overall shape and character of space itself.
Yet, we can make these observations, and we can apply that math, and we can couple them to discover what a hole in spacetime 260 quadrillion kilometers away is doing as it tosses around multiple-octillion ton stars.
Why do we do this? Because we’re curious. Because we’re smart. Because we want to discover, and, most importantly, to understand.
This has driven us to investigate the Universe, itself...and to know our place in it.10
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I want to write him a summary of the Soviet Army officer's career path, what service branches are available, etc., but nothing I can find tells me the basic stuff. It's all focused on generals and stuff. (Looked on Wiki, looked on Google, neither helped. I found a monograph on dtic.mil that was from 1975 and provided *some* detail, but expected me the reader to know more than I do to make sense of stuff.)
To quote his draft summary: "(1) Early life. Born in 1959, he follows a similar course to Putin (joining the military instead, but attached as an "adviser" to one of the Soviet Bloc countries after a tour in Afghanistan which gave him a scar on his upper right arm from a Taliban attack). He resigned with a TBD officer's rank in the middle of the 1991 coup attempt (a la Putin; he's simply younger) rather than join in the attempt (which he percieved as doomed)."
He's trying to figure it out in more detail than that, but the problem is that he (the player) and I (the GM, one of two, responsible for helping him draw up his character - he does the important work of figuring out policies and stuff, the meat of gameplay, himself) can't find anything much about anything re the company-grade and field-grade officers of the Soviet Army and how they were trained, or how their careers progressed, or anything.
1. As the character was born in 1959, presume he enters officer training from civilian life sometime around 1977. How long is his officer training, and how is it decided whether he goes, say, infantry or airborne troops?
2. What's the career path like from initial officer training (including "what rank does he enter service at?" - the materials I can find state "Lieutenant", but the Soviet Army has 3 Lieutenant ranks!) to, say, battalion command?
3. What additional school-type training would he undergo during that career path, and at what times during his career? (I can help the player figure out good tour-of-duty mixes once I have that information.)
4. What service arms existed in the Soviet Army? I often hear of officers referred to as a "Colonel of Infantry", "Colonel of Air Defense", "Colonel of Strategic Rocket Forces" - but what are the possible options for the "of x" formula?
5. Were ordinary officers even assigned as "advisors" to Warsaw Pact forces, or only Political Officers?
I know these are really detailed questions in some regard. I'm trying to keep them general, but even the general stuff is hard to figure out. My objectives for this are:
B. Figure out what his career would have looked like - where would he have served, at what levels, doing what? (Especially key to figure out when he would have served in Afghanistan.)
C. Figure out if the early life posited is *plausible*.
I thus don't need to know deep details (at least not until a player requests a detailed bio of their Russian adversary from their intel people, at which point I may be back...), but only be able to work out a summary. I can do the hard part of the work myself and with the player, but I need help figuring out the foundational stuff before I begin that.
(Edited to add: Link to something Google *did* dredge up for me, and my note that what I was sent was a draft summary of the character, not a full bio. We'll be working on the full bio once we have the summary agreed to.)
( What with the LOVELESS quotes and the misuse of the word honour, it's little wonder Sephiroth decided to hang with his alien mother and destroy humanity. )
In terms of backlog statistics:
- 103 games in my backlog
- 15 games left before I hit 50% backlog
- It will apparently take me 175 days and 13 hours to complete my backlog according to How Long to Beat.
I am not a biologist. Like any field of science, I find biology fascinating, and love to find ways to learn more about it. My lack of formal training in biology means I’m an educated layperson when it comes to the field, though, so I like it when I find a good, solid introduction to a topic I hadn’t really considered before.
Like, say, how did life go from simple single-celled structures to more complex multi-celled organisms? This huge jump in evolution happened long ago, but how? I had some vague idea about it (cooperation was a survival advantage somehow), but I’ll be honest and say that, if grilled, I’m not sure I would have been able to come up with a concrete example.
But good news! Artist and science communicator Jon Perry and his team have a series of videos called “Stated Clearly,” in which they, well, clearly state how lots of biological and evolutionary processes work. They make them simple (though not too simple; that is, oversimplifying to the point where vital information is lost) and engaging, and fun to watch.
They created a wonderful one about multicellular cooperation, called “What Caused Life's Major Evolutionary Transitions?” and it’s well worth your time to watch, even if you know more biology than I do:
So, how did cooperation evolve? In the video, Perry mentions one recent experiment in which protists couldn’t eat algae that had stuck together, so this became a factor that selected bigger clumps for survival. Within a few generations, most algae had developed multicellular cooperation.
Of course, that’s just one experiment. There are further examples, but the point isn’t so much that these examples show how it happened specifically, but instead 1) that it can, in fact, happen, 2) there were probably countless further ways this could have happened, and 3) it only takes the conditions to arise for this to happen. By that last one, I mean that once the situation is primed for cooperation to become an advantage, cooperation happens.
I know there are countless details and huge areas of understanding this doesn’t cover, but it does give the basics, and makes my understanding of this better.
I’m discussing the personal impact this had on me for a reason. For one, I’m delighted when I get to learn something, especially something at a lower level I might have missed. But it’s also a reminder that not everyone knows all the basics about everything. I’ve been in love with astronomy for so long that it’s second nature to me to know how the Moon’s phases work, or why we don’t get an eclipse every two weeks. But to others, even smart, well-educated people, these sorts of things may have never occurred to them. And it might be easy to blame our education system, but it’s a big Universe, folks, and there’s a lot to know. Some stuff — even stuff you know in and out and hold dear and true to your hearts — will be only hazily known to others.
For some, that might be an opportunity to condemn others, to snark about their lack in some manner. But I choose to think of this as an opportunity to share that knowledge and make the world a little bit more knowledgeable. As my friend Randall Munroe so wisely put it:
Ignorance is fixable, and when it is you get a delightful, shiny new outlook to try out and fantastic, wondrous new things to know.
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I have been taking a few days off. Well, I’ve been sort of taking a few days off – I think they only feel like days off because I’m not riding really far, and putting up a tent and taking it back down again and trying to manage email and doing nine jobs all at once. Instead I’ve been riding my bike a little, to get around town, and to the beach, and to the marina to sail with Joe. The house is a still a disaster, the mountain of neglected work on my desk needs my attention now, but it has felt good to snuggle a baby, come up with a plan of attack, and enjoy the summer a bit. Also – knit. Not little bits of knitting found here and there, not just a plain sock because it’s all I can muster, but real, proper knitting – done in nice chunks, with a fancy pattern and beads and concentration and without worrying that the needles will puncture an air mattress.
I’m tackling Snow Angel (a little ironic for a summer knit, I know) and it’s lovely. I had about ten million balls of Findley left over after Elliott’s blanket, and it’s such a pleasure to knit with that I’m using it again. (It’s got 730m per ball. I can’t explain the yarn insecurity that led me to buy so much. I’m rather glad I like it, because I’ll be knitting with it for the rest of my life.)
I’ve still got a pair of socks running in the background, because beaded lace isn’t exactly the sort of knitting that goes well with taking the subway or walking or going to meetings, and also I’m me, so I wouldn’t quite know what to do with myself without a pair of socks in my bag, but I’m mostly knitting on this, and hoping to get it bashed out pretty quickly. The first section went by so fast that I got optimistic about it only taking a few days, but as with all things top-down, that initial thrill’s worn off as the rows get longer.
I’ve got just a little time to knit on it today before I head out for a meeting (and I have to do something about the kitchen. It’s sort of sticky. All of it. I don’t know how cupboards get sticky, but they are.) Maybe I’ll finish the first big chart – but I’m already dreaming of what I’ll make next. Shall I finish the paper/linen Habu thing? Maybe a pair of fancy socks? Perhaps a sweater for one of the littles, or a hat for the Christmas box, or… What are you making?
I promised I’d wrap up the Karmic Balancing gifts when I got back – so here’s a start. (It’s going to take a bit. You’re a generous bunch – I’ll do as many as I can each day.
Mary S found a wonderful way to give this year, she went for a nice long stash dive and came up with five (yup, five) beautiful presents for her fellow knitters. (Doesn’t she seem like a lovely person? Good taste in yarn, too.)
How old is TRAPPIST-1?
This is a tough question to answer, but it’s actually important. It’ll tell us a lot about how stable planetary systems are, and how likely it is we’ll find more like our own solar system.
TRAPPIST-1, as you may recall, is a very low-mass and very dim red dwarf star about 40 light-years from Earth — pretty close by, as stars go. In February 2017, astronomers made the stunning announcement that it had seven planets around it and, even more amazingly, all seven were roughly the same size as Earth!
On top of all that, three of the planets —TRAPPIST-1e, f, and g — orbit in the star's habitable zone, at the right distance from the star to have liquid water on their surface. Well, theoretically. We can’t detect that directly, and it depends on a lot of factors. After all, Venus and Mars are technically in the Sun’s habitable zone, and look at them! Venus is hot enough to melt metal, and Mars is dry and cold and, as I’ve heard, ain’t no kind of place to raise your kids.
All seven planets huddle pretty close to the star, too. The most distant, TRAPPIST-1h, is still just 9 million km from the star, far closer than Mercury is to the Sun. The star is so feeble, though, that the temperature on that planet is probably like Antarctica’s! Even so, its “year” is a mere 19 Earth days long.
The planets are all so close together as they orbit the star that their gravity affects each other, too. As they pass one another their gravity speeds up or slows down the others, and this changes how quickly they orbit. These changes were actually detected in the observations.
You might think that sort of tugging would disrupt the planets’ orbits, sending the system into chaos. But a complicated physical process called “resonance” — where the orbital periods of the planets are simple whole number ratios of each other, like 24/15 and 24/9 — actually works to keep them stable, perhaps over long periods of time. One study indicated the planetary configuration can last for over 50 million years.
But how long can it stay that way? It’s not clear, and that’s why knowing the age of the star (and therefore, presumably, the planets) is important.
There are various methods to determine the ages of low-mass stars like TRAPPIST-1, but they can be really hard to implement and tend to yield huge ranges for the age. Sometimes you can only get a lower limit; for example, low-mass stars tend to use up all their lithium supply in about 200 million years or so; after that, it’s all fused into helium. So if you don’t see lithium in a low mass star, it’s probably older than 200 million years.
There have been several papers published on the age of the system, but each one tends give a different age, and a wide range of possibilities. So a pair of astronomers (Eric Mamajek and my old pal, Adam Burgasser) decided to work it out. They used a series of age indicators to get the likeliest age of the star, including how fast it rotates (older stars tend to spin more slowly), how much heavy element abundance there is in it, and even its velocity through the Milky Way (that method is complicated, but the way the star moves as it orbits the galaxy is tied to how old it is).
When all was said and done, they found the best estimate for the star’s age is 7.6 ±2.2 billion years — older than the Sun! Our star and planets are about 4.55 billion years old, give or take, so if this research pans out TRAPPIST-1 was already billions of years old when the Earth was born.
... and that’s pretty interesting. We don’t really know if our own solar system is stable in the long term. It’s been around a long time, sure, but things change. Our models now indicate that the outer planets moved around a lot, toward and away from the Sun over time, messing around with the dynamics of the solar system in the process. I’d guess that we’re good for quite a long time yet, but this result about the age of the TRAPPIST system implies that multiple planetary bodies can exist for a substantially decent period.
I’ll add that the resonance I mentioned above not only helps, but may be critical. As planets move around, that resonance helps shepherd them into “safe” orbits, ones that keep them from destabilizing the entire system and throwing it into chaos. Our solar system doesn’t have that (though there are some resonances among the moons and other small bodies, the major planets are not in one; the gravitational interactions between them are currently very small, though). How important is this for long-term stability in a solar system? Knowing the age of TRAPPIST-1 is a step toward understanding that.
TRAPPIST-1 was discovered only in 1999, and the first three planets found in 2015, with four more just two years later. We’ve really only just begun exploring it. Do the planets have moons? Are there more planets orbiting the star? What are the planets made of, and do they have atmospheres?
We still aren’t completely sure how big the planets are; this new research to find the age also revealed the star may be slightly bigger than previously assumed — 0.121 times the Sun’s diameter, or about 168,000 km ... not much bigger than Jupiter. That, in turn, means the planets are probably somewhat bigger (by about 3%) but also less dense, by 11%. That means some are lower-density than Earth. Could that be because they have thick atmospheres, or oceans? These would help them survive the blasts of radiation TRAPPIST-1 sometimes puts out ... and while I wouldn’t speculate overmuch about the actual habitability of these planets, that’s something we may understand a lot more about over time as we study this weird little system.
And we’ll have plenty of time. Low-mass stars are very conservative with their nuclear fuel, and TRAPPIST-1 may still be shining much as it is today for the next couple of trillion years. Yes, trillion. It existed before we did, and will shine on long after our Sun is a dead white dwarf and our planets either consumed by the long-deceased star or frozen due to its cessation of energy production.
Still, it would be nice to know more about it before then! I suspect that the James Webb Space Telescope will be used to take a look; it may even be able to detect the atmospheres of any of these planets, should they exist.
Patience is a virtue astronomers must have sometimes. It’s a big Universe, and learning about everything in it will take some time.
P.S. In the research paper acknowledgment section comes this gem: “The authors … thank the Hon. John Culberson of Texas’s 7th congressional district, US House of Representatives, for asking about the age of TRAPPIST-1 during his visit to JPL in February 2017, which spurred the writing of this paper.” Heh. How often has that happened?5
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