Architect of Worlds – Step Fifteen: Determine Orbital Period

September 8, 2020 Sharrukin Comments 0 Comment

So, for the first time in over two years, here is some new draft material from the Architect of Worlds project. First, some of the introductory text from the new section of the draft, then the first step in the next piece of the world design sequence.

The plan, for now, is to post these draft sections here, and post links to these blog entries from my Patreon page. None of this material will be presented as a charged update for my patrons yet. In fact, there may be no charged release in September, since this project is probably going to be the bulk of my creative work for the next few weeks. At most, I may post a new piece of short fiction as a free update sometime this month.

Designing Planetary Surface Conditions

Now that a planetary system has been laid out – the number of planets, their arrangement, their overall type, their number and arrangement of moons, all the items covered in Steps Nine through Fourteen – it’s possible to design the surface conditions for at least some of those many worlds.

In this section, we will determine the surface conditions for small “terrestroid” worlds. In the terms we’ve been using so far, this can be a Leftover Oligarch, a Terrestrial Planet, a Failed Core, or one of the major satellites of any of these. A world is a place where characters in a story might live, or at least a place where they can land, get out of their spacecraft, and explore.

Some of the surface conditions that we can determine in this section include:

Orbital period and rotational period, and the lengths of the local day, month, and year.
Presence and strength of the local magnetic field.
Presence, density, surface pressure, and composition of an atmosphere.
Distribution of solid and liquid surface, and the composition of any oceans.
Average surface temperature, with estimated daily and seasonal variations.
Presence and complexity of native life.

In this section, we will no longer discuss how to “cook the books” to prepare for the appearance of an Earthlike world. If you’ve been following those recommendations in the earlier sections, at least one world in your designed star system should have a chance to resemble Earth. However, we will continue to work through the extended example for Arcadia, focusing on the fourth and fifth planets in that star system.

Step Fifteen: Determine Orbital Period

The orbital period of any object is strictly determined by the total mass of the system and the radius of the object’s orbit. This is one of the earliest results in modern astronomy, dating back to Kepler’s third law of planetary motion (1619).

Procedure

For both major satellites and planets, the orbital period can be determined by evaluating a simple equation.

First Case: Satellites of Planets

To determine the orbital period of a planet’s satellite, evaluate the following:

$T\ =(2.77\ \times{10}^{-6})\ \times\sqrt{\frac{D^3}{M_P+M_S}}$

Here, T is the orbital period in hours, D is the radius of the satellite’s orbit in kilometers, and M_P and M_S are the masses of the planet and the satellite, in Earth-masses. If the satellite is a moonlet, assume its mass is negligible compared to its planet and use a value of zero for M_S.

Second Case: Planets

To determine the orbital period of a planet, evaluate the following:

$T\ =8770\ \times\sqrt{\frac{D^3}{M}}$

Here, T is the orbital period in hours, D is the radius of the planet’s orbit in AU, and M is the mass of the primary star in solar masses. Planets usually have negligible mass compared to their primary stars, at least at the degree of precision offered by this equation, and so don’t need to be included in the calculation.

Examples

The primary star in the Arcadia system has a mass of 0.82 solar masses, and the fourth and fifth planet orbit at 0.57 AU and 0.88 AU, respectively. The two planets’ orbital periods are about 4170 hours and 7990 hours. Converting to Earth-years by dividing by 8770, the two planets have orbital periods of 0.475 years and 0.911 years.

Alice has decided to generate more details for the one satellite of Arcadia V. This is a moonlet and so can be assumed to have negligible mass, while the planet itself has a mass of 0.65 Earth-masses. The moonlet’s orbital radius is about five times that of the planet, and Alice sets a value for this radius of 28400 kilometers. The moonlet’s orbital period is about 16.4 hours.

Architect of Worlds: The Next Chunk

August 24, 2020 Sharrukin Comments 1 comment

While I’m waiting for my consulting editor to have a look at The Curse of Steel, I’ve turned back to a project that I’ve been neglecting for too long: the world-building book Architect of Worlds. Several sections of that book already exist in a rough draft, which can be found at the Architect of Worlds link in the sidebar.

The bulk of the material I’ve already written is a design sequence, permitting the user to set up fictional star systems (or to fill in details for real-world systems). The idea is to let SF writers, game designers, tabletop game referees, and so on design locations for interstellar SF settings, using whatever combination of random chance and deliberate choice they prefer. The emphasis is on “hard SF” realism, as far as the state of exoplanetary astronomy will permit, and no dependencies on any specific tabletop rules system.

So far, the draft system permits one to place stars, planets, and moons, and get gross physical properties (mass, density, surface gravity) and dynamic parameters (orbital radius, eccentricity, and period) for each.

The next slice of the system will involve generating the surface conditions for such bodies, at least for the small “terrestroid” worlds that are likely to provide environments for SF adventure. At this point we’re talking about things like surface temperature (average and variations), atmospheric composition and pressure, the amount and state of water (or other volatiles) on the surface, what kind of native life might be prevalent, and so on.

I’ve been mulling this section over for a few years now, since the science involved is a lot more complicated and more difficult to reduce to a set of game-able abstractions.

When I designed a system like this for GURPS Space Fourth Edition, I made a deliberate design choice to reduce all the possibilities to a specific set of archetypes. That provided some backward compatibility with earlier versions of the GURPS system, and with the older Traveller systems that were an inspiration for both. For this book, though, I want to give the readers as much detail as I can, and let them decide what to use and what to set aside. That complicates the design.

So, a very rough overall outline of what’s going to be involved for a given “world” (that is, a terrestrial planet or moon with some likelihood of a solid surface):

The rotation rate of the world (including cases where the world is tide-locked or resonant with a primary). As a sidebar, this gives us quantities for the length of the natural day, month, and year.
The blackbody temperature and incidence of stellar wind for the world, based on the properties and distance of its primary star.
The strength of the world’s magnetic field, and the consequences for the size and strength of its magnetosphere (if any). If the world is a moon (for example, the satellite of a gas giant planet), then the primary’s magnetic field and magnetosphere may be relevant as well.
The world’s initial budget of volatiles – how much in the way of possible liquid or gaseous compounds was the world left with after its process of formation.
Atmospheric composition – what volatile compounds are likely to be gaseous at local temperatures, and can the planet hold onto them?
Atmospheric mass and pressure.
Hydrospheric composition – what volatile compounds are likely to be liquid or solid instead?
Hydrospheric mass and prevalence – how much of the world’s surface will be covered by what kinds of liquid or solid stuff?
Average surface temperature.
Estimated variations in surface temperature with the position on the surface, time of day, and so on.
Presence and complexity of native life – which may require a loop-back to adjust characteristics of the atmosphere, hydrosphere, and surface temperature.

All that’s the minimum for what the next section of the book needs to cover. There are a lot of dependencies back and forth here, which is one reason why I’ve struggled for so long to build this piece. I’m beginning to think I see how to design something workable, though. At least enough to get started. More over the next few weeks.

Editing the Novel

August 17, 2020 Sharrukin Comments 0 Comment

My plans regarding The Curse of Steel have evolved with remarkable speed over the past few days.

My novel-writing process seems to boil down to the following:

A long period of chaotic brainstorming, tinkering, and world-building work, in which the overall concept of the story can change many times. This stage can take several years and is likely to produce a lot of abortive partial drafts. Most of the novels I’ve worked on have never gotten past this point.
Eventually, the concept stabilizes in my head enough that I can produce the first complete draft of a novel. This has happened exactly three times in my entire career as a writer.
The first draft tells a complete story, but it probably has all kinds of plot holes, undeveloped characters, and vagueness of setting in it. After all, I was making it up as I went along – I seem to be much more a “pantser” than a “planner.” So now I go back and write a second complete draft, one that rounds out the story and patches most of those holes.

About eight years ago, my first mature original novel reached that second-draft stage. That was The Master’s Oath, a tale of time travel, alternate histories, and Hermetic magic that will absolutely never be seen again outside my dead files. It wasn’t until I was finished with that one that I had a “What in God’s name was I thinking” moment and realized the thing was utterly unpublishable. Decently written, not a bad adventure story, but bound to mortally offend big chunks of my audience. Lesson learned.

Now, as of last week, The Curse of Steel has reached the second draft stage. Lo, the creator looked upon his work, and he was pleased.

Now what?

Well, to be honest, my workflow doesn’t exist yet past this point. The Curse of Steel is the first original novel I’ve ever written that I honestly believe is publishable.

I spent a couple of weeks putting together a cover image for the book. While I worked on that, I thought about what the next steps should be. Should I just publish the second draft as is, and hope for the best?

The more I thought about that, the less comfortable I was with the idea.

I know my prose style is reasonably clean. When I was a freelance writer, more than one editor remarked on that. As an editor, I’ve seen enough prose from other people to be able to compare.

Meanwhile, I’ve had a few people reading my drafts, and they’ve been encouraging about the story.

On the other hand, a novel is a very different beast from a non-fiction book, there are necessary skills I may not have developed in full, and none of my early readers are experienced editors. I don’t have a decent writer’s circle to help me hammer my drafts into submission. What if I’m missing something?

No, scratch that, I know I’m missing something. Maybe two or three novels from now, I’ll have a better idea of what to do at this point. Right now I’m still not sure.

The obvious solution would be to hire an editor.

Of course, a skilled and reliable editor costs money. Not to mention, there are a lot of people out there ready to take advantage of would-be authors, offering cheap book-preparation services for top dollar without any guarantee of results. Ever since deciding to pursue self-publishing, I’ve been very cautious about laying out cash for such services.

On the gripping hand, I can afford to spend some money on the experiment.

So over the past week or so, I’ve done some research and developed two lines of attack.

One line is to search for software that can help a novelist pick nits in his prose style. Sure, everything has a spelling-and-grammar checker these days, but strong prose writing needs more than that. I need to be able to ferret out filler words, excess adverbs, phrases that I repeat too often, that kind of thing. I could do that by eye, but the process would be slow and painful, and I would be likely to miss the weaknesses in my own style.

Enter AutoCrit.

Autocrit is billed as a “self-editing platform,” and it certainly works as such. It’s essentially a web-based word processor, but it’s specifically designed to carry out a wide variety of specialized text searches and basic statistical analyses. It compares your text to a huge corpus from published novels, helping you find and carve out the flabby bits of your prose.

Using AutoCrit over the past three days, I’ve been able to rework The Curse of Steel with surprising speed and efficiency. Already I’ve cut a little over 2000 words of material, mostly filler words and repetitive phrases that didn’t add to the sense of each passage.

It’s been quite the eye-opener. Every writer needs something to rub his nose in the shortcomings of his prose style, or he isn’t likely to improve. Lacking an editor or a ruthless critique circle, something like this may be the next best thing.

AutoCrit isn’t ideal. It’s web-based, which I don’t care for. It chokes if you hand it more than 50,000 words of text at once, which means I have to edit my novel in chunks. It doesn’t handle special characters gracefully, so all my conlang words that have accents and umlauts in them get snarled up. Its import from Word, and its export back to Word, are both a little kludgy.

Still, I suspect I’ll have a third complete draft, with much tighter prose, by later this week.

The second line of attack is that I have, indeed, hired an editor. This involved a fair amount of searching through the Web, looking for editorial networks that are competent, reliable, and not outrageously expensive. The SFWA site was fairly helpful here – they don’t explicitly recommend editors, but they have an excellent checklist of things to consider in the process.

The editor I ended up with is being hired specifically to do a manuscript assessment, not a complete edit of the novel. This will set me back a few hundred dollars, and it may not end up being part of my usual workflow in the future. Still, the experiment should be worthwhile. I’m hoping he’ll be able to provide actionable feedback that I can use while producing a final complete draft – the last step in my development process before the book goes out the door.

At the moment, the plan looks like this:

Finish working through The Curse of Steel with AutoCrit (to be completed by about 21 or 22 August).
Wait for my editor to complete his review of the draft (probably about the end of September).
Produce the final release draft (to be completed by late October).
Publish the book!

So it looks as if The Curse of Steel will finally hit the virtual shelves by Halloween. There will be much rejoicing . . . and then I’ll get started on The Sunlit Lands, the second book in the series. One assumes that one won’t take nearly as long to reach fruition.

In other news, that four- or five-week gap in September, while I wait for my editor to finish his task? I think I may sit down and work on Architect of Worlds for a while. No promises . . . but I think my research, and the subconscious work in the back of my head, have reached the point where I may be able to develop a rough draft of the third chunk of the world design sequence. We’ll see how things go.

Star System Generation: A Neat Automated Tool

July 28, 2020 Sharrukin Comments 0 Comment

Today I came across a neat example of automated star-system generation, based on the design sequence I wrote for GURPS Space, Fourth Edition back in the day.

It looks like a robust code base, supporting a web-based interface. You can generate star systems at random, possibly forcing a few parameters (existence of a garden world, position in an open cluster, and so on). You can pick from several naming schemes for the resulting planets.

The output includes a neat animated map of the system, and hierarchically tabulated information for randomly generated stars, planets, and moons. All in all, it looks very slick, and it seems to reflect the original game rules pretty accurately.

The source code for the project can be found at Jan Sandberg’s GitHub repository. The redditor Myrion_Phoenix hosts an instance of the application on his website as well.

I’ve mentioned my own more recent work on Architect of Worlds – it would be neat to see a similar automated version of that once it’s ready for release. In any case, this application looks very useful for folks who are running hard-SF games, whether using GURPS Space or something similar.

2019 in Review

December 31, 2019 Sharrukin Comments 0 Comment

Well, this has been a year. Twelve months of doing my best to pass by the madness that seems to be sweeping the world, keep my family prospering, excel at my day job, and keep making progress on my creative projects. With some success, as it turned out.

Let’s be honest, this is the year a lot of things seemed to come together, as I built workflows I could use to set up and finish creative projects. I designed my first full constructed language, one which is actually usable for literary work. I drew up several maps. I hacked my brain in such a way that I could do world-building work in service to an actual story for a change.

I managed to write (at least in the first draft) my first mature, full-length, original, publishable novel: The Curse of Steel. That’s a pretty big deal.

So while 2019 wasn’t altogether sunshine and roses, I do feel as if I’m in a reasonably good place in my creative life. Still more work to be done, to be sure, but I’m more confident that I once was.

This blog seems to have reflected that. I’m still not sure who is reading this thing regularly – most of you don’t have a lot to say – but traffic keeps growing, slowly by steadily. The top ten (new) posts for this year were:

As usual, about 40% of the hits on the blog just start at the home page and go from there. There’s also a lot of perennial interest in some of my old Architect of Worlds posts from 2018, as well as that extended exercise in world-building I carried out based on the Bios: Genesis and Bios: Megafauna games. That’s always in the back of my mind as I consider what to work on next.

As always, let’s hope that the coming year is prosperous and productive for all of us . . . and that the world manages to hang onto sanity in the coming months.

New Creative Directions

December 5, 2019 Sharrukin Comments 1 comment

It’s not the end of the year yet – that being when I usually take stock and make plans for upcoming creative work – but a few things have happened recently that may turn out to be productive.

The Obvious Task: The Curse of Steel is finished in the first draft. I’ll be spending the next few months on a second-draft rewrite of the novel, with a planned milestone of having it ready for publication in the spring. After that, I’ll be getting started on the second novel in the series, The Sunlit Lands.

Preparing for Patreon: Now, as one element of preparing for publication, I’ve been thinking about re-opening my Patreon campaign, which has been shut down for several years. Hopefully, that can help me gather an audience for the novel(s), as well as raise a little money to help pay for professional cover art or editorial services. With the novel series underway, I certainly won’t have any problem producing material that patrons can enjoy for the foreseeable future.

World-Building Material for Patrons: However, while working on the novel series, I’ve been coming up with a lot of world-building material: maps, constructed language, cultural descriptions, character writeups, and so on. Most of that material hasn’t been posted here. I imagine some of my readers would be interested in it, either on its own or as support for tabletop gaming.

The stumbling block here is that when I frame my own world-building notes in terms of a tabletop game, the game system I normally use is GURPS. Steve Jackson Games is fairly strict about licensing the GURPS system for third-party publishers – there’s no Open Gaming License for it, for example. It’s possible to work with them to get a license, and several publishers have done so, but for someone like me who would just be publishing material for a small audience via Patreon, that’s not worthwhile.

Fortunately, a solution came to me a few days ago: publish game-ready material using a “generic” character description format of my own design, one which could easily be converted to GURPS – or to any number of other game systems, for that matter. That way I can publish the material for patrons and still avoid any danger of infringing on SJG’s online policy.

Just as a trial balloon, I’ve started pulling together the design I have in mind, and it’s surprisingly simple. I suspect I could publish a reference document, under a Creative Commons license, that’s no more than a dozen pages long. So that looks like it’s going to be part of the strategy.

Some New Simulations for Evaluation: Entirely unconnected to the above, I received a shipment from Sierra Madre Games earlier this week – two games that I ordered many months ago and that have finally been released.

Bios: Origins (Second Edition) is the final game in Phil Eklund’s Bios trilogy, which began with Bios: Genesis and Bios: Megafauna. This game picks up where Megafauna left off – at the point where the primitive human species (or some other pre-sapient species on an alien world) first attains a spark of consciousness. It’s a Civ-like game, which traces the history of a world from the Paleolithic all the way to the dawn of the Space Age.

As with Phil’s other games, this has oodles of thematic interest, and I suspect it could be used rather handily as a world-building tool. You may recall that I did a series of “world-building by simulation” articles a while back, using Genesis and Megafauna to design an alien world and its dominant sentient species. Now I think I’m going to tinker a bit with Origins and see if I can turn it to similar purposes. There may be a fair number of blog posts about that over the next few months.

Meanwhile, Pax Transhumanity is a game by Phil Eklund’s son, Matt Eklund. It’s a thematic simulation of future history – the period over the next century or so, during which technology is likely to completely transform human society (again, still, as always). It fits in well with the Transhuman Space setting I helped design for Steve Jackson Games back in the day.

I’ve been waiting for Pax Transhumanity for a long time, hoping to use it to re-inspire me for another of my creative projects: the “Human Destiny” setting, in which humanity becomes part of a polyspecific interstellar community over the next couple of centuries.

The Human Destiny stories started off reasonably well – I actually published one of them via Amazon a while ago – but I ran into a brick wall with them. Largely because, in the current concept for the setting, human beings have very little agency! They’re the passive subjects of an alien empire, which came to manage Earth and human destiny because we proved unable to succeed on our own.

Okay, I will admit that I’m fairly pessimistic about human prospects. My evaluation of my species is that we’re just smart enough to get ourselves into a world of difficulty, but not smart enough to save ourselves from the consequences. That doesn’t make for very hopeful or interesting storytelling, though.

So for a long time, I’ve been trying to find ways to convince myself anew that humanity actually has a hopeful future, preferably without divine intervention or helpful aliens to save us from our own folly. I want to develop a fictional world in which we muddle through and eventually manage to solve the problems we cause for ourselves. Going back and re-reading Transhuman Space has helped a little, since that’s exactly the assumption we made for that setting. Tinkering with Pax Transhumanity might help too.

All of which means that I might be re-working the Human Destiny setting over the next few months. More material for this blog, the Patreon, and eventual publication, hopefully.

Architect of Worlds: I still need to get back to work on the Architect of Worlds project, of course – that’s been stalled for a lot longer than I originally planned. Even so, every once in awhile someone comes across it and gets good use out of it, even in its incomplete state. One of these days I’ll have to set everything else aside and just get the next big section written . . .

Hmm. This is reading a lot like a “prospects for the new year” post, isn’t it? Even if the above list is all I work on, that’s more than enough to keep me busy for months. I suppose that’s okay. When the muse calls, you answer, no matter what the calendar says!

An Interesting Result

August 21, 2019 Sharrukin Comments 2 comments

Just a short note, to call your attention to an interesting result in recent astrophysics that’s quite relevant to the Architect of Worlds project.

It’s well known that we’ve discovered thousands of exoplanets in the last couple of decades. Now the state of the art is approaching the point where we can get clues about the environment on those planets. For example, one recent result (here’s an article in Scientific American) is the first indication we have of the kind of atmosphere that exists around an Earth-sized rocky exoplanet. In this case, the planet is in its primary star’s habitable zone, and it’s more than large enough to retain a significant atmosphere against thermal or Jeans escape. Yet there doesn’t seem to be much if any atmosphere there.

I’ve long since worked out a model for Jeans escape; that much was in the world-design system I wrote for GURPS Space back in the day. (If you’ve used that system, you may recall a “minimum molecular weight retained” or MMWR calculation. That’s specifically relevant to Jeans escape.)

The problem is that thermal loss isn’t the only way a planet’s atmosphere can get stripped off. If the primary star is prone to flares and has an energetic stellar wind, that will do the trick too. This is specifically relevant to red dwarfs, like the star LHS 3844 which has the planet mentioned above. Red dwarf stars punch well over their weight in the stellar-wind and flare department, especially early in their lives. Thus, any rocky planet close enough to be in the liquid-water zone will probably get a serious sandblasting early on.

This is kind of a new area in astrophysics, and there are a lot of competing models out there. Some scientists are predicting that Earth-sized planets should be able to retain their atmospheres in at least some cases, others are much less sanguine. The LHS 3844 result certainly seems to support the pessimistic case.

For Architect of Worlds, I’ve been thinking in terms of assigning each planet a “volatiles budget” from its formation and early years, modified by things like the planet’s MMWR, whether it formed inside the snow line, whether there’s a dominant gas giant to fling comets in-system, and so on. A big random factor as well, since it looks as if this feature is strongly subject to chance. Then we would reduce that volatiles budget to reflect non-thermal processes of atmospheric escape, photodissasociation of water molecules, and so on. (Hmm. Maybe have a separate budget just for water, since that goes through some significantly different processes and might not be correlated with atmospheric volatiles.)

The devil’s in the details, of course, and for all my tinkering I have yet to come up with a model that satisfies me (or even fits all the cases we know about). This might actually be the biggest obstacle to getting the third section of the design sequence hammered out.

Status Report (16 August 2019)

August 16, 2019 Sharrukin Comments 0 Comment

Busy week at the office – I’ve been teaching a course most of the week – so not much time or energy left over for writing or world-building work. I’ve been plugging away at my regional map, at least.

As time permits, one thing I’ve been tinkering with is an application of the draft Architect of Worlds material to design an alternate Solar System for the world where The Curse of Steel takes place. I want the setting to be just a little exotic; just as this alternate Earth has different geography, different landforms and seas than ours, I also want it to have a different sky. To this end, I’ve designed a primary star almost identical to Sol, and a habitable world almost identical to Earth, so that the day-to-day environment isn’t clearly alien – but the system is otherwise different in a lot of details.

More detail on that design later. For today, I’ll note that in conjunction with this work, I’ve been using a virtual-planetarium application that I highly recommend: Space Engine.

Space Engine has been in development for several years, almost entirely by the Russian astronomer Vladimir Romanyuk, although he recently released a beta of the application on Steam to raise money for further development. It’s unique in that the entire universe notionally resides in the engine – while the vast majority of it is procedurally generated, known stars, exoplanets, and so on are also in the engine’s catalogs. It’s a great toy for exploring the universe from the comfort of your desktop.

It’s also not all that difficult to insert your created star systems and worlds into the Space Engine catalogs, and have the engine render them in place in the virtual universe. Space Engine uses somewhat different world-building assumptions than I do, but the differences are pretty minimal. It’s not at all difficult to take the results of work with Architect of Worlds and drop them into the Space Engine universe. So I’ve done that, with the intention that I’ll be able to use the simulation to determine what the sky looks like at any given point of the story.

For example, here’s a rough-draft render of the alternate Earth where Kráva lives and will have her adventures. Really astute observers might be able to figure out about where I’ve placed her world in the real galaxy:

I think it’s possible to create new planetary textures and bump-maps for created worlds in the engine, but that’s beyond me so far, so the landforms you see here are not definitive. Still, I can “land” the viewpoint on the planet at any given point in latitude, longitude, and time, and see what a character standing at that spot would see in the sky. For example, here’s an early-evening image from a latitude roughly equivalent to where the story begins:

The bright object low on the horizon is the system’s secondary star, a red dwarf orbiting at a comfortable distance of 100 AU or so. Brighter than our own Moon, it doesn’t wax and wane, and I think it may even be circumpolar so it’s always visible in the northern hemisphere. Handy for characters who need to move around at night!

Space Engine can do a lot of things for me – model an alien sky consistently and in great detail, tell me with a mouse click what apparent magnitude objects might have, and so on. For a few hours of investment, I can include the kind of exotic but consistent astronomical perspectives that (e.g.) Tolkien needed endless painstaking pencil-and-paper work to provide.

More about all this later, if and when it seems appropriate while I work on the story. I must say, though, it’s nice to find tools that can make the obsessive world-builder’s attention-to-detail easier.

Architect of Worlds: Reality Ensues

March 29, 2019 Sharrukin Comments 3 comments

One element of work on the Architect of Worlds project is that real-world science in this area has been advancing by leaps and bounds for years. Not once but several times, I’ve settled on a method for modeling some feature of planetary formation, only to see some new result published that seems to demand a different model. On one occasion, while I was testing the current model by generating planetary systems for nearby stars, I literally saw the first publication of new exoplanets in a star system I had just done randomly a few days before. This can be frustrating, although I have to admit it’s also rather exciting!

Now it seems to have happened again. The current model I use for planetary system formation implements a combination of the Nice model and the Grand Tack hypothesis, which together describe how Jupiter may have formed and migrated through the early solar system before settling down in its current location. The assumption is that a planetary system’s primary gas giant will normally form near the “snow line” and then migrate inward (and possibly outward) to its final position. This is all implemented in Step 10 of the current sequence.

Now there seems to be evidence that these models aren’t telling the whole story. In a new paper, “The consequences of planetary migration on the minor bodies of the early Solar System,” computer simulation seems to suggest that the core of Jupiter must have formed much further out than the Nice model suggests. It may have formed as far out as four or five times the snow-line radius, and then migrated inward very quickly.

I need to read the Pirani paper in more detail, and see if there’s been any discussion as to how to reconcile those results with the Nice model. To be honest, the Nice model isn’t entirely consensus in the community, so a new model that fills in some of its problematic details might work.

Still, if the Pirani paper seems supportable, it may be necessary to do a significant rewrite of the second chunk of the design sequence. It’s possible that the result may actually be simpler than what I’ve got now. I’ve thought of a way to cut out some of the current sub-steps and computation, making the process a little smoother, that might work. We’ll see what develops.

“Architect of Worlds” Page Now Active

February 24, 2019 Sharrukin Comments 5 comments

Recently I’ve noticed a big uptick in traffic to posts under the architect of worlds tag. I suspect someone out in the wilds of the Internet has called people’s attention to the project.

I’m up to my eyebrows in other projects at the moment, but today I took a few moments to create an Architect of Worlds page, accessible under the Sharrukin’s Worlds section in the sidebar. If you’re interested in the project, the advantage of that page for you is that it will include links to current PDFs of the completed draft sections. No more having to weed through old blog posts!

Incidentally, I do hope that people who find the material useful will let me know that, and provide any feedback they can as to how well or poorly the system works for them.

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