Archive for the 'Worldbuilding' Category

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System Book 2: Xibalba is now available!

Lately I’ve been busy writing a new System Book for Spica Publishing, and I am pleased to announce that System Book 2: Xibalba is now available for purchase!

Xibalba originally started off as a one-paragraph writeup for the (now probably dead) Spica Sector book – but we were looking for interesting things to release as smaller products, and we figured it’d be fun to expand upon it and release it as the next System Book. Quite a bit of science went into designing this system to be as realistic as possible (like System Book 1: Katringa before it, which I co-authored), which is named after the asteroid belt that orbits its white dwarf primary. I evolved the star itself and incorporated the effects of the star’s red giant phases on its worlds – one planet was consumed during the giant phase, another’s surface was completely melted, and all of the planetary orbits expanded outwards as the primary lost its mass during its planetary nebula phase (again, Gravity Simulator proved very useful for this!).

The ‘adventure hook’ is that there are strange hauntings and manifestations occurring in the system that have so far defied explanation, and there is plenty for any visting PCs to investigate. I wanted to bring some mystery and a sense of wonder and of the unknown to the setting, but it’s designed to be more “spooky” than “horror”. Inspirations include the movies Solaris, Event Horizon, and the Terran Trade Authority: Spacewreck book. It may be smaller (and cheaper) than System Book 1: Katringa, but there’s still plenty to explore!

Are you brave enough to Visit Xibalba?

Spica Publishing is pleased to announce that its latest product – System Book 2: Xibalba – is now available from RPGnow and DrivethruRPG. This 9-page PDF is written by Constantine Thomas, and is available for $3.99.

Spica Publishing presents System Book 2: Xibalba – a complete planetary system around a white dwarf star. This supplement is compatible with the current edition of the Traveller or any other SF RPG, and can be incorporated into an existing campaign or used as the focal point of an adventure. Inexplicable events plague the inhabitants of the system – are they really haunted by the ghosts of the dead, or is there a more rational explanation for the manifestations?

System Book 2: Xibalba includes:
– A realistic planetary system, based on current astrophysical knowledge.
– Details of the worlds in the system, including the barren worlds of Akabna, Balamna, and Chamna, the Xibalba belt, and the distant gas giant Sisna.
– A description of the small mining community on the asteroid of Nuevo Tikal.
– A brief history of the system and its major events, including the madness that destroyed the Caracol habitat.
– Ideas and suggestions for the strange ‘manifestations’ that haunt the inhabitants of the Xibalba system.
– Adventure seeds to occupy Player Characters while in the Xibalba system.
– Rules for incorporating Xibalba into Spica Publishing’s Outer Veil setting.

Download it today!

“Traveller” and the Traveller logo are Trademarks owned by Far Future Enterprises, Inc. and are used with permission. The Traveller Main Rulebook is available from Mongoose Publishing.

[Stellar Mapping] Brown Dwarf dataset added, plus some major updates!

I’ve added a new Brown Dwarf dataset to the Stellar Mapping page (thanks to LiNeNoiSe for pointing this out to me)! This should hopefully be the last major update to the stellar datasets for a while – the next project on the list is to figure out what the reworked Arms for 2300AD might look like based on the realistic data.

The new catalogue is the LDwarf dataset – this is a list of brown dwarfs taken from the IPAC Brown Dwarf Archives (this dataset was last updated on 14 Feb 2011). It is not a complete list of all known brown dwarfs – these are the only the ones for which parallax data is provided there.

L Dwarf dataset, looking Corewards

While some of the distances presented in this dataset are derived from trigonometric parallaxes, others are derived instead from (spectro)photometric parallaxes. Trigonometric parallaxes are derived by measuring the angular shift of a star relative to the background stars as the earth moves around the sun on its orbit (the stellar distances in the HIPX, RECONS and other datasets here are derived using this method) – these are generally more accurate than photometric parallaxes. “Photometric parallaxes” are techically not really “parallaxes” at all – instead the spectral type of the object is checked against luminosity models to get an estimate of its luminosity, which is used along with the observed visual/IR magnitude to calculate the distance to the object. Unfortunately this method is not very precise, and some of the photometric parallaxes for these objects in the LDwarf dataset have very large error bars – but this is the best data that is currently available.

One of these systems – SDSS J141-134 – is listed in the original data as having a (photometric) parallax of 127 +/- 27 mas. This places it almost in the right location to allow a 7.7 ly link between Xi Bootis and CE Bootis, which would be very useful in the 2300AD setting. I have changed its parallax to 122 mas on this list (which is comfortably within its error bars, and allows it to connect those two stars and link to the stars around Arcturus). The original (127 mas) data for this system is listed in the text file in the file if it’s needed.

It should also be noted that two Brown Dwarfs (UGPS J072227.51-054031.2 and DENIS J081730.0-615520) are located within the RECONS sphere. These are not listed in the RECONS data, but are retained here since their parallaxes indicate that they are within 22.8 lightyears of Sol (even given their large error bars). They do not make a significant difference to the 2300AD route distribution.

Some of the Brown Dwarfs in this list are members of multiple systems that are listed in other datasets presented on this site. These are listed as complete multiple star systems on this list (the other components are duplicated here using the original data) – the datasets should merge seamlessly when combined (the ID numbers are preserved in both lists) but some components may be duplicated – this should not create problems since they will have the same name and position.

Other Updates

I’ve also made several other updates to the datasets, so you’ll need to download them again to get the latest versions!

  • The Pleiades Corridor has been updated to use Extended Hipparcos data.
  • The Yale and Gliese 3 Historical Datasets have been moved into a blog article to separate them from the more accurate datasets on the Stellar Mapping page.
  • The Extended Hipparcos and CTIOPI datasets have been updated to include Multiple Systems. A and B components of some of the multiple stars in the original data were separated by several lightyears due to parallax inconsistencies – these were listed separately, but now they have been combined nto Multiple star systems that are located at the XYZ co-ordinates of the original A component.
  • The Further Stars list is still using New Reduction Hipparcos (and other) data. I will be updating it to HIPX at a later date, but it does contain duplicate stars in different positions and should be considered to be less accurate than the other datasets!
  • [Stellar Mapping] Extended Hipparcos dataset added!

    I’ve now replaced the New Reduction Hipparcos data with the new Extended Hipparcos (HIPX) dataset published in 2012 by Anderson & Francis (see this paper for all the details). The HIPX dataset expands the original dataset to include luminosities, spectral types and much more useful astronomical data from a variety of sources, making this the definitive source of information about these stars! The searchable online HIPX catalogue is located at

    The HIPX data replaces the New Reduction Hipparcos data on this website – Astrosynthesis and Galactic XYZ data have both been updated! In most cases the HIPX XYZ data is identical to the New Reduction Hipparcos XYZs, but issues with the parallaxes for some of the multiple systems in the New Reduction data led to significant inaccuracies there – in those cases, the parallaxes were reverted back to the original Hipparcos parallax data (again, refer to the XHIP paper for further explanation).

    The XHIP data includes more star names (including common/arabic names), which are also presented here. However, note that Gliese numbers higher than 3000 have been removed for ease of reference. Technically these numbers aren’t “Gliese numbers”, they’re “NN” or “Wo(oley)” numbers. Because this could cause confusion, I decided to remove them instead of editing them all, but this isn’t a huge loss since the stars can still be tracked using their HIP numbers or other names.

    If you’ve been using the New Reduction data, then be sure to head over to my Stellar Mapping page to download the new Extended Hipparcos dataset!


    In other news, my Stellar Mapping page now has the Atomic Rockets Seal of Approval! This is Winchell Chung’s way of saying that he likes my work, and I’m very happy about that because I’ve been a fan of his Atomic Rockets website pretty much since it first appeared online (it’s a great resource for any SF fan)! His 3D Starmaps site is also one of the main inspirations for my own stellar mapping efforts! Thanks, Winchell! 🙂

    [Stellar Mapping] CTIOPI dataset added, Stellar Mapping page reorganised!

    I have now added the CTIOPI (Cerro Tololo Interamerican Observatory Parallax Investigation) dataset to my Stellar Mapping page! CTIOPI is another dataset from the RECONS group, aimed at locating red, white, and brown dwarfs that are within 25pc of Sol – it adds 164 stars that are mostly contained within 300 ly of Sol. However, it only covers (roughly) the southern sky as viewed from Earth, so only about half of the volume around Sol contains stars from this dataset – that said, the distribution of CTIOPI stars could be used as a guideline for adding fictional stars in the rest of the volume.

    CTIOPI dataset, looking corewards.

    I have also edited the DENSE dataset to remove all the stars that were duplicated in CTIOPI and HIPPARCOS datasets – the most accurate data has been retained (the original DENSE dataset is no longer available here, though I may make it available again in a later blog update). The CTIOPI dataset has also been edited somewhat to remove duplicates (none of the CTIOPI stars have HIP numbers though, though it does include one star – HIP 3856 – that is missing from the Hipparcos dataset). All CTIOPI entries within 22.7 lightyears have also been removed to avoid overlap with RECONS.

    This means that there should now be no duplicated stars at all if the RECONS, DENSE, CTIOPI and HIPPARCOS datasets are used together, so the combined dataset is now about as accurate as it can be. Full details of these edits can be found in the “CTIOPI-DENSE merging details” section in the Astrosynthesis.txt and Galactic.txt files contained in the new file available from Section 2 of the Stellar Mapping page.

    I’ve also updated and reorganised the Stellar Mapping page to (hopefully) make it easier to decide which datasets to use. If you have already downloaded the DENSE dataset then you should download it again to make sure you have the latest version!

    [Stellar Mapping] RECONS list updated!

    Oops! Gliese 667 slipped through the cracks and wasn’t included in any of the original stellar datasets on my Stellar Mapping page! This is slightly embarrassing since it’s a bit famous for having planets around it! It was within 22.8 ly from Sol, but for some reason wasn’t on the RECONS list – and because it was so close it wasn’t included in the Hipparcos dataset either.

    I’ve now added Gliese 667 to the RECONS CSV files, so if you’ve already downloaded the RECONS data, you’ll need to download the new version so you can include Gliese 667! (I only found it because I was checking the stars on the American Arm for 2300AD!). There shouldn’t be any other missing stars there – I checked the border between RECONS and HIP and couldn’t find any other HIP stars within 22.8 ly that weren’t already on the RECONS list.

    [Stellar Mapping] How to make your own stellar database!

    Looks like my new Stellar Mapping page has been well received so far – thanks to everyone who has shown an interest in it, I hope you’re finding it useful!

    In this article I’m going to show you how to make your own stellar database, with the same tools I used to construct the ones I presented on my mapping page. For this exercise we’ll be relying on something called VizieR, which is a huge online database of thousands of star catalogues. You’ll need to have a basic understanding astronomy to make the most out of this, but it’s not that tricky.

    Let’s say you want to make a database of stars in a corridor between Sol and the famous Pleiades star cluster (if you’re familiar with the 2300AD RPG, this is essentially the path the Bayern took to the Pleiades). We’ll be using the Hipparcos star catalogue, since it has the most accurate parallax measurements (from which we can derive distances).

    Continue reading ‘[Stellar Mapping] How to make your own stellar database!’

    Website Update: Stellar Mapping page updated!

    My new Stellar Mapping page is finally online! This is a complete rewrite of my previous “Realistic Astrography” page, and now includes Equatorial to Galactic co-ordinate conversion files, the complete RECONS (2012) and DENSE star lists, as well as all the data from the Hipparcos, Gliese 3, and Yale catalogues for stars out to 300ly from Sol! And the Further Stars list is also in there too 🙂


    RECONS dataset, looking towards the galactic core.

    The focus has moved away from Traveller and its hex map format (I realised that I was taking accurate data and then making it inaccurate by forcing it into hex map format, so I’ve dropped that completely) and moved towards raw data and Astrosynthesis, but this will still be very useful for anyone interested in using realistic data for the stars near Sol.

    You can check it out at

    I’ll be writing some articles in the coming weeks to expand this – this will include how to use the Vizier stellar databases, and what this means for the 2300AD RPG!

    Website update: Further Stars List uploaded!

    EDIT: This has been superseded by my new Stellar Mapping page!

    I’ve finally added the “Further Star List” to my Realistic Near-Sol Astrography webpage – it’s an excel file containing accurate locations of a selection of major stars (including Vega, Deneb, 51 Pegasi, Spica, Bellatrix and Algol) that are more than 10pc from Sol.

    The format is a bit raw (and I’m not entirely sure why I selected those specific stars to list!). The dark red X/Y/Z columns show the distances in each direction (Sol is the origin, +X is Coreward, +Y is Spinward, +Z is “above” Sol). If you have trouble interpreting it, let me know!

    You can doublecheck the stars too – you can use the Convert spreadsheet in Section 1 of the mapping page to convert the RA/Dec of any stars into X/Y/Z coordinates. If you have astronomy software like Celestia, open it up and activate the Galactic Grid and rotate it so that you’re facing 0° latitude and 0° longitude – you’re now looking directly along the +X axis. Turn to look at 0° Lat, 90° Lon and you’re looking directly along the +Y axis. Look at the Galactic north pole, and you’re looking directly along the +Z axis. You should be able to find your stars using this (e.g. Aldebaran is pretty much directly along the -X direction, and down a bit on the Z axis. Look towards 180° Lon direction and -20° Lat, and there it is!).

    I’ve been sitting on this for six and a half years (!!) and finally decided that I’m never going to draw hexmaps showing these stars, so I may as well just release the data and let other people figure it out! Enjoy! 🙂

    The link is at

    Kepler discovers the first extrasolar rocky planet!

    Artist's impression of Kepler 10-b (Credit: NASA/Kepler Mission/Dana Berry)

    Full story at
    Star and planet stats at: (Kepler ID is 11904151)
    Discovery paper at:

    Big news today – Kepler has discovered its first extrasolar rocky planet, around a sun-like star about 564 lightyears away! Full stats, including the transit lightcurve can be found here. Interestingly the star may be very old – the age estimate is around 11.9 billion years – about as old as stars can get in our galaxy!

    Continue reading ‘Kepler discovers the first extrasolar rocky planet!’

    [Review] Fun with Gravity Simulator

    Lately I’ve been playing around (again) with a very interesting program called Gravity Simulator. I’ve been using it on and off for the past four years or so, and it’s proved to be a very useful tool for worldbuilding.

    Gravity Simulator is a Windows-based program that allows you to create celestial objects orbiting eachother and see what happens to their orbits under the influence of gravity. You can create planets orbiting stars, satellites orbiting planets, and even asteroid belts – if it can orbit something, it can be made to work here. The algorithms used in the program don’t quite account for everything (for example, the change in orbit caused the transfer of angular momentum between two bodies by tidal forces is not calculated), but the results are still very accurate.

    Planetary orbits evolving (spiralling outwards) while a star loses mass

    The good points are that it’s a very powerful orbital modelling tool, and known phenomena such as orbital resonances and the Kozai mechanism (where a planet’s eccentricity can be increased by interactions with a nearby massive object in an inclined orbit) have been known to naturally come out of the simulations. It can also output to a data file that you can then use to plot graphs of parameters using Excel (e.g. semimajor axis vs time), and can output screenshots too so that you can make animations if you have movie-making software.

    To create a system, you just enter the mass and orbital parameters for all the objects and then set it going – you can even create entire asteroid belts by getting it to create many objects with a range of parameters that you specify (though the more objects you have, the more processing is required which obviously slows things down). The program uses a ‘timestep’ system, in which it recalculates everything once per timestep – a smaller timestep means that the resolution of the interactions is higher and they are more accurate as a result, but the downside is that it takes longer to do the calculations. If the timestep is set too large however then the accuracy can be compromised – so the trick is to find a value that is a balance between processing speed and accuracy, which varies depending on what you’re looking at. If you do it right though, you can run a simulation for hundreds of thousands (or millions) of years of simulated time if your system is left running for long enough. This literally brings stuff that formerly was done on supercomputers into the hands of desktop users!

    To show off a bit, here’s a relatively basic example of a sim I made – 10 closely spaced planets the same size and mass as Earth, separated by 0.1 AU between 1 and 2 AU from the sun. This is what happens when the system is left to run for 175000 years (every second of video corresponds to the passage of 747 years of simulated time) – all of the action is in the first 2:50 mins of the video, after that nothing much happens other than a bit of precession of the remaining orbits. The planets start off in circular orbits but then they start to get unstable and individual worlds eventually start making close approaches to eachother, which really disrupts their orbits. This one has it all – orbital precession, collisions, and planets thrown into very eccentric orbits! At the end of the run, only four planets are left, and I suspect that if I’d left it running for longer one or two of those might eventually be lost too.

    Orbital Evolution of 10 close planets, simulated over 175,000 years

    There’s a good discussion forum for it too, and the author of the program is there quite often and is very helpful. Being a rather specialised program, only a handful of people post to the forums on a regular basis (I am one of them – I post there as “EDG”) but there’s a lot of interesting material posted there (especially by frankuitaalst, who posts a lot of very interesting animations and graphs of resonances). I’ve done some investigations myself of the Kozai mechanism, and used the program to track the evolution of asteroid orbits while a star loses mass as it changes from red giant to white dwarf.

    This is why I think Gravity Simulator is so great – it’s an excellent tool for curiosity-driven science (the best kind of science, I think!). I know that more often than not I didn’t have a clue what the result would be when I started running my simulations, and it’s really fun to see how a complex system turns out. As a result, it’s fantastically educational too.

    The downside is that the program is a little fiddly to use, and it’s probably going to be a bit scary at first if you haven’t had any previous experience with orbital dynamics. There are example simulations that you can download from the gravity simulator website though, and you can find the Tutorial/Help File there too which explains how everything works (you can also access this page through the Help menu in the program). Plus you can always ask for help on the forums if you’re stuck!

    Another thing to be aware of is that the version of the program that you can download from the website via the download page there is somewhat old – once you’ve installed it from there, you should grab the latest beta of the executable from the forums, copy that into the folder you installed it to, and use that as the executable instead. This adds some very handy functionality, including the ability to create new objects with a range of values (handy for asteroid belts) and to dynamically vary the timestep so that it slows down when objects get close enough to gravitationally interact.

    Overall, Gravity Simulator is a great educational tool and produces some fascinating results. It’s pretty much unsurpassed as an general orbital modelling tool (I’m sure orbital dynamicists use their own custom programs that are way more technical, but this is great for us non-professionals!), and there’s a lot of support for it (many sample simulations can be found on the rest of website as well as on the forums). It’s well worth checking out and playing around with anyway, and if you have any interest in orbital dynamics then it’s a must-have!