Stellar Data

[ovka]

CT, MT, and TNE all had a set of tables with stellar data. The data looks to be pretty much the same across the versions.

Reading through CT-B6, the orbital distances were determined using the Titius-Bode Law (which may be valid and may just be a mathematical curiosity). Whether or not it is valid is immaterial. It produces interesting results usable in our beloved game.

CT-B6 also has tables for stellar magnitude, luminosity, temperature, radius, and mass. Can anyone tell me where this data came from? I have some calculations that I would like to perform, but I would like to do a slightly deeper dive into the numbers first.

I have heard good things about GURPS Space 4e in this regard, and I've taken a look at the Gurps Handbook of the Planets spreadsheet (though I haven't seen the actual book). CT-B6 has some oddities like values that decrease and then increase as you move through the table. GHotP does not appear to have this.

CT-B6 says to extrapolate between the X0 and X5 values (where X is one of OBAFGKM, e.g. K1 is 1/5 of the way between K0 and K5). It also says (along with some other sources including T5) that K5IV through M9IV stars are impossible. T5 also lists habitable zone orbits for K1IV, K2IV, and K3IV. It isn't possible to extrapolate values between K0IV and K5IV, because none of the tables have values for K5IV.

I know there are some aspiring (perhaps even actual) astro-physicists on this board who know more about this than I do. Can anyone offer me some assistance?

Cheers,

Baron Ovka

 

[aramis]

The TBR doesn't hold up even in our system. What the Sciences have detected also doesn't fit the TBR.

It's one of the known divergences of the OTU from the real universe..

Note that T20 uses the same tables modified slightly for better fit to the stellar catalogues.
T4 as well.

T5 includes some additions to capture more of the real universe, but sticks to the TBR.

The TBR makes systems more "sensible" in a way; too bad it doesn't work in the real world. (It doesn't even work for the satellite orbits of the transjovian worlds in our systems.)

As for extrapolations - find a good scientific HRD ... and approximate the curve... You can find temperature and absolute luminosity using it. You can also look up class VI subdwarfs on it, for some editions, and VII subdwarves on a few... (VII are not on the current ones, but big cloud "white dwarves" are.)

Also note - M10-M19 are used right alongside the parralel Type L 0-9; differences in the emission lines, not temperature, seem to be the division, with some prefering M with subscripts to the newer L designation. (In the 70's, the M10 was N0 and M15 or so was S0, but no N0-S9 stars were detected, and S got reused elsewhere... then, after 2000, M10-M19 stars started showing up in numbers, and there's no agreement on whether they're supposed to be L0-9 or M10-M19... T and Y are both supposed to be below deuterium-Protium fusion temps/pressures, and Y is below ANY stable hydrogen fusion, but big enough to emit significant thermal radiation for billions of years.

Since there isn't a consensus on L/T/Y vs M10-20+... it's a bit early to make those leaps.

Note also: Similar diagrams to the HRD exist plotting mass vs color...

I once had access to a graphing typewriter... I used it to draw the curves for mass vs stellar type, and was able to extend them. That exercise COULD be repeated...

 

[tjoneslo]

Reading through CT-B6, the orbital distances were determined using the Titius-Bode Law (which may be valid and may just be a mathematical curiosity). Whether or not it is valid is immaterial. It produces interesting results usable in our beloved game.

If you read more carefully in book 6, there is an option to set the orbit of a world to plus or minus a few tenths of an orbit. Rather than accepting the value as given on the table, you can adjust it. For example, instead of every world at orbit 3, you can have worlds at orbit 3.5 or orbit 2.8.

I know that GT: First in uses the Titus-Bode law but with a variation. The original TB, the orbits are determined by two numbers, a starting orbit and a multiplier, and a formula. GT:First in uses the same formula, but alters both the starting number and multiplier (three options for each one). This gives more variations in the orbits.

If you want the ultimate in orbital selection, you can use both.

The one thing I have not seen any version do is supply orbital eccentricity. The systems assume circular or pretty close to circular orbits. Probably for simplicity and stability of the system.

 

[GypsyComet]

The one thing I have not seen any version do is supply orbital eccentricity. The systems assume circular or pretty close to circular orbits. Probably for simplicity and stability of the system.

I seem to recall Grand Survey/WBH having a roll for eccentricity.

 

[G. Kashkanun Anderson]

The one thing I have not seen any version do is supply orbital eccentricity. The systems assume circular or pretty close to circular orbits. Probably for simplicity and stability of the system.

LBB6 presents it as a 'color' issue. There's a table near the back of the book, on the same page where the tables for albedo, axial tilt and the rest are located, but there's no exact presentation on how to set it up other than by Referee fiat. Also, it assumes that 0.25e is about as eccentric as you should expect any orbit to get.

CT-B6 also has tables for stellar magnitude, luminosity, temperature, radius, and mass. Can anyone tell me where this data came from? I have some calculations that I would like to perform, but I would like to do a slightly deeper dive into the numbers first.

Broadly speaking, the numbers look about good enough for the type V stars (which covers about 99% of all living stars), and can be sourced just about anywhere. A caveat, though, in that the LBB6 tables appear to be built around the assumption that the star you're looking at is at Sol's state of evolution (about halfway through its Main Sequence phase). A G0V star, for example, is not going to have a 1.03Sol radius and a bolometric luminosity of 1.21Sol at 2 billion years, 6 billion years or 8 billion years, since that number represents where a typical one would be at about 3-4 billion years (the G0V equivalent to where a G2V star is at about 4-5 billion years). So if you start looking up random real life G-Type Main Sequence stars for comparison, don't be surprised if their values make the LBB6 numbers look wonky, especially if the star's age (and/or metallicity) is far afield of Sol's values.

CT-B6 says to extrapolate between the X0 and X5 values (where X is one of OBAFGKM, e.g. K1 is 1/5 of the way between K0 and K5). It also says (along with some other sources including T5) that K5IV through M9IV stars are impossible. T5 also lists habitable zone orbits for K1IV, K2IV, and K3IV. It isn't possible to extrapolate values between K0IV and K5IV, because none of the tables have values for K5IV.

Type IV stars are just an evolved version of type V stars (the Sun is going to be one in about 5.5 billion years), so you could kludge a broad relationship between K0IV and K5IV by looking at the relationship between its K0V and K5V neighbors. Keep in mind, though, that as an intermediate phase between V and III, the actual values for any given type IV subgiant are potentially all over the place -- it's a smooth gradient along a rapidly (by interstellar standards) changing set of values, not an abrupt shift. Actually, you could say that about any of the explicitly post Main Sequence stellar types (the subgiants plus any of the G through M giant classes).

 

[Blue Ghost]

I want to do some write-ups for systems. Is there a good text on the topic ovka is referring to?

 

[tjoneslo]

I want to do some write-ups for systems. Is there a good text on the topic ovka is referring to?

Are you looking for real science information or a gaming reference?

For the latter, I just got GURPS:Space for GURPS 4th. I will say it has the best (science accurate) system generation I've seen. It has all the topics discussed above, with formulas and tables, excellent descriptions of why things are and where to break rules for more interesting results. Except for the final 20 pages of the book there are no GURPSy rules. Highly recommended.

 

[Enoki]

If you read more carefully in book 6, there is an option to set the orbit of a world to plus or minus a few tenths of an orbit. Rather than accepting the value as given on the table, you can adjust it. For example, instead of every world at orbit 3, you can have worlds at orbit 3.5 or orbit 2.8.

I know that GT: First in uses the Titus-Bode law but with a variation. The original TB, the orbits are determined by two numbers, a starting orbit and a multiplier, and a formula. GT:First in uses the same formula, but alters both the starting number and multiplier (three options for each one). This gives more variations in the orbits.

If you want the ultimate in orbital selection, you can use both.

The one thing I have not seen any version do is supply orbital eccentricity. The systems assume circular or pretty close to circular orbits. Probably for simplicity and stability of the system.

That's why I usually simplify things from Scouts. I round off the orbits to whole numbers and then adjust things where necessary (usually with the main world) using stuff like the temperature formulas to make the main world the "right" temperature, etc. You can also adjust the temperature, etc., of the star some to "fix" this problem too.

Eccentricity and axial tilt are on pg. 48 of Socuts at least in the LBB original version.

 

[Nathan Brazil]

There are a few websites that break it down to to individual stellar class, decimal and stellar size combination.

Searching for "Stellar Classification Table" on Google, this first one seemed nice. http://www.isthe.com/chongo/tech/astro/HR-temp-mass-table-byhrclass.html was pretty nice. It also has the RGB hexidecimal values of the star in question, if you want to display the actual color of the star on a web page or some other such thing.

It readily admits that some data was approximated, but it cites its sources in case YOU want to dig further. I did, some are on archive.org.

I am not too concerned. The main things I want from a stellar characteristics table is diameter/radius for the minimum orbit allowed (Bode's Law or just AU distance), 100d limit of the star's Jump Shadow, the mass should I ever play Book 2 Combat by a star again, and luminosity for the habitable zone.

 

[Blue Ghost]

Are you looking for real science information or a gaming reference?

For the latter, I just got GURPS:Space for GURPS 4th. I will say it has the best (science accurate) system generation I've seen. It has all the topics discussed above, with formulas and tables, excellent descriptions of why things are and where to break rules for more interesting results. Except for the final 20 pages of the book there are no GURPSy rules. Highly recommended.

I was looking for hard scientific data for the purposes of doing a game write up for publishing.

I'm tempted to just make stuff up, but fear the rules-lawyer citing some text about how my planetary data is impossible.

 

[77topaz]

I was looking for hard scientific data for the purposes of doing a game write up for publishing.

I'm tempted to just make stuff up, but fear the rules-lawyer citing some text about how my planetary data is impossible.

If you're the one who's written the published product, though, it doesn't matter what the rules-lawyer says, what you've written is canon (for your TU, at least). :devil:

 

[Nathan Brazil]

I was looking for hard scientific data for the purposes of doing a game write up for publishing.

I'm tempted to just make stuff up, but fear the rules-lawyer citing some text about how my planetary data is impossible.

Some things might seem cool, but sometimes reality, as science can currently explains it, not so much. Verisimilitude sir. Gotcha. Really, you should worry if it bothers you more.

Homo erectus being transplanted to 40+ different environments and evolving to still be mostly interfertile to one another 300,000 years later Blue Ghost. :CoW: Just saying. Yea, the OTU is always real hard science, right.:rofl:

 

[aramis]

I was looking for hard scientific data for the purposes of doing a game write up for publishing.

I'm tempted to just make stuff up, but fear the rules-lawyer citing some text about how my planetary data is impossible.

You'll get that anyway, since there are about three major schools of thought on exoplanetary formation that I've noticed, and the only thing they agree upon is that "classical accretion isn't fully correct" and "The Titus-Bode Relationship isn't an accurate relationship for formation, no matter how nicely it seems to work for the inner planets' orbits"...

Simply put, the extant dataset invalidates the 1970's models upon whcih Traveller was based. So, if you use Real World data, it's not traveller generatable.
If you use any of the current major theory-sets, it won't jive with the others... and it won't match traveller.
If you use Traveller, most results are within the possible range for at least one theory set, but maybe not all, and it's highly likely to be complained about for being "not realistic enough."

Simply put, it's a no-win situation, so pick a method you're comfortable with, and go for it.

 

[Blue Ghost]

....

.... Okay

So just ... just make "stuff" up then? I can do that. Watch me work my magic

 

[aramis]

....

.... Okay

So just ... just make "stuff" up then? I can do that. Watch me work my magic

Well, that is an option... Make it plausible enough and there won't be too much griping.

 

[GypsyComet]

Make it plausible enough and there won't be too much griping.

Particularly since "plausible" is a moving target that is running for the horizon at considerable speed.

Traveller's system detailing is getting less plausible by the month just for not being weird enough.

 

[Blue Ghost]

Particularly since "plausible" is a moving target that is running for the horizon at considerable speed.

Traveller's system detailing is getting less plausible by the month just for not being weird enough.

Which is why I asked, because the Weather Channel did a "Most Dangerous Space Weather" TV series, and they ended with a gas giant that orbits a sun every five days or so, and has wind-speeds up to 9000mph.

Try flying your Type-S in that o:

I'd heard of various "laws" or apparent patterns, but it's like anything goes out there. And really what I'm just curious about is given a world's spin, whatever atmosphere it may have, distance from a given star type, and any magnetic field, what would it's climate/temperature be like. But I guess it's more or less a case of being scientifically alert as to what I create.

 

[GypsyComet]

Which is why I asked, because the Weather Channel did a "Most Dangerous Space Weather" TV series, and they ended with a gas giant that orbits a sun every five days or so, and has wind-speeds up to 9000mph.

Try flying your Type-S in that o:

I suspect that inner zone gas giants are poor candidates for skimming in general. Outer zone gas giants are hostile enough...

 

[G. Kashkanun Anderson]

I suspect that inner zone gas giants are poor candidates for skimming in general. Outer zone gas giants are hostile enough...

Not in the rule set, but if I had my druthers, I'd choose to skim from a gas dwarf.

 

[Blue Ghost]

Yea, the OTU is always real hard science, right.:rofl:

In my best Buzz Lightyear voice; "You're, mocking me, aren't you."