Hi All
I've a Question on System descriptions displayed on the Galactic map. This has perplexed me for some time now and would like some clarification either with links to explanations / data or general information with reply's. if possible please.
Okay, when I'm looking at systems on the map there are / is various data shown for that system which is displayed thus (for one example) ...F4 VI, M1 VA.
I understand that 'F' 'M' or 'A' 'B' etc. refers to the star type, and a system can contain various star types designated by these letters and numbers, (I presume a letter followed immediately by a number is an indication of the type and size of the stars?
How do you then pre-calculate (Before you enter that system) whether that system will perhaps contain other bodies in that system, Gas giants, Water worlds, ELW's etc. etc. or is it totally random in this respect?
So basically with the information displayed initially before you enter that system does that give you any indication of probable bodies contained?
My experience is that what these letters and numbers indicate isn't always what you'd expect when you finally enter that system!
Any information appreciated.
Edited for poor grammar
Jack
This is a job for
@Sapyx !
I have been summoned from my yetidom...
The stellar classification system described here (eg. "F4 VI") is essentially the same one that real-world astronomers use to describe real-world stars. Since we can't actually see stars up close becasue we don;t actually have real-world FTL starships, this classification system invented in the early 1900s relies on factors that we can actually measure from Earth, like the visible-light spectrum.
In the example above - "F4 VI", the "F" is the spectral class - in essence, how hot the surface is, and/or the "colour" of the star. M is red, G is yellow, B is blue, and so forth. TGhis letter is the one we can select in the navigational filter for star class.
"4" is the spectral subclass; these numbers range from 0 to 9. Real-world stars are a continuum of temperatures, with no sharp boundary between red "M" and orange "K". So we have these numbers to give an indication of where within the "F" range the star in question lies. An F4 star is roughly in the middle of the F range, partway between "A" and "G", but slightly closer to the cooler "G" end of the F range. An "F0" star is so hot it's almost a class A, while an F9 star is so cool it would be almost a G.
The roman numeral at the end is an indication of the absolute magnitude (or size) of the star. Group I is the largest, the hypergiants. Group II is supergiants, Group III is regular giants, group IV is subgiants. Group V are main sequence or "normal-sized" stars, also known as "dwarf stars". Group VI are "sub-dwarfs" (smaller than normal stars) and Group VII are white dwarf stars. Within a group, star classes are generally proportional to size and mass - a M7 V star is slightly smaller and cooler than an M5 V star, but an M5 III star will be much bigger and heavier, because it's a red giant.
So, for an example, Sol - Earth's sun - is class G2 V: breaking this down, G means yellow, 2 means at the (
edit)
warmer end of the "yellow" range, and V means a normal main-sequence star. So if you find another G2 V star, it ought to be about the same size and brightness as our own sun; a G4 V star would be slightly smaller and cooler, a G0 V star slightly bigger and brighter.
In essence, this data is just telling you basic information about the star, how big and bright it is. It tells you nothing about any planets which might or might not be within the system.
There are correlations between what star type the primary star is, and the likelihood of there being interesting or valuable planets in the system. It is in effect "random" - I've put "random" in quotes because it's chaotic procedural generation rather than true mathematical randomness, but our puny human minds cannot intuitively tell the difference. In theory, you could pre-calculate a star system no-one has ever been to, if you simply enter the star system's name into the algorithms the Stellar Forge uses to generate planetary systems. But since those algorithms are super-secret secrets, the best way of running those algorithms is to actually play the game.
As a general rule, the hotter a star, the bigger the "Goldilocks zone" is within that star system and the more likely it is you'll find valuable planets like ELWs and terraformables. But there is a sharp cutoff - data-crunchers have found that stars hotter than about A5 suddenly have far fewer Earth-like planets. This is why the standard advice for ELW-hunters seeking to min-max their output is "set filters to star class F". While star classes A9 to A6 are even better than F at generating ELWs, the fact that A0 to A5 are much worse and the fact that you can't set the filter to subclasses means that overall it's most worthwhile to just set it to F, where the whole range F0 to F9 are good. Empirically, about 1 in 40 class F systems have an ELW in them, and about 1 in 5 have at least one valuable terraformable.
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