Reading stellar types

[Daddicus]

The last few items on the Second Survey Format don't seem to have any definitions. On page 407, Regina is listed, with the notation

PBGW A Stellar

above the values

703 8 Im F7 V DM M3 V

However, I can't find any definitions for some of the abbreviations used.

• PBG is Population, Belts, and Giants.
• W is Worlds
• I'm not sure what A is
• I'm not sure what F7 V DM M3 V refers to. See below.

My guess is that F7 is spectral type F decimal 7.

V does not seem to be defined (although I found the table where it is chosen: page 412, bottom middle/right). (Both after F7 and also later, following M3.)

I can't figure out at all what DM means.

M3 seems to be another spectral type and decimal, with another V tossed in for good measure.

Can anybody explain what they mean?

 

[Magnus von Thornwood]

I think I have this....

The "A" is Aligence and the "F7 V DM M3 V" is one Main Squence F star with as you guessed a spectral decimal of 7, the DM (if I remember correctly) is Dwarf Star and the last is an M3 Main Squence.

No, I don't have a page ref, but it was early in SysGen.

If, I am wrong, hopefully someone will give us the correct answers.

 

[tjoneslo]

The last few items on the Second Survey Format don't seem to have any definitions. On page 407, Regina is listed, with the notation

[*]PBG is Population, Belts, and Giants.

Correct, Though the generation of these values is scattered over the next few pages. P is on p.409 at the bottom of Population table. GG and belts counts are p. 413. But there is no definition of how or why these values go together.

[*]W is Worlds

Correct. Again on page 413

[*]I'm not sure what A is

Allegiance, see page 412. This is now also wrong as T5SS has moved to using 4 character allegiance code.

[*]I'm not sure what F7 V DM M3 V refers to. See below.

Stellar types, see the bottom of p. 412. The descriptions given are not explained and assume you know the existing (real world) stellar types.

Stars are defined by Spectral Type (OBAFGKM) and Size (Ia Ib II III V IV). There are two exceptions: BD which is a brown dwarf, a "star" dimmer than M and D (or DM) which are white dwarf star, which occur when a smaller star reaches the end of it's life.

The book does need an explanation of the stellar types/sizes.

Does that help?

 

[pendragonman]

I suspect the rest is placement information

While we have the START of a nice example in Regina on 407, it needs to be finished, explaining every entry in the line clearly and openly.

 

[aramis]

The last few items on the Second Survey Format don't seem to have any definitions. On page 407, Regina is listed, with the notation

PBGW A Stellar

above the values

703 8 Im F7 V DM M3 V

However, I can't find any definitions for some of the abbreviations used.

• I'm not sure what F7 V DM M3 V refers to. See below.

My guess is that F7 is spectral type F decimal 7.

V does not seem to be defined (although I found the table where it is chosen: page 412, bottom middle/right). (Both after F7 and also later, following M3.)

I can't figure out at all what DM means.

M3 seems to be another spectral type and decimal, with another V tossed in for good measure.

Can anybody explain what they mean?

F7 V = Size V (main sequence dwarf) color F7
DM = Size D color M - stellar remnant subdwarf (also called size VII)
M3 V = Size V dwarf of color M3.

The O/B/A/F/G/K/M/L/T/Y sequence denotes color, with O hotter and Y cooler, and each is subdivided into 10 subunits, indicated by 0/1/2/3/4/5/6/7/8/9, with 9 being cooler and 0 the hotter end.

The roman numeral, when capitalized is listed after a space; when no space is used, it's typically in lower case to avoid confusion

EG:
F7v = F7 V
G2v = G2 V

Names for families by size:
Ia Brightest supergiants
Ib Bright Supergiants
II Supergiants
III Giants
IV Giants (sometimes subgiants)
V Dwarfs
VI Subdwarfs
VII white dwarfs (in Traveller, using the older alternate D_ naming method)

Note that size VII is about O5vii to K5vii... but eventually, they're going to all fade to Y9vii or be absorbed by black holes. But that will take at least another 5 billion years.

Brown dwarves, by the way, tend to be size category V... in L0v to T5v ranges.
Traveller lists them as BD...

Anyway, the typical is that if you have a smaller (higher roman numeral) between two larger ones, it's a companion of the one before it.

There's a reason people are wanting to add brackets, braces and parenths to delineate what's there.

 

[Daddicus]

Thanks, guys! It all makes sense now!

 

[aramis]

Thanks, guys! It all makes sense now!

One other thing - there are other real world color codes which Traveller doesn't use -

R_, N_ - Carbon stars - Generally, compare to G5 through L5 ranges, Numbers are about double the width of the G/K/M/L sequence, with N ranges being equivalent to L ranges...
C_,_ replaced R and N with a two axis numbering, first temperature, 2nd carbon ratio. In the 1960's.
C-R and C-N brought back R and N, but with some tweaks. in 1993 or so...
Also added C-J, C-H, and C-Hd.

S - Zirconium Oxide stars.Similar to K5 to M_ range Numbers go S0 to S10. Big ones, at that - Size III typically, if I understand the use. "giants"... but some mean III and IV, rather than III with "giants".

W_ are Wolf-Rayet stars.... comparable to O, but no longer have outer Hydrogen shells.
WN2-WN11, WC4-WC11, and WO1-WO4 are various kinds of Wolf-Rayet stars.
Note that any worlds around them would have been blasted with Hydrogen plasma when the Hydrogen shell left...

Also, lowercase letters other than v and i (usually before them) are appended to number to indicate various anomalies in the spectral signature. So, real world can get funky...

Oh, also, subscripted numbers - they're used with Carbon stars in place of the second number being comma separated.

 

[Macus74Bishop]

Variable Stellar Types

There is an article on Freelance Traveller on Variable star types. (July 2015, Issue #67).

 

[Original_Carl]

I often refer to this when going through MTU data:

https://en.wikipedia.org/wiki/Stellar_classification

I hope it helps you, too.

PBG always gets me, as well. Don't know why I have to look that up all the time.

 

[aramis]

I often refer to this when going through MTU data:

https://en.wikipedia.org/wiki/Stellar_classification

I hope it helps you, too.

PBG always gets me, as well. Don't know why I have to look that up all the time.

THink of it as after a full meal...
Pop the Belt, Gas follows...