Stellar Mass and size

[Blue Ghost]

A pet peeve of mine is cruising the net and seeing the plethora of adventure or system writeups using the extended system generator to determine stellar mass. It seems like there are no systems with dwarf stars or super/hyper giants, and every star in Traveller is a "main sequence star".

Here's a chart to give you a better idea of what main sequence and NON main sequence stars are;

http://calgary.rasc.ca/images/HR_Diagram1.jpg

 

[whulorigan]

A pet peeve of mine is cruising the net and seeing the plethora of adventure or system writeups using the extended system generator to determine stellar mass. It seems like there are no systems with dwarf stars or super/hyper giants, and every star in Traveller is a "main sequence star".

Here's a chart to give you a better idea of what main sequence and NON main sequence stars are;

http://calgary.rasc.ca/images/HR_Diagram1.jpg

Keep in mind that 80% of stars are Red Main-Sequence (i.e. Red Dwarf) Stars, and that a significant percentage of the remainig 20% are Main-Sequence (i.e. Dwarf) stars of type K, G, and F, in decreasing frequency in that order. The number of A-type stars are fairly rare (to say nothing of the extremely small number of Type-B and Type-O).

Also, B and O Type Stars have very short lifespans on the universal time scale (on the order of millions of years, not billions), so the few that do form die fairly quickly. Most of them will already be white (degenerate) dwarfs (or more likely neutron stars) unless they are located in an active star-forming region.

White (degenerate) dwarfs (former Type-A thru Type-K Main-sequence stars) account for approximately 6% of the stars observed in the galaxy.

 

[Blue Ghost]

Well, as I graduate away from here I feel the need to clarify short comings of the setting and game in general, and this has always been one of them.

It just seems to me that there'd be a greater variety. If we use your statistics, then most colonized or developed worlds orbit red stars (not necessarily giants or dwarf stars), but there seems to be a real emphasis on Earth clones orbiting Sol clones.

What's even more interesting is that in the extended write ups I've read there will be a label of "main sequence star" for a something that is clearly not in the main sequence (a star in the middle band on the chart). Example, I wish I could remember the link, but I think I came across someone's write up of Aldebaran, and they called it a "main sequence star", when it's clearly a supergiant.

All that sounds like nitpicking, but in terms of gaming, particularly for starship oriented adventures, I would think the color of the natural light on a world or in space to be important for not just atmosphere and setting, but for identifying targets or classifying flora and fauna.

 

[inexorabletash]

In the T5SS reviewed sectors, 23668 stars total:

B: 1 = 0.0042% - real is 0.13%
A: 203 = 0.86% - real is 0.6%
F: 2315 = 9.78% - real is 3%
G: 2935 = 12.40% - real is 7.6%
K: 4254 = 17.97% - real is 12.1%
M: 13817 = 58.38% - real is 76.45%
D (white dwarf): 142 = 0.6%
BD (brown dwarf): 1 = 0.0042%

(Real numbers from http://en.wikipedia.org/wiki/Stellar_classification)

So... M is slightly underrepresented, F/G/K are somewhat overrepresented, but not hugely. If you allow that empty hexes might have stars considered uninteresting (i.e. no planets) there may be a selection bias in the data.

 

[Blue Ghost]

Like my astronomy professors used to say; "Oh, be a fine girl and kiss me." That's interesting. I suppose it could be fixed in the write up as our section of the spiral arm has so many different types of stars.

But your breakdown indicates that there's one blue hypergiant (how do you set a game around that?), 203 supergiant blue stars, with the rest being main sequence. But even then we don't really know their mass, just their spectral distribution.

 

[aramis]

In the T5SS reviewed sectors, 23668 stars total:

B: 1 = 0.0042% - real is 0.13%
A: 203 = 0.86% - real is 0.6%
F: 2315 = 9.78% - real is 3%
G: 2935 = 12.40% - real is 7.6%
K: 4254 = 17.97% - real is 12.1%
M: 13817 = 58.38% - real is 76.45%
D (white dwarf): 142 = 0.6%
BD (brown dwarf): 1 = 0.0042%

(Real numbers from http://en.wikipedia.org/wiki/Stellar_classification)

So... M is slightly underrepresented, F/G/K are somewhat overrepresented, but not hugely. If you allow that empty hexes might have stars considered uninteresting (i.e. no planets) there may be a selection bias in the data.

It's worth noting that there is a VERY strong distance bias in the real data. We literally cannot see the dim red M_V's far away, let alone the Class L and T stars. And the distant M_III and M_IV are still less able to be detected at a distance due to lower luminosities than even a small class F_V or F_VI.

And distinguishing an L5V dwarf from a L5 Brown Dwarf is a matter of estimating if it's ever experienced fusion... basically, is it an older ≥13 M♃ that's cooled, or a still young and warm ≤13 M♃ substellar object. Either way, it's about 1.1 jupiter diameters in diameter...

And note that the scale is no longer OBAFGKM - it's OBAFGKMLTY. Certain older texts used OBAFGKMNS, but N and S got used for other stuff instead, because no one was finding those dim things... and then, they found them around the turn of the century... and now they readded three categories past M... Y is cool enough to not have any visible light emission....

T8 is 500-600° C... a Y class object is only about 300°-400° C...

http://www.uni.edu/morgans/astro/course/Notes/section2/spectraltemps.html
http://www.skyandtelescope.com/astronomy-equipment/the-spectral-types-of-stars/

 

[Blue Ghost]

Interesting.

Does that mean that inexorabletash's postulation about empty hexes might be correct? Has Marc Miller considered this for the map?

 

[Carlobrand]

Interesting.

Does that mean that inexorabletash's postulation about empty hexes might be correct? Has Marc Miller considered this for the map?

It's certainly a way of bailing players out of a tight fix, and of introducing elements like secret pirate bases. MWAHAHAAAAA! :devil:

 

[Blue Ghost]

Another pirate thread?

Seriously, it might be worth writing up. A hidden pirate base on some world orbiting an undetected brown dwarf.

 

[Blue Ghost]

This group of scientists explain the classification, and in fact use the very same chart I posted.

https://www.youtube.com/watch?v=R6_dZhE-4bk

 

[GypsyComet]

some world orbiting an undetected brown dwarf.

I believe the H2G2 phrasing is more suitable in an age of densitometers, easy placement of observation platforms at the edge of a system, and ships everywhere. Brown Dwarf stars and rogue planets are less likely to be undetected, and more likely to be simply "unregarded".

Most won't have planets, everything is bone chillingly cold, and there is always the risk of an entropy shock if you land (see The McAndrew Chroncles).

Local navies and/or the IISS may survey the nearby stuff, particularly if it might get into the jump lanes and grab passers by or be useful for, yes, pirates.

 

[Blue Ghost]

Interesting. Do you think that perhaps it might be tougher to find one the further away you got from a known "bright" main sequence star?

I think that would make for some interesting pirate scenarios; secret maps to the secret pirate base, or perhaps to some foreign / enemy listening post or something. Maybe the pirates have slaves there too :CoW:

We haven't had a good old fashioned pirate thread in a while...

 

[GypsyComet]

I think a recent estimate is that there are lots and lots of rogue planets and smaller masses in deep space. Some will be part of the local cluster and largely at rest compared to those stars, while others are relics of other clusters passing through at considerable velocity.

While observational astronomy is going to be a much more local science in the Third Imperium (why observe from 50 LY when you can hop in a ship and go look up close?), the technology of detection of cold objects has likely, if you take a cross edition view, gotten easier. I would prefer to think that it still requires large installations in remote locations, if only for the adventure possibilities so enabled (not to mention those possibilities squashed by having observational astronomy be too easy), and to get all those buzzing little fusion plants and physics-bending M-Drives out of your field of view. One or two big and properly coordinated Survey Densitometer Arrays (ie. not your garden variety ship sensor densitometers) parked in the outer system should be able to spot and plot a fair percentage of Oort Cloud objects (little stuff up close) and the medium to large-sized rogues a bit farther out. If some mystery is desired, even this is not going to get you all the way to the next system, but I know some people will insist that a TL15 SDA would be able to find a Scout Ship in the next Oort Cloud over.

The effect *should* be to provide somewhat incomplete records of rogues and brown Dwarf stars close to the big developed worlds, and fragmentary records everywhere else. Big Astronomy is not something most Pop 4 or 5 worlds are worrying about.

That said, any system with traffic, and thus some modicum of traffic control, is eventually going to spot a deep Oort or rogue object that suddenly warms up, so deep space pirate bases still need to be careful about emissions.

 

[Blue Ghost]

Interesting. I guess that begs the question of what methods TL10 to TL15 can employ to find a rogue body. If it was orbiting a dim brown dwarf, then I would think finding the star, measuring wobble and what not, to be sufficient. And I think that would make for a good player scenario (or even campaign) with the proper story line.

But would a cold (or perhaps just vacuum) world be as easy? Especially if it was say two hexes out instead?

Also, what exactly is shock-entropy?

 

[aramis]

I think a recent estimate is that there are lots and lots of rogue planets and smaller masses in deep space. Some will be part of the local cluster and largely at rest compared to those stars, while others are relics of other clusters passing through at considerable velocity.

While observational astronomy is going to be a much more local science in the Third Imperium (why observe from 50 LY when you can hop in a ship and go look up close?), the technology of detection of cold objects has likely, if you take a cross edition view, gotten easier. I would prefer to think that it still requires large installations in remote locations, if only for the adventure possibilities so enabled (not to mention those possibilities squashed by having observational astronomy be too easy), and to get all those buzzing little fusion plants and physics-bending M-Drives out of your field of view. One or two big and properly coordinated Survey Densitometer Arrays (ie. not your garden variety ship sensor densitometers) parked in the outer system should be able to spot and plot a fair percentage of Oort Cloud objects (little stuff up close) and the medium to large-sized rogues a bit farther out. If some mystery is desired, even this is not going to get you all the way to the next system, but I know some people will insist that a TL15 SDA would be able to find a Scout Ship in the next Oort Cloud over.

The effect *should* be to provide somewhat incomplete records of rogues and brown Dwarf stars close to the big developed worlds, and fragmentary records everywhere else. Big Astronomy is not something most Pop 4 or 5 worlds are worrying about.

That said, any system with traffic, and thus some modicum of traffic control, is eventually going to spot a deep Oort or rogue object that suddenly warms up, so deep space pirate bases still need to be careful about emissions.

The garden variety ships can do reasonable sky surveys (1m or larger optics, 10m & up synthetic aperture EMS kits..) in a typical system, if part of your docking fees is to upload an assigned image vector imaging scan or 4, and each Class A/B/C starport has a miniframe for handling it... everything within 1000AU will be catalogued with reasonable quality stills for aligned image automated blink comparator work.

Given even one or two ships a week, the level of "in system" information is going to be well beyond what we currently have. A 5 minute imaging sec centered on the same stars from 100D and 1D will be a nearly free addition and will generate 2-10 different windows of data per ship, and can rapidly detect a huge raft of data.

In a major system like Regina, the least well tracked area is likely to be orbit, simply because stuff keeps getting added and knocked down!

a handful of solar orbiting data-gathering scopes are likely to be de rigueur for most systems with populations. If you are looking for enemy scoutships, you're still likely to notice 10m asteroids, too... similar magnitudes at range in visible. It's likely the IN has mapped every rock above 3m within 1000 diameters of every pop 7+ world within 12 Pc of the border... simply to prevent false positives.

 

[Blue Ghost]

But a system doesn't take up an entire hex on a subsector map. If you map everything out to just beyond the Oort cloud, then what about stuff that's truly in interstellar space?

Also, you did say 12 parsecs, didn't you? Meaning 12 parsecs out beyond the Imperial border. I would think political considerations would stop that kind of data sharing. Maybe for law enforcement purposes the Zhos and others would swap data, but if they got a listening post, or even a hidden full fledged base out in deep space around an "uncatalogued" rogue world, I would think they would keep that kind of thing secret.

 

[GypsyComet]

Interesting. I guess that begs the question of what methods TL10 to TL15 can employ to find a rogue body. If it was orbiting a dim brown dwarf, then I would think finding the star, measuring wobble and what not, to be sufficient. And I think that would make for a good player scenario (or even campaign) with the proper story line.

But would a cold (or perhaps just vacuum) world be as easy? Especially if it was say two hexes out instead?

Also, what exactly is shock-entropy?

A Densitometer Array isn't dependent on reflected light, but remains, IMO, a limited range device. Cold objects that have enough mass for their range will show up easily. The trick is getting that big piece of hardware to the right place. Densitometers start, in MT, at TL10, so they are likely a near sky tool in any system with the infrastructure. IMO a Survey Array is beyond the size that Adventure Class ships can transport even at TL15, so big money and big infrastructure is required.

Shock-entropy is posited in one story of Charles Sheffield's McAndrew Chronicles, though he didn't call it that. A body so cold and devoid of external input that entropy is all but stopped. Whether it was the nature of the drives those stories use or simply the act of landing, the added energy of landing on the body, including the kinetic energy of landing and walking around and the added heat of the ship and the person, was enough to cause local earthquakes, break the ground near the ship, and nearly kill the explorer. Similar in some ways to the fate of the Chinese ship in Clarke's 2010. Adding energy to a very low energy environment can have unintended consequences.

 

[Blue Ghost]

Shock Entropy; well, it would be an interesting scenario. I imagine it would have to be an aggregate body, possibly mostly made of up various ices. In order for it to come together it would have had to have done so in deep space, possibly intergalactic space, and then get caught up by the Shapley gravity-well...it is a posit, but it is interesting. I've never read 2010 nor that work you cited.

Loose tangent; back in the early 90s I wrote some fiction about a team of adventurers hired by a patron to explore an Amber Zoned world. It was Amber because there was an Ancient site on it. It was very Earth-like, and there the Ancients (or somebody) had constructed a network of subterranean habitable nodes connected by a freeway like lattice. The problem I had, and how this relates to this topic, was that the Imperial Navy was hot on their heels. So I had the adventurers escape into the underground highway network.

The only problem is that military grade naval sensors/scanners can penetrate deep underground (MegaTraveller era). So I stopped writing (I may revive the concept now).

With such powerful gear for detection, I did wonder how any pirate could operate, and how there might be any unexplored or undiscovered stars and worlds as per Book-6 (assuming Book-6 could be applied to MT).

Very interesting.

 

[GypsyComet]

The only problem is that military grade naval sensors/scanners can penetrate deep underground (MegaTraveller era)...

With such powerful gear for detection, I did wonder how any pirate could operate, and how there might be any unexplored or undiscovered stars and worlds as per Book-6 (assuming Book-6 could be applied to MT).

Very interesting.

MT went overboard on sensors in several directions. The MT version of densitometers are waaay too powerful for Traveller standards, being more in line with Star Trek. The MT Neutrino Sensor is also in that category. Later editions dialed it back a bit, which is why I see Densitometers with serious range as being BIG regardless of TL, while neutrino sensors are a survey tool, not a combat sensor.

The garden variety ships can do reasonable sky surveys (1m or larger optics, 10m & up synthetic aperture EMS kits..) in a typical system, if part of your docking fees is to upload an assigned image vector imaging scan or 4, and each Class A/B/C starport has a miniframe for handling it... everything within 1000AU will be catalogued with reasonable quality stills for aligned image automated blink comparator work.

...

It's likely the IN has mapped every rock above 3m within 1000 diameters of every pop 7+ world within 12 Pc of the border... simply to prevent false positives.

Possibly, but 1000 AU is still small potatoes. One map hex is around 200,000 AU across. For illustrative purposes, I recommend grabbing the digital version of the Judges Guild overland hex map at http://judgesguild.org/download/ . This is a large hex with a smaller grid 25 hexes across within it. If we take the large hex to be a Traveller standard space hex, the smaller hexes are ~8,000 AU across. Pick one small hex for our system. All of our planets vanish into a tiny dot in that hex. Our Oort Cloud extends about 6 hexes out from that. The rest of the big hex is Rogue territory...

 

[aramis]

MT went overboard on sensors in several directions. The MT version of densitometers are waaay too powerful for Traveller standards, being more in line with Star Trek. The MT Neutrino Sensor is also in that category. Later editions dialed it back a bit, which is why I see Densitometers with serious range as being BIG regardless of TL, while neutrino sensors are a survey tool, not a combat sensor.




Possibly, but 1000 AU is still small potatoes. One map hex is around 200,000 AU across. For illustrative purposes, I recommend grabbing the digital version of the Judges Guild overland hex map at http://judgesguild.org/download/ . This is a large hex with a smaller grid 25 hexes across within it. If we take the large hex to be a Traveller standard space hex, the smaller hexes are ~8,000 AU across. Pick one small hex for our system. All of our planets vanish into a tiny dot in that hex. Our Oort Cloud extends about 6 hexes out from that. The rest of the big hex is Rogue territory...

1000 AU is plenty for safety purposes. It's just shy of 6 light days. If you can spot a 10m object at 1000AU, you can spot a 100km object at 10,000AU ... because, given similar albedo, that's about the same apparent magnitude.

Note: reason for the fourth power function: 1/x^2 energy per area recieved at target, and 1/x^2 of that back to sensor.