Problems with nebulas in Traveller

[Tom Kalbfus]

Lets say you are in a star system, and 2 parsecs away is a nebula that is 1 parsec away, there is another star system you want to jump to which is in another direction than the nebula, so the nebula is not in the way. However if you apply the 100 diameter rule, nobody within 100 parsecs of this nebula can make a jump, since the nebula's "diameter" is 1 parsec.

 

[simonh]

The galaxy is quite a bit bigger too, and we're actualy inside it.

But the rules say you have to be one hundred diamaters from any object. I don't think nebulas and galaxies count as objects. At best they are composites made up of many smaller discrete objects (planets, dust particles) and as long as you're more that 100D from all the individual components of them, you're good.

Simon Hibbs

 

[Reynard]

I answered this in that other thread but the main point is nebulas on the galactic scale is a lot of transparent gas for the purpose of jumps.

Blackhole are another story when it comes to gravity issues.

 

[simonh]

Blackhole are another story when it comes to gravity issues.

Sure, but not necessarily any more than the star they formed from. But the issue is how do you determine the diameter? I suppose from the event horizon, but that would mean their jump shadow would be a lot smaller than that of the star they formed from. I suppose for many black holes you might calculate the diameter based on the size of the accretion disc.

Simon Hibbs

 

[Condottiere]

I'm fairly sure the intent was around the diameter of a significant gravitational focus.

 

[F33D]

Lets say you are in a star system, and 2 parsecs away is a nebula that is 1 parsec away, there is another star system you want to jump to which is in another direction than the nebula, so the nebula is not in the way. However if you apply the 100 diameter rule, nobody within 100 parsecs of this nebula can make a jump, since the nebula's "diameter" is 1 parsec.

Incorrect. A "nebula" is just gases. There is no rule in Trav about not jumping where there are gas molecules floating around. Otherwise one could not jump anywhere in space.

 

[GypsyComet]

A nebula that has not become a stellar nursery is pretty difuse, and probably lacks the gravitational field to prevent jump.

A stellar nursery nebula, on the other hand, could get pretty sticky to try jumping through.

 

[F33D]

A stellar nursery nebula, on the other hand, could get pretty sticky to try jumping through.

ONLY in the immediate vicinity (a few A.U.) of where a star is convalescing.

 

[GypsyComet]

A stellar nursery nebula, on the other hand, could get pretty sticky to try jumping through.

ONLY in the immediate vicinity (a few A.U.) of where a star is convalescing.

Which is why I said "could".

And I think the word you were looking for is "incubating".

It is an open (and largely conceptual, non-RAW) question whether the gaseous clumping that precedes stellar coalescence or the disk of pre-planetary matter around a young star would be enough to interfere with jump. For plot purposes, the answer will probably be "yes it would", but not everyone thinks that way.

 

[Reynard]

The problem we're stepping in to is how much does the nebular gases have to coalesce towards a protostar stage to have a significant central gravity.

 

[Condottiere]

https://www.youtube.com/watch?v=oD9ARfF9x0o

 

[Tom Kalbfus]

What happens if an inhabited star system in the OTU was in the process of drifting into a nebula that is at least a parsec across? Lets say it is a dark nebula like the Horse head nebula or the coal sack nebula for instance. Over a short distance, say a few parsecs, the Sun continues to shine through the nebula, but space is rather dirty and the nebula blocks out the more distant stars. The night sky as seen from the planet is dark gray, reflecting back light shining from the primary, the planet gets colder, because not all of the sunlight is making it to the planet, so entry into the nebula triggers an ice age, though the planet is still habitable. The sky is still blue during the day, the Sun appears hazy and a bit diffuse even in the clearest sky. If one can't see any of the stars, it may be hard to make an astrogation check in order to jump, though perhaps a radio telescope or infrared might determine the positions of stars.

 

[GypsyComet]

All it would take is an old tradition that informs of the stars they cannot see. By the time they are seriously thinking about space travel, they'll know they live inside a veil.

Note that moving from open space to being completely veiled by a nebula is not quick.

 

[Reynard]

If there is no knowledge of other stars or it's more of a superstitious legend with no present evidence, I'd say there would be no incentive for science to ever bother conceiving travel beyond their star system. What would be the point? That's akin to sailing off the edge of the world.

Make an interesting adventure for player characters if they somehow jump into such a system.

 

[simonh]

What happens if an inhabited star system in the OTU was in the process of drifting into a nebula that is at least a parsec across? Lets say it is a dark nebula like the Horse head nebula or the coal sack nebula for instance.... the planet gets colder, because not all of the sunlight is making it to the planet, so entry into the nebula triggers an ice age, though the planet is still habitable.

I don't think even dark nebulae are so dark that they would have a noticeable effect over such short ranges as one or two AU. The Colasack is roughly 10 parsecs across, so 1 AU is about one 50 millionth of the diameter of the nebula and the dimming effect would be proportionately lower compared to that of the nebula as a whole. The night sky would be pretty dark, with few stars visible, but objects within the same solar system would not be noticeably obscured.

For scale, imagine a very diffuse cloud 1 kilometer across, so dim objects on the far side are obscured but bright lights are still visible. If that was the coal sack, for scale 1 AU is the equivalent of 0.02 millimetres, which is about the thickness of the very finest human hairs.

Simon Hibbs

 

[Condottiere]

Krikkit is a planet located in a dust cloud composed chiefly of the disintegrated remains of the enormous spaceborne computer Hactar.

 

[Nathan Brazil]

Not nebula, but similar, for example have any of you read The Mote in God's Eye?

Oh yea, and precursors to Droyne and Black Globe generators...

 

[F33D]

[For plot purposes, the answer will probably be "yes it would", but not everyone thinks that way.

For "plot purposes"? Is that like you are 101 diameters out but "for plot purposes" you are 90 diameters out? :lol:

 

[GypsyComet]

[For plot purposes, the answer will probably be "yes it would", but not everyone thinks that way.

For "plot purposes"? Is that like you are 101 diameters out but "for plot purposes" you are 90 diameters out? :lol:

No. More like "that's just gas, it won't knock us out of Jump" followed by loud noises, smoke, and everyone leaning to the left as the ship takes on vacuum. :roll:

 

[F33D]

[For plot purposes, the answer will probably be "yes it would", but not everyone thinks that way.

For "plot purposes"? Is that like you are 101 diameters out but "for plot purposes" you are 90 diameters out? :lol:

No. More like "that's just gas, it won't knock us out of Jump" followed by loud noises, smoke, and everyone leaning to the left as the ship takes on vacuum. :roll:

That works for those players who don't know what gravity is. But, for those who finished 4th grade, not so much... :roll: