Subject:
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The "geography" of local space
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Newsgroups:
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lugnet.space
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Date:
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Wed, 3 Nov 1999 09:03:14 GMT
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Viewed:
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561 times
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Hi there!
I have been lurking on LUGNET for a few months now. This is my first
post to LUGNET, and I should probably introduce myself before jumping in
to a discussion, but whatever... I will post a personal intro. over in
lugnet.people under the title "Saying Hello", after I'm done with this.
I've been reading the proposal for an integrated space milieu. There
is a question about what the geography (cosmography?) of this Legoverse
should be. Some people have suggested that what we currently know about
local space should be taken as a starting point. This makes sense --
minifigs are rather human-looking, after all. It is only natural to
assume that they call a Lego Earth their home.
If there has been any argument against using reality as a starting
point, it seems to be that nobody here is that sure what real space
looks like. Tom McDonald says:
> I also am not against someone wanting to do real research about • "what's real" though I
> think that once we establish some sort of map, it should be "first • come, first served" so that
> if someone finds out that IRL there's a huge black hole where we've • put a densely
> populated set of solar systems, then the hole has to be relocated.
Well, I've done a little of that research -- astronomy is one of my
hobbies (I have too many of those!). I'll share what I know with you
here.
As for building models to add to the "Datsville universe" -- well, I'm
not quite ready to do that! First, I have to negotiate with my son for
the pieces. 8^) I'm also kind of a "hard" science fiction fan, and
disinclined to accept FTL travel... but I'm not building anything, so
you can ignore me! 8^) 8^)
> I think it might be cool to just start with what we *very* generally • know about how real
> space is arranged so far, and then let imagination take over. That • way we could still use
> some known real names and objects, but are not strictly limited to • them.
> * How about we start with 100 parsecs (pc) / 326 light years (ly)? Too
big? Too little?
How big should your bubble of explored/explorable space be? Well, it
depends how exotic a setting you want. See comments immediately below.
> ** If you all want to see it, I've got a map from which we could • possibly start. It's from an
> old Star Trek Tech Manual which shows major stars (48 of them in fact) • in a sphere within
> 7 pc, 22.82 ly, centered round our own star Sol (though the original • Federation was much
> bigger than that, more along the lines of 4kpc+). And it does not • show any other objects,
> such as nebulae, black holes, etc.
I wouldn't expect to see any nebulae or black holes on the small-scale
Star Trek map. It is well established that the nearest nebulae and
black holes are much farther than 7 parsecs from the Sun! If such
things were that nearby, life would probably be very different here.
Life might not even exist here at all. We live in a pretty boring
corner of the cosmos, and that's probably good for life. For example,
black holes emit LOTS of X-rays, either through mangling the daylights
out of matter thery're ingesting, or through a more subtle process known
as Hawking radiation. X-rays are quite bad for living things.
Now, the Star Trek manual (Is this the original '70's Trek manual? I
think I still have a copy of it myself somewhere) is likely to have been
fairly accurate -- but it is clearly incomplete. There are about 100
stars known within 7 parsecs of Sol. Most of those have been known for
decades, so it is likely that Trek left off some minor, dim stars. Do
you care about these dim, "red dwarf" stars? Well, they're actually the
most numerous type of star! They're under 1/10 as bright as the sun,
and they're unlikely to have planets where you can walk around on the
surface in your shirtsleeves. One theory holds that they're unlikely to
have any planets at all. But, it's your universe. What kinds of
interesting things might you find in such places?
In that 7 parsec-radius bubble of space, two red dwarf stars were found
in just the past three years. It is estimated that, within this same
radius, there are about 20 more stars waiting to be found. They will
all be red dwarfs. The nearest 25 star *systems* can be found inside a
sphere, centered on Sol, that is 4.01 parsecs in radius. Nine of these
star systems are double or triple stars. There may be more, incredibly
dim stars to be found, even in this close.
If you wanted to keep the Datsville universe this small, there will
almost certainly be planets to explore. Some of them might even prove
to be habitable. (If there is interest, I will be happy to discuss
planets in more detail -- but I'll try to stick to stars in this post,
it's getting long enough already.) But there won't be any exciting
*stellar* objects. Where is the closest known black hole? Neutron
star? Nebula? I can't answer these questions definitively, but I can
state with confidence that you will find no such objects within 50
parsecs of us. We wouldn't fail to notice them, if they were in so
close. We would probably be able to see them by eye, and we would
certainly spot them with even modest telescopes.
The closest "interesting stellar object" is probably the star Vega.
Vega is interesting because it's a young star that still has a disk of
dust and gas circling around it. It is believed that this dust and gas
will eventually condense and form planets. Vega is 7.8 parsecs away.
Next is the red giant star, Arcturus. It's 11.3 parsecs from Sol. The
three nearest blue giant stars are all on the order of 100 parsecs away
(it gets difficult to measure distances accurately, out that far) --
Canopus, Spica, and Acrux. These are supernovae in the making -- and,
mercifully, far from Earth.
You want a nebula? The nearest one that I can find in my references is
the Pleiades. This is a cluster of newborn stars, swaddled in wisps of
gas. The Pleiades are 155 parsecs from the Sun, plus or minus about
10%.
Cygnus X-1 has been called "the closest black hole to Earth." I found
two distance estimates on the Web, and their disagreement shows just how
bad we are at measuring the distance to far-away objects. Once source
says 300 parsecs, another 1800 parsecs. Furthermore, I seem to recall
that a somewhat closer candidate black hole had been located recently.
Use your imagination, I guess!
I can't find any statement claiming that a particular object is "the
closest neutron star." The Crab Nebula contains a famous one. Distance
estimates to the Crab Nebula range from 1100 to 2000 parsecs. Same
problem as the black hole, you see. Nobody is that sure how far away it
really is.
> As it's not very detailed, it'll leave plenty of room for creativity. • I don't want to imitate Star
> Trek (or any other established paradigm necessarily, though I imagine • it'll happen to a
> degree or two), except possibly by convenience of adopting spacial • measurements.
> Which reminds me: if we use faster than light (FTL) velocities, what • kind of velocity scale
> do we want to adopt?
This depends on where you want to go, and how quickly you want to get
there. If your imagination tells you that you should be able to travel
from Earth to the Crab Nebula in a week, parsecs per hour is a
reasonable unit of measure.
> Unless, maybe, someone wants to go to the trouble of staging an • emergency mass-exodus
> of moving civilizations because a rogue black star is approaching! • That could be another
> story :-)
Sounds like fun! But realistically, you would have thousands of years'
warning. The relative speeds of objects within the galaxy (and its
attendant globular clusters) are pretty low -- no more than about 50
kilometers per second, which works out to one parsec every 19,600
years. An object moving much faster than this would have to come from
far outside the local galactic group, and to my knowledge no such object
has ever been found.
--
John J. Ladasky Jr., Ph.D.
Department of Structural Biology
Stanford University Medical Center
Stanford, CA 94305
--
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Message has 4 Replies:
 | | Re: The "geography" of local space
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| (...) Welcome! (...) Perhaps, but we can find out, so it's not impossible. I know I don't have a starmap in my head <:) Having a universe without going through a lot of research was what I was aiming at, and I didn't think anyone else would want (...) (25 years ago, 4-Nov-99, to lugnet.space)
| | | Re: The "geography" of local space
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| Hey John (and all)- Astronomy is an armchair hobby? Well, I'm a historian (not done with the PhD just yet, but give me just a couple more years) who started out as a palaeontologist and astronomer--so I come at it from a different angle, but I've (...) (25 years ago, 4-Nov-99, to lugnet.space)
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