Subject:
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Re: 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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Fri, 5 Nov 1999 10:46:41 GMT
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Viewed:
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671 times
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Hello again,
I''m glad I generated some interest here! I hope, however, that we do not
stray too far from discussing LEGO -- I have noticed complaints in at least one
other LUGNET newsgroup.
Mr L F Braun wrote:
> 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
Both quite rewarding, but difficult fields in which to find work -- I
sympathize!
Actually, your background is interesting. What kind of a dissertation could
you write? How about "The use of 'dragon bones' and astrology for divination
in the Shang Dynasty"?
> --so I come at it from a different angle, but
> I've had a long standing interest in the "demography" of the local
> population of heavenly bodies (no snickering).
Aw, shucks.
> > 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.
>
> That seems most logical. And if we presume that various unknowable factors
> might affect human life (background radiation, tidal forces, etc), a point
> here in the "seen" interstellar region, on a spiral arm, outside the dust
> lanes, would probably be most plausible.
>
> > [Tom McDonald:]
>
> > 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.
>
> If you want a local map of the nearby stars, the best I've seen (aside from
> processing the information in Sky Catalogue 2000.0--both volumes of which
> I've got--and Burnham's, all three volumes of which I own) is in GDW's old
> "Traveller 2300" game. You have to figure out what some of the stars really
> were, but it's fairly accurate out to c. 100 ly.
The position of a star on the globe of the sky is pretty easy to determine.
The best way to measure the DISTANCE to a star is by triangulation. You
measure the position of the star, relative to more distant background stars, on
a given night. Then, six months later, you measure again. The Earth is on the
opposite side of its orbit from where you took the first measurement. The
closer a star is to the Sun, the more it will appear to move against the
background.
Turbulence in Earth's atmosphere limits this method. It turns pictures of
stars from pinpricks into blobs. At ten parsecs, trigonometry is only accurate
to ten percent. Objects beyond this distance are pretty hopeless. The errors
begin to exceed the average distance between the stars.
Guesses at the distances of more remote stars were made by looking at the
star's color and apparent brightness. But this isn't accurate to more than
about a factor of two, and it works a lot better if one has reference stars of
the same color inside the 15-parsec limit. As I mentioned in my first post,
many colors of stars, particularly blue giants, are not found anywhere near
that close to us.
There is better data, and it was collected just two years ago. The Hipparcos
satellite, a project of the European Space Agency, took trigonometric
measurements of stellar positions from space, above the atmosphere.
http://astro.estec.esa.nl/Hipparcos/
Hipparcos measured distances accurate to 10% at 100 parsecs. Distances to 10
parsecs are accurate to one percent! The only shortcoming of the data is that
the dimmest stars, below a visual magnitude of 12, were not observed. So many
of those nearby red dwarfs that I mentioned in my first post are not in the
data set.
ESA has placed the Hipparcos data on-line. However, the search program that
they have provided only allows you to look up stars by name or by position on
the sky -- not by distance. So it's no easy matter to make a 3D map of local
space.
At this point, then, the material in both the Sky Catalogue and Burnham's are
probably out of date. And I don't think that the Traveller game had anything
more than these catalogs.
Successor missions to Hipparcos are in the works at both NASA and the ESA.
They will measure dimmer and more distant stars with greater accuracy.
> Burnham's gives you lots of
> proper names for obscure stars and phenomena, however. ("No, it's not Alpha
> Centauri, it's Rigel Kentaurus...*grumble grumble Visigoths*")
>
> > 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^)
>
> Yes, but even "hard" sci-fi fans (like you and I) who dislike superluminal
> travel can still deal with space-folding, wormholing, and the like--there
> are ways around it. ;) But I believe that beyond 200ly you begin to get
> "weird." See below.
Even if FTL travel is possible, by any means, current theories say that the
amount of energy that would be required to make it work are enormous -- a lot
more than what we would need to send a ship somewhere at sub-light speeds.
My professional calling is biology. I see biological progress as being faster
than progress in the mechanics of space travel. I believe that we will triple
human life span, and/or figure out how to place a human body in suspended
animation, centuries before we harness the energies needed to break the
light-speed barrier. Oh yes, and we will have a colony on Mars, which might
make an interesting LEGO setting. If we have not found any indigenous life
there, we will also be well on our way to terraforming the Red Planet, before
that first interstellar spacecraft sets sail.
One more thing -- we will have telescopes that allow us to SEE the planets
orbiting around other stars right here from home, without having to go
anywhere. This technology is actually already in the works at NASA. We
already know that Jupiter-sized bodies orbit some nearby stars. If the
short-sighted folks who find their way into the American government don't
destroy the current plans, we should have a crude picture of an extra-solar
world by 2020.
The LEGO mothership that is a gleam in my eye is full of little high-tech
sarcophagi, in which the minifigs will spend decades in hibernation on their
way to the stars. Think of the spacecraft "Nostromo", from the movie _Alien_.
Periodically, some of the crew may be awakened to check on the condition of the
ship, and perform any needed maintenance before going back to "sleep." If
there's a place in the Datsville-in-space future timeline for a millennium or
so of slower-than-light, interstellar exploration of local stars, there might
be a place for my models. I like the idea of interstellar space travel being
really expensive and difficult at first. That's how travel to Earth's orbit is
right now, and that's how it will remain for the foreseeable future.
Will the people of the LEGO universe discover extraterrestrial life before or
after the hyperdrive? It matters. We didn't send the Pathfinder to Mars armed
to the teeth, because we assumed that there's nothing out there to harm it. My
hypothetical LEGO mothership is actually quite lightly armed -- and if it
should have a chance encounter with a hostile ET, it might well get its butt
kicked! And when the video transmission of the encounter makes it back to
Earth, the engineers will begin redesigning the fleet...
My best guess on this matter is that we will greet ET by radio, even before we
leave the solar system. What happens next? Do they have FTL travel? Will
they see us as friend or foe? Are we too pathetic to worry about, or are we
immediately threatening? Will we become threatening ONLY when we start
travelling to other stars? Will they come to subdue us, or take our pretty
planet from us?
> Okay, Cygnus X-1 is out for the holiday vacation...next! (Then again, this
> doesn't preclude races or entities that aren't subject to carbon-water
> chemistry. Hal Clement wrote a nice essay about why H20-C (imagine
> subscript) chemistry is most likely, but you never can be sure...though I
> think silicon for all but artificial life is out.)
Last time I checked through my minifigs, I didn't see any non-human life forms.
Then again, I don't own any UFO or Insectoids sets. Nor do I have any Star
Wars sets, so no Gungans. Was anyone out there planning to develop their
corner of Datsville in space with non-humans? That could be cool. (Maybe I
should buy some of these sets? Are they lame?)
> > 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?
>
> John's 100% right here. The Traveller manual included red stars, but
> interestingly as you got nearer the edges of the map, there were fewer red
> stars! That's because (drum roll) they're hard to see from here. How many
> people know about the C component of Rigel Kentaurus?
Do you see that excited hand waving to you from the back of the classroom? :^)
> But what may be even
> more numerous than red dwarves are *brown* dwarves--stars so small that they
> "abort"--sort of super-Jupiters, like Van Biesebroeck 8B and the sort. They
> give off heat, and can have habitable tidally locked moons, but they're
> really too small to light up like a red star.
Yeah, I didn't want to talk about these, because I have found so little
information on them. There is no good census of brown dwarfs yet. They have
seen so few. There might be many, but so far they're just too darn hard to
see.
> > 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.
>
> Double and multiple systems are probably the rule, not the exception. Many
> astronomers (and not all "rogues" or weirdos) feel that the Sun may be or
> may once have been part of a multiple system. They call the extant
> iteration the "Nemesis Theory," for the name of this unseen, M5-or-fainter
> companion. I wasn't aware about the new dwarves, though--I presume they're
> M3 or less. Where are they?
Visit http://cfa-www.harvard.edu/~thenry/RECONS.html for all the information
you would ever want to know about a concerted effort to study nearby and dim
stars. Yes, the new discoveries were all type M (very dim, and very red)
stars. They have a map of the 25 nearest star SYSTEMS, which include 36
stars. Unfortunately, it's a two-dimensional map, but you could make the 3D
map from the data table which they also provide. (The 71 nearest stars as
defined by Hipparcos are listed at
http://www.csi.cc.id.us/support/museum/staff/cja/cja_stardist.html -- these,
plus the data from RECONS, could be used to make a decent map that is missing a
few dim red dwarfs.)
The Nemesis theory comes and goes. I must warn you that if you do a Web search
on the subject, you will come up with a lot of crackpot pages. For some
reason, there are a lot of folks out there who are convinced that the Biblical
flood and other mythical and historical events are connected to the existence
of a "dark" companion to the Sun.
Yet just last month, an actual scientific report on something like Nemesis has
appeared. I apologize for not having a link to hard science for this one, but
here's a decent news article:
http://www.msnbc.com/news/320182.asp
Two groups have proposed that one or possibly two separate objects, somewhere
between Jupiter's mass and three times that much, might be orbiting the Sun at
a distance of 0.4 to 0.5 light-years. Looking at this another way, the
hypothetical objects are 800 to 1000 times farther out than Pluto. The
researchers have reached their conclusions by looking at patterns in the orbits
of comets. Of course, the error bars in the data are huge. So there may be
nothing at all out there, OR it's possible that there's something even larger
out there. The threshold at which a body becomes a star rather then a planet
is estimated to be about eighty Jupiter masses.
Do we want Nemesis to exist in the Legoverse? Should it be a small sun instead
of a big planet? Will it have planets of its own? (Please, no aliens that
speak ancient Sumerian...)
> > The closest "interesting stellar object" is probably the star Vega.
>
> Sure, it's a matter of opinion, but I've gotta disagree--I think it's
> probably the white dwarf B component of Sirius, else the white dwarf B
> component of Procyon. But Vega is indeed an interesting star. Arcturus is
> interesting because it's a heavy-element-poor Pop II star--so probably no
> planets except for maybe gas giants. If VB8B exists, that might be more
> interesting still.
What's VB8B? (Maybe you should answer this question by email?)
> > 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!
>
> Again, darnit. See above. I was trumped again! But they can't use direct
> parallax to measure the distance--so you can be pretty sure it's not within
> 300pc.
I think you're mistaken here. Before Hipparcos, the 10% accuracy limit on
trigonometric (direct parallax) measurements of stellar distance was *ten*
parsecs. At 300 parsecs, the error by parallax from the ground would be huge.
Even with Hipparcos, the error at 300 parsecs would be unacceptable -- about
33%.
> > > Which reminds me: if we use faster than light (FTL) velocities, what
> > > kind of velocity scale do we want to adopt?
> what no sci-fi/space/Space system has done in my knowledge is utilize
> *multiple* ways around the problem. The CW is that there can be only one
> circumvention possible of the luminal speed limit. Why not more than one
> method? Bubble-universes, superstring manipulation, space-folding, and warp
> drives all--could such things all exist together?
Now you're trumping me! Above, I said that I was interested in
slower-than-light travel. But what if another race has FTL before humans?
Your idea, that there might be many ways to travel faster than light (some
better than others?), is the logical extension of my thoughts. Actually, I
seem to recall that the Star Trek series hints at this. Remember the ST III
movie, and the trans-warp drive? I also had a glimpse at one of the new ST
technical manuals in a bookstore a while back, and I seem to remember a
discussion of ship travel speeds that mentioned "warp speed old scale" and
"warp speed new scale".
> This is interesting, and worth pursuing--I think a "Space datsville" would
> be a lot of fun to populate, and I'm convinced we wouldn't be wanting for
> planets.
So, shall I start the thread on planets and habitability now? :^)
--
John J. Ladasky Jr., Ph.D.
Department of Structural Biology
Stanford University Medical Center
Stanford, CA 94305
--
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Message has 2 Replies:
 | | Re: The "geography" of local space
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| (...) It's in the context of creating a datsville, so I don't know how anyone can be *angry*. (...) Yeah--my girlfriend's father got his PhD in palaeobotany; not exactly a field in demand, so he ended up being a groundskeeper and specialist for (...) (25 years ago, 5-Nov-99, to lugnet.space)
| | | Re: The "geography" of local space
|
| John J. Ladasky Jr. wrote in message <3822B586.38355581@m...ja.com>... (...) Hipparcos (...) 10 (...) that (...) many (...) that (...) on (...) local (...) What it does do, however, is give a link to the VizieR service that I found a couple of (...) (25 years ago, 7-Nov-99, to lugnet.space)
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Message is in Reply To:
| | Re: The "geography" of local space
|
| 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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