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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Wed, 17 Nov 1999 09:17:04 GMT
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Viewed:
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692 times
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Hi, Tim,
Tim Courtney wrote:
> At 11:10 PM 11/13/1999 , Tom McDonald wrote:
> > > I have a question about this discussion. Is this to make an 'official' all-
> > > encompassing required map of Lego Space? I'm not fully understanding where
> > > this is going.
> >
> > No, you understand fine, though I'm not sure how 'official' it would have
> > been. The idea was to have something functional like Town's Datsville in
> > space.
>
> Ok, cool.
>
> > > It would be nice to have a star chart based on the actual
> > > known universe (Zacktron uses it..).
> >
> > Yes, but it can be real *work* depending on how detailed folks want to get.
> > Some folks aren't very detailed, while others are incredibly so. To each his
> > own here.
>
> Yeah. I'd just need maps of the Sol system, Alpha Centauri, and Barnard's
> Star and how they relate to each other as far as distances go for
> Zacktron. Most other stuff is unexplored space to the Z universe. But a
> useful tool.
Maps? You mean, with planets? Wouldn't we all like to have that! I can provide
brief summaries of what we know about these three star systems -- though you
probably already know all you need to know about Sol.
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Alpha Centauri, aka Rigil Kentaurus, is a trinary star system. At a distance of
1.347 parsecs, this is the closest star system to our own, but I'm sure you
already knew that. Alpha Cen. A and Alpha Cen. B are both quite similar to our
own Sun, in mass and in brightness. They orbit each other at a distance that
varies. At closest approach, they're separated by about the same distance as the
Sun and Saturn. The maximum distance is about the same as the distance between
Earth and Pluto.
I won't go into the math, but in a double-star system, planets cannot orbit just
anywhere. Any planet that is going to stay put in orbit around either A Cen. A or
B PROBABLY cannot be farther out than Mars is from Sol. The theoreticians are
still arguing over exactly which planetary orbits are stable in a double-star
system. Fortunately for our imaginations, the "comfort zone" -- that is, the
distances at which liquid water could exist on a planet -- is inside the
currently-understood limit for stable orbits, for both of the stars.
We don't know yet whether such planets actually exist! In recent years, you may
have been hearing in the news that planets have been discovered orbiting other
stars. The count stands at about thirty planets. These are not seen directly in
a telescope, because the glare from the parent star washes out the reflections
from any nearby planets. The existence of the planets is inferred by subtle,
Doppler-effect changes in the color of light coming from the parent star, as it is
gently tugged by the gravity of the unseen planet. The SMALLEST planets that we
are able to measure using this technique are about half the size of Jupiter. It
is probably safe to say that there are no gas giants orbiting either Alpha
Centauri A or B. There may be planets that orbit *both* stars, starting at about
10 times the Sun-Pluto distance. These, of course, would be really dark and cold,
and probably small. But even a large planet would not have yet been detected, if
it was far out. Again, use your imagination!
Alpha Cen. C, also known as Proxima Centauri because it is (presently) the closest
of the three stars in the system, is a red dwarf star. C orbits much further out
-- it's a whole 0.055 parsecs away from the other two. Proxima is not considered
to be a good candidate for finding indigenous life or easily-colonizable worlds.
In the first place, it's dim and red. Proxima is also a variable star. Its
intensity can change. It's my understanding that these changes are unpredictable
and rather significant (a change of two- or three-fold in a matter of a few
days). Alpha Centauri A and B are stable, like the Sun.
Still, Proxima may be the only star for which an *actual photograph* of a planet
may have been taken. The data is very thin -- two pictures from the Hubble space
telescope taken last year. Still, if the data is correct, Proxima may have a
companion, about ten times the mass of Jupiter. It could be a gas giant, or it
could be a brown dwarf.
For considerably more detail about the Alpha Centauri system (but ignore the
distance measurements since they're not from Hipparcos), visit these web pages:
http://monet.physik.unibas.ch/~schatzer/Alpha-Centauri.html
http://scivax.stsci.edu/~kochte/low-mass.html
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Barnard's Star is a dim, red dwarf star like Proxima Centauri. Barnard's is the
central star of the second-closest star system to Sol, at a distance of 1.821
parsecs. It is a solitary star, like the sun and unlike Alpha Centauri A. Some
early reports that it might have a large, unseen companion have been discredited
over the years. The limits of detection are estimated at about half the mass of
Jupiter. So, smaller bodies may exist. And unlike Proxima, the solar output is
stable, so habitable planets are more plausible.
Because Barnard's is dim, any planets that existed in the "comfort zone" around
this star would have to be really close, on the order of one tenth the distance
between the Earth and the Sun. Current theory says that planets this close would
be locked to their parent star the same way that the Moon is locked to the Earth.
In other words, one side of the hypothetical Barnard's planet would always be in
sunlight, and the other would always be dark. If such a planet had an atmosphere,
weather would be pretty weird by Earth standards.
Here's one Barnard's star web page of many:
http://www.seds.org/~spider/spider/Misc/barnard.html
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A useful distance table for Zacktron:
Sun to Alpha Centauri (A/B) : 1.347 parsecs
Sun to Barnard's Star : 1.821 parsecs
Alpha Centauri (A/B) to Barnard's Star : 1.880 parsecs
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Anything else in Zacktron is unexplored space? Well, the next three (known) stars
out from Earth are two more dim red dwarf stars, known as Wolf 359 and Lalande
21185; and then, the brightest star in our sky, Sirius.
I won't swamp you with the details of my search through the catalogs for nearby
stars that are most likely to allow human habitation (or other life like us). But
none of the very nearest stars are that great. The Alpha Centauri system is a
possibility, however there is the problem of orbital stability. After our own
solar system and Alpha Centauri, the three next closest candidates are Tau Ceti
(distance = 3.647 parsecs), Eta Cassiopeiae A (5.953 pc), and HD 191408 (6.052
pc). You would therefore need a MUCH bigger map to encompass just five plausible
systems for life as we know it.
-----
I just revisited your pages over at zacktron.com. I had forgotten that you
already had a working time line that runs about two centuries into the future.
Cool -- though it's a little depressing that humans start slugging it out among
the stars no sooner than they arrive!
Your models are cool, and beautifully rendered. Still, from the data you provide
I'm not sure where the models you show fit into your story line. And you have
one-person vessels, about the size of a mini-van, that can travel at three times
the speed of light? Whoa. Things got high-tech in the Zacktron universe awfully
fast! Not enough time for my big, clunky Classic Space models.
Tag, you're it!
--
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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| Oops. (...) Actually, it's 1.876 parsecs. You really needed to know, right? 8^) Cheers! -- John J. Ladasky Jr., Ph.D. Department of Structural Biology Stanford University Medical Center Stanford, CA 94305 -- (25 years ago, 17-Nov-99, to lugnet.space)
| | | Re: The "geography" of local space
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| (...) Apparently they actually got occlusion readings from a near star in the last week--by "near" I'm talking ~40pc. I can find the article and the star name, but it's one of the HDs (that narrows it down to several hundred thousand objects....;) (...) (25 years ago, 17-Nov-99, to lugnet.space)
| | | Local space -- here's a real map!
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| (...) Hey, look what I happened to find in my archive of downloads -- a 3D map of exactly these stars! (URL) is actually one double star system, UV Ceti, that MIGHT be closer than Sirius, which is not pictured on this map. Various studies disagree. (...) (25 years ago, 20-Nov-99, to lugnet.space)
| | | Re: Local space -- here's a real map!
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| (...) Those were basically the stars that were being considered. The Alpha Centauri system is occupied by the Zacktron Alliance (Blacktron, M:Tron, Ice Planet, Futuron, Exploriens) and Spyrius (their enemy). Unitron forces (part of Earth (...) (25 years ago, 20-Nov-99, to lugnet.space)
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Message is in Reply To:
| | Re: The "geography" of local space
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| (...) Ok, cool. (...) Yeah. I'd just need maps of the Sol system, Alpha Centauri, and Barnard's Star and how they relate to each other as far as distances go for Zacktron. Most other stuff is unexplored space to the Z universe. But a useful tool. (...) (25 years ago, 14-Nov-99, to lugnet.space)
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