posted
There is a newly-discovered planet in the Fomalhaut system, about 25 ly away. This discovery of a Saturn-like planet suggests earth-type planets there, or witht he potential of evolving - Fomalhaut is only a fraction of the age of our star (4.6 billion years old), and still full of stellar formation debris. Interestingly, they're looking at a similar star again - Vega, which was the star in question for the excellent Jodie Foster movie "Contact".
Anyway, has anyone done the research on correlating real stars to those which are supposed to have Trek planets around 'em? I don't have the Trek charts book yet, has any work been done there?
I would more accurately say "...the excellent Carl Sagan novel and mediocre Jodie Foster movie adaptation Contact."
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capped
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the majority of stars that we have (in canon and in fandom) associated with Trek planets wont likely support life.. but my supposition in my previous post makes sanse to explain why they could.. moving planets was a hobby of both those races.
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posted
I liked the movie far better than the novel. They were essentially two different stories anyway.
Back on topic - I believe we're getting closer to a wide-scale realization that a sizeable chunk of stars will have planets orbiting them. When technology catches up to the point were we can readily identify and classify even the smaller ones, we'll finally have someplace to go if someone figures out insterstellar travel.
What I'm getting at is the degree in this context to which Trek has yet to imitate life. And as an extension, since we're purportedy able to determine the size, number and even atmosphere of extrasolar planets, how would that affect space exploration even in the TNG era?
posted
I'm no expert on the full properties of radiation emitted by stars... but isn't it possible for an Earth-like planet to be in orbit around ANY star, provided it's at the right distance? The hotter the star, the further out it has to be -- but it could still be possible, if the planet orbited at about the distance from Sol to Jupiter.
-------------------- “Those people who think they know everything are a great annoyance to those of us who do.” — Isaac Asimov Star Trek Minutiae | Memory Alpha
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posted
I think he's talking about the naturalism philosohpy... Stars outside of the range are probably not going to last the billions of years required for life to evolve--- but that forgets ours can't even last long enough for that either [the sun is burning up too fast, it would have been touching Earth's orbit going back that far in the past].
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quote:Originally posted by J: I think he's talking about the naturalism philosohpy... Stars outside of the range are probably not going to last the billions of years required for life to evolve--- but that forgets ours can't even last long enough for that either [the sun is burning up too fast, it would have been touching Earth's orbit going back that far in the past].
That doesn't make much sense, and probably ignores several known facts about stellar evolution.
What's the reasoning about F-class stars other than 8-10 not being able to support Earthlike worlds? Or more than K1?
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posted
Simple. The spectral class letters are part of a system of stellar "fingerprinting" that identifies the main sequence star's temperature and gives clues to its mass and luminosity. A-type stars are the hottest, brightest and most massive main sequence stars (with rare exceptions, namely types O and B, which are even hotter, brighter, and more massive), whereas M-types are the faintest, coolest and least massive.
Each class is subdivided into 10 subcategories: A0 is hotter, brighter and more massive than an A1, which is above A2, etcetera.
Now on to the reasoning bit. Bright stars pay dearly for their splendor. It takes a lot of stellar fuel to emit vast quantities of light and heat. The penalty is a short lifespan as a main sequence star. Conversely, the inconspicuous, cool M stars may be around to see the end of the universe.
Life as we know it (that is, carbon based) seems most likely to evolve on a planet that has a stable temperature regime. It must be at the appropriate distance from its sun so that water is neither frozen nor boiled away. The planet has to be the appropriate size so that its gravity doesn't hold on to too much atmosphere (like Jupiter) or too little (like Mars). But the main ingredient in a life-bearing planet is its star. And its star is the only thing we can study since planets of other stars are far too faint to detect directly. In other words: the star has to be similar to the Sun.
Main sequence stars are basically stable for long periods of time. Stars in spectral class G have stable lifespans of around 10 billion years (and ours is in its midlife crisis). We can look forward to the Sun remaining much as it is for another five billion years or so. Stars of class F4 or higher have stable burning periods of less than 3.5 billion years, and these have to be ruled out immediately. Such stars cannot have life-bearing planets because, at least based on our experience on our world, this is not enough time to permit highly developed biological systems to evolve on the land areas of a planet (intelligent life may very well arise earlier in water environments, but since we have not yet had meaningful communication with dolphins -- highly intelligent creatures on this planet! -- let's skip that possibility). Though we may be wrong in our estimate of life development time, there is another, more compelling reason for eliminating stars of class F4 and brighter.
Spectroscopic studies of stars of class F4 and brighter have revealed that most of them are unlike our Sun in a vital way -- they are rapidly rotating stars. The Sun rotates once in just under a month, but 60 percent of the stars in the F0 to F4 range rotate much faster, as do almost all A-types. From recent studies of stellar evolution, it seems that slowly rotating stars do so because they have planets. Apparently the formation of a planetary system robs the star of much of its rotational momentum (because angular momentum of the whole solar system that formed from interstellar gas and debris must be conserved).
For two reasons, then, we eliminate stars of class F4 and above:
1) Most of them rotate rapidly and thus seem to be planetless, and
2) Their stable lifespans are too brief for advanced life to develop.
Another problem environment for higher forms of life is the multiple star system. About half of all stars are born in pairs, or small groups of three or more. Our Sun could have been part of a double star system. If Jupiter was 80 times more massive it would be an M6 red dwarf star. If the stars of a double system are far enough apart there is no real problem for planets sustaining life. But stars in fairly close or highly elliptical orbits would alternately fry or freeze their planets. Such planets would also likely have unstable orbits.
Further elimination is necessary. Some otherwise perfect stars are labeled "variable". This means astronomers have observed variations of at least a few percent in the star's light output. A one percent fluctuation in the Sun would be annoying for us here on Earth. Anything greater would cause climatic disaster. Could intelligent life evolve under such conditions, given an otherwise habitable planet? It seems unlikely, so we're forced to scratch all stars suspected or proven to be variable.
This still leaves a few F stars, quite a few G stars, and hoards of K and M dwarfs, but unfortunately, most of the Ks and all of the Ms are out too: although they quite likely have planets, M-types and Ks below K4 have two serious handicaps that virtually eliminate them from being abodes for life. First, these stars occasionaly fry their planets with lethal bursts of radiation emitted from erupting solar flares. The flares have the same intensity as those of our Sun, but when you put that type of flare on a little star it spells disaster for a planet that is within, say, 50 million kilometers. The problem is that planets have to be that close to get enough heat from these feeble suns. If they are farther out, they have frozen oceans and no life.
The close-in orbits of potential Earthlike planets of M and faint K stars produce the second dilemma -- rotational lock. An example of rotational lock is right next door to us: the moon, because of its nearness to Earth, is strongly affected by our planet's tidal forces. Long ago our satellite stopped rotating and now has one side permanently turned toward Earth. The same principles apply to planets of small stars that would otherwise be at the right distance for moderate temperatures. If rotational lock has not yet set in, at least rotational retardation would make impossibly long days and nights (as evidenced by Mercury in our solar system).
After all this pruning, only the G stars remain along with F5 through F9 and K0 through K4. It has been suggested F5, F6 and F7 stars should also be eliminated because they tend to balloon to red giants before they reach an age of five billion years, which is cutting it a little close for intelligent species to fully evolve (admittedly, this parameter is based on our one example of intelligent life -- us -- but it's the only one that's available). K2, K3 and K4 stars are poor prospects as well because of their feeble energy output and consequently limited zone for suitable Earthlike planets.
What we are left with are single, nonvariable stars from F8 through the G-types, to K1.
Well, until silicon-based life shows up, anyway.
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posted
Ah, I forgot about the lifespan issue of the larger stars. That's a good point.
However, I think that the rest of the argument depends far too much on assumptions... and besides, astronomers just found a Jupiter-sized planet in a close binary system. (read the article)
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posted
Those interested might also note that there are two parts to being "Earthlike." An "Earthlike" planet in terms of size and temperature might be possible around various stars, but the only reason we have oxygen to breathe is plant life... if a planet has never evolved plant life, the likelihood of significant oxygen is slim. So while there might be thousands of potential Earth's that never get a human-ready atmosphere because there aren't Earthlike plants.
posted
The November issue of Discover magazine has an article entitled "Circles of Life", which deals with how eccentric an orbit Earth could have and still be capable of supporting life. The article mentions the work of geoscientist Jim Kasting, who first nailed down the dimensions of the zone around the sun where life could exist. It says, "in the early 1990s, Kasting used computer models to determine the zone's exact dimensions: between 79 million and 140 million miles from a star (farther out for hotter stars, closer in for cooler stars)."
A book from Writer's Digest Press entitled "World Building" is designed to help budding science fiction authors create more realistic solar systems, and one of its chapters deals with putting a planet in a proper setting around its sun. If you can find it in your local library, it makes for an interesting read.
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