Hatrack River
Home   |   About Orson Scott Card   |   News & Reviews   |   OSC Library   |   Forums   |   Contact   |   Links
Research Area   |   Writing Lessons   |   Writers Workshops   |   OSC at SVU   |   Calendar   |   Store
E-mail this page
Hatrack River Writers Workshop Post New Topic  Post A Reply
my profile login | register | search | faq | forum home

  next oldest topic   next newest topic
» Hatrack River Writers Workshop » Forums » Open Discussions About Writing » Planetary Help...

   
Author Topic: Planetary Help...
skadder
Member
Member # 6757

 - posted      Profile for skadder   Email skadder         Edit/Delete Post   Reply With Quote 
I need to create a planet which has seasons that take years (20 or so) to pass. So I am looking for 20 year winters, followed by a thaw and a summer (it can be brief, perhaps a few years or equally as long as winter--doesn't matter.)

I know nothing about what sort of orbit such a planet would have or if this has an impact on other factors such as mass/gravity. I wanted the gravity to be near Earth's, if possible. Would this planet have to orbit a binary star to have this profile? I don't know.

Is there anyone who knows about such things or can direct me to somewhere (a program, perhaps) where I can find out.

Obviously in describing such a planet, I need to know stuff about major things like gravity, rotational speed, inclination etc. So if you know this stuff and can supply it--great. Otherwise directions would be equally great (but more work! ).


Posts: 2989 | Registered: Oct 2007  |  IP: Logged | Report this post to a Moderator
MartinV
Member
Member # 5512

 - posted      Profile for MartinV   Email MartinV         Edit/Delete Post   Reply With Quote 
Gravity is all about the mass of the planet. Unless your planet revolves so fast the centrifugal force would be an important factor but I think such a planet would not be habitable for humans.

As for the seasons, well, it's a bit about the distance between the planet and the sun but more importantly about the tilt of the planet's axis against the ecliptic (the plane on which the planets circle the sun).

If the planet's axis is tilted 90 degrees (Uranus has that) then the planet is practically rolling along on its path, making one half of the planet constantly illuminated, the other constantly in the dark. I confess I've given some thought about using this in a story myself.

A binary star system gives you options such as:
- if the planet is far away from both stars, then it's circling them like any single star system. You can have 'Tattooine' sunsets but that's just about it.
- if the planet is close to one star but far from the other, then the other star can be a moon-like object in the sky but a lot brighter.
- if the distance is just right, the planet can circle BOTH stars but each at a time. Meaning, your planet is making a double loop around them both, drawing a number 8 with the stars in the loops. That would cause some pretty exotic seasons.

None of these can give you 20-year winters though. So my suggestion is to give your planet a very eccentric orbit, sort of like asteroids that are usually very far from the sun but come very close every so often. The sun would be far away most of the time but when the planet comes closer it would get quite warmer.

One final note: if you indeed create a planet like this, it would probably not be from the same solar system but would need some celestial event to bring it to the current star system. Real planets (except Pluto) were formed by the condensing gas which also formed the sun (at least according to some theories). That is why the planets are all on the same plane (ecliptic).

[This message has been edited by MartinV (edited July 16, 2009).]


Posts: 1271 | Registered: May 2007  |  IP: Logged | Report this post to a Moderator
DWD
Member
Member # 8649

 - posted      Profile for DWD   Email DWD         Edit/Delete Post   Reply With Quote 
Uranus has 20-year seasons. By adjusting the type of sun and the mass, you should be able to use a similar extreme spin axis tilt (82 or 98 degrees, depending on which way you measure it), long orbital period (for Uranus one orbit = 84 years), and extremely slow precession (for Uranus, north and south poles alternately face the sun on a 42-year cycle), you should be able to make it work without having to resort to an elliptical orbit.

Here is a link to a graphic of how this works for Uranus.

[This message has been edited by DWD (edited July 16, 2009).]


Posts: 88 | Registered: Jun 2009  |  IP: Logged | Report this post to a Moderator
MartinV
Member
Member # 5512

 - posted      Profile for MartinV   Email MartinV         Edit/Delete Post   Reply With Quote 
I thought science fiction is about being inventive.

The problem with Uranus is that it gets far too little heat from the Sun. It's not in the habitable zone. Raising the sun's temperature or mass changes things. For starters, the light would have a different color, meaning chlorophyll would have problems. The sun/planets mass and momentum ratio would be different and that would cause complications.

You can always do what GRR Martin did in A song of Ice and Fire: don't give any explanation, just use it.


How would Uranus have a long winter AND a short summer? I thought this was the case here. I'm not trying to be pain, I'm honestly asking your opinion to see an alternative way of thinking.

[This message has been edited by MartinV (edited July 16, 2009).]


Posts: 1271 | Registered: May 2007  |  IP: Logged | Report this post to a Moderator
DWD
Member
Member # 8649

 - posted      Profile for DWD   Email DWD         Edit/Delete Post   Reply With Quote 
quote:
So I am looking for 20 year winters, followed by a thaw and a summer (it can be brief, perhaps a few years or equally as long as winter--doesn't matter.)

...so I think equally long summer/winter cycles would work for him.

We can certainly be inventive, yes. But I was just trying to come up with the simplest option. For example, I would think that a planet could orbit around a large F-class star (with maybe 1.5 times the Sun's mass and five times its luminosity) on a 20-year orbital period, with an 80+ degree axial tilt and a precession roughly equal to the orbital period, and you'd get your 20-year winters without having to be so far away that you're out of the star's habitable zone.

But I'm certainly no expert; just going by info I could dig up when I saw this post.


Posts: 88 | Registered: Jun 2009  |  IP: Logged | Report this post to a Moderator
DWD
Member
Member # 8649

 - posted      Profile for DWD   Email DWD         Edit/Delete Post   Reply With Quote 
Thinking about this a bit more (and I'll stop with this and get back to work), I think there are only two "requirements" here:

1. An axis of rotation that is tilted to near 90 degrees, so that the planet's rotation is largely irrelevant in terms of its effect on what faces the sun. In other words, the planet is rotating like a bead on an abacus.

2. A very slow orbital rotation that causes a pole to face the sun every 40 years. In other words, the orbital rotation is nearly perpendicular to the planetary rotation.

If these two criteria were met, I would think the mass, orbit, and star type could be identical to Earth. Turn the Earth on its side and get it spinning very slowly perpendicular to its axis of rotation (a 40-year precession), and you'd have it.

But I'm probably missing something. "I'm a programmer, Jim, not an astrophysicist." (apologies to Dr. McCoy)


Posts: 88 | Registered: Jun 2009  |  IP: Logged | Report this post to a Moderator
DWD
Member
Member # 8649

 - posted      Profile for DWD   Email DWD         Edit/Delete Post   Reply With Quote 
Oops - one more thing. I guess in order to have the 20-year winter not also be a 20-year night, you would have to have a binary system with a distant second star orbiting outside this primary system.

This would look something like the 8th, 9th, and 10th graphics here.

[This message has been edited by DWD (edited July 16, 2009).]


Posts: 88 | Registered: Jun 2009  |  IP: Logged | Report this post to a Moderator
skadder
Member
Member # 6757

 - posted      Profile for skadder   Email skadder         Edit/Delete Post   Reply With Quote 
Thanks for the answers...I ahve a couple of questions:

So that would be like a twenty-year night? You would only see the sun when spring arrived and it just stuck it first stuck head above the horizon....a little more each day.

If I cut the orbital period down to 30 years, you would still get an effective winter of 20 years (it would take some time for the melt to happen) followed by a warmer period lasting 10 years or so.

Would the orbit around the sun be slow slow? Wouldn't it degrade and fall into the star? ("I'm not even a programmer, Cap'n.")


Posts: 2989 | Registered: Oct 2007  |  IP: Logged | Report this post to a Moderator
Natej11
Member
Member # 8547

 - posted      Profile for Natej11   Email Natej11         Edit/Delete Post   Reply With Quote 
Yes, if it was orbiting slowly enough to take 40 years to go around the sun at one AU (astronomical unit, the distance between the earth and the sun), then the orbit would rapidly decay and it would fall into the sun. Since primarily solar mass has an impact on the orbit of objects circling the sun, the only way around this is to make the planet farther away.

At that distance in order to make life sustainable you'd have to have a much thicker atmosphere so the greenhouse effect would keep the temperature livable. A side effect of that is that a thick atmosphere keeps the global temperature fairly constant regardless of which side is facing the sun (think of Venus). This, of course, effectively eliminates seasons caused by axis tilt, as well as temperature disparity between night and day. So the only way you could have season changes would be globally, caused by distance from the sun.

Another alternative would be to make the sun have a higher energy output. The only real way to do that is to make it more massive, which makes it so the distance to have a stable orbit increases even more. There might be a point where the mass/energy output ratio provides a planet where life is sustainable, but I don't know the math for it.

Another solution is to have a binary system with the planet making a roughly figure 8 orbit around the two suns. It would approach closer to one sun than to the other, allowing for a "summer" at one phase and a "winter" at another.

Or summer when the planet is between the two suns and thus getting the full effect of both their energy outputs, and winter when it gets to the extreme side of either sun at the outside loops of the 8.

A third solution is to have the planet behave like mercury (or the moon), where it rotates at exactly the same rate as it orbits, so one side is always facing the sun. With a thin atmosphere that makes it so that the side facing the sun is very hot, and the side facing away is very cold. If the rotation is slightly off from the orbit then you could have one side facing the sun for long periods of time, ie summer, and when it finally does rotate so that area is on the dark side you have winter. This creates the problem of constant day or constant night.

Fantasy is a lot easier. You can pull a George R. R. Martin and not have to explain why there's long winters and summers, and the duration of them varies unpredictably.

Edit: Corrected a faulty assumption.

[This message has been edited by Natej11 (edited July 16, 2009).]


Posts: 620 | Registered: Mar 2009  |  IP: Logged | Report this post to a Moderator
DWD
Member
Member # 8649

 - posted      Profile for DWD   Email DWD         Edit/Delete Post   Reply With Quote 
I'm saying you don't have to slow down the orbit or change the types or masses of any of the bodies involved. The orbital period can be the same as Earth's, as long as the planet's axis of rotation is close to 90 degrees and it has a 40-year relative precession so that it wobbles very slowly almost perpendicular to its axis, taking 40 years to show both its north and south poles to the sun.

Then the only problem left (well, the only one obvious to me, anyway) is that pesky 20-year night, which you solve by either (1) making this a binary system with an outer sun that provides dim "daylight" (but then you have very long "days" and the orbit becomes very complex because of the gravitational interactions between the two suns); or (2) having one or more large, bright moons with orbital planes that take them around the darkside and provide reflected light. You probably need this anyway to get that extreme near-perpendicular wobble to be stable.

Or, um, something else altogether. I don't know.

[This message has been edited by DWD (edited July 16, 2009).]


Posts: 88 | Registered: Jun 2009  |  IP: Logged | Report this post to a Moderator
Zero
Member
Member # 3619

 - posted      Profile for Zero           Edit/Delete Post   Reply With Quote 
I like the idea of not explaining it, scientific explanations often slow things down and bore readers most of whom don't care. The hardcore science readers will criticize any explanation you come up with since, ultimately, it's fiction.

I think it was Asimov who gave the advice to explain what something does but not how it does it. Most readers, I've found, are put off by (especially lengthy) explanations of why the science "works" in a sci-fi story. Mostly we just want to know what the significance is not the science itself.


Posts: 2195 | Registered: Aug 2006  |  IP: Logged | Report this post to a Moderator
Natej11
Member
Member # 8547

 - posted      Profile for Natej11   Email Natej11         Edit/Delete Post   Reply With Quote 
I agree with ^.

The only place where it would be a big deal is if the story revolved around the detail of it in some way, like where something the characters do is only possible because the planet is the way it is.

Hardcore science fiction used to be popular, and disciples of that genre would lynch you for trying to just say "this is how it is" explaining it. And heaven help you if it happens to be impossible >.<. Thankfully that's fallen by the wayside.

P.S. DWD wasn't trying to correct you, just thought it was easier to put everything in. Your posts were informative, I just like to type.


Posts: 620 | Registered: Mar 2009  |  IP: Logged | Report this post to a Moderator
keithjgrant
Member
Member # 8678

 - posted      Profile for keithjgrant   Email keithjgrant         Edit/Delete Post   Reply With Quote 
It's worth noting, too, that a "year" is basically defined by one orbit around the star. Uranus, for example, has seasons that are 20 Earth years long, but only one quarter of a Uranus year (if the information posted above is accurate)... so how your characters think about this is probably dependent on whether or not this is their native planet.

[This message has been edited by keithjgrant (edited July 16, 2009).]


Posts: 18 | Registered: Jun 2009  |  IP: Logged | Report this post to a Moderator
rstegman
Member
Member # 3233

 - posted      Profile for rstegman   Email rstegman         Edit/Delete Post   Reply With Quote 
If the orbit is eliptical, passing really close to the planet for the summer, and a long ways away from the planet from the winter, there need not be any tipping of the axis such as the 90 degree suggestion. The more eliptical, the bigger the effect.

Another thing to consider on this is how powerful the sun would be, and how big a difference between summer and winter would be.

I am not sure of this but the star could be a pulsar which increases and decreases energy output over a forty year cycle. There might be energy problems with this but it is also something to think about.


Posts: 1002 | Registered: Feb 2006  |  IP: Logged | Report this post to a Moderator
DWD
Member
Member # 8649

 - posted      Profile for DWD   Email DWD         Edit/Delete Post   Reply With Quote 
@Natej11: No worries. I was just posting as things occurred to me.

@Zero: I agree; there's no need to go into boring detail about what the orbit is, what the tilt axis is, etc. That has for sure gone out of fashion in all but the hardest SF.

I do think, though, (just personal opinion) that the resulting world needs to be plausible in terms of things like

* what constitutes a day throughout the seasons, since you may (depending on how you end up "building" the star system) have something like what happens in Alaska in terms of length and intensity of daylight/twilight/night over the course of a year. I actually wonder, to keithjgrant's point, whether an orbital period or the precessional period would be the defining interval for people on such a planet. One orbit wouldn't really mean much unless you use the binary system option.

* what the "in between" seasons are like (esp. if the planet is rotating "sideways" and you live near the equator)

* what the long-term effect is of having solar radiation bombarding one face of a planet for such a long period of time

Besides, that kind of stuff makes for very interesting plotting possibilities, IMO.

Sorry if I'm over-posting here, but I do thank skadder for posting something so interesting! I love to think through problems like this--even when I really don't know what I'm talking about.

Edited to add this: Here I was claiming to be trying to find the simplest solution, but rstegman's suggestion might be the easiest if you can get the right combination of rotation, orbital period, and solar intensity. Might be hard, though, to come up with an orbit with a big enough ellipse to give you a 20-year winter without baking the planet at perigee and turning it into a cold dead rock at apogee. I'd be willing to suspend disbelief at that level, though. As several people have said, it's the more story we tend to care about these days than the specifics of the underlying science.

And now I really will quit. I promise. Really. I mean it.

[This message has been edited by DWD (edited July 16, 2009).]


Posts: 88 | Registered: Jun 2009  |  IP: Logged | Report this post to a Moderator
Doug Bradshaw
Member
Member # 8559

 - posted      Profile for Doug Bradshaw   Email Doug Bradshaw         Edit/Delete Post   Reply With Quote 
Skadder, that's a fun question.

Orbital period scales as r^(3/2)M^(-1/2), where r is the length of the orbit's semi-major axis and M is the mass of the central body (the sun). (Wikipedia, Orbital period)

Brightness scales as r^(-2)M^3.9 for stars on the main sequence. (Wikipedia, Luminosity)

If we require that the orbital period be greater than that of Earth by a factor of 20 and that the brightness be equal to that of the Earth, this gives two equations in two variables. If we normalize r and M to the semi-major axis of the earth's orbit and the mass of the sun, we can write the equations as

a^(3/2)M^(-1/2)=20

and

a^(-2)M^(3.9)=1

Turning to Wolfram Alpha gives, if I did it correctly, M=3.44, and r=11.1221. In other words, the sun must be 3.44 times more massive than our sun and the semi-major axis must be 11.1221 times larger than our semi-major axis.

One caveat is that radiation from a brighter sun will likely be hotter and so blue-shifted. You can correct for that with an atmosphere that acts as a filter or use it as part of the story.


Posts: 32 | Registered: Apr 2009  |  IP: Logged | Report this post to a Moderator
Doug Bradshaw
Member
Member # 8559

 - posted      Profile for Doug Bradshaw   Email Doug Bradshaw         Edit/Delete Post   Reply With Quote 
I want to make couple of additional points after reading the thread more carefully. First, I now see that you want winter to be 20 years. My calculations were for a year that lasts 20 years. So if winter is half of the year then you can plug 40 in in place of 20. If winter is a fourth of the year then plug in 80.

Second, it's worth noting that the length of an orbit is independent of the eccentricity of the orbit. Changing the eccentricity will change the nature of the seasons in a year but not the length of the year. An eccentric orbit might be interesting because of the potential for a planet-wide winter.


Posts: 32 | Registered: Apr 2009  |  IP: Logged | Report this post to a Moderator
DWD
Member
Member # 8649

 - posted      Profile for DWD   Email DWD         Edit/Delete Post   Reply With Quote 
Nice! Real calculations! :-)

That's very interesting, Doug. Brings up a question I had when I was looking at the need for increased solar intensity in one of these scenarios. Material I was reading today seemed to indicate that a star that much more massive than ours would burn through its main sequence too quickly to support the evolution of complex life forms on any of its planets.

Of course, if the planet in question is colonized and all higher forms of life are seeded, this wouldn't be an issue. Just wondering, though, what the relevant variables are, if they exist. Or perhaps these are hard and fast calculations based solely on mass.


Posts: 88 | Registered: Jun 2009  |  IP: Logged | Report this post to a Moderator
micmcd
Member
Member # 7977

 - posted      Profile for micmcd   Email micmcd         Edit/Delete Post   Reply With Quote 
With respect to the just-do-it-and-don't-explain-it POV advocated above, I'm inclined to disagree. I know that hard-core scifi isn't particularly popular these days, and that a reader can get very bored if you go into lengthy discussions. Even if you never tell the reader how it happens, it helps for the writer to know. You can get more ideas for how seasons progress, etc, and this can lead to plot revelations. Also, you might want to reveal a little bit of it to the reader, and it helps to have a plausible explanation for things. It can also keep you from stumbling into a science foul-up so bad that it actually annoys a fair number of readers. Even in a primarily fantasy story, it can get on my nerves when, for example, Superman runs at ultra-sonic speed and just grabs a mere mortal off the street with out splattering them to bits.

It's speculative fiction, but it helps to be as scientifically (and sociologically, for society-building purposes) rigorous as possible, even if you hide every last bit of your research from your readers.


Posts: 500 | Registered: May 2008  |  IP: Logged | Report this post to a Moderator
skadder
Member
Member # 6757

 - posted      Profile for skadder   Email skadder         Edit/Delete Post   Reply With Quote 
Thanks for all the reponses...

@Doug

So, broadly--an earth-sized planet can orbit a star 3.4 times the mass of our sun with a 20 year orbit if it does so at 11.1 AU from the star? Correct?

Would this not give earth-like seasons spread across the globe? So the equator would be similar to our equatorial regions (apart for the blue shift) and temperate regions would have seasons that were 5 years long? The artic circle would have 10 years of darkness followed by 10 years of day?

The presumes a tilt (not the correct word--axial inclination?) similar to earth's.

I suppose I could have one small continent and have everyone on that (Very long winter), but you say this planet would be hotter than ours...would this not negate the effects of the winter period--in that warm air would circulate from the warmer regions.

I want ice cold winter (they are aliens) for 20 years, preferably with no where warmer on the planet for them to wander to. They have to stuck in the cold (and dark) until spring comes.


Posts: 2989 | Registered: Oct 2007  |  IP: Logged | Report this post to a Moderator
snapper
Member
Member # 7299

 - posted      Profile for snapper   Email snapper         Edit/Delete Post   Reply With Quote 
Let me see...

You want a planet that experiences a 20 year ice age, a warming period, then balmy summer for a few years, correct? Here's how you do it.

Ice planet Skadder circles a small sun, about the mass of Jupiter (maybe a bit a larger). The orbit is circular with virturally no tilt. One season, winter.

The small star orbits around a large one, probably should be a bit bigger than Sol. The small star orbit is elliptical, commet like (not so drastic though).

Two things happen when the planets small star gets close to the primary one. The dual heat from the two stars makes things warmer. The gravity pull of the large star draws the planet into an elliptical one so when the planets orbit is behind its parent star it is also closer to its own sun. Tidal effects would be drastic, just to let you know.

I would make the small suns comet like orbit run from a range of a 500 million to 100 million. The heat from the dual suns wouldn't be so great to make your planet lifeless. I would make the orbit of the planet around its parent star at about a million miles.

[This message has been edited by snapper (edited July 17, 2009).]


Posts: 3072 | Registered: Dec 2007  |  IP: Logged | Report this post to a Moderator
Teraen
Member
Member # 8612

 - posted      Profile for Teraen   Email Teraen         Edit/Delete Post   Reply With Quote 
A 90 degree tilt of the axis doesn't cause seasons. Seasons are caused by an off-tilt of the axis, so that sunlight is more direct for part of the year on one hemisphere, then less direct for the other. So, the greater the tilt, the larger the difference in seasonal climate, a 90 degree tilt would be all sun for one season, with no nighttime, and then all night for the next season.

The length of the season is determined by time of orbit. Our orbit takes one year, so our seasonal cycle is one year. If you want a 20 year seasonal cycle, the planet has to orbit its sun once per 20 years. The closer the planet to the sun, the faster it orbits, so you will need to place it farther away than earth. To create a habitable zone farther from earth, you will need a brighter star.

Here's some general links, good luck!

http://en.wikipedia.org/wiki/Season
http://en.wikipedia.org/wiki/Habitable_zone


Posts: 496 | Registered: May 2009  |  IP: Logged | Report this post to a Moderator
philocinemas
Member
Member # 8108

 - posted      Profile for philocinemas   Email philocinemas         Edit/Delete Post   Reply With Quote 
How about this idea -

Why don't you just put a giant volcano (like Yellowstone) on the planet. Once about every 50 years it blows its top and fills the atmosphere with enough dust and debris where it creates a nuclear winter that lasts for approximately 20 years. As the CO2 in the atmosphere begins to deplete, the greenhouse effect takes hold and causes the atmosphere to heat up steadily. The cycle then repeats itself.

Twa-la - Instant 20 year winters.


Posts: 2003 | Registered: Jul 2008  |  IP: Logged | Report this post to a Moderator
philocinemas
Member
Member # 8108

 - posted      Profile for philocinemas   Email philocinemas         Edit/Delete Post   Reply With Quote 
If you need to, you can give the system a gas giant that comes near the planet once every 50 years that causes the volcano to erupt.
Posts: 2003 | Registered: Jul 2008  |  IP: Logged | Report this post to a Moderator
Doug Bradshaw
Member
Member # 8559

 - posted      Profile for Doug Bradshaw   Email Doug Bradshaw         Edit/Delete Post   Reply With Quote 
quote:
So, broadly--an earth-sized planet can orbit a star 3.4 times the mass of our sun with a 20 year orbit if it does so at 11.1 AU from the star? Correct?

Right.

quote:
Would this not give earth-like seasons spread across the globe? So the equator would be similar to our equatorial regions (apart for the blue shift) and temperate regions would have seasons that were 5 years long? The artic circle would have 10 years of darkness followed by 10 years of day?

quote:
The presumes a tilt (not the correct word--axial inclination?) similar to earth's.

I suppose I could have one small continent and have everyone on that (Very long winter), but you say this planet would be hotter than ours...would this not negate the effects of the winter period--in that warm air would circulate from the warmer regions.


You're right about the tilt. My goal when I made the calculation was to make the planet as Earth-like as possible while still giving it a year that is 20 times as long as ours.

However, I guess I didn't communicate clearly when I said the sun would be hotter. I meant that the sun would be hotter, not the planet. That means that a rainbow from their sun would look brighter on the blue, indigo, violet side than a rainbow from ours would. Brightness gives a measure of the energy that reaches the planet from the sun and that was set to be equal to that of Earth. When I said that the sun might be hotter what I meant was that the colors would change. You can treat stars roughly like black body radiators. When a black body gets hotter, blue light is enhanced faster than red (and ultraviolet faster than blue, etc.) meaning that the sun will have a different color than ours.

quote:
I want ice cold winter (they are aliens) for 20 years, preferably with no where warmer on the planet for them to wander to. They have to stuck in the cold (and dark) until spring comes.

If you want the whole planet to be affected simultaneously then you might abandon tilt and go completely with distance. An eccentric orbit would be a nice way to make this a repeating, stable cycle.

In such an orbit, the planet spends most of its time far from the sun. Then it falls toward the sun, picking up speed, and circles it at maximum speed. This gives a long winter and a short warm season that are world wide. (The Equator will be the warmest all year, but it will get cold and hot over the course of the orbit.) The nice thing is that eccentricity is independent of the luminosity of the star and of the orbital period. You can dial in and choose the length and severity of the winter and the brevity of the summer.


Posts: 32 | Registered: Apr 2009  |  IP: Logged | Report this post to a Moderator
philocinemas
Member
Member # 8108

 - posted      Profile for philocinemas   Email philocinemas         Edit/Delete Post   Reply With Quote 
Just to play devil's advocate - the main problem with the eliptical orbit theory (causing 20 year seasons) is that this does not allow enough time for life to develop. The only way this could happen is if another sun or other large gravitational force stretched out the orbit of all of the planets after life had already taken hold. If it's only one planet with this orbit, it will get pounded as it crosses the orbits of other planets.

There are lots of factors that we believe affect the development of life (plant or animal): distance from sun, mass and type of sun, mass of planet, liquid (water), tilt of planet, rotation of planet, platonic movement, magnetic field, volcanic activity, atmospheric conditions, etc.

I also don't see how a planet orbiting binary stars in a figure 8 (if that's possible) could stand a chance of supporting life. I don't remember all of the suggestions listed above, but most did not seem very promising.


Posts: 2003 | Registered: Jul 2008  |  IP: Logged | Report this post to a Moderator
Doug Bradshaw
Member
Member # 8559

 - posted      Profile for Doug Bradshaw   Email Doug Bradshaw         Edit/Delete Post   Reply With Quote 
philocinemas, I like the idea of the volcano, especially if the winter can be a one-time thing.

When you said that there wouldn't be enough time for life to develop on a planet with elliptical orbits, did you mean that a more massive sun would burn out more quickly? Did you mean that the warm seasons between the long winters would be too short? Did you mean that the orbit would be unstable?

The first two points seem valid but not necessarily definitive. The third could be valid if, as you posit, other planets have orbits that interfere with the orbit of the planet of interest.

If we want to get more speculative another option might be a star that undergoes periodic flair-ups and periods of relative dormancy. It could be like a pulsar, but much slower . . .


Posts: 32 | Registered: Apr 2009  |  IP: Logged | Report this post to a Moderator
snapper
Member
Member # 7299

 - posted      Profile for snapper   Email snapper         Edit/Delete Post   Reply With Quote 
quote:
Just to play devil's advocate - the main problem with the eliptical orbit theory (causing 20 year seasons) is that this does not allow enough time for life to develop. The only way this could happen is if another sun or other large gravitational force stretched out the orbit of all of the planets after life had already taken hold. If it's only one planet with this orbit, it will get pounded as it crosses the orbits of other planets.


Not if Skadders world orbits my smaller jupiter mass star in a binary system. The star would have absorbed all the the other planets, asteroids, smaller debris in the first hundred million years or so. In fact, Skadders world could be one of the early developing worlds early in the star systems life.

Just think of it this way. Earth orbits Jupiter. Jupiter throws off heat, enough to warm Earth to an average temperature -20, -30 C of our mean tempature now. Give Jupiter a comet like orbit. Halleys, but less drastic. When Jupiter swings near the sun, Earth experiences a brief warming peroid.

The physics are there. Jupiter could support a planet of Earths mass. Elipitical orbits exist. Add the two together and you have Skadders world. A hellish frigid existence with a few hot rocky moments spaced apart.

Call the planet Marriage.


Posts: 3072 | Registered: Dec 2007  |  IP: Logged | Report this post to a Moderator
skadder
Member
Member # 6757

 - posted      Profile for skadder   Email skadder         Edit/Delete Post   Reply With Quote 
@Doug,

So if you had this elliptical orbit in system, I would presume that collision/intersection of another planetary body's orbit to be most unlikely as a ellipsis capable of bringing about said winter would not need to be enormous--would it?

If you had your original planet, circling a star 3.4. times our solar mass at 11 AU and stuck it in a system without any nearby planets (Mars-Mercury) you would have enough space, wouldn't you?

The planet's orbit could have been disturbed by something large, in the past, brushing close to it before crashing into the sun...other planets could have been on the other side of the sun and unaffected.

@Philo...wouldn't the above have allowed life to develop prior to the near collision and after there would have been a mass extinction, with only those capable of surviving evolving.

I presume this elliptical orbit would allow for winters days with weak sunlight...

@snapper

This Jupiter-size star would not produce light? Just heat? From what I gather a Jupiter-size mass is incapable of igniting as a star due to a lack of mass. The lack of light is not a major issue, but I guess the heat would make it tolerable.

Technically it would be a moon...which i quite like. The summer would need to be longer than a few brief moments...

[This message has been edited by skadder (edited July 18, 2009).]


Posts: 2989 | Registered: Oct 2007  |  IP: Logged | Report this post to a Moderator
Doug Bradshaw
Member
Member # 8559

 - posted      Profile for Doug Bradshaw   Email Doug Bradshaw         Edit/Delete Post   Reply With Quote 
@Doug,

quote:
So if you had this elliptical orbit in system, I would presume that collision/intersection of another planetary body's orbit to be most unlikely as a ellipsis capable of bringing about said winter would not need to be enormous--would it?

The size of the orbit is dictated by the length of the year and the mass of the sun. It's a big orbit because the years are long. It's eccentric because the seasons are lop-sided. But as far as I know, we haven't seen enough solar systems to establish any rule about the distribution of planets. And even if there were such a rule it would have exceptions. I don't see any reason for there to be interfering planets if you don't want them.

quote:
If you had your original planet, circling a star 3.4. times our solar mass at 11 AU and stuck it in a system without any nearby planets (Mars-Mercury) you would have enough space, wouldn't you?

Right. If nearby planets are gone, so is the problem.

quote:
The planet's orbit could have been disturbed by something large, in the past, brushing close to it before crashing into the sun...other planets could have been on the other side of the sun and unaffected.

Sounds fine to me.

I think Snapper's variation sounds fun. The math about orbits remains the same only now it's the large planet/minor star that needs to have an eccentric orbit with a semi-major axis large enough to give you the year length you want. You could dial down brightness of the primary star a bit to compensate for heat from the gas giant.


Posts: 32 | Registered: Apr 2009  |  IP: Logged | Report this post to a Moderator
snapper
Member
Member # 7299

 - posted      Profile for snapper   Email snapper         Edit/Delete Post   Reply With Quote 
I see two nearby systems that support me thesis. My Jupiter mass star appears to be too small but there is a star that fits in the range I was thinking about, and it has a planet within its habital range.

Alpha Centari

http://en.wikipedia.org/wiki/Alpha_Centauri

It is a binary system (with a straggler star(proxima centari) that they are unsure of). One star is a bit bigger than ours, the other a bit smaller. Star A is the center of the system. Star B revolves in an orbit like the one I suggested. Its ellipitical path takes it from a Pluto point at its furtherist to a Saturn one at its closest. (That's 2 billion at its furtherest and 1 billion at its closest)

Gliese 581

This is a red dwarf star. It has a mass, lumination, and size of about 30% of our own. It has a planet that is in an orbit that will support life, less than 20 million miles from the star.

You could take that dwarf star (it is a very stable star, older than ours) shrink it a bit, make the planet orbit it at 15 million miles, then orbit that star around the bigger one. The small star could have an orbit that is 35 of our years long. 20 could be ice age cold, then a five year warming spring, five year scorcing summer, and a five year cooling fall.


Posts: 3072 | Registered: Dec 2007  |  IP: Logged | Report this post to a Moderator
Corky
Member
Member # 2714

 - posted      Profile for Corky   Email Corky         Edit/Delete Post   Reply With Quote 
What if you had your planetary system move into a part of space that had enough dust in it to interfere with the sunlight for long enough for your 20-year "winter?"
Posts: 603 | Registered: Jul 2005  |  IP: Logged | Report this post to a Moderator
Teraen
Member
Member # 8612

 - posted      Profile for Teraen   Email Teraen         Edit/Delete Post   Reply With Quote 
Had another idea (though its similar to one already posted...) Your planet orbits either a small star, or is very far away, so you have a constant winter condition. Every twenty years or so, a comet comes by. The comet is another sun and therefore heats up the planet during its transit.

I also think the idea of an "Old Faithful" volcano is my favorite so far...


Posts: 496 | Registered: May 2009  |  IP: Logged | Report this post to a Moderator
   

Quick Reply
Message:

HTML is not enabled.
UBB Code™ is enabled.
UBB Code™ Images not permitted.
Instant Graemlins
   


Post New Topic  Post A Reply Close Topic   Feature Topic   Move Topic   Delete Topic next oldest topic   next newest topic
 - Printer-friendly view of this topic
Hop To:


Contact Us | Hatrack River Home Page

Copyright © 2008 Hatrack River Enterprises Inc. All rights reserved.
Reproduction in whole or in part without permission is prohibited.


Powered by Infopop Corporation
UBB.classic™ 6.7.2