Question on planetary position for making said planet a lush green world.

I have just been reading the Episode II novel and (No spoilers) and Anikan was on Naboo talking with Padme’s father about how beautiful the plant is.

I got to thinking, would Anikan be more comfortable in the deserts of Naboo? But then it struck me…by the looks of things in the movie, Naboo had no deserts of sand, so…

How far away would a planet have to be in order for it to have a lush green ecosystem without having hot and dry deserts? (Or maybe this is just something that The Bad Astronomer can chock up to Bad Astronomy in the movies.)

I don’t think it’s a question of distance or temperature. You can have a desert at any latitude - in fact Antarctica is mostly desert, in the sense that there’s very little precipitation. The equatorial areas of earth isn’t too hot for plants to exist; the deserts are the places where, due to climate patterns, rainfall is small.

There are a lot of factors that would go into determining if a planet has deserts or not.

  • Size of the system’s sun (i.e. total energy output).
  • Distance of planet to the sun (not to mention how eccentric its orbit is…how close at perigee and how far at apogee).
  • How much water the planet possesses.
  • Composition of the planet’s atmosphere.

Roughly speaking I once heard that life on earth, at least as we know it today, wouldn’t be possible if the earth was only 2% closer or further away from the sun than it is now. That’s vague recollection though so take it with a grain of salt.

As you suspect, Whack-a-Mole, that 2% figure is a hooey. The Earth’s current orbital eccentricity is 0.017, so the Earth’s distance from the Sun varies almost 2% every year. The Earth’s eccentricity has probably been higher at various times in the past, as well.

I’m a big Star Wars fan, but George Lucas is not an astrophysicist. Desert planets and forest moons make for tidy storytelling, but most life-bearing planets would have a variety of biomes: deserts, jungles, prairies, tundras, etc.

Even worlds without life demonstrate this. Jupiter’s weather is different at the equators than the pole. Triton is half-covered with ice. Mars’ weather patterns make some areas particularly prone to dust storms and water vapor clouds.

Venus, on the other hand, has pretty much uniform temperature from equator to pole due to greenhouse effect of its thick atmosphere. Eh, well, speculation on this point is notoriously unbounded by fact or theory. We barely understand weather and climate on Earth.

I hear ya but I think they (whoever ‘they’ were) were saying if you shrunk earth’s orbit by 2% such that at apogee it would be roughly where the earth is at perigee today you’d screw-up life on earth. In that scenario the earth at perigee would get too hot and life would be screwed ar at least our planet would look very different. Reverse that growing the earth’s orbit by 2% for the same idea except now the earth gets too cold.

I’m still not saying I’m correct about this. I’m just trying to explain what I understood that figure to mean.

As I recall, Naboo had water-filled caves passing all the way through the planet’s core, through which Jar-Jar and the Jedi (band name!!) passed when getting from Gungan City to Theed. Naboo’s climate is largely due to it having a lot more water than Earth has. I don’t think you need to question its orbit, except so far as is needed to keep the water within a reasonable range of the triple point.

There are about as many estimates of the “Goldilocks Zone” as there are planetary astronomers. I’ve seen models that put the outer edge of the zone outside the orbit of Mars, for instance. About the only thing that everyone agrees on is that Earth is in it.