Posted on 06/19/2012 3:36:59 AM PDT by SunkenCiv
Lars Buchhave and his team selected more than 150 stars with known planetary systems that were cataloged by NASA's Kepler mission. They then studied these stars' metal content and the size of the planets in their solar systems. What they found was that gas giant planets were more likely to form around metal rich stars, whereas terrestrial planets were equally likely to form around metal rich or metal poor stars.
As the team explains, the reason for this fits neatly into the "core accretion" model of planetary formation. Each gas giant has a metal core which hydrogen and helium accumulate around. However, if there is no core to collect around, the lighter elements will be blown away by stellar winds while the star is still relatively young. If a star has a high enough metal content, its potential planets might be able to form a large metallic core quickly, before the winds do their work. The core will then gravitationally attract the remaining gas to itself and a new gas giant is born.
On the other hand, the formation of terrestrial planets is not dependent on helium and hydrogen and therefore not subject to the same time constraints. If a star has lower metal content it might take longer to form terrestrial planets, but all the ingredients are still there. Essentially, there is no upper time limit for a terrestrial planet to form whereas a gas giant must develop quickly to keep its hydrogen and helium trapped within the solar system.
(Excerpt) Read more at universetoday.com ...
With all that space dust out there, we should shoot some Dyson vacuum cleaners into space to clean the mess up. Oh, wait, with their circular technology, they would probably form a sun and burn us all to a crisp.....never mind.....
Why haven’t aliens with advanced space travel come to Earth yet?
If they are that advanced, they must be conservatives.
They don’t want to infect their societies with socialism.
Been there. It takes just about a year at 1G, then the same amount to decelerate. What is more interesting, is how long would it seem to take to the person on the ship to perform the entire maneuver.
I recently re-read a story called (I think) "A path less travelled" that was linked off one of the SF pings here that had exactly that as it's main point. Extra-galactics never discovered atomics and advanced rocketry because they discovered the secret to anti-grav when they were at the level of matchlock/flintlock rifles. I really do think that a once the principle of a ZPM module is discovered, it will probably be something that will be incredibly simple and extremely obvious in hindsight. I got nothing to back that up with, but I believe we are meant, by our Creator, to travel to the stars to explore and experience His grandeur and the marvels He has created for us, because if not, mankind as a species will simply not survive. Even if you take the entire solar system into account, there is only a limited supply of resources, and we know that the sun has a limited lifespan.
The road not taken, by Harry Turtledove.
The story itself is a great example of outside the box thinking that once read, shifted my whole perception on the issue and sends me off in a whole new direction of thinking. I had certainly never considered the possibility of a less advanced race coming to earth. We could be surrounded by alien races that simply have no curiosity about us or are afraid of us.
That's it. Thanks. I'd have never found it again with google. I really mangled it, while keeping the sentiment.
Another original beauty, cc! Thanks for sharing your work with us.
Ooooh! It has atmosphere! M-Class.
I’m going to start “borrowing” these, with your permission?
Yeah you can use them.
Thank you. You’re very kind.
“No kill I”
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