Skip to comments.Terrestrial Planets Could be More Common Than Gas Giants
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 ...
This artist's conception shows a newly formed star surrounded by a swirling protoplanetary disk of dust and gas. Credit: University of Copenhagen/Lars Buchhave
Alien Earths Could Form Earlier than ExpectedPrevious studies have shown that Jupiter-sized gas giants tend to form around stars containing more heavy elements than the Sun. However, new research by a team of astronomers found that planets smaller than Neptune are located around a wide variety of stars, including those with fewer heavy elements than the Sun. As a result, rocky worlds like Earth could have formed earlier than expected in the universe's history. "This work suggests that terrestrial worlds could form at almost any time in our galaxy's history," said Smithsonian astronomer David Latham (Harvard-Smithsonian Center for Astrophysics). "You don't need many earlier generations of stars." ...Astronomers call chemical elements heavier than hydrogen and helium "metals." They measure the metal content, or metallicities, of other stars using the Sun as a benchmark. Stars with more heavy elements are considered metal-rich while stars with fewer heavy elements are considered metal-poor... They measured the stars' metallicities and correlated that with the sizes of the associated planets. Large planets tended to orbit stars with solar metallicities or higher. Smaller worlds, though, were found around metal-rich and metal-poor stars alike. "Giant planets prefer metal-rich stars. Little ones don't," explained Latham. They found that terrestrial planets form at a wide range of metallicities, including systems with only one-quarter of the Sun's metal content.
David A. Aguilar & Christine Pulliam
Wednesday, June 13, 2012
Harvard-Smithsonian Center For Astrophysics
|· join · view topics · view or post blog · bookmark · post new topic · subscribe ·|
|Google news searches: exoplanet · exosolar · extrasolar ·|
Seems to me that if we’re alone, God has given it to us to explore and populate.
;’) Nicely done! Also IB “it’s only a theory”, “just in it for the grant money”...
And lets not forget the ever popular, “We’ll never be able to go there anyway”.
Even worse is someone who wants to pretend to do the math first, *then* tell us “we’ll never be able to go there anyway”. ;’)
If our new found “planetoid” category counts, then our solar system has more rocky planets than gas giants (4 vs. 5+). So this isn’t that wild a concept.
Invent warp drive, start colonizing!
because of the vast distances between stars, I believe at least one of three things need to be true.
Personally, I hope that all three are possible, and BTW, I want a ZPM to run my motorcycle.
There are lots of Class M planets. They visited a new one almost every week on Star Trek.
They even found a planet on which there was silicon based life, as opposed to the carbon based life found on earth. So there could even be life in forms we wouldn’t think about, such as silicon based life, out there in the cosmos.
Figure out how long it would take to accelerate to 90% of the speed of light at one gravity of constant acceleration.
Then, of course as you approached your destination you would then have to decelerate at one gravity for the same amount of time.
There are a lot of very interesting little understood things going on at the sub atomic level which could potentially be harnessed for our own use.
“Spooky action at a distance” as Einstein called it or quantum entanglement has the potential of communicating instantaneously over billions of light years.
Obviously we aren’t going far right now but that’s what science is for. Its also possible that we simply haven’t stumbled across or conceived of something extremely simple
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”
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.