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Are We Alone in the Universe?
cynic10508 writes "CNN is running a story about how ours might be a unique solar system. Of the 100+ systems currently known to contain planets, all contain seemingly only gas giants. However, this may be a case of current technology and techniques being unable to detect planets similar to Earth." There are also
BBC and Space.com stories.
It involves five methods currently (all of which are outlined in the article):
One thing that frustrates me about the articles I've seen on this subject is that they don't explain why formation of big, close-in gas giants precludes formation of Earth-like planets farther out. Accretion disks are really, really big; surely parts of them can clump into gas giants while others slowly form smaller, rocky planets?
Here's the explanation: gas giants have to form farther out, past the "frost-line" where ices can first freeze out of the gas disk. In order to be a hot Jupiter, the have to migrate inward toward the star. That migration is slow, but if the planet encounters a terrestrial planet then the terrestrial planet is in trouble because the giant planet will either scatter it out of its way (either out of system, into the Sun, or at least into a fairly eccentric orbit, none of which is good for habitability) or accrete it. And if there is a terrestrial planet, the giant planet will encounter it on the way in since, by the standard model for planet formation, the terrestrial planets will be in the giant planet's path.
My impression is that these particular planets are so close to their stars (closer than Mercury is to the Sun!) that any moons they might have would be sterile chunks of very hot rock -- not to mention that the orbital dynamics would be a nightmare, and a moon would probably end up getting thrown into either the star or the planet pretty fast, or flung out of orbit entirely. OTOH, the idea of Earth-size moons orbiting gas giants a little further out, in the "life band," and supporting life, seems entirely reasonable.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
No, it isn't about tides or about denser stuff settling out. (That's a buoancy effect that occurs in fluids with pressure-support. That doesn't really occur in disks, which are mostly just in orbit.)
The difference in planets is due to temperature in the disk. Since it's colder farther out, ices can freeze and be used to build the cores. Once the core is large enough, you get gas capture and jovian planets.
"Absence of Evidence is not Evidence of Absence. Why is this even being posted here?"
Though you are correct, this is not what the article is saying. It's suggesting that the theoretical model for how planets are formed may not be accurate. If what they're saying turns out to be true enough, then Earth-type planets could be extremely rare. They do not say that we're alone. They do not say they have evidence that we are alone or close to it. Instead they've come up with an alternative that may provide a reasonable assumption that it'll be a LOOONG time before we find another earthish planet.
Scientists just don't work that way.
"Derp de derp."
As it should be but if anything it would make people fight against each other even more. Religion fuels a lot of our current social problems. What the hell is it going to do when we fight intelligent life that wasn't created in what our cultures felt was "God's vision"?
Oh please. There might be some wackos out there that may take that issue but there are pleanty of other wackos out there too. I don't think that most "Christians" would have any problem with the idea that God created life elsewhere and didn't bother to give us details.
Not everything is analogous to cars. Car analogies rarely work.
One thing that frustrates me about the articles I've seen on this subject is that they don't explain why formation of big, close-in gas giants precludes formation of Earth-like planets farther out. Accretion disks are really, really big; surely parts of them can clump into gas giants while others slowly form smaller, rocky planets?
These large gas giants have very eliptical orbits around their sun. Imagine a planet at least as large as jupiter getting as close to the sun as mercury for part of the year, then going back as far as pluto. Now imagine how much disturbance that would cause to any planets in between, I'm sure that would send any planets spiraling off either into the sun or out of the solar system, if not just crash into the planet. Plus from what I've seen, most of these large gas giants dont have that long of a life span, because they're constantly sling-shotting themselves off the sun, they usually end up either crashing into the sun or sending themselves out of the suns orbit relativily quick.
As Bill Waterson said (creator of Calvin and Hobbes,) "Sometimes I think the surest sign that there is intelligent life out there is that it hasn't tried to contact us yet."
(as closely as memory serves.)
"Space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space."
Though the parent to your post was correct, you are off by just a tad.
The basis for the assertion that there's a problem with the model is based on the current population of known extra solar planets. It's almost completely made up of big planets close their stars.
Well, duh.
We have only detected short period orbits because we need to see multiple passes of a planet in front of its start to confirm it's presence. This technique finds the shortest periods first. We have to keep watching to catch the longer periods.
The bigger the planet, the bigger the wobble, the easier the confirmation of the presence of a planet.
Big planets on short orbits are the first off the assembly line.
We have to wait longer to detect longer orbits (if an orbit takes 10 earth years, and we need three passes of the planet to call it a dedection...)
Smaller planets don't make their stars wobble enough to be detected in the current manner.
The original post is absolutly correct, there's no news here.
I just KNOW somebody's getting a new grant to take a look at this possibility, though.
-ave
...or maybe not.
You wouldn't happen to be an Atheist like me would you? BIBLICAL CONTRADICTIONS
I like this one,
"... I have seen God face to face, and my life is preserved." -- Genesis 32:30
"No man hath seen God at any time..."-- John 1:18
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