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Solar Systems Like Ours Are Likely To Be Rare
KentuckyFC writes "Astronomers have discovered some 250 planetary systems beyond our own, many of them with curious properties. In particular, our theories of planet formation are challenged by 'hot Jupiters,' gas giants that orbit close to their parent stars. Current thinking is that gas giants can only form far away from stars because gas and dust simply gets blown away from the inner regions. Now astronomers have used computer simulations of the way planetary systems form to understand what is going on (abstract). It looks as if gas giants often form a long way from stars and then migrate inwards. That has implications for us: a migrating gas giant sweeps away all in its path, including rocky planets in the habitable zone. And that means that solar systems like ours are likely to be rare."
But that doesn't make them not rare. If there's 100 billion star systems, and even just 1 million stars in each, you are looking at 100,000,000,000,000 star systems. Even if there is a .000001% chance of a star system like ours existing, it means that there are 1,000,000 star systems that are like ours. So they could be both very rare, and yet still very likely to happen.
Anthropic principle: We see the universe the way it is because if it were different we would not be here to see it.
That's Gliese 581c, which is merely five times the mass of the Earth --- and they only detected it because it orbits at one fourteenth of Earth's orbit. In other words, it's a heavy planet very, very close to its sun. The only reason it was described as 'Earth-like' is that Gliese 581 itself is a red dwarf, which means it's much cooler than Sol, which puts 581c in the star's life zone.
So, while it's theoretically possible that 581c could support life, it's still not really Earth-like. We're still a long way off from being able to detect Earth-sized planets at Earth-orbit distances from Sol-like stars.
Haha. I don't know about sending Bruce WIllis, but this does make me wonder why we have never (to my knowledge...) sent a probe INTO one of the gas giants.
Your geek credits have been officially revoked.
Galileo had a probe that was dropped into the atmosphere of Jupiter and it transmitted data for 58 minutes before it stopped. Hell, we even crashed the Galileo spacecraft into Jupiter to prevent contaminating Europa or Callisto with organisms from Earth.
"There are no facts, only interpretations." --Friedrich Nietzsche.
The method used to find these systems are changes in the star's brightness when the planet passes in front of the star - so systems with large planets in close orbit are the ones to be noticed first. If you have a planet like Jupiter with an orbital period of around 12 years, you're much less likely to catch that event compared to those "unexpected" systems with short periods.
I'm aging rapidly, I bought a new game and had no idea if my machine was good for it.
The interesting data is not how many hot Jupiters are found, but how many stars do not have hot Jupiters.
Here's a list of extrasolar planets (last updated in January); and another list. Note the large number of stars that have planets found with mass less than Mj. The converse of that is that those stars do not have planets of mass greater than Mj. The problem, of course, is that negative results are much less published than positive results. However, here is a list of three published papers that listed stars with no planets found (that is, no planets large enough to detect-- which is to say, no hot Jupiters. This list is somewhat out of date, as of 2006.)
So the story is a little incomplete. Some solar systems have hot Jupiters, which in their migration inward disrupt smaller, earthlink planets... but by no means all.
http://www.geoffreylandis.com
We have.
in 1995 by the Galileo a probe was dropped into Jupiter.
http://apod.nasa.gov/apod/ap951207.html
But if you think it will just sink in until it 'hits' then check your physics on large gas giants again.
RogerWilco the Adventurous Janitor
Whatever... this is naval gazing and conjecture, no more credible than Intelligent Design. These guys have a few data points, they create a highly convoluted system that seems to account for their data points, then the moment they get more data, they start over. Again and again.
Data points which are skewed by the fact that planets with a large mass (relative to the star) orbiting close to the star are easier to detect by techniques based on star wobble and transit light level and so are going to be massively over represented in the list of known planetary systems.
These comments are my personal opinions and do not necessarily reflect the opinions of the other voices in my head.
Outsider theories always have the burden of proof on their own shoulders. To paraphrase someone famous, "there are many questions fools can ask that wise men struggle to answer." There's no where this applies more than in science. Creation Science can throw out some sticky questions and make some points that are hard to disprove.
But Science is about proving things, not suggesting every possible idea and disproving them one by one. For a well established idea that has made a lot of successful predictions, even a known incomplete idea like the standard cosmological model, to be tossed aside, there needs to be an overwhelming amount of evidence, not just some compelling questions.
If an alternative model of the universe explains the preponderance of evidence we already have (such as the background radiation, the count of galaxies, the scarcity of structures above a certain scale, the calculated mass of galaxies, the total amount of gamma radiation etc.) as well as a current theory, as well as making successful new predictions that existing models failed to make, then over a process of several years, people in the field would become convinced, and as the literature is peer reviewed, the dogma would shift. But established scientific ideas are SUPPOSED to be dogma. It isn't politics. Equal time isn't given to competing ideas, that's not the way it works. There are too many bad scientists and professional crackpots, the system would collapse without a hierarchy of opinion.
And all science works this way and always has. Even the sciences that cure disease and deliver technological miracles. Since those things keep happening, I'm confident as a semi lay person that science, while certainly getting many small details wrong and making mistakes and sometimes taking too long to come to the right conclusions, is still heading in a monotonically positive direction.
In Capitalist America, bank robs you!
The most important thing that you need to understand is that the large number of "hot jupiters" that have been found have essentially disproven existing theories of solar system formation. This is not a case where a new theory is proposed to replace an existing theory that already explains most of the evidence ala Einsteinian physics replacing Newtonian physics. This is a case where we have essentially no theory at all that explains the observed evidence.
The cake is a pie