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after finding alien planets. They have found that our solar system is unique in many respects and the manner of planetary orbits is one of them. The study of alien worlds and stars are affirming in the minds of many that our planet is far more unique than once thought. It's not that other planets outside our system don't exist; they are quite abundant, but are they anything like Earth is the question and that is a far harder thing to know.

Other facts found about these extra solar planets are fascinating: some extra solar planets are bigger than Jupiter and some have storm winds up to 6000 mph! Extra solar planets and their formation has taught astronomers that we are not unique in ways we thougt we were previously and that we are unique in other ways. There are many planets out there but planets that can sustain complex life like Earth are rare, if they exist. So what are Earth like planets? They have to meet certain requirements. Water is needed in some form, the right atmospheric conditions, the planet needs to be rocky and it needs to have a stable, circular orbit, it needs the right kind of moon(s) and it needs to be within it's star's habitable zone for starters and that's not all. Astronomers have found a few planets that might fit the bill of sustaining life in the future: Gliese 436b and Gliese 876d. Gliese 436b is an interesting one because it is an ocean planet. In fact, it has no surface, much like what Earth used to be like billions of years ago. However, the water on Gliese 436b may not be anything like what we know it. Astronomers say that the water molecules are so dense that the structure of it is more like ice, except that it isn't cold. Why are they so dense? Most liekly because water is so abundant on the planet that all of its surface is completely covered. Then there's Gliese 876d which is 6-7 times Earth's mass. It was once thought to be a rocky planet, like Earth. It sits just on the edge of its star's habitable zone. It may have a rocky surface or not. Some astronomers now think that it too may be a water planet completely devoid of a surface. As far as anyone knows, neither of these Earthlike planets can hold complex carbon based life forms even though they may seem similar to Earth. The issue becomes complex because there are many factors that go into creasting the right conditions for life and so far the Earth like planets don't have not enough to support life. Like Mars, Venus and a few moons in the outer solar system like Europa, Io they have some features that make them seem likely candidates but not enought to be true sister planets to Earth. They are more like distant cousins of Earth.

So the search goes on for Earthlike alien planets. It is fascinating and has earned a respected place in astronomy that reveals more and more about the wonders of the universe. It also reveals what we know already about our place in the universe and reveals what we don't yet know. Perhaps one day we can travel closer to these planets for better study and exploration and continue our pursuit of knowledge of other planets and their stars.

Learn more about this author, Victoria Jeffrey.
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