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are extra solar planets out there and some of them seemingly Earthlike. Planets and stars move along their common center of mass. Planets have a wide berth to their orbits, naturally, but even stars have their own much smaller orbit around their own center of mass which is detected as a wobble. It's like watching a person use a hula hoop. The hoop represents the planet's wide swinging orbit around the star and the person swinging the hoop around their hips represents the star slightly moving within its own center of mass. This is one way astronomers began to detect that there were other planets outside of our solar system. Another way is the Doppler Shift or Doppler Effect, studying the frequency emitted from waves, in this case, from stars and planets. Like soundwaves, lightwaves appear to shift in frequency from the objects emitting them depending on whether they were going forwards or backwards. As a star wobbles, the lightwaves coming from a celestial body appraoching us seem blue while the lightwaves shifting away appear red. by using these techniques and their knowledge of the Doppler Effect, astronomers can tell whether there is a planet moving around a star very far away and where that planetary body is moving in relation to its star.

What we have learned about our own system and other star systems are very surprising and have challenged astronomer's perceptions of what they know about how our solar system works. First, most extra solar planets that have been found do not orbit anywhere near the habitable zones of their stars. Also, the phenomenon of "roasters" or hot Jupiters as they have been termed, gas giants like Jupiter, that orbit extremely close to their stars have challenged long held assumptions about how gas giants form and where they are usually located in a solar system. Old assumptions are now falling by the wayside. It was thought that gas giants were only able to form outside of the snow zone, far away from the star they orbit. Another very interesting thing that surprised scientists are the elliptical orbits of most planets everywhere, except in our own solar system. In our sytem circular orbits are the norm and elliptical orbits are considered odd. Because Pluto's orbit is elliptical it was knocked off of its "major planet" pedastal and has been demoted to dwarf planet status, or even simply a Kuiper Belt object. Comets have elliptical orbits, it was thought, not true planetary bodies. Astronomers were wrong about planetary orbits

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