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[NEW_MAN]

http://teacher.scholastic.com/resear...ce/planets.htm


Why are there nine planets?


Instead of eight or ten? As far as I know, there is no special reason.

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PLANET MASS RADIUS SURFACE GRAVITY (g)
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto

NOTES:
MASS, RADIUS, and SURFACE GRAVITY are all compared to Earth. Earth's radius is about 3,800 miles. If you could weigh Earth, it would weigh13,000,000,000,000,000,000..... (24 zeros) pounds! Whoa! That's heavy!

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Do scientists think there might be a tenth planet in our solar system?


For some time, astronomers have tried various ways to search for a tenth planet. But we now think that there are no new planets. One big reason is that the Infrared Astronomy Satellite, known as IRAS, did a very good map of the sky in infrared light. If any new planet were out there, IRAS should have found it. But it didn't. So we think that there are no more planets in our solar system


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Have there ever been any other planets that dinosaurs could have survived on?


I don't think so, at least for any of the planets in our solar system. Mars may have had some liquid water millions of years ago, and life might have started. But the atmosphere is too thin and too cold for life to have evolved very far. Venus is a horrible hothouse with acid rain. Mercury is terribly hot. Jupiter and the other planets are way too cold.

Of course there could be another planet circling another star where life exists. But we don't know enough about those other planets yet to even say how many there are, much less whether dinosaurs (or people) could live there. But the universe is a very big place. I believe that there are living creatures out there somewhere!