The 10th planet? Hmm. But how does one define a planet?
Measurements suggest Sedna’s diameter is almost 2000km the biggest find in the solar system since Pluto was discovered 74 years ago. It is believed to be made of ice and rock, and is slightly smaller than Pluto.
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5 responses to “Sedna”
But how does one define a planet?
It’s a big round thing orbiting the sun! 🙂
For practical purposes I use self-gravity to deliniate a planet from a rock or asteroid. Over a certain mass the gravity of the object will deform the material — rounding it out. Asteroids on the other hand can be very irregular (peanut shaped even) because the rock is stonger than the weak accretion force of the small mass.
I think the term “planetessimals” is very cool!
Knowledge is simply a syetem of classification, maximised for the convenience of the user. The current debate over the planetry status of Sedna must be interpreted in this light. I propose that we arbitarily assign Pluto to be the minimum size for status as a planet. Why? If we must draw a line somewhere, shouldn’t it be at the place where it is most convenient to do so? Senda should not qualify as a planet.
Hehe, very funny Frank. And that is a nice word Trish. Althought I am tempted to go along with Christopher – thought now I hear the new body has a buddy, a moon.