Pluto and Charon

The International Astronomical Union has published its definition of a Planet. Under this definition Pluto will be a Planet as will its "moon" Charon and two others UB313 And Ceres. This report by Pallab Ghosh.

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The debate took a new twist earlier this year when astronomers calculated that another far flung object called UB313 was slightly larger than Pluto so should that be called a planet too?

Now, after years of deliberation, a committee of astronomers have come up with a scientific definition of a planet. They say that it’s something that's round (because of its gravity) and orbits the Sun. If approved, this'll mean that Pluto keeps its planetary status. But it’ll also mean that its large moon Charon is also upgraded to planetary status as are UB313 and an erstwhile planetoid called Ceres.

That takes the total number of planets in our solar system to 12. With better telescopes that's likely to rise yet further as more worlds are discovered in the future.

Pallab Ghosh, BBC

Listen to the words

at the fringes of
at the edge of or less important part of something

stripped of
take something important away from something or someone - here, take away the status of planet from Pluto

far flung object
something that is a very long way away

deliberation
[a formal word] a discussion about something

orbits the Sun
follows a curved path around the Sun

planetary status
official position as a planet

erstwhile
[a formal word] former, before this current time

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