Tag Archives: definition of planet

Planet or Not? How About “Planetoid”?

I’ve argued that Pluto shouldn’t be a planet, and I’ve also argued that we don’t know enough to rigorously define the word “planet”. Now, I want to take a closer look at how and why we divide our own Solar … Continue reading

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How to “Define” the Word “Planet”

So the IAU has declared that Pluto is not a planet. I agree with this assessment, but I also think that the IAU’s definition is poorly written. So how should that word “planet” actually be defined? It’s not simple.

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Why Pluto Really Shouldn’t be a Planet

(But the IAU is Wrong, Too.) In 2006, the International Astronomical Union (IAU) voted that Pluto was not a planet, just months after the New Horizons spacecraft was launched with a mission to…visit the last planet that had never been … Continue reading

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2012 VP113: a weird new “dwarf planet”

Astronomers Chad Trujillo and Scott Sheppard announced this week the discovery of a new icy world in the outer Solar System, named 2012 VP113. Trujillo is a colleague of Mike Brown, who discovered the dwarf planet Eris, which is larger … Continue reading

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Planets of failed stars

A brown dwarf is a failed star. It’s about the size of Jupiter, but anywhere from 13 to 80 times as massive. It is too small to shine by burning hydrogen, like a star, but it is massive enough to … Continue reading

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