Category Archives: Planets

TESS Lifts Off

NASA’s Transiting Exoplanet Survey Satellite (TESS) lifted off on a SpaceX rocket last night. TESS is a follow-up to the wildly successful Kepler mission that will hunt for transiting planets—that is, planets that pass in front of their stars, blocking … Continue reading

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Kepler-1625b I: The First Exomoon…Maybe

So, the big science news of the day is the potential discovery of the first known “exomoon”—that is, a moon orbiting an extrasolar planet. (Scientific paper here.) Scientists have been looking for such moons for years, only to turn up … Continue reading

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Planet 9: A New Planet in Our Solar System?

“In my day, Pluto was a Planet!” said everyone over the age of…15 or so. Pluto was demoted from planet status ten years ago (a decision I do agree with–see here), and now we only have eight planets–or do we? … Continue reading

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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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NASA Discovers the First “Earth-Like” Planet for the Third Time

There’s been buzz in the news about the latest planet discovered by NASA’s Kepler space telescope, Kepler-452b. It’s being hailed as a major discovery. It’s the first ever Earth-sized planet found in the habitable zone of a…boy, this sounds familiar, … Continue reading

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