Tag Archives: Planet

The Scale of the Solar System – a 3rd attempt

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Some time ago, we featured a poster created by the Planerary Society’s Emily Lakdawalla which showed all of the Sun’s largest satellites (or at least, everything we know of that’s bigger than 400km across), to scale.  She has since refined the image to correct perspective effects that made Saturn look bigger than Jupiter, and you can see the result to the right.  Gas giants, rocky planets, minor planets, asteroids, moons, they’re all there.  Click the image to see it in … Continue reading →

Mars

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Mars is the third of the classic planets. It is not one of the brightest, but it stands out for two reasons: It has a vivid orange-red colour and it makes large retrograde motions in the sky every year and a half. As we watch Mars from night to night, it slowly moves to the East. Every now and then (whenever Earth overtakes Mars in its orbit), Mars stops moving and reverses direction. After about a month, it resumes its normal … Continue reading →

Why is Pluto not a planet?

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In 1930, Clyde W Tombaugh completed the search for Planet X, the outermost planet at the far reaches of the solar system.  This object was named Pluto.  Then, on 24 August 2006, the IAU (International Astronomy Union) formally voted on a new definition of the word ‘Planet’, which excluded Pluto.  For seventy-six years, our solar system had been understood to have nine planets, then suddenly it went back to eight.  The response was furious. Both the astronomical community and the … Continue reading →