Author Archives: Allen Versfeld

About Allen Versfeld

Allen is an amateur astronomer, an IT professional, a podcaster, a father of five growing kids, a barely competent chess player, and the owner and publisher of the Urban Astronomer podcast and website. He has formerly served as Director of the Astrophotography and Citizen Science sections of the Astronomical Society of South Africa. You can find his personal social media feed on Mastodon!

Photographed: Apollo landing sites

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Apollo 17 landing site imaged by Lunar Reconnaissance Orbiter. Credit: NASA’s Goddard Space Flight Center/ASU A few months back, while debating the moon landing hoax with a relative, I was asked “Why don’t they just prove it by pointing a telescope at the moon and showing us the landing site?”.  I tried to explain how even the most powerful telescopes ever built could not resolve something the size of a car from 350,000 km away, and especially not while looking … Continue reading →

Mining Weekly interviews SASRA president

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As we’ve mentioned before, the South African Space Resources Association (SASRA) is a body dedicated to bringing South African mining and engineering experience into the field of space resource utilisation.  If humankind is ever to leave the cradle, we must learn to gather resources from the moon, asteroids, and planets.  South Africa probably has more expertise and experience in mining under extreme conditions than any other country in the world, so we have a lot to offer. There are increasing … Continue reading →

What is a planet?

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That’s a dangerous question!  Last time somebody asked it seriously, they demoted Pluto!  A planet is any object orbiting the Sun which is heavy enough to both squeeze itself into a spherical shape and clear the space around its own orbit (in other words, its gravity must be powerful enough that anything nearby gets drawn in and either smashes into the planet or gets catapulted away into space).  By this definition, we have eight planets in our Solar System.  It’s … 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 →

What is the smallest planet?

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Mercury is the smallest planet known, with a diameter of just under 4900km.  Until it was disqualified as a planet in 2006, though, Pluto held the title at somewhere over 2300km – less than half the size!  Thanks to the formal definition of a planet, Mercury is not likely to lose its place at the bottom of the size ranks for a while: we can see quite clearly that there is nothing smaller in our Solar System which meets all … Continue reading →