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!

Mars Science Laboratory already at work

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A short while ago, the Curiosity rover was sent on its long journey to Mars, where it will study the red planet to determine whether the planet has ever been capable of hosting life, and whether it could do so in future.  But even though at is still over 200 days from its destination, at least one instrument in its on-board laboratory is already hard at work, collecting data and reporting back to Earth:  the Radiation Assessment Detector (RAD), which … Continue reading →

Newton’s Principia available online

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The University of Cambridge, as part of their Digital Library project, have digitised over 4000 pages of Isaac Newton’s writings and made them freely available on the web.  Available works include some old college notebooks, his rough work from when he developed his theories of calculus, and the mighty Philosophiæ Naturalis Principia Mathematica.  The Principia (as it’s more commonly known) was his crowning glory, in which he states and proves his Laws of Motion and his theory of Universal Gravitation. … Continue reading →

What causes a halo around the Moon or Sun?

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A few days ago, a newspaper received a photograph of a Lunar Halo from one of their readers and asked me to explain what was going on.  You can click on the above link to read my answer, but it was by necessity rather short, and incomplete.  So what’s the full story? What we see in the image to the right is a full moon, surrounded by a colourful halo, with the constellation Scorpius faintly visible along the top border. … Continue reading →

Huge Slow Fireball over Tel Aviv

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A few nights ago, on 7 December 2011, a camera mounted on the roof of the Kaplun building in Tel Aviv University captured this incredible meteor entering the Earth’s atmosphere.  It is surprising for both its brightness and how slowly it crossed the sky.  Watch the attached recording on the left. The camera belongs to ILAN, and is actually intended to record lightning and related phenomena – a browse through their archives will reveal a number of videos of TLE’s … Continue reading →

Voyager 1 poised at edge of Solar System

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The human race’s first ever interstellar space craft is about to leave the Solar System.  With over 34 years and almost 18 million kilometres on the clock, Voyager 1 is busy passing through a stagnation layer marking the very edge of the Sun’s influence, which is turning out to be a rather strange place.  The Sun has a powerful magnetic field, and pumps out a stream of energetic charged particles called the Solar Wind.  But interstellar space has its own … Continue reading →