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!

MOND theory gets a boost

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One of the stranger concepts in modern astronomy is Dark Matter.  Developed to explain certain discrepancies in the motions of stars within galaxies, it says that there must be a significant mass of material distributed widely through and around galaxies which we cannot detect from here on Earth – it’s “dark”.  There is another theory, though, called Modified Newtonian Dynamics (MOND).  The idea is that Newton’s laws of gravity, accurate and reliable as they are, are only useable within a … Continue reading →

Arietids

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The Arietids meteor shower, as it’s name suggests, has its radiant in the constellation Aries.  It lasts from late May till early July and peaks between the 7th and 8th of June.  The meteoroids of this shower enter the atmosphere at speeds of about 38 kilometers per second, and are usually “earthgrazers”, meaning we see them hitting the atmosphere at a shallow angle, ploughing slowly right across the sky.  But most interestingly of all, the Arietids are a daylight shower. … Continue reading →

Beer, Telescopes and Bonfires

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A few weeks back, an old friend of mine invited me to her birthday party.  She lives out of town, on a farm owned by a builder who specialises in  thatched roofs, and has built a large entertainment complex of thatch-roof restaurants, gazebos, sleeping shelters and a boma.  The entire thing sits empty all year around, so she colonised the facility last weekend for her celebration.  But there was one extra attraction: A man with a telescope who was going … Continue reading →

What is a neutron star?

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  When a star runs out of fuel to burn, it’s outer layers get ejected into space and it’s core collapses under gravity into a white dwarf.  If the star was really big, more than about 8 times the mass of our Sun, then it continues to collapse, becoming denser and denser until the very atoms themselves are crushed.  The enormous gravitational pressure overcomes the Weak Nuclear Force, so that electrons fall out of their orbit and touch the protons … Continue reading →

What is a white dwarf?

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  Stars go through a number of changes as they pass through different life stages.  If a star doesn’t have more mass than about eight times that of our own Sun, then it will end its life as a White Dwarf.  White dwarfs are extremely small, hot and compact objects, composed of degenerate matter, and are all that remains after the original star runs out of fissionable fuel and ejects its outer layers into space.  What remains is usually around … Continue reading →