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!

What is an asteroid?

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The official definition of an asteroid is ambiguous, and boilds down to asteroids being rocky, dusty objects orbiting the Sun that aren’t planets.  They come in all sizes with the largest (named Ceres) being over 900 kilometers across and the smallest being mere specks of dust.  Some have been found to have small amounts of ice on them, so that nobody’s quite sure whether to call them asteroids or comets, and others cross over into the definition of Minor Planet. … Continue reading →

Herschel finds more Water

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A week ago, we reported that the European space agency’s Herschel Space Telescope had studied the water signature of a nearby comet and found it to be the same as the water in Earth’s oceans.  Then, a few days later, we learned of a discovery by the Spitzer telescope that comets had been found swarming through a distant solar system.  And shortly after that, Herschel was back in the news for its discovery of vast reservoirs of water around a young … Continue reading →

Distant solar system pelted by comets

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Data returned to Earth by the Spitzer space telescope suggests that the solar system around northern star Eta Corvi not only has comets, but that they are currently swarming in huge numbers and possibly raining down violently on whatever planets may be orbiting close to the star. Eta Corvi is a bright star in the constellation Corvus (The Crow), and Spitzer recently observed that it had a bright ring of dust, at about the same distance as Earth is from the … Continue reading →

Earth’s water comes from comets

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One of the mysteries of the formation of the Earth is where it got its oceans from.  One popular theory is that, in the early years after the Solar System‘s formation when the inner planets were heavily bombarded with leftover material (we can still see the results in the scarred, cratered face of the Moon), Earth would have been pelted with comets.  According to the theory, water ice from these comets would have vapourised and condensed into the water we … Continue reading →

French meteorite impact

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The Comettes are a normal French family, with a home in Paris’ southern suburbs.  While they were on their summer holidays, a chondritic meteorite fell from the sky onto their roof, smashing through a tile and embedding itself into the insulation.  Some time later, when the family noticed that the roof had started leaking during the rain, they called in a contractor who was astonished by what he’d found.  He said “You’d have to be superman to break a roof … Continue reading →