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 →
Dear Urban Astronomer Talking about the thunder storm in Pretoria last night, a co-worker of mine mentioned that she covered all the mirrors in her house because they can “catch and reflect” lightning… She said that lightning can behave like light and be reflected. I argued that lightning is not light, but a raw, electrical charge… I have never heard of this practice, and although it sounds like superstition to me, I was wondering if there is any truth in … Continue reading →
“Nebula” is the Latin word for cloud. It was originally used to describe anything in the night sky that had a cloudy or diffuse appearance, and that wasn’t a comet. Early in the 20th Century, however, it was discovered that some of these nebulae were actually “island universes” (galaxies or globular clusters). Since then, the word refers to specific types of objects: Planetary nebulae are usually spherical and are the expanding shells of material ejected from dying stars. They get … Continue reading →
Meteor showers have their origins in comets, and the eta Aquarids come from the most famous of all: Halley’s Comet. Every time it swings past the Sun, the comet heats up and sprays particles of dust out along its orbit and twice a year the Earth blunders straight into the debris streem. When these bits of grit hit the atmosphere, they flare briefly before burning up and we see a meteor. The first time we pass through the stream each … Continue reading →
In an earlier article, I dealt with one of the most annoying questions that astronomers seem to get asked routinely: “What’s your sign?” But even more frequent and way more annoying, is being described as an astrologer by people who don’t seem to know the difference between astronomy and astrology! To help those people, I’m going to answer the question that they never seem to ask, and really should: What is Astronomy? Well, astronomy is a science. It deals with the … Continue reading →
