A short history of astronomy

Astronomy is the oldest science by far. As long as mankind exists we have looked up to the skies and wondered what was out there. Almost every culture throughout history has studied the Sun, Moon and stars, and watched how celestial bodies move across the sky. For early civilisations, like the ancient Egyptians, astronomy was a way to keep track of the changing seasons. They used it to know when it was time to plant and harvest crops and it was used to make calendars and sundials to keep track of time. In 1000 BC, Indian and Babylonian astronomers had already calculated length of a year as 360 days (which resulted in a 360 degree circle, with each degree representing a solar day). Later the ancient Egyptians refined this calculation to 365.25 days. The most important discoveries

What are constellations?

The first constellations were patterns of stars that ancient peoples used for navigation, timekeeping and storytelling. Most constellations used now, stem from patterns recognised by ancient Greeks and Romans, and they carry myths and legends from that time. However the ancient Greeks were not the first to recognise patterns. The 47 constellations they used were introduced by a Greek astronomer called Euxodus, who had learned them from priests in Egypt. They in turn had adopted them from Babylonian culture and they were originally created by the Sumerians around 2,000 BC. The oldest surviving star catalogue dates from

Brightness and magnitude of stars

If you look up to the sky you see stars with different brightness. Some stars are very bright, while others are just faint. This is partially because some stars are more luminous than others, but also because some stars are much further away than others. For an example have a look at the two pointers of the Southern Cross for instance. Alpha Centauri (the one the furthest from the Cross) seems brighter than Beta Centauri, also called Hadar (the one closest to the Cross). The reason for this is its proximity; it is in fact our closest stellar neighbour. The double stars in Beta Centauri are much more luminous than the triple stars in Alpha Centauri, but they are about 120 times further away. This causes the star to look less bright because the light is spread out over a much larger area as it travels away from the star.

Absolute Magnitude
To compare how stars would look if they were all at the same

Three galaxies

A beautyfull picture of three galaxies close toghether in Leo. http://apod.nasa.gov/apod/ap110803.html

Astronomy for everyone

You don’t need an expensive telescope to enjoy astronomy. There is a lot to see and view with the naked aye or with a good pair of binoculars. This is how Corné and I also started, just looking up at the sky and curious to learn more about it.

Before you go out to look at the stars, take a little time to prepare. You will need to find a dark place, as far away from artificial lights as possible or at least shielded from direct light. Before you set out, have a good look at the star chart or planisphere so you have an idea of what you can see. For special phenomena, like eclipses and meteor showers etc. there are sky guides available or you can look at the internet. Your eyes will need about 20 minutes to fully adapt to the darkness and, as the pupil opens, more detail and fainter objects will become

Meteor showers

This time of year there are several meteor showers that we can see.  From half July till half or the end of August we can see the Pisces Australids (between 21:30 and 5:00 hour), the S. Delta Aquarids (between 22:00 and 5:00 hour) and the Alpha Capricornids (between 20:00 and 4:00 hour). But what are meteor showers?

A meteor, or “shooting star”, is a particle of rock or dust that enters the Earth’s atmosphere and causes a streak of light when it burns up. In general meteors appear in the upper atmosphere, at an altitude of between 80 to 120 kilometres and disappear between 60 and 80 kilometres high. If the object is big enough, some of it will reach the surface and is then called a meteorite. Most meteors entering the atmosphere are sporadic, particles travelling through space in isolation. But several times a year, the Earth passes through streams of particles left behind by comets