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

great picture

Another great picture from NASA

The Milky Way

On a clear, moonless night away from the city lights, you can see a pale white band stretching across the sky. This hazy band of light is our own inside view of the city of stars that form the galaxy we are part of, the Milky Way Galaxy.

There are many myths involving the formation of the Milky Way, but the best known is probably the Greek myth of Hercules. In Greek mythology, Hercules was the son of Zeus and a mortal woman. It was said that when Zeus’ wife, while suckling Hercules, found out that his mother was a mortal woman, she pulled her breast away and her milk flowed among the stars.

But what is the Milky Way really?It is a spiral shaped galaxy, a vast collection of stars, gas and dust of which the solar system with our Sun and its system of planets, is a part. We are located about halfway

Scorpius

Scorpius is one of the easier recognisable constellations, not to confuse with Scorpio, the name for the astrological sign of the Zodiac. At the moment Scorpius is right above us here in the southern hemisphere.

In the Greek mythology the scorpion was send by the gods to kill Orion, the great hunter, after he had boasted to kill all animals on Earth. They fought for a whole day and finally were exhausted. When Orion fell asleep the scorpion stung him, Orion woke up and killed the scorpion but then died from the poison. The gods placed them amongst the stars in the sky but far apart so they could not fight anymore.

The tail of Scorpius lies in the Milky Way, the city of stars in which we live. When we look at the tail of Scorpius

Distant galaxy

NASA regularly posts great pictures of the universe, with a short explanation. Like this picture of a distant galaxy called NGC 2403.

Regards from the bush
Miriam

Rings around the planets

Saturn is well known for its rings, but fewer people know that the other gas giants have rings as well. They are less spectacular and not visible with amateur telescopes. They were only discovered in the last decades of the twentieth century. Many of the mechanisms behind some of the ring’s properties still remain under debate. Planetary rings have always been incidental discoveries. They have fascinated and mystified for as long as we have known about them.

Jupiter
In 1979 the space probe Voyager 1 discovered the rings around Jupiter. Technically they are visible from Earth with the strongest telescopes, but they are faint and were therefore overlooked so far. The main ring is flat and about 7.000 kilometres (4.350 miles) wide and less then 30 kilometres (18 miles) thick. It is the brightest component of the ring system. Outside it lay

Our closest star, the Sun

The Sun is our very own star. It gives us light, energy and warmth and without it, life could not exist on Earth. But what is a star and what kind of star is our Sun?

A star is a huge sphere of very hot, ionised gas. Because of the pressure and temperature in the core of a star, a nuclear reaction takes place that forms helium from hydrogen. This generates enormous amounts of energy, which is slowly carried outward until it finally reaches the surface and radiates out into space in the form of heat, light and other forms of radiation. This journey of energy to the surface can take up to a million years. Our Sun is a quite small and average star in the main sequence. Its surface has temperatures of about 5.500 degrees Celsius, which results in a yellowish light. Hotter stars will appear

A Moon Corona

Yesterday evening, we sat a round the campfire with our guests. It was almost full Moon but it was quite clouded. A little later in the evening the sky became clearer, except for some fast moving, high clouds. Then we saw something beautiful; as the thin clouds passed the Moon, a darker ring formed around it at a little distance. At some point the ring had even some colours in it and almost looked like a pale, circular rainbow. When the clouds moved on, the corona disappeared again.
Corona’s are produced by refraction of the moonlight (which is of course reflected sunlight) from ice crystals in the upper atmosphere. The hexagonal (6 sided) shape of the ice crystals focuses the light into a ring. If there are few ice crystals, you will see no clouds but a thin ring

The edge of the universe

Distance does strange things to our perspective. Astronomers have found a galaxy at the astonishing distance of 13 billion light years. It was born soon after the Big Bang and since its light has travelled so long to reach us, we see it as it was just after it was born. So the image we see is of a very young galaxy, at the same time it is very old, 13 billion years to be precise. Viewing galaxies so far away in our ever-expanding universe, introduces several bizarre twists in understanding. The very old, yet young galaxy is one of the least bizarre. Another thing that happens when you look at something that far away is that it looks bigger than it should at that distance. At the same time it looks dimmer than one would expect. The reason for this is

Our closest neighbour, the Moon

The Moon is our only natural satellite. Despite its proximity to Earth and the fact that man has visited the Moon, there are still many questions about the Moon. Scientists still struggle to answer some fundamental questions like: What is the nature of the Moon’s core? What is the structure of the mantle? And, despite recent evidence of substantial water on the Moon, why is there so much less than on Earth? According to the most accepted theory, the Moon formed roughly 4.5 billion years ago, when a large body the size of Mars hit the young Earth. The debris of both the impacting body and the Earth’s outer layers formed our Moon. Almost immediately, gravitational forces

Breathtaking stars

As a child I already had a fascination for stars. I think I was about nine years old when my brother in law pointed out the Big Dipper to me for the first time, and from that moment I was hooked. Although I already owned a book about astronomy when I still lived in the Netherlands and had looked up to the breathtaking sky of the southern hemisphere during our travels, the real fascination came when I came to live here in South Africa. Especially in winter the sky here is so clear that you can see the Milky Way beautifully.

Corné also got interested and

Saturn, Lord of the rings

The planet Saturn can be seen beautifully now in the night sky. Saturn is one of the most fascinating planets because of its rings. Through our 10 inch telescope you can clearly see the rings sticking out on both sides of the planet. Some of the larger moons can be seen as well. Saturn is one of the gas planets and the second largest planet in our solar system, after Jupiter. The planet is about Milky Way. You can see Scorpio beautifully and Sagittarius is rising. The Southern Cross is getting lower now and Arcturus in the constellation Bootes is one of the brightest stars in the sky. It is a great time of year if you love astronomy like us.

introducing myself

Hi,

I'm Miriam and since 2004 I live with my husband Corné in South Africa, in the Balule Private Nature Reserve to be precise. We have build our own lodge here in the bush where we receive guests. Our two sons, Niels of four and Dennis of two are born here and grow up in this beautifull environment.


The reserve where we live is close to the famous Kruger Park and all animals that live there, including the Big Five, occur in our park as well.
Life here in the bush