This is a difficult question to answer, because the number keep growing.
Almost every year astronomers find new moons, using better telescopes on Earth and spacecraft flying through the solar systen. Some moons are so small that that their width is smaller than most cities on Earth.
In 1888 German scientist Friedrich Reinitzer extract a compound known as cholesterol from carrots. He found that when he heated the liquid it changed from an orange colour to clear due to the crystal structure within the liquid.
In 1962 electronics engineer Richard Williams found that he could make the crystals move when he applied an electric current to them. A few years later the first liquid crystals displays (LCD) were built. These simple back and white (silvery-grey) displays first appeared in watches and calculators. Today LCD are also found in televisions, mobile phones and laptop computers.
Want to travel to Mars in in the next year or two? Well maybe you can’t go, but NASA is happy to take your name there instead.
The Mars Science Laboratory rover will leave Earth in 2011 and landing on Mars, driving and looking for signs of life and water.
On board will be a microchip full of names of people from planet Earth. To add your name to the microchip, visit the ‘Send Your Name to Mars’ web page (http://bit.ly/martianname) and enter your name, country and postcode.
You can print a certificate of participation to put on your wall and look at a map showing where other names are from.
Volcanoes on Earth have rivers of red hot lava pouring down the sides or massive explosions of gas, rock and dust rising into the sky. But in space volcanoes are quite different.
Mars has four large volcanoes – the biggest is Olympus Mons. It is 27 kilometres high (three times the height of Mount Everest) and 500 kilometres wide (bigger than Tasmania). The volcanoes on Mars haven’t erupted for more than two million years.
The planet Venus always has ancient volcanoes on its surface. The biggest is Maat Mons – eight kilometres high. From above, some of the volcanoes look like pancakes and others have strange patterns that make them look like ticks. Continue reading
Stars come in different many different sizes and the bigger the star is, the faster it will burn its fuel.
Our sun is an average star and will take about 10 billion years to burn its fuel. The brightest star in our night sky, Sirius, is 21 times the size of our sun and may only last a billion years. Some stars will burn so brightly, they last less than 10 million years.
We can tell how old a star is by looking at its colour – what scientists call its spectra. A spectra is like a chemical fingerprint, showing what is inside the star. Young stars have simple chemical elements, such as hydrogen and helium. As the star gets older, heavier elements like carbon and oxygen appear.
The spectra of our sun tells astronomers that it is 5 billion years old, or about half way through its life.
