Most of the time the Sun is quiet, shining in space beaming out light and heat. But every eleven years it gets cranky – covered in dark spots and fiery eruptions. This is a time called solar maximum, or solar max for short.
The Sun, like all stars, is a big ball of plasma – mostly hydrogen and helium. Because the Sun is so big – 100 million times bigger than Earth – it has a lot of gravity. The gravity squeezes the plasma so hard that it gives off heat and light. Scientists call this nuclear fusion.
Twenty years ago, the answer this question was ‘only one that we know’. Most astronomers believed that the Sun was no different to most stars in the universe. So if we had a star with planets and moons – a solar system – than why don’t others.
In 1992, the first planet orbiting another star – sometimes called an exoplanet – was detected. Since then, astronomers have used larger telescopes and faster computers to find more than 450 exoplanets orbiting more than 300 stars.
A sail is something you’d expect to see on a boat in ocean, not in space. But that’s just what a Japanese spacecraft called Ikaros is using to fly through the solar system.
Astronomers measure the distance to other galaxies by looking at their colour. The more red a galaxy is, the faster it is moving from us and the further it is away.
Another way to measure distance is to look at the brightness of exploding stars – called supernova. These explosions are brighter the closer they are to us. By measuring the brightness it is possible to know how far away they, and the galaxy they live in, are from us.
Using these techniques astronomers have seen galaxies more than 13 billion light years away.
Space telescopes that measure cosmic background radiation, which are the remains of the Big Bang explosion. It is thought to be the outer edge of our Universe and is 13.7 billion light years away.
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.
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.
If you had to decide which moon in the solar system to explore, where would you go? With so many to choose from, it’s not an easy decision.
After many meetings, scientists from the European Space Agency and NASA recently agreed to send robotic spacecraft to two of Jupiter’s moons – Europa and Ganymede.
NASA will build the spacecraft that will travel to Europa, which scientists believe has an ocean of liquid water beneath its icy surface.
If water does exist there, along with heat and nutrients (new-TRI-ants), then it may be home to alien life.
“Europa is just a tremendously exciting water world. It has an underground ocean with probably more water in it than the Earth does,” said NASA scientist Jim Green.
The second spacecraft, being built by the Europeans, will orbit the largest moon in the solar system – Ganymede.
Called Laplace, the spacecraft will use special cameras to look below the moon’s icy surface and study its magnetic field. It will also study the planet Jupiter and its other moons, including Io and Callisto.
Both spacecraft are expected to launch in 2020 and arrive at Jupiter five years later. After spending 2026 orbiting the moons, the spacecraft will then crash into the surface.
The two moons were chosen ahead of Saturn’s moon Titon. Titon has a thick atmosphere (at-MOSS-fear) of nitrogen and methane, similar to what the Earth was like billions of years ago. This mission may still go ahead sometime after 2030.
Imagine what it would be like to be the first astronaut to travel to Mars.
You can pretend what it would be like with the latest version of Google Earth (version 5.0).
It includes new NASA photos of the red planet, including surface pictures from the Mars rovers and landers.
Use Google Earth to look at the red planet from above and explore volcanoes, canyons and sand dunes in 3D. It is even possible to see the Phoenix lander and its parachute.
Click on the Opportunity and Spirit rover buttons to see where they have travelled. Zoom in and you can see the surface of Mars from the ground.
To access the Mars mode, download Google Earth at http://earth.google.com and click on the small Saturn icon in the top toolbar.