Our Universe is full of many wonders and mysteries - here are a few of these questions answered that you may have had...

1. How big is our galaxy?

Surprisingly the galaxy has been measured for size and it is considered to be 1,500 million billion kilometres across !!

2. What are stars made of?

Stars are mainly made of superheated gas, mainly hydrogen and helium. This gets denser and hotter toward the centre resulting in nuclear reactions that cause the light and heat we see. Stars also contain the other base elements we are aware of on Earth.

3. Would it be possible to escape a black hole?

It all depends on how close you to get to one and how big it is. If you come close to what is called the 'event horizon' you would not be able to escape. But the point of this horizon depends on the mass of the black hole. One that has the same mass as the Earth would be the squashed into the palm of your hand - you therefore would not notice it until you were very close to it.

4. What is a red dwarf?

A red dwarf is small start that has cooled over time. At one point it would have been bright white, but as its hydrogen fuel has been used up it becomes a red giant, a swollen expanse of gas at low temperature. A small, low mass star will lose this outer gas and a small white core will remain - a white dwarf. This further cools, and goes yellow, red, brown and then black. This could take trillions of years to happen.. What would be left is a ball, maybe the size of our planet, but extremely dense and maybe covered in thin ice and with an atmosphere.

5. What shape is the Universe?

It is considered to be a hypersphere, which is quite difficult to visualise as it is a four dimensional sphere, altering with time. An analogy with an onion may help explain. If the Universe is like an outside layer of an onion today then looking out into the universe as it is now, you would be looking around this shell. If you could look far enough you would look right round it and see the back of your head. But we cannot do this because as we look out we are looking back in time. The further away you look, the closer you are looking to the centre if the onion. But these layers do not exist anymore as they have moved with the expansion of the Universe. It is hard to visualise !!

6. How many stars are there in a constellation?

The number varies and they are counted by measuring the number within an area of sky. The Southern Cross has lots of stars - 19.6 per 100 square degree of sky, whilst most others only have 5-6 per 100 degrees.

7. Why does the atmosphere on any planet not leak into space?

This is due to gravity and molecular energy. Some molecules do leak into space, but many do not have enough energy as they are too heavy.. Atmospheres are replenished by biological or planetary activity (such as volcanic eruptions).