Topic of the month: Distance

OUR Milky Way galaxy is like a vast pancake-shaped object 100,000 light years across and containing around 200 billion stars.

It’s really difficult to visualise the size of our galaxy because it’s so huge.

To put it into context, start by thinking about our solar system (our Sun and all the planets right out to Neptune, orbiting our Sun at nearly three billion miles away). Imagine our solar system reduced to the size of a 10p piece, with the Sun in the centre and Neptune orbiting round the furthest edge. On this scale how big would you guess our Milky Way galaxy would be?

A few hundred metres? A few kilometres?

The answer in fact is approximately the size of Europe!

And there are objects way further away than our galaxy.

Andromeda galaxy is the furthest thing people can see with their naked eyes.

It’s a faint blur of light in the night sky which is 2.5 million light years away, 25 times the distance across our galaxy. Although most other galaxies are moving away from the Milky Way galaxy because of the expansion of the universe, Andromeda is actually racing towards our galaxy at a speed of over 200,000 miles per hour.

However Andromeda is so far away that it won’t crash into our galaxy until it reaches us in another three to four billion years.

But this crash will be different to typical crashes.

Because suns are such vast distances away from each other, both galaxies will pass right through each other and there will be very few suns actually hitting each other. But the effect of gravity will pull the two galaxies together, creating a new super galaxy formed from the merger of both original galaxies.

The merger will also bring vast clouds of gas and dust together creating the right conditions to create a huge number of new stars, so the new merged super galaxy will look completely different from the two original galaxies. Objects in the universe are constantly evolving and changing and enormous changes will continue to happen for billions of years.