If you look up on a clear night far from city lights you will see a faint, fuzzy band of light crossing the night sky from near the constellation of Scorpio, through Cygnus, Cassiopeia, Perseus and towards Canis Major. This is what we call the Milky Way.
The true nature of the Milky Way puzzled observers of the Night
Sky for centuries until in the sixteenth century astronomers looked at it through a telescope.
They saw that it was not just a fuzzy band but was made up of thousand upon thousands of
stars. Photographs taken with one of today's large telescopes show it containing many
millions of stars. Even quite a small telescope will show many stars - the photograph shows
part of the Milky Way in Perseus taken with a 200 mm reflector.
However it was
not until the twentieth century that astronomers realised what the Milky Way really was.
When we look at the Milky Way we are actually looking through our galaxy.
If you
read the file called Galaxies in the 11-14/ Astronomy/Text section you will understand that
our galaxy is a huge spiral structure of some 100 000 million stars, 100 000 light years
across and with the Sun about two thirds of the way from the centre in one of the arms of the
galaxy. When we look at the Milky Way we are looking across the galaxy and that is why we
see so many stars. Turn at right angles to this direction and we would be looking out from the
galaxy into deep space.
The red arrow shows the direction
towards the centre of the galaxy. If you looked in this direction you would see very many
stars – this is the Milky Way. Looking at right angles to this, the blue arrow, you would see far
fewer stars as you would be looking out of the galaxy into deep space.
The two
photographs are galaxies similar to our own galaxy but again one is taken showing the face
of the galaxy and the second edge on.
