Milky Way is our galaxy. You can see part
of it on really dark nights, as shown on your Star
think the Universe started with a big explosion called
the "Big Bang." Sometime after that
stars, then globular clusters, then galaxies formed.
picture shows M31, our nearest large galaxy.
The Milky Way has a similar shape.
the galaxy are two companion galaxies in orbit. The
Milky Way has similar companions; the Large and
Small Magellanic Clouds, which can only be seen from
the southern hemisphere.
galaxies like M31 and the Milky Way are mostly flat,
but there is a bulge near the centre. This bulge consists
mostly of old yellow stars.
the very centre of many galaxies is a massive black hole.
Our galaxy's black hole has the mass of 4 million suns
packed into a sphere smaller than the orbit of Mercury. The
mass is found from the orbits of stars around it, shown
on this video. Just as with planets in our Solar System,
stars closer to the centre orbit faster.
the bulge, the galaxy is mostly flat. The disc
is made of younger stars, the brightest of which are blue.
They form into spiral arms. Our Solar System is about halfway
from the centre of the Milky Way to the outer edge.
we look along the flat disc of the Milky Way, we can
see many stars. When we look perpendicular to the disc,
we see fewer stars. The
star Fomalhaut can be seen to the South on October evenings. It's
below the Milky Way. Ancient astronomers, who had no idea
of our galaxy’s shape, called it the "Lonely
Star of Autumn."
This image by Robert Gendler, shows NGC 4565, a similar
galaxy to ours but viewed from the edge.