millions. Like the Sun and the Moon, the atara appear to more
slowly aocroaa the aky but in fact it is we who are moving as
the Barth rotates.
COHSTELLATIOH3. In ancient tiaea, people were reminded ot
the outlines of aniaala and gods in the sky and gave their names
to the groups of stars that they saw. These groups are called
constellations.
These are not in fact actual groups of stars that are near
each other in space - some may be near us while others are far
away. But dividing the sky into these recognizable patterns helps
ua to nap the sky.
GALAXIES. Through a powerful telescope, vast groups of stars
called galaxies can be seen. Our Sun in fact belongs to a galaxy containing about 100,000 million other stars; when we look at the Milky Way ( UaeiHldl Dyri. ), we are looking at our own Galaxy. Millions of other galaxies are scattered throughout space.
Many are shaped ( BWtt $oi>*y ) in a flat dl"c like our Galaxy, and made up of spiral arms of stars reaching out from a central hub ( EiBHTp ) of stare. Our Galaxy is retailing slowly and the Solar System, situated along one of the spiral arms near the edge of the Galaxy, makes one circuit every 225 million years.
MEASURING DISTANCES. Distances are ao vastin astronomy that they are measured in light year - the distance light travels in a year. One light year is nearly 9vf million        kilometres and our Galaxy is 100,000 light years across;
THE LIFE OP A STAR. Stara tona as hydrogen comes together in clouds that contact with gravity and eventually begin to burn. Many stars burn for millions of years and then expand into a red giant star before contracting ( czBUaTbCJI ) to a cold dwarf ( KapJittK ) star, their fuel used up. But some stare end their lives in a gigantic explosion. An exploding star is called a gu-pernova and is very bright indeed.

The nine planets of the Solar Systea are very different