Elliptical galaxies are round collections of old stars. They contain very little gas and dust and have no features within them. They come in a range of different sizes and shapes. They can look circular, oval or even rugby-ball shaped.
Ellipticals are classified by how squashed they look. Circular balls are called E0. The more squashed one looks, the higher the number it is given. The most flattened ellipticals are classed as E7.
The smallest ellipticals are called dwarf ellipticals. They contain tens of millions of stars. The largest ones can contain over a trillion (1,000,000,000,000)! Some ellipticals can be very dim and some very bright. This is mainly down to how many stars they contain.
Elliptical galaxies are very old. They formed their stars a long time ago. With the gas and dust long since gone, there is no material left to make new stars. Without any young, blue stars, ellipticals look yellow-red in colour. They are the most common type of galaxy found in clusters.