Audio Guide：

Astronomer Edwin Hubble categorized star systems into three groups based on their shapes: ellipticals, spirals, and lenticulars. Ellipticals are mainly composed of old stars with very little dust and interstellar matter, whereas spirals and lenticulars have many young stars and a large amount of dust. This system of classification is known as the Hubble sequence or Hubble’s classification scheme. Because the shape of the diagram resembles a tuning fork, the sequence is also often referred to as the Hubble tuning fork diagram. It is worth noting that the Hubble sequence only classifies star systems based on their shape and is not related to their evolution.

You can rotate the images of the star system with your hand motion to learn more about star systems.