The color of the stars - CESAR
THE COLOR OF THE STARS 
The general instructions and the material for the are provided on the Space Science Experience Home. In this experience, we explore the Color of the Stars.
The Universe has about 200 billion galaxies. Our Galaxy, the Milky Way is a very normal spiral galaxy.
The Hubble Ultra Deep Field is seen in ultraviolet, visible, and infrared light. Image Credit: NASA, ESA,H.Teplitz and M. Rafelski (IPAC/Caltech), A.Koekemoer (STScI), R.Windhorst (Arizona State University), and Z. Levay (STScI).
The stars are hosted mainly in the spiral arms of the galaxies. We are located quite far out of the Galaxy spiral arms. If this would be our galaxy we would be located here:
The Sun, so important for us as the source of our life, is a very standard star compared to others in the Galaxy (the Milky Way) and other galaxies.
Depending on the place and conditions where the stars form they will begin with a more or less sophisticated chemical components, be more or less massive, be isolated or accompanied (see The Herztsprung-Russell diagram).
From a visual point of view, we can know some of the properties of a star by their colors (spectra).
Eta Carina Nebulae, collected by a Cassegrain Telescope 16" f/3 (1200mm). Credits:Johannes Schneider
For example, cold stars are redder. This will be because they are old or because they do not have much mass. Massive and younger stars are bluer.
When we look at the stars from the Earth, we see them moving along the night. If we took a picture of the sky at night, exposing for the whole night, we would be able to see a picture such as the one below. As you can see all the stars are move around a fixed position (the center of the circle). In the Earth north hemisphere, this reference point is the polar star.
Teide Sky Trails. Credits: Daniel Lopez