ocr: MAIN SEQUENCE After being born, stars appear as a narrow band in the H-R diagram, , in- cluding most of the stars in the universe. This long and stable phase, after a star is born and when its fusion reactions have started, is known as the main sequence. After the main sequence most stars become giants. The stars in the main sequence are in the luminosity class V (see dwart). Our Sun will be in its stable main sequence for approximately another five billion years, or as long as it has already existed. After that if will be- come a red giant, swallowing up the Earth. The giant phase will last f ...
