Which stars have the highest absolute brightness? The HR diagram is shown with Absolute Brightness on the y axis from negative four to six and Surface Temperature on the x axis from 40,000 to 2,500 degrees Celsius. There are several dots plotted between four and six absolute brightness and 10,000 to 2,500 degrees Celsius labeled Supergiants. There are several dots plotted between 1. 5 and three absolute brightness and 7,500 to 2,500 degrees Celsius labeled Giants. There are several dots plotted between negative four and negative two absolute brightness and 30,000 to 7,500 degrees Celsius labeled Dwarfs. Down the middle, there are several dots plotted diagonally from ordered pair 40,000 and five down to 2,500 and negative three labeled Main Sequence. Supergiants Giants Yellow stars Dwarfs.