The hottest stars featured right here on J4P

Do you ever find yourself wondering how hot our sun is compared to the rest of the stars in the sky? No, I didn't think you did. However, is the kind of thing that appears to exercise my mind, when I wake up at 4 am for a wee wee. Because it was bugging me virtually all day at work, I couldn't wait to get home and find out. Thankfully, I located this nice illustration pretty quickly. This shows the relationship between the brightness of the star and its surface temperature. I'm now wondering why the white dwarfs and the supergiants don't lie on the same axis as the rest. Presumably this is something to do with a distortion caused by strange gravitational effects associated with these objects. But how does gravity affect surface temperature and the luminosity of the star? All ideas and explanations are welcome as I don't have time to look it up. The sizes shown are not to scale. To get a better idea of the difference in sizes of some stars compared to our sun look here.