Here's why:
* High temperature: White dwarfs are incredibly hot, with surface temperatures reaching tens of thousands of degrees Celsius. This is because they are the dense remnants of stars that have exhausted their nuclear fuel.
* Low luminosity: Despite their high temperature, white dwarfs are very small and have a low surface area. This means they emit relatively little light, making them appear faint.
Key takeaway: The HR diagram plots stars based on their temperature and luminosity. White dwarfs occupy a unique position on the diagram because they are hot but faint due to their small size.
