what are the largest stars in the HR diagram called?

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The largest stars in the HR (Hertzsprung-Russell) diagram are called "supergiants." These are extremely massive stars that have reached the later stages of their evolution. They are located in the upper-right portion of the HR diagram, representing stars with high luminosities (brightness) and low temperatures.

To understand this concept and find the answer, you can follow these steps:

1. Familiarize yourself with the HR diagram: The HR diagram is a graph that plots the luminosity (vertical axis) against the temperature or spectral class (horizontal axis) of stars. It helps classify and understand different types of stars based on their properties.

2. Identify the location of the largest stars: In the HR diagram, the upper-right region typically represents the largest and most luminous stars, including supergiants. These stars have high luminosities due to their big size, but their temperatures are relatively low because they are in advanced stages of their life cycle.

3. Define supergiants: Supergiants are massive stars that have evolved beyond the main sequence stage and have increased in size and brightness. They are often identified by their location in the upper-right corner of the HR diagram.

Based on these steps, you can conclude that the largest stars in the HR diagram are called supergiants.