You're describing the Hertzsprung-Russell (H-R) Diagram . This is a fundamental tool in astronomy that plots the luminosity (brightness) of stars against their surface temperature.

Here's a breakdown of the H-R Diagram:

* X-axis: Temperature (usually in Kelvin, with higher temperatures on the left side)
* Y-axis: Luminosity (usually in solar luminosities, meaning how many times brighter the star is compared to our Sun).

Recursos -chave:

* Main Sequence: A diagonal band running from the top left (hot and bright) to the bottom right (cool and faint). Most stars in the universe spend the majority of their lives on the main sequence, fusing hydrogen into helium in their cores.
* Giant and Supergiant Stars: Found above the main sequence, these stars are much larger and cooler than main sequence stars of similar luminosity.
* White Dwarfs: Found in the bottom left of the diagram, these are very hot but faint stars, remnants of the cores of dead stars.
* Red Giants: Cooler and brighter than main sequence stars, red giants are stars in the later stages of their lives.
* Red Supergiants: The largest and most luminous stars, found in the upper right corner of the diagram.

Uses of the H-R Diagram:

* Classifying Stars: It helps astronomers categorize stars based on their properties.
* Understanding Stellar Evolution: The H-R Diagram shows how stars change over their lifetimes.
* Determining Stellar Properties: Scientists can estimate a star's mass, age, and radius based on its position on the diagram.

Visual Representation:

You can find numerous visual representations of the H-R Diagram online. Aqui estão alguns exemplos:

* Wikipedia: [https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram](https://en.wikipedia.org/wiki/Hertzsprung%E2%80%99Russell_diagram)
* Space.com: [https://www.space.com/23099-hertzsprung-russell-diagram.html](https://www.space.com/23099-hertzsprung-russell-diagram.html)

Let me know if you'd like to know more about any specific aspect of the H-R Diagram!