An HR (Hertzsprung-Russell) diagram is a scatter plot that illustrates the relationship between the luminosity (or absolute magnitude) and the surface temperature (or spectral type) of stars. It is a fundamental tool in stellar astrophysics and provides valuable insights into the properties and evolution of stars. HR diagrams are essential for understanding the life cycle of stars, from their formation to their eventual death. They are a powerful visual tool for comparing the properties of different stars, studying star clusters, and investigating the overall structure and evolution of the universe.
 

How to Use the Interactive HR Diagram Below:

1. Axes:

   • The x-axis represents the surface temperature of stars, with hotter stars on the left and cooler stars on the right.

   • The y-axis represents the luminosity (or absolute magnitude) of stars, with more luminous stars higher up and less luminous stars lower down.

   • You can click on a certain location on the diagram, and/or drag your cursor around to see how stars change during their lifetime

2. Show Regions

   • Main Sequence

     • The main feature of an HR diagram is the main sequence, which is a diagonal band where the majority of stars are located.

     • Stars on the main sequence are fusing hydrogen into helium in their cores, which is the longest and most stable phase of a star's life.

   • Supergiants​

     • Supergiants are among the most massive and luminous stars.

     • These stars are much larger than giants and are typically at a later stage in stellar evolution, undergoing fusion of heavier elements.

     • Supergiants are often precursors to supernovae, especially in the case of more massive stars.

   • Giants​

     • Giants represent a class of stars that have left the main sequence after exhausting their hydrogen fuel in the core.

     • As they evolve, they expand and cool, leading to a significant increase in luminosity and size, placing them above the main sequence on the HR diagram.

     • They can be subdivided into different types such as red giants, which are large, cool, and luminous, and blue giants, which are hotter but less massive than supergiants.

   • White Dwarfs

     • White dwarfs occupy the lower left region of the HR diagram. These stars represent the final evolutionary stage of stars that do not have enough mass to become supernovae.

     • They are typically remnants of stars that have shed their outer layers, leaving behind a hot, dense core.

     • While their surface temperatures can be high, they are less luminous due to their small size. As white dwarfs cool, they gradually fade and dim over time.

3. Other features​​​​

   • The other miscellaneous tools include: showing isoradius lines, showing nearest/brightest stars, show cursor values, and use exaggerated colors​

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