Special Sub-Topic: H-R Diagram Click Here To Play: H-R Diagram

What is the proper name of the H-R Diagram?

Hertzsprung- Russell Diagram. It is named after its two designers Ejnar Hertzsprung and Henry Norris Russell.

What does the H-R Diagram plot?

spectral class and absolute magnitude. The H-R Diagram plots spectral class (aka temperature) and absolute magnitude (aka luminosity).

What is the most commonly used mnemonic for spectral classification?

Oh Be A Fine Guy/Girl Kiss Me. The spectral classes in order of decreasing temperature are: O, B, A, F, G, K, and M. One uncommon variation of this mnemonic is "Oh Be A Fine Guy/Girl Kiss My Lips Tenderly". It was made to include L and T, which are given to stars that are so small they do not generate enough heat to begin nuclear fusion.

The majority of the stars in the H-R Diagram are found where?

main sequence. A star spends most of its life in the main sequence burning hydrogen fuel. Once the star has stopped burning Hydrogen, it leaves the main sequence, evolves, and dies.

The H-R Diagram can also be used to find:

distance. Distance can be found by both main-sequence fitting for stellar clusters, and by spectroscopic parallax for individual main-sequence stars.

Where are the solar diameters of stars is plotted on the H-R Diagram?

Diagonal lines (top left to bottom right). The solar diameters of stars are plotted on diagonal lines that cross the diagram. Our Sun (at one solar mass) is on the most central diagonal line.

White dwarfs are found at the bottom-left corner of the H-R Diagram.

t. They are very small (that is why they are at the bottom), but also very bright (B or A spectral type).

There are more supergiants than giants on the H-R Diagram.

f. Supergiants are rare, giants are more common and found on the RGB (Red Giant Branch).

Which of these is not typically found on the H-R Diagram?

red dwarfs. Most H-R Diagrams exclude red dwarfs, although they exist. When they are included in the H-R Diagram they are found in the bottom-right corner.

Our star (the Sun) is part of the main sequence.

t. The Sun is now a part of the main sequence. In a few billion years the Sun will move up in the H-R Diagram, becoming a red giant, and eventually, a white dwarf.