Main Sequence stars vary widely in effective temperature but the hotter they are, the more luminous they are, hence the main sequence tends to follow a band going from the bottom right of the diagram to the top left. These stars are fusing hydrogen to helium in their cores.

Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. About 90 percent of the stars in the universe, including the sun, are main sequence stars. These stars can range from about a tenth of the mass of the sun to up to 200 times as massive.

The main sequence stretching from the upper left (hot, luminous stars) to the bottom right (cool, faint stars) dominates the HR diagram. It is here that stars spend about 90% of their lives burning hydrogen into helium in their cores. These stars are very hot but have low luminosities due to their small size.

The Hertzsprung–Russell diagram, abbreviated as H–R diagram, HR diagram or HRD, is a scatter plot of stars showing the relationship between the stars’ absolute magnitudes or luminosities versus their stellar classifications or effective temperatures.

Make an H-R diagram for the brightest stars by graphing b-v and absolute magnitude for the 26 stars above….A Simple H-R Diagram.

The Scientists and Science Behind the H-R Diagram The way the stellar wavelengths appear gives clues to the chemical elements in the star. They can also reveal information about its temperature, motion through space, and its magnetic field strength.

The Supergiants are cool stars, which are very large and very bright. They are located towards the top right of the graph. The Giants are cool stars, which are a little smaller and dimmer than the Supergiants. The White Dwarfs are very hot stars, which are small in size and relatively dim.

Hertzsprung-Russell diagram, also called H-R diagram, in astronomy, graph in which the absolute magnitudes (intrinsic brightness) of stars are plotted against their spectral types (temperatures).

In general, the more massive a star is, the shorter its lifespan on the main sequence. After the hydrogen fuel at the core has been consumed, the star evolves away from the main sequence on the HR diagram, into a supergiant, red giant, or directly to a white dwarf.

A Simple H-R Diagram. Once you know the luminosity and temperature (or color) of a star, you can plot the star as a point on the H-R diagram. Plot the luminosity on the y-axis with brighter stars going toward the top.

The position of Canopus in the H–R diagram indicates that it is currently in the core-helium burning phase. It is an intermediate mass star that has left the red-giant branch before its core became degenerate and is now in a blue loop.

Red stars

The Different Types of Stars

• Protostar. A protostar is what comes before a star has formed – a collection of gas that collapsed from a huge molecular cloud.
• T Tauri Stars.
• Main Sequence Stars.
• Red Giant Stars.
• White Dwarf Stars.
• Red Dwarf Stars.
• Neutron Stars.
• Supergiant Stars.

At the lower left corner of the H-R diagram are the smallest stars. Stars like Sirius B and Procyon B are just the opposite of the supergiants. They are extremely hot, dense, and dim.

Two of the brightest stars in the evening sky lie at opposite corners of the rectangle: bright orange-red Betelgeuse at the northeastern corner (upper left in the photo) and even brighter Rigel at the southwest (lower right in the photo). Betelgeuse is at least 300 times the Sun’s diameter, and perhaps much more.

There are seven main types of stars. In order of decreasing temperature, O, B, A, F, G, K, and M. This is known as the Morgan–Keenan (MK) system.