Classifying Stars

Stars are classified by size, temperature, color, and brightness Classifying Stars Stars are classified by size, temperature, color, and brightness

Star Size  Stars vary in size from small dwarf stars to very large supergiants Star size is controlled by density Density is the amount of matter in a defined amount of space. Density = mass / volume   Dwarf stars are very dense while Supergiants are less dense than our atmosphere

Color and Temperature The color of stars tells us about the star’s temperature. Blue stars – Hottest 30000C+ White - 7500 –30000C Yellow – Medium 5000 – 7500 Orange - 3500 – 5000 Red stars- Coolest under 3500 Our sun is a yellow star

Brightness Brightness depends on a star’s temperature, size, and distance from us. Brightest stars: Blue & white stars, Supergiant & giant stars, and stars that are close to us.

Magnitude Magnitude means Brightness Apparent Magnitude – What we see – mainly depends on distance from us Absolute Magnitude – What it is – depends on temperature and size The absolute magnitude of our sun is average, the apparent magnitude of our sun is the largest of any object in our sky.

HR Diagram Hertsprung and Russell came up with a chart that relates a star’s brightness to its color and temperature. Three main categories: Main Sequence – contains most stars, found along the diagonal in the chart Supergiants & Giants – found at the top. Dwarf stars – found along the bottom. Our sun is a main sequence star

Parts of the HR Diagram X axis –shows temperature of the star and the color Temperature increases as it moves to the LEFT Temperature decreases as it moves to the RIGHT Star color goes from Blue-white (left) to Yellow to Red (right)

Parts of the HR Diagram Y axis – Shows the true brightness and size of a star Brightness increases as you move up the diagram Size increases as you move up the diagram

Dwarf stars are found at the bottom of the diagram. Dwarf means small.

Dwarf stars are found at the bottom of the diagram. Dwarf means small.

Supergiants and Giants are found at the top of the diagram Supergiants and Giants are found at the top of the diagram. Giant means big.   Dwarf stars are found at the bottom of the diagram. Dwarf means small.

Supergiants and Giants are found at the top of the diagram Supergiants and Giants are found at the top of the diagram. Giant means big. Main Sequence stars are found on a descending diagonal line on the diagram. Dwarf stars are found at the bottom of the diagram. Dwarf means small.

Supergiants and Giants are found at the top of the diagram Supergiants and Giants are found at the top of the diagram. Giant means big. Main Sequence stars are found on a descending diagonal line on the diagram. Dwarf stars are found at the bottom of the diagram. Dwarf means small.

Supergiants and Giants are found at the top of the diagram Supergiants and Giants are found at the top of the diagram. Giant means big. Main Sequence stars are found on a descending diagonal line on the diagram. Dwarf stars are found at the bottom of the diagram. Dwarf means small.

HR Diagram Dwarf stars are found at the bottom of the diagram. Dwarf means small. Name an example of a white dwarf star on your diagram

HR Diagram Dwarf stars are found at the bottom of the diagram. Dwarf means small. Name an example of a white dwarf star on your diagram

HR Diagram Dwarf stars are found at the bottom of the diagram. Dwarf means small. Name an example of a white dwarf star on your diagram

HR Diagram Supergiants and Giants are found at the top of the diagram. Giant means big. Name an example of a Red Supergiant found on your diagram.

HR Diagram Supergiants and Giants are found at the top of the diagram. Giant means big. Name an example of a Red Supergiant found on your diagram.

HR Diagram Main Sequence stars are found on a descending diagonal line on the diagram. Name a super-hot main sequence star from your diagram.

HR Diagram Main Sequence stars are found on a descending diagonal line on the diagram. Name a super-hot main sequence star from your diagram.

HR Diagram Main Sequence stars are found on a descending diagonal line on the diagram. Name a ordinary yellow main sequence star from your diagram.