Properties of Stars Apparent Magnitude: the brightness of a star as it appears from Earth. Size Temperature Distance Absolute Magnitude: how bright the star actually is. Two stars with the same apparent magnitude may not have the same absolute magnitude. Two stars with different apparent magnitude may have different absolute magnitude.

Properties of Stars Color and Temperature Stars with the highest temperatures appear blue (53,500oF). Stars with middle temperatures appear yellow (8,500-10,300oF). The coolest stars appear red.

Properties of Stars Hertzsprung-Russell Diagram: shows the relationship between the absolute magnitude and the temperature of the stars. Temperature is also related to size: the bigger the size of the star, the Cooler the temperatures.

Properties of Stars Binary Stars: pairs of stars that orbit each other. These stars are used to determine the stars’ masses. The stars move in a circle around a center of mass. If the center of mass is directly in the middle between the 2 stars, the masses are the same. If the center of mass is closer to one of the stars, then that star is larger.

Properties of Stars Variable Stars: stars that fluctuate in brightness. Cepheid variable star: brightness alternates at a regular interval called a light period. (Bright  dim  bright, etc.) Nova: sudden brightening of a star usually due to a nova eruption. The brightest moment is seen within a few days, remains bright for a few weeks, then returns to normal brightness within a year.

Properties of Stars Nebulae (interstellar matter): clouds of dust and gases. If this matter gets too close to a hot star, it will glow. This is known as a bright nebulae. There are two types of bright nebulae. Emission Nebulae: turns energy into visible light which fluoresces. Reflection Nebulae: dense clouds of dust reflect the light from nearby stars

Assignment The Hertzsprung-Russell Diagram Worksheet